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And another overheating issue

8K views 44 replies 16 participants last post by  Roverlike 
#1 ·
Good afternoon everyone, I need the brains of the MG heroes here on the forum. The amount of issues this MG TF 135 sprint has given me is beginning to make my sanity look questionable. The issue I am having now is an overheating issue when idling. I first noticed it when I was on a long run on the motorway and when I come to a complete stop, after about 15 minutes of idling, the temp gauge started to rise. I plugged him in to my OBD2 reader and no fault codes. I am not experiencing any coolant lose, if anything I am experiencing coolant rise! I have attached a picture, this certainly isn't normal is it!? When he's cold he is sitting bang on the max line. I did a 500 mile round trip over the bank holiday with no problems... As long as he's moving and doesn't idle longer than 5 - 10 minutes, he behaves fine. The front fan is kicking in religiously at around 220f. At this point in time I suspect an airlock... Any help would be greatly appreciated! Many thanks
 

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#2 ·
I would have thought idling for 15 minutes would cause a temperature increase if there is no flow through the radiator until the fan cuts in?
Is the problem the fan does not control the temperature after it cuts in initially...it should switch on and off as required to control the temperature.

If the fan can't bring the temperature down, the rad could be partially blocked internally, among other things.
 
#3 ·
Thanks for your reply, funny you should say that I took it to an apparent mg specialist garage, which I shall not name, and said to them exactly that - I don't think my rad is good. They gave the classic 'it's yer 'edgasket mate', which was somewhat surprising as I used them for work in the past and they proved to be pretty good. The irony is these guys changed my underfloor coolant pipes about 4 months ago and didn't bleed the system from all three points. They only bled from two because apparently one is a 'pain in the arse' to get to.

By the way yes that's exactly it - the fan cuts in but doesn't seem to be able to bring the temperature down.
 
#4 ·
If the system has not been properly bled then that would be the first thing I would do, or get done.

As yet I have not done it myself but I am sure there are plenty of forum members who can give detailed advice on doing it.

There are other indicators of HGF like oil emulsification or deposits in the coolant tank, or persistent coolant loss. It is too easy for garages to blame all ills on gasket failure, although that is always a possibility.
 
#10 ·
Coolant expands when it gets hot, but not enough to fill the expansion tank and overflow!

However temperature of the coolant is the reason the coolant overflows when the cap fails to hold pressure!

Science bit:-:nerd:

Water at atmospheric pressure boils at 100 degC
Water at 1 bar above atmospheric pressure (cooling system pressure) will boil at about 125 deg C

When water heats up it first gently releases dissolved gasses (nitrogen and oxygen), which causes the pressure rise in the coolant system. In a closed system, such as the F/TF cooling system, this building up of pressure provides equilibrium to prevent the coolant boiling. (In a sealed pressure vessel water will never boil!!!).
So long as the temperature of the water does not exceed the boiling point, for its pressure, then the coolant system stays in equilibrium and will not boil.0:)

The F/TF cooling system keeps the coolant temperature at about 110degC and a maximum pressure of 1Bar over atmosphere, so as long as the system is pressurised to 1bar, and the temperature does not exceed 125degC it will not boil :smile:

However if the pressure is reduced to atmospheric, with a leaking cap for instance, its boiling point will be reduced from 125degC to 100degC but the actual coolant temperature is still about 110degC.

As the water now starts to boil it now rapidly releases large quantities of water vapor (steam) which is a lot less dense than water so expands in volume. This forms large bubbles in the coolant (like when a kettle boils) which displace the coolant out of the expansion bottle, casing it to overflow.

So excess temperature at reduced pressure, cause the water to boil, which displaces the water out of the expansion bottle.

You did ask >:)
 
#12 · (Edited)
hence my interest in pressure sensing to determine the systems correct function... i still have my pressure gauge permanently in system... and know pretty much how the pressure system behaves over time in all conditions... its been a valuable tool... pretty vital to give one forewarning of incorrect system operation since the pressure status reacts far more fluently and in shorter time than temperature sensing can - to condition changes and the action of the pump...

for example the recent hot weather has shown me, that though the pressure in the system hasnt changed, i loose small amounts of coolant over time... and its because the cap isnt a complete seal.. it cant be.. because the system must be able to prevent a vacuum... as it cools.. so the cap breathes, both in expansion and contraction.. of the coolant.. and vapour escapes because of that... and so the coolant level will change in time.. even though the system is working just as it should... its more apparent when the outside temp around the engine has a high ambience.

ive yet to install an electronic gauge instead of the dial gauge ... but its told me ( and i hope Sundance too) how important knowing how the system works and its reaction to change.. is.

i moved the boot temp sensor. from its position to one very close to the head outlet coolant pipes... ive now ty wrapped it to them... and the engine bay fan now comes on much sooner in the hot weather we have been enjoying... it means when i stop the car or get stuck in traffic... the fan runs and help circulate the air in the engine bay better..
 
#13 ·
...... i loose small amounts of coolant over time... and its because the cap isnt a complete seal.. it cant be....the cap breathes.... and vapour escapes because of that... and so the coolant level will change in time
If you are losing coolant, you have a leak somewhere. The degree of venting through the cap is negligible, and once the system has gone through a few hot/cold cycles, there won't really be any venting via the cap unless there is a significant overheat (and resultant expansion of coolant). It's a one way valve to relieve excessive pressure, so won't allow air to be drawn back into the system unless the valve is faulty.

I replaced the head gasket on my ZR four years ago, and since then, the coolant system level has been unchanged, and has required no topping up whatsoever. Venting via the cap is certainly not causing any coolant reduction in this case.
 
#14 ·
I agree completely with "man in the Car".

If the system starts at atmospheric temperature and pressure (remove cap and re-fit) then as it heats up the pressure builds up. So long as the pressure does not exceed the pressure cap rating, then as the system cools back down to the original ambient temperature there should be no Vacuum drawn, as the pressure will return to the original atmospheric pressure.

Only by loosing coolant, and reducing the coolant volume, will a vacuum be drawn when cooled back down.The cap does not normally "breath".

I am unsure if the F/TF cap has a negative pressure relief valve. I will have too take a look one day!

However it seems your system is leaking and no longer operating in equilibrium.

I have never had to top the coolant up in either of my TF's in three years (other than when the head gasket failed on one of them, one month after I bought it, dumping water into the oil!!).

Even when driving from Liverpool to Lake Constance (1800 mile round trip to German/Swiss/Austrian/French border) in two days in 80 deg weather and never had to put a drop in (though kept checking it:grin:).
 
#15 ·
Just a quick few comment- you are overfilling your expansion bottle- its only supposed to be up to the join inside the bottle. A cheap way to start first is the bleed and replace the filler-cap on the bottle. it does sound like air in the system, but then again- if your pipes were replace- then did the engine overheat and was any damage done. is your oil effected- any mayonnaise? I had Russel around to look at my coolant-loss and he pressure-tested and confirmed both my used and spare caps were ok. he found no leaks- so 'off with his head' and new HG fitted- even though i had receipts to show it was changed by a rover dealer about 4 years ago. As someone correctly pointed out on here- with no visible leaks, OAT doesn't evaporate! Well, a year on and my temp gauge never creeps up the the half-way mark and fans kick in if stuck in traffic etc. Im a daily-user of my TF160, so I know its habits and HG was the only solution. Russel charge me £300 and for that money, it wasn't worth me guessing or getting it wrong. he's first class and Essex for him is a breeze- he's based in Meopham.
 
#16 ·
Hi Pat, yeah that was my point when posting this - despite filling it to the max line (half way) it would rise all the way to the top and overheat. Changing the cap fixed this problem, it was Russell who found this out. I have used him for the past four years and he has proven to me time and time again that he should be the only guy/girl to look at my TF!
 
#17 · (Edited)
i dont want to get drawn into an non beneficial argument again . its why i removed the topic i started before, that i and Sundance contributed too.

at normal operating pressure, is a point beyond which the cap begins to open.. it begins to bleed.. it allows expansion of the coolant.. its normal.. the pressure is maintained at that point..

BUT... if the pressure cap has opened at all, ( IT DOES ) then the mass in the system has changed.. its not as big as it was... both air,, and a very small amount of coolant escape when it does..


the point the cap does that isnt the same for every single cap... its a median point.. and it affected by the coolant pump its self.. the pump can push the cap to point of opening pressure even when the coolant is cold...

and.. its very likely that there other hose joints that breathe in the same way... let air in, and push fluid out in tiny amounts.. under particular circumstances... the whole system is unable to be completely sealed, even if one cant see any obvious change in the coolant level... i would say your not looking hard enough...




i made a video of it doing that.. just by revvimg the engine.. and watching the calibrated pressure gauge..



if you bought say five caps and measured the point of opening on them like i and Sundance have done.. its unlikey that any of the five would open or close at the same pressure..

the cap breathes.

as the hot coolant cools... and the mass inside the system has changed, then as it cools to prevent a difference between outside and inside pressure ( a vacuum ) the cap lets air in.. ( IT DOES)


at equilibrium, the outside pressure and inside system pressure, will be the same... the cap enables that to happen..

its not a sealed closed system.. one can like Sundance and i have done.. use gauges to measure what happens.. its how i know the pump speed affects the system pressure regardless of temp.

the amount of coolant that can leave the system at any time except at total cap venting.. is small.. hardly noticeable.. but it does occur over time, the venting is humid.. its full of water vapour.

when the cap does fully vent - open completely, its very sudden and dramatic... it might only click fully open for a second or less.. but because the system is fully venting under pressure the pressure loss in that one second is huge... its like opening an air line or the tyre valve on a tyre.. ive done that test on purpose.. to see what happens, at temps below the normal boiling point... i dont reccomend trying it unless you have good calibrated equipment to know what will happen,

The temperature of the coolant doesnt change so fast.. one doesnt loose three or four degrees of temp in that time.. it remains the same.. so.. that hot coolant now boils vigorously.. but one can loose over 5ps pressure in that time.. less than a second.. ive seen it.


so.. i will just say.. in normal operating conditions.. the cap breathes.. it lets pressure in and out... its not fully closed or fully open.

i did contemplate, when Sundaance and i were considering these effects of pressure, if i could make an alteration to the top cap. to allow its breathing to vent into an external container, so i could see the effect of that breathing into a pipe that went to a separate container with the end of the pipe submersed in coolant in that external chamber... so i could see it.. BUT.. its not an easy thing to do... one would need a way of enclosing the cap completely with an external pipe into a second chamber. its laboratory stuff... not everyday motoring..:)
 
#25 ·
WARNING

The following post contains facts, lots of them, and most totally uninteresting and irrelevant to your enjoyment of the MG F/TF

There is no benefit in reading any of this!

If you value your time do not read any further:grin:

If you do read further do not blame me for loosing your sanity and the will to live!


i dont want to get drawn into an non beneficial argument again . its why i removed the topic i started before, that i and Sundance contributed too.
Hey!

Don't forget I contributed to it also.

I put a lot of effort into trying to help you understand what you were observing. You deleted my posts without consulting me at the same time.

There was a lot of interesting information in it, but you deleted it because:-

1 You didn't understand it
2 You didn't agree with it
3 You could

I promise not to go on about absolute pressure and gauge pressure :wink:

Just got to comment on so many errors!

at normal operating pressure, is a point beyond which the cap begins to open.. it begins to bleed.. it allows expansion of the coolant.. its normal.. the pressure is maintained at that point..
If the cap starts to vent, then the cooling system pressure is too high. The cap opens due to excessive pressure. At normal operating pressure the cap will not open for any reason!

BUT... if the pressure cap has opened at all, ( IT DOES ) then the mass in the system has changed.. its not as big as it was... both air,, and a very small amount of coolant escape when it does..
Why would it open unless the cooling system has gone into fault condition and over-pressurised?


the point the cap does that isnt the same for every single cap... its a median point..
Unless the cap is faulty, the range of operating pressures should be very small (1-2 psi max). Mass production methods and statistical process control result in high repeatability.

and it affected by the coolant pump its self.. the pump can push the cap to point of opening pressure even when the coolant is cold...
In a closed system, a pump will only generate pressure where the fluid movement is restricted. Where a restricted flow opens up into a larger chamber (such as the expansion bottle), the pressure will fall. To establish what the system pressure on the filler cap is, empirical measurements will need to be made in the expansion tank, not on the hoses that feed it. How have you kept the coolant cold while revving the engine enough to activate the pressure relief valve in the cap.

and.. its very likely that there other hose joints that breathe in the same way... let air in, and push fluid out in tiny amounts.. under particular circumstances... the whole system is unable to be completely sealed, even if one cant see any obvious change in the coolant level... i would say your not looking hard enough...
You mean if the system is leaking. We have established that a well maintained cooling system does not leak, and should not leak.

i made a video of it doing that.. just by revvimg the engine.. and watching the calibrated pressure gauge..
What was the pressure gauge calibrated against??
As above you were observing the pressure build up due to pushing coolant through restricted pathways in a closed system. The pump can not increase the mean closed system pressure. If the pressure increases at one point, a reduction in pressure will be observed somewhere else (inlet to pump, or where the restricted passageways open up into less restricted passageways). Closed system fluid dynamics are not the same as open system fluid dynamics mainly because atmospheric pressure is taken out of the equations.

if you bought say five caps and measured the point of opening on them like i and Sundance have done.. its unlikey that any of the five would open or close at the same pressure..
What is the manufacturing permitted tolerance on the pressure caps. When Rover made them they would have been part of a strict SPC (Statistical Process control) to ensure the parts were all (or an acceptable percentage) produced within specified tolerances. Can this be said of aftermarket caps?

the cap breathes.
:hysteria:

as the hot coolant cools... and the mass inside the system has changed, then as it cools to prevent a difference between outside and inside pressure ( a vacuum ) the cap lets air in.. ( IT DOES)
Why would the mass change, other than if you have had a loss of coolant? If the coolant system is working well, then after an initial loss of coolant, due to over filling, an equilibrium will develop, where the volume increases due to a rise in temperature, then drops back to the original volume when cooled down again. The volume changes, but the mass stays constant, unless you have a leak. The cooling system is designed to accommodate the change in volume (hence the expansion tank) under normal condition.

(science bit warning)
The pressure in the system changes partially due to the increase in water volume as it heats up (its density decreases with temperature) but mainly due to the release of dissolved gasses within the water. This is why the pressure increases before the coolant reaches the phase transition condition (boiling point).


at equilibrium, the outside pressure and inside system pressure, will be the same... the cap enables that to happen..
That is what equilibrium means!, but the cap does not enable this, unless there has been a change in the coolant mass due to a leak.

its not a sealed closed system.. one can like Sundance and i have done.. use gauges to measure what happens.. its how i know the pump speed affects the system pressure regardless of temp.
Please show me your experimentation and results that demonstrates that it is not a sealed closed system? How are you measuring the change in coolant volume and mass, or the ingress or regress of air from the system through the cap. The pressure changes you see are due to the restrictions in the system as the flow increases (explained by fluid dynamics). However the overall average system pressure will not be changed!

the amount of coolant that can leave the system at any time except at total cap venting.. is small.. hardly noticeable.. but it does occur over time, the venting is humid.. its full of water vapour.
So over time it is necessary to keep re-filling the coolant system up? If you have to then you have a leak. Presumably a very small leak that you find manageable, but a leak non the less!.

when the cap does fully vent - open completely, its very sudden and dramatic... it might only click fully open for a second or less.. but because the system is fully venting under pressure the pressure loss in that one second is huge... its like opening an air line or the tyre valve on a tyre.. ive done that test on purpose.. to see what happens, at temps below the normal boiling point... i dont reccomend trying it unless you have good calibrated equipment to know what will happen,
That is what the cap is designed to do. In a catastrophic fail condition, the cap vents excess pressure to prevent a hose bursting, or blowing off, which could cause injury or damage elswhere. Imagine if one of the heater matrix hoses burst near your feet. The cooling system will be designed to survive something like 2-3 bar, but the pressure cap will relieve the pressure well before the pressure gets this high.
This is the pressure caps sole function...to prevent excessive cooling system pressure.

The temperature of the coolant doesnt change so fast.. one doesnt loose three or four degrees of temp in that time.. it remains the same.. so.. that hot coolant now boils vigorously.. but one can loose over 5ps pressure in that time.. less than a second.. ive seen it.
Finally a point we can agree on:rocker:


so.. i will just say.. in normal operating conditions.. the cap breathes.. it lets pressure in and out... its not fully closed or fully open.
I knew that wouldn't last :frown:

i did contemplate, when Sundaance and i were considering these effects of pressure, if i could make an alteration to the top cap. to allow its breathing to vent into an external container, so i could see the effect of that breathing into a pipe that went to a separate container with the end of the pipe submersed in coolant in that external chamber... so i could see it.. BUT.. its not an easy thing to do... one would need a way of enclosing the cap completely with an external pipe into a second chamber. its laboratory stuff... not everyday motoring..:)
This is the way many cars operated in the 70's and 80,s. There were two seals on the cap. One at the top, and one on the spring loaded pressure disk. As the system pressure rose the pressure relieved past the first seal, and was contained by the second seal. A small pipe directed the water vapour into an external header tank when it would condense. As the system cooled again, another valve opened in the cap to allow the water to be sucked back into the cooling system.

I think my 1970 MGB used this system or was it my fiat Strada :| No it might have been my MKII ford consul, or was it the herald. Dont think it was the P6, but it could have been. I know for certain it wasnt my Citroen GS!
 
#18 ·
Sorry, but you are talking complete twaddle. If you don't want to get "drawn into non beneficial arguments", why make a non-beneficial (and totally erroneous) post??????

The system begins with the coolant and air space in the expansion tank at a finite volume. The pressure in the system is roughly equal to 1 atmosphere.

When the coolant gets heated to operating temperature, the coolant (and air in the tank) will expand, and due to the sealed nature of the system, the presure increases, which in turn raises the boiling point of the coolant. The pressure setting of the valve in the expansion tank cap means that it will not open and let presssure out at all if the system is correctly filled with the correct volume of coolant. It will only open to relieve pressure if the system over heats to the point where the coolant boils (coolant in the gaseous state form boiling has a vastly bigger volume than in the liquid state, and without the relief valve in the cap would cause a catastrophic increase in coolant system pressure. If the valve in the cap opens at normal operating temperature and pressure, it is faulty (and from what I and others have found over the last 20 years, a very high proportion of the cheap aftermarket expansion tank caps do in fact do this and are absolutely useless, which is why we always recommend people to buy a genuine MG Rover cap).

When the engine is stopped and left to cool, the volume of coolant within the system returns to the same as it was when the engine was cold originally, and the pressure in the system returns to 1 atmosphere. Thus there is no negative vacuum in the system, and if you are finding that air is being drawn into the system through the cap valve or seal when your engine cools then a). you have a leak of coolant somewhere which has causes a decrease in the volume of fluid in the system, and b). your expansion tank cap is knackered. It could be that if the cap is not sealing, there may lie the source of your system fluid loss.

BUT: however much you may try to argue against the laws of physics, a good expansion tank cap, functioning correctly as it is designed to do will NOT allow loss of coolant during normal engine running. There are enough of us out here who never have any need to top our coolant up to prove that beyond all doubt.

Basically, if the valve in your cap is 'breathing' as you put it, it is jiggered.
 
#21 ·
:popcorn:...............................
 
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#23 ·
Let’s take some err pressure off this thread… :err::getcoat:

Joking apart the moderators and I are not happy with the tone of some the posts in this thread, totally needed.

So over the years we know that the MG/TF system should be pressurised at all time regardless of temperature of the system. There should be no coolant loss, indeed my TF went from 2009 after its second HGF to 2015 when the water pump let go without topping up the system.

However if the pressure gets too high the valve opens to allow the extra pressure to vent, however the design is poor and the valve 9 times out of 10 will not shut properly. This issue has often been attributed to the main reason for head gasket failures, it would seem often even if the gasket hasn’t gone…

Furthermore around 80% of OEM caps from Xpart made approx. 10 to 12 years ago were found to be faulty brand new off the shelf. It may well be that there are some of these caps still being sold as NOS (new old stock). So in other words a new cap isn’t a guarantee of a working cap.

Another thing to consider is that if PRT has been fitted, that someone well-meaning has put a conventional thermostat back in the old housing removing the blanking ring. It has happened before with the coolant doing strange things.
 
#26 ·
Still doesn't help me with my cooling problem on my 53 TF, can have the flow to rad pipe so hot you can't hold it unless wearing a glove and pressure is so high it feel like a steel pipe not rubber but the return colder than a dead chicken in a fridge. Rad isn't blocked, suspect there is a blockage somewhere, changed the PRT for a spare but makes no difference. Think I will take all small bore pipes off and check for blockages.
 
#27 ·
You didnt read that post above did you!

I did warn you!

can have the flow to rad pipe so hot you can't hold it unless wearing a glove and pressure is so high it feel like a steel pipe not rubber but the return colder than a dead chicken in a fridge.
Be aware two conditions will give the same results!

1 The radiator is working very very well, and taking out large amounts of heat from a large volume the coolant (GOOD)
2 The flow through the radiator is low, and the radiator is taking out lots of heat from a SMALL volume of coolant, as the coolant is staying in it for a long time! (BAD)

If it really is as cold as a ...."dead chicken in the fridge"...then I might suspect number two, as the radiator would struggle to cool a high volume of coolant from 110degC to 3 degC (or depending on how cold you have your fridge :wink:) unless the water was in there for a long time! (also the thermal efficiency of the engine would be disastrous!)

I do not know what temperature differential you would expect to see across the radiator in a healthy cooling system but would hazard a guess of about 20-40 degC with a very good flow of air.

I work with industrial hydraulic cooling systems (heat exchangers), and seeing a large temperature differential always sets alarm bell ringing in my head. Normally the temperature differential is only a degree or three on full load.
 
#28 ·
"If the cap starts to vent, then the cooling system pressure is too high. The cap opens due to excessive pressure. At normal operating pressure the cap will not open for any reason!"

NO.

the cap opens at its mechanical settings.. they are reasoned but not all the same. in fact..

not lie..
 
#30 · (Edited)
"In a closed system, a pump will only generate pressure where the fluid movement is restricted. Where a restricted flow opens up into a larger chamber (such as the expansion bottle), the pressure will fall. To establish what the system pressure on the filler cap is, empirical measurements will need to be made in the expansion tank, not on the hoses that feed it. How have you kept the coolant cold while revving the engine enough to activate the pressure relief valve in the cap."

i started a cold engine with a calibrated pressure gauge in line in the header tank.. and revved the engine to red line. and watched the pressure gauge..

it reached a pressure beyond the caps design vent pressure.

i.e the cap should be opening... the pressure was high enough.. and the temperature? far less than boiling point at normal atmospheric pressure.. the coolant was cold... the pressure was high and me revving the engine to redline, did that.. and the only pressure enabling thing to make that possible.. was the pump.

i sensed the cap venting.. but it didnt open fully



HOW WOULD YOU DO IT?

i did it.
 
#31 ·
Erm just to bring it back to basics, my F had a very and I mean very small coolant loss not really noticable until I marked the level with felt pen, even then not much, but on the cooldown cycle sir was getting on causing the coolant to rise and over heat, not oil in coolant or coolant in oil, borescope in 1 and 2 cylinders showed coolant getting in but burnt off when starting, sniff test priced negative. Sorted now with new headgasket but was a head scratcher for months.

Sent from my SM-J500FN using Tapatalk
 
#38 · (Edited)
1Leigh, its easy to check on the car in situ... since if one does that one can see what the whole system does.. not just one bit.

this pic show my pressure gauge and schrader valve assembly, shoe horned into the the jiggle pipe return pipe to the header tank, the first time i explored the pressure effects.

so its showing the pressure in the whole system... at the header tank.

you can see its reading about 9 psi in the pic.. and this would be around normal operating pressure just after engine switch off... if the system is good.. it will continue to fall very gradually... it will take around 2 hours to fall from around 6 psi to zero.


if one revs a cold engine the pressure will rise in motion with the revs.. and if one redlines.. it will reach cap opening pressure at @ 15 psi... at that point.. if one holds the revs... the cap will fractionally open and close.. and the pressure gauge will pulse slightly up and down as it rapidly opens and closes..

its not fully opening.. its fractional.. but if one reaches rev cut off point... the cap might click fully open.. and the pressure will drop rapidly when it does. loosing 5 psi or more until it closes... not a problem with a cold engine... just when its at normal operating temp..


normal operating pressure is between 8 and maybe 12 psi...

its going to be slightly different for any car, dependent on gauge and pressure security governed by pipe joints and hoses permeability.

a hot revved engine at turn off will loose pressure over time.. the cap bleeds.. its designed to..

if there is a big leak.. the cap will loose pressure rapidly, less than an hour from 6 psi to zero would be of concern.. since either the cap is leaking too much or a pipe joint etc..

ive timed the pressure drop... it might take four hours from normal operating pressure at switch off.. to reach zero.. ie 12 psi to zero.. its dependent on temp, both outside the car, and the engine bay, and the composition of the coolant, the nature of the cap, and hose joints and hoses... so it will be slightly different for any f. tf derivative.. But if it only takes 5 minutes to fall from 5psi to zero for example.. even though it reaches normal operating pressure and the car runs fine with no apparent faults.. and holds normal operating pressure until switch off.. you have a big leak somewhere.

when i first tried this test, in 2015 - trying to find the cause for coolant loss in my freestyle. i couldnt get pressure above 2 psi.. though the car started and ran fine... it was the cap... but the cause of the coolant loss wasnt just the cap. even though the car went without fault, the head gasket was failing... eventually it failed emissions.. the ecu didnt tell me that... it was the mot test.

 
#41 · (Edited)
yes, on purpose . i think. but exactly what your purpose is g0rsq, i cant define and offer no solution. this mo. so any directive you have on your purpose, would enable folks to know what you seek a solution for. Maybe you do not seek a solution but deny any..? i understand that.. black can be white... but.. if the only reason you seek is to deny.. then what is your favour? is your favour to deny? then what is your truth? or do you just deny everyone and have no truth?
are you a lie in denial g0rsq?

?
 
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