How to change a PRT - MG-Rover.org Forums
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post #1 of 26 (permalink) Old 05-09-2011, 21:21 Thread Starter
CJJ
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How to change a PRT

The thermostat (or stat) is responsible for keeping your engine at a working temperature and is key to the efficient running of your car.

The idea is that when you first start the car the thermostat only allows the coolant to circulate around the engine. This allows the engine to heat up to working temperatures quicker and save fuel.

When the temperature is reached, the thermostat opens and allows the coolant to flow through the radiator to aid in getting rid of the unwanted heat.

This then explains 2 symptoms of a failed thermostat.

If the thermostat was to remain closed the coolant will never be diverted to the radiator and will get hotter and hotter as the engine cannot get rid of the heat. This can lead to pipes/hoses or expansion bottles rupturing and steam everywhere. It can also result in overheating the engine, which can cause damage on the k-series engine.
If it is stuck open then the engine will take a very long time to reach itís correct working temperature as the coolant will always be going through the radiator. This will cause excess fuel consumption, emissions and lack of power as the ECU will be running in cold start mode and using more fuel.

The TF thermostat, from around 2003, is a little more complicated and is also operated by a pressure differential in the system. As the water pump is directly driven by the engine, an increase in revs will produce an increase in pressure and operate the PRT. In effect, this is anticipating a rise in temperature before it happens, reducing thermal cycling and shock to the engine.

Some useful information on PRTs can be found here http://www.mgf.ultimatemg.com/group2...ifications.htm



So, if you are having any of these symptoms then it might be time to replace the PRT.

On a TF from about 2003 onwards the PRT is relatively easy to change.

First of all, you need to raise the car off the ground so that you can work underneath. Only work underneath the car if it is secure. You should use ramps or axle stands and ensure that the car cannot roll off.



Obviously, to change the thermostat you will have to drain the system of coolant.

I only replaced the coolant recently, so at around £40 to replace it I thought I would catch it and reuse it unless it was contaminated.

So I bought me a shiny new bucket. Donít use a bucket that you will use for other things, such as fish tank water changes, as traces of coolant can be very toxic.



My favoured way of draining the coolant is to open the expansion tank



Open the heater control valve all the way to hot



Now place the bucket under the front of the car where the metal underfloor pipes meet the radiator rubber hoses



And undo the jubilee clips



Now CAREFULLY push the screwdriver down between the steel pipe and the rubber hose. Be careful not to damage or hole the rubber hose. Once the seal is broken the coolant should start to flow.



Let the coolant flow until it starts tapering off and the go around the bleed points opening them up one by one.

There are 3 points.

One is at the top nearside of the radiator. Be careful removing this as it is basically a plastic bolt and has been known to shear off.






One under the plastic cover in the bonnet compartment







And one in the metal coolant pipe that runs over the top of the gearbox in the engine compartment.





Now let the coolant drain completely.

Check the coolant for contamination and if OK decant it into suitable containers.





Now move to the rear underside of the car and you should see the PRT near where the subframe joins the body.



Using pliers or screwdriver if you have used jubilee clips, disconnect and remove the rubber hos that connects the PRT to the underfloor pipes. Be aware that there will be some residual coolant still in the system.





Now, using the pliers, compress the spring clips and move them up the hoses at the engine side.





Now manipulate the PRT and pull it down to disconnect it from the engine hoses. Note which way the hoses connect to the PRT. The angled outlet goes to the nearside.



The old and the new.



Now push the new PRT into place, refit pipes and reconnect the clips.



Make sure that you have reconnected and tightened all connectors and jubilee clips, including the ones at the front end of the car where you drained the coolant. Also wipe all the joints dry. This will help after refilling so that you can see if the system is leaking or not.



Refit and tighten all of the bleed points.

Now refill the expansion tank. It should take some filling.



As it settles, fill it to the top



And then reopen the bleed points, starting at the radiator. If you have a helper get them to keep an eye on the expansion tank level and keep it topped up. If it drops below the bottom of the tank then you will introduce air into the system. If you donít have a helper then only open the bleed point for short periods of time and top up as necessary.

Bleed until only coolant comes out without any bubbles.





And retighten the bleed point. Make sure you donít overtighten as it is quite fragile.

Do the same with the heater matrix under bonnet bleed point, making sure the heater is turned fully to hot.



And then do the same with the engine compartment bleed point.



Top up the coolant to the correct level. Now start the engine and run for a minute with the coolant cap off. You should be able to see a constant flow of coolant and make sure the level doesnít suddenly drop.



Now refit the cap and let the engine get up to temperature.

Keep an eye on the hose connections you have disturbed in case there are any leaks



Once the engine has run up to full temperature, stop the engine and get under the car, checking all the connections for signs of leaking. Also once the coolant has cooled, check and adjust to the correct level.

Once you are happy, lower the car off the axle stands and take the car for a test drive.

Keep an eye on the temperature gauges and try the heater to make sure it is blowing hot when required.

The car now has a new PRT.
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post #2 of 26 (permalink) Old 05-09-2011, 23:27
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Brilliant as usually!
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post #3 of 26 (permalink) Old 06-09-2011, 02:15
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Good info Clive.
It looks like you've been doing a bit of off-roading!
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post #4 of 26 (permalink) Old 06-09-2011, 06:41 Thread Starter
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Originally Posted by RichinVancouver View Post
Good info Clive.
It looks like you've been doing a bit of off-roading!
Devon mud.
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post #5 of 26 (permalink) Old 06-09-2011, 07:13
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Nice work once again Clive

£40 for coolant though?? £22 for 5ltrs of concentrate at Halfords giving 10ltrs
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post #6 of 26 (permalink) Old 06-09-2011, 07:50 Thread Starter
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Originally Posted by Copperknob View Post
Nice work once again Clive

£40 for coolant though?? £22 for 5ltrs of concentrate at Halfords giving 10ltrs
Buy the ready mixed and it's more. I didn't though. Just saying if you can save the coolant you can save a bit of expense.

Anyway, I'm starting to see a pattern on your posts in my how tos.

Quote:
Originally Posted by Copperknob View Post
Top job Clive

just one thing,

And hammer over the edges of the lock tab, one edge up and one edge down so that the joint cannot come free.

Your pic shows both up??



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post #7 of 26 (permalink) Old 06-09-2011, 08:32
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Brilliant as always.

Surprised you stayed with the heavier spring cream though and not the lighter spring grey.
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post #8 of 26 (permalink) Old 06-09-2011, 15:18 Thread Starter
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Brilliant as always.

Surprised you stayed with the heavier spring cream though and not the lighter spring grey.
I've had no problems with the current set up so didn't see the need to change.
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post #9 of 26 (permalink) Old 06-09-2011, 22:06
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? few things

Clive couple of things, although someone beat me to one of them, as i was going to ask when you had started off roading in a tf.

Main things i was curious about was, in your demo after draining of your coolant , it looked like you only had a bit over 5litres, maybe 6.
I think in your previous post re refilling and bleeding coolant you said the amount for system is 10ltr?

Other thing is prt a replacement for a thermostat or as well as? and what is a prt?

I previously posted a question regarding the redesign/modification of the cooling system, by a owner(not mg) which basically altered amonst other things the relocation of the thermostat, this was done by some people using to thermostat housings, facing each other in line on one of the cars pipes.
Opposed to say a lot of cars where the thermostat would be in/near the block/head.
When i asked about this the general reply was oh yeah thats the prt.
I dont think that is what i am talking about(prt) but a different configuration of the cooling layout.

Could you or someone please explain further?

for example was there a mod done buy owners at some point, then mg/rover pick up on this, and from a given date all new cars produced had this modified cooling system.

It worries me slightly, when the car MGF+TF have such a poor reliability record, particularly re HGF.

As some one said today, the lotus elise is also mid engine and K series but doesnt seem problematic.
Did lotus get something right, re the cooling that rover didnt?
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post #10 of 26 (permalink) Old 06-09-2011, 23:55
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A lot of coolant (and I mean a LOT) remains inside the engine and the galleries when you drain it. Only a flush gets this out. But it's considered the minority when you change coolant and won't effect performance, you end up adding much more fresh coolant than what's left inside the block or radiator.

I found out just how much coolant is left inside when I dropped my subframe and tilted the engine. Several litres at the least.

HELLO PINK FLOOD ON THE GARAGE FLOOR.
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post #11 of 26 (permalink) Old 07-09-2011, 06:03
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The PRT was introduced by MGR around MY03 to reduced thermal shock to the engine, thereby reducing the possibility of HGF.
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post #12 of 26 (permalink) Old 07-09-2011, 15:59
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prt

But is the prt a different manufacturer, modification to the original configuration and nothing to do with the reconfiguration/mod that a member came up with,that featured a relocated thermostat?
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post #13 of 26 (permalink) Old 07-09-2011, 16:11
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Originally Posted by Masterbateson View Post
But is the prt a different manufacturer, modification to the original configuration and nothing to do with the reconfiguration/mod that a member came up with,that featured a relocated thermostat?
eh ?? it was introduced by MGR in 03, it has an MGR part number, they were the manufacturer, it is a repositioned thermostat.
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post #14 of 26 (permalink) Old 07-09-2011, 16:56 Thread Starter
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Originally Posted by Masterbateson View Post
But is the prt a different manufacturer, modification to the original configuration and nothing to do with the reconfiguration/mod that a member came up with,that featured a relocated thermostat?
I think somebody fitted a PRT nearer the radiator.

As Pete says, it was a genuine modification made to TFs from 03 onwards and replaces the stat in the engine under the inlet manifold.

You can buy the parts to modify an older car.

Strangely, my k-series Freelander, which is a 2000 model, has a PRT.
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post #15 of 26 (permalink) Old 07-09-2011, 18:07
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There was an mgf owner called David Monks who datalogged the temps in the head on his pre prt f. He found the thermal shock could be alleviated by adding a second thermostat to introduce warmer coolant rather than just using the local thermostat on the coolant inlet on the head. His solution was cheap but didn't use the pressure derived bleed that CJJ has explained. The sad part is that David's F was written off after he ran into a car abandoned in the middle of a dual carriage way at night.
The first remote thermostat (again no pressure bleed in) was used by a Lotus Elise owner who kept blowing gaskets, track racing, this was the QED thermostat.
The original white PRT was wasn't designed for the F but was used as a stop gap, the grey PRT brought in later has a weaker spring so opening at a 82 rather 87 degC.
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post #16 of 26 (permalink) Old 07-09-2011, 18:48
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right

Right now were getting to the bottom of it, as in what i wanted to know.
Before i got my car i had been browsing the web about info about possible causes of HGF.
I had decided that as soon as i got a TF, the first job i would do would be to do this thermostat mod.
Then i heard about this prt, but thought it was something different.
So to summarise, with my car being an 03 plate, i do not need to do this re'routing of thermostats/pipes (as done by this member fella) as a precaution.
Because my car should have this PRT? in situ already(i'll be checking if it ever dries up)
And a prt is a thermostat?

If all this has been done as of 2003, are we saying that any cars after 03 with this prt do not suffer from HGF? or are less susceptible to HGF?

If not and it doesnt work/fix the situation completely, what other measures have been tried?
I mean other than coolant sensor,metal locating pins rather than plastic for the head and improved multi layer(metal?)gaskets.

Is the K series just a Cr&p engine at the end of the day?
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post #17 of 26 (permalink) Old 07-09-2011, 19:02 Thread Starter
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Although the PRT is a more efficient system (and a damn site easier to get to) there is no proof that it lessened HGF and post 03MY cars still suffer the dreaded HGF. It is a part of the improvements rolled out over the years, including better head dowels, upgraded head gasket and uprated oil rail in the sump.
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post #18 of 26 (permalink) Old 07-09-2011, 19:12
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Doh!!!!

Oh how i wish i had seen/noticed this
Quote:
Some useful information on PRTs can be found here http://www.mgf.ultimatemg.com/group2...ifications.htm
at the Beginning of this post!!!doh!
Now things are a bit clearer.
So should we all be fitting additional recirculation pumps and twin fans i wonder.
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post #19 of 26 (permalink) Old 07-09-2011, 19:17 Thread Starter
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Originally Posted by Masterbateson View Post
Oh how i wish i had seen/noticed this

at the Beginning of this post!!!doh!
Now things are a bit clearer.
So should we all be fitting additional recirculation pumps and twin fans i wonder.
It all depends on your level of paranoia.
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post #20 of 26 (permalink) Old 23-10-2014, 10:34
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I have a R 25, 1994cc, diesel, year 2000 ... my thermostat is in oil cooler ... and it's tiny open and it's warm up verry slow...

How can i bypass that oil cooler? I understand that many R 25 don't have this oil cooler ....

Or, ... if i remove the thermo from that oil cooler and i pun an old model of thermo in the hose that go to oil cooler...could it do something wrong to my car?

p.s. I attach a link of an old thermo...to see what i am talking about....

http://www.piesedaciaonline.ro/termo...acia-1300.html
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