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rover 75 diesel cooling system.

13K views 42 replies 11 participants last post by  The Wildman 
#1 ·
Hi Good morming. can anybody tell me how the cooling system works. ie water from the bottom hose goes to the pump, normally water from the thermostat goes to the top of the rad, but it doesnt seem to do this on the 75 cheers Ian
 
#2 ·
The cooling principle in the diesel is the same as any other engine. The physical layout may look different, but coolant flow is basically the same.

The flow from the head/thermostat goes to the radiator top through the large upper (tapered) hose. Several members have inserted an inline stat within this hose to improve (increase) the running temperature.

TC
 
#5 ·
Do you know where inline stat should be placed?
Looking at French Mike's image, it goes in the large central hose running from top of engine to top left corner of radiator (as viewed from front).The hose is cut to insert an aluminium housing. I believe an alternative is to use an in-hose type, which presses into the hose (no cutting).

why the rad and bottom hose stays cold?
Coolant exiting the bottom of the radiator has normally flowed down through it and is therefore colder than the upper input. With the diesel, the input is often quite cool anyway due to stat failure. Typically 60-70C, which in engine running terms is cool. After passing through the radiator this fluid will be distinctly cold.

TC
 
#7 ·
hI. AND THANKS FOR INPUT. on the diesel the thermostat is the other side of the engine, water flows across the head, and exits from the side on its way to top of rad.

does any one know where the coolant is fed to from the filling resevoir, i suspect the engine block?

trying to get as much info as possible on the cooling system. and experimenting with inline thermostats.

objective is to inprove engine and heater operating temp.

also ideal to be able to replace stat if necesary. maybe an in hose stat? as used on some cars.

when i get a workable system, will share for others the results.
cheers Ian
 
#8 ·
Does any one know where the coolant is fed to from the filling resevoir, I suspect the engine block?
It's all explained in French Mike's image. The header tank isn't part of the circulation loop. It simply ensures that the loops remain flooded by being positioned higher than the engine. Coolant added to the header passes into the system via a T-piece in the heater pipework. Once coolant gets into the coolant flow, it never gets back into the header, other than through temperature expansion or a severe overheat.

TC
 
#10 ·
Hi.

Just like to say i have just fitted an inline stat from: http://www.specialist-components.co.uk/

and it works a treat.

They have a few listed on ebay, they an't cheap at nearly &£70 (roughly) but it takes 15 mins to fit and top the coolant back up, as oppssed to the estimated 3-4 hours to replace teh original unit.

and it looks nice aswell, is a nice turned aluminium unit.
Not sure what stat it has inside but im sure its just a universal 88degree unit.
 
#11 ·
and it looks nice aswell, is a nice turned aluminium unit.
Not sure what stat it has inside but im sure its just a universal 88degree unit.
It's a 90c stat from a Chevrolet.

I had one, but never got chance to fit it. My engine died (not related to the stat or temp) and I had a replacement fitted, so I had them fit a brand new OEM stat while the engine was out. Sold my Specialist Components stat to another 75/ZT owner.
 
#24 ·
I think during winter months the risk of overheating is slight due to the thermal efficeincy of the engine and think you will find that during very cold temperatures you will never see your thermostat open but as the temperatures rise towards summer you might find unacceptable engine temperatures. I look forward with interest to your future posts regarding this, please keep us updated.
 
#28 ·
I'm 31 years old since yesterday, and before I bought this car 80k ago I decided this was the last car I'd ever own. I fully intend to stick to that. The engine running nice and warm will contibute to it's longevity. The fact that if you abuse it lots it can still last a long time doesn't mean that treating it nicely (and I reckon making sure running temp is high enough is part doing that) doesn't increase the chances of it lasting longer does it.

P.S. I use Miller's XFS 5w30, it's sublime, and instantly increases MPG, though I have yet to run a proper comparison with increased running temp.
 
#29 ·
Good luck to you with keeping it long term and agree the better you look after it the longer it will last. Mine's done 292K and there is still no appreciable wear in the engine - it doesn't even burn oil between services which is a good wear indicator for the piston rings and bores.

Regarding running these engines warm you will struggle when running at light loads as they are so thermally eficient that they do actually run cool in comparison with other engines. There will be a limit to what can be achieved by changing the thermostat as any thermostat can only work with the heat available to it.

Always interesting to try things out though so let us know how you get on.

Mike
 
#30 ·
Any engine, the diesel included, will reach whatever temperature you require if the coolant flow through the radiator AND the heater matrix is controlled. Of course most people want their heaters to warm their toes and just doing that may, in many cases, dissipate too much engine heat to maintain optimal running conditions. All internal combustion engines run most efficiently at 95-105C. The petrol engines in these cars more or less do that normally, but the diesel struggles in standard form. Even with a 90+C thermostat, it will take extra load to get the running temperature much above 90C. It will achieve that though if the heater loop is blanked off. Just turning the heater 'off' won't do it because coolant flows through the heater matrix all the time.

TC
 
#32 ·
Agreed TC, and in practical terms this is why the engine runs cool - the heater matrix is in effect a radiator and on a cold day when using cabin heating on light loads then you could block the thermostat completely and you will still not reach high operating temperatures.
Which of course is why the fuel burning heaters were fitted.

Mike
 
#33 ·
Instead of inserting an in-line thermostat in the main coolant hose, I'd contamplate inserting a ball valve. That way, I'd be able to contol radiator flow absolutely. If that wasn't enough, a similar device in the heater line could throttle total flow to a level where I got a high running temperature and thereby, hot toes as well

TC
 
#34 ·
rover 75 diesel

Hi ALL. does anyone have a diagram showing coolant from thermostat across the head to rad please.

normally after thermostat opens water goes to rad, but not on the rover 75 it comes out of the side of the head to rad, why is anyones guess, seems a strange set up.

My estate 53 plate is a Maroon colour, does anyone know the official colour name and code?

Thanks for any help Ian
 
#35 ·
Hi ALL. does anyone have a diagram showing coolant from thermostat across the head to rad please.

Normally after thermostat opens water goes to rad, but not on the rover 75 it comes out of the side of the head to rad, why is anyones guess, seems a strange set up.
I think may be comparing the flow of the diesel with the flow of a petrol engine fitted with a PRT. They are not directly comparable, even though the principles are similar. In petrols fitted with a standard thermostat located near the head and pump, the coolant flow is the same as the diesel.

THe diagram you refer to shows the coolant flow, though it doesn't detail the pump outlet flow across the head. All that is below the engine cover shown in the drawing. However the outlet from the head in both cases goes to the top of the radiator, which is shown in the drawing.

Can you elaborate on your concerns?

TC
 
#36 ·
rover 75 diesl cdti THERMOSTAT

Hi Guys, SEEMS WE ALL HAVE THE SAME PROBLEM, if only the design was better, to allow replacement.

however we now have to find a cure, ideally a housing can be adopted/adapted to allow future replacement thermostat.

from the head coolant goes to heater and top of rad. Rover K series engines have a remote thermostat housing that allows for replacement, and has the pipe fittings, thermostats come in a range of different openings ideally 88 degress.

problem to be overcome, blanking of original heater feed, cutting hoses to fit new housing, if this solves the heating problem then the work and expence can be justified.

also looking at in hose thermostats. As my Dad used to say O the joys of motoring.
 
#37 ·
rover 75 diesl cdti THERMOSTAT

Hi T Cut. thanks for your reply and imput.

Just trying to get as much info on the cooling system as possible, and trying to get my head around, why the coolant comes out of the side of the engine, before going to heater and red.

In an ideal world surely this would have been the ideal place to fit the originally thermostat housing,

WHY AFTER LEAVING THE THERMOSTAT, DOES COOLANT TRAVEL ACROSS THE HEAD TO GO TO THE RAD???? and not go across the head to a thermostat, then on to the rad??

cheers Ian
 
#38 ·
How to remove the bottom rad hose?

What I'd like to know is:
How the heck do you get the bottom rad hose off?
I cannot get my big hands in between the gap to get to the hose clip from the bottom and no chance from the top either as it is too far away.
The clip is a type that needs clamping the two tabs together to loosen as opposed to a jubilee clip.
I think I'll need to cut it off with a Dremel tool.
I'll fit a jubilee clip on after.

I can't get to the drain plug on the block. Can't even see it. (I can't jack the car up as I live on a slope).
 
#40 ·
What I'd like to know is:
How the heck do you get the bottom rad hose off?
I cannot get my big hands in between the gap to get to the hose clip from the bottom and no chance from the top either as it is too far away.
The clip is a type that needs clamping the two tabs together to loosen as opposed to a jubilee clip.
I think I'll need to cut it off with a Dremel tool.
I'll fit a jubilee clip on after.

I can't get to the drain plug on the block. Can't even see it. (I can't jack the car up as I live on a slope).
If you want to drain the rad its easy to undo the other end of the bottom hose - it connects to a steel pipe just in front of the engine. You'll have to jack it up and remove the undertray first though.

My drive is on a slope and jacking the car up on it is no problem. Just make sure that the handbrake is on, the rear wheels are chocked and the car is safely blocked before you go underneath.

Mike
 
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