Jump to content

Disco 2 V8: Cooler thermostat?


jagwit
 Share

Recommended Posts

Does anyone know if those external in-line thermostats used on discovery and Range rover are available with lower thermostat opening temp ?

I have installed a VDO temp gauge into my car and find that it runs at around 100degC which is needlessly hot IMHO.

Link to comment
Share on other sites

Standard one is what 88 degrees? Ealry carb-engined RRC were lower, perhaps 82 degrees.

The Lucas EFi is still fuel enriching at about 78 degrees, I can't rememeber exaclty but the engine has to run hot to avoid over-fuelling once hot,

I don't like to ask but are you sure the VDO guage is accurate? does it have a voltage regulator?

Rovacom or testbook can tell you what tempt the engine ECU thinks the engine is running at.

Link to comment
Share on other sites

That will have the p38 4.0 won't it ? IF so, they're made to run hot to get around the emissions etc :( 96 deg iirc, but don't quote me on that.

The thermostat is in a little bowl on the bottom hose of the rad. I've heard of people opening that up and replacing for a lower temperature version - how successful, and to what effect i don't know.

G

Link to comment
Share on other sites

Depends where your gauge sensor is measuring vs where the stat is.

Yes, I recon that is most relevant. I've got my VDO sensor in-line with the pipe running from the inlet manifold next to the ecu clt sensor to the expansion tank . Normally coolant will run from this outlet next to the ecu clt sensor to the throttle body and then to the expansion tank but I have deleted the part where it runs to the throttle body so it now runs directly to the expansion tank. My engine needs cooler air - not hotter air.

Link to comment
Share on other sites

  • 7 months later...

Hi Philip,

Greetings from Down Under. I too would like to fit a cooler thermostat for my DII V8. I fitted a Scangauge II OBDII to check the coolant temperatures and in normal driving, the coolant temperatures fluctuate between 92 to 98 degrees Centigrade with the standard thermostat. Sometimes, with the a/c on and idling for ages in summer, the coolant temperature creeps up to around 100 deg C, and if the ambient temperatures are very high (say 38 deg C), idling in traffic can see the coolant temperature go as high as 105 deg C.

The Land Rover part number for the standard thermostat is PEM100990 and there does not seem to be an alternative.

However, since Land Rover share many components with MG, there is a cooler thermostat which is about 8 deg cooler. I think they introduced that thermostat due to the overheating and head gasket failures that plagued the 4 cylinder K series engines used in the MG convertibles.

The part number of that thermostat is PEM101020.

I am tempted to try this cooler thermostat but I am guessing that it could actually cause problems - the engine's ECU may think that something is wrong due to the cooler running engine.

If you are willing to give it a try and report back, I'd be most interested! :)

EDIT: I did some more digging around, and there is a Land Rover equivalent of that same thermostat and the Land Rover part number is PEL500110. I'm now trying to find out what the difference is between PEL500110 and PEM101020.

Link to comment
Share on other sites

OK, I think I've worked it out - you want the PEL500110 if you need your HVAC heater to work in a cold climate and PEM101020 if you live in the tropics and the HVAC's heater is rarely used.

Both the PEL500110 and the PEM101020 have a main valve that opens earlier than the standard PEM100990, but the difference is that the PEL500110 has a softer spring for the by-pass flow valve than PEM101020.

The spring holds the by-pass flow valve closed. The by-pass flow valve's function is to aid the engine's warm up. When the engine is cold, the main thermostat valve is closed to cut off circulation to the radiator. When the thermostat is closed, and the engine is idling, the coolant pump does not produce sufficient flow and pressure to open the by pass valve. In this condition the valve prevents coolant circulating through the by-pass circuit back into the engine. What results is maximum flow of coolant through the heater matrix only. The purpose of creating this higher flow of coolant through the heater matrix is to improve passenger comfort in cold conditions, i.e. more of the available engine heat goes through the heater.

When the engine speed increases above idle, the coolant pump produces a greater flow and pressure than the HVAC system's heater can take. The increased pressure acts on the by-pass flow valve and overcomes the spring's pressure, thus opening the by-pass valve and thereby reducing the pressure to the HVAC heater circuit.

The by-pass flow valve modulates to provide maximum coolant flow through the HVAC heater circuit, and yet allowing excess coolant to flow into the by-pass curcuit to provide the engine's cooling needs at higher engine revs/min.

PEL500110 has a stronger by-pass valve spring than PEM101020.

Both these two thermostats will run cooler than the standard PEM100990 thermostat, by around 6 degrees, from what I can find.

Hope this helps! :)

Link to comment
Share on other sites

I'm perplexed at the idea of "needlessly hot" - I always seek to get my engines running as-hot-as-possible because that's the most-efficient.

Something like 99 degrees coolant temp (assuming you have 50% glycol as the coolant) and 110-130 degrees bulk-oil temperature seems good. That's what we aim for on the big Caterpillar turbodiesel generators I play with for my day-job. Cool-running loses you both engine-life and fuel-consumption.

--Tanuki

"Consider a perfectly-spherical cow, of point-mass"

Link to comment
Share on other sites

Honestly, I think it comes from the slipped liners/cracked blocks that everyone seems so fearful of in a Rover V8... it could well be a contributing factor as they were never originally designed for that kind of operating temperature -IIRC it was a 74C stat in the Rover P5B when introduced, either that or it was in the very early Rangie -whichever, I ran one for a while -too cool IMHO, and went to an 82C instead -perfect compromise, where mine was originally at 88C

:) :)

Link to comment
Share on other sites

The main reasons I want to run mine at 83degC is:

1) I recon its hot enough - the difference in emissions etc to 88degC being academic most likely

2) have lots of reserve capacity in hot weather;

3) prevent wires and pipes from becoming brittle in that hot engine bay.

Having said that...

I have 83degC stats in my D1 4.6 under Megasquirt engine management. In really cool weather temps will hover around 83degC. Slightly warmer and we go to 85 - 88deg C. In really hot weather going up long hills with foot flat, I will see 100degC anyway BUT.... then the viscous fan will clutch in an bring temps down to 88degC at which point the fan clutches out again.

So...

It would seem that now I need a "cooler" viscous clutch... :blink:

Link to comment
Share on other sites

It would seem that now I need a "cooler" viscous clutch... :blink:

Yes, you have nailed the understanding of engine cooling now :)

I run twin electric and switch with Megasquirt, so not a worry for me (TBH I doubt I could fit a viscous to my P38 unit anyways :))

Link to comment
Share on other sites

The main reasons I want to run mine at 83degC is:

1) I recon its hot enough - the difference in emissions etc to 88degC being academic most likely

2) have lots of reserve capacity in hot weather;

3) prevent wires and pipes from becoming brittle in that hot engine bay.

Having said that...

I have 83degC stats in my D1 4.6 under Megasquirt engine management. In really cool weather temps will hover around 83degC. Slightly warmer and we go to 85 - 88deg C. In really hot weather going up long hills with foot flat, I will see 100degC anyway BUT.... then the viscous fan will clutch in an bring temps down to 88degC at which point the fan clutches out again.

So...

It would seem that now I need a "cooler" viscous clutch... :blink:

I wonder why I can't edit my profile to put down my name and vehicle details, etc. :-( I've tried a few times and it doesn't seem to add my signature line. Anyways, back to the topic.

I did think more about why I'd like to run the engine cooler, but I suspect that all this will do will increase the temperature range in which the engine will be subjected to. So let's just say I'm driving along with a cooler thermostat. The engine will be running cooler at say 84-85 deg C, but when I find a steep hill and there's a lot of extra work required of the engine, the temperatures will start rising due to the cooling system maxing out at some point. So even with the cooler thermostat fitted, the engine temperature will climb because the cooling system can't provide any further cooling. And I may end up at around 105 deg C anyway. So now the differential is increased - going from 85 to 105 is 20 degs. Then when I am over the top of the mountain and coming down on the descent, the engine is not working hard anymore and the thermostat is still wide open. So the cooling system will drag the temperatures back down to 84-85 deg C again.

What I'm thinking is that this bigger temperature drop of 20 deg by using a "cooler" thermostat may in fact be bad for the engine because the heads and blocks are now subjected to a much bigger temperature variance. If I stuck to the standard thermostat, yes the engine will be running hotter, but the temperature swings will be over a smaller temperature band. Smaller temperature swings = less stress to the head gaskets.

Does that sound right? :huh: I've spent so much time thinking about this last night, about such a scenario, and this morning, your post above suggests that this is exactly what happens, i.e. the temperature surfing now is across a much wider temperature range.

Based on what your observations, I've nearly come to the conclusion that it's probably best not to mess around with what Land Rover have designed.... :unsure: I am interested to know what your thoughts are regarding widening the temperature delta between light load and heavy load, and its impact on the longevity of the engine, head gaskets, etc.

Link to comment
Share on other sites

The Rover V8 has not really changed since its inception. If anything it has become less heat tolerant with the thinner walls introduced with the 3.9 onwards. The older motors use to run a 78 to 83C thermostat. This was considered ideal. The higher temperature thermostats introduced on later models were only a result of EPA laws. They have nothing to do with the better running of the motor only vapourising the fuel more so that less unburnt fuel goes out the exhaust. I don't think anyone will try to argue that the later cams, etc, introduced for EPA and fuel economy reasons actually improved the performance or longevity of the motor. The problem with running a cooler thermostat on EFI motors is that the ECU expects a hotter engine and can pump more fuel in if it thinks the motor is still warming up. So you should not go below a low 8o'sC thermostat in EFI motors.

Link to comment
Share on other sites

TempestV8, your theory is sound if you run a standard cooling system (viscous fan and normal radiator). I

f you run temperature controlled electric, or a 'cooler' vicous fan (if indeed one exists) then you will run at the temperatures that the fan switches on and off, or locks up and unlocks in the case of the viscous unit.

Link to comment
Share on other sites

TempestV8, your theory is sound if you run a standard cooling system (viscous fan and normal radiator). I

f you run temperature controlled electric, or a 'cooler' vicous fan (if indeed one exists) then you will run at the temperatures that the fan switches on and off, or locks up and unlocks in the case of the viscous unit.

If you are out on the open road the temp that a fan cuts in will have little affect. That is, a fan should not come on at over 50mph as it will have little or no impact on cooling. I have found that with a 80C thermostat on a hot day my Rangie sits on around 90C and on cool days it sits right on 80C. 80C is only where the thermostat starts to open, not where it is fully opened. So I have set my thermo fans to come in around 93 or 94C. This is around the same temp that the Viscous fan would cut in anyhow. The final stage of cooling are the standard factory electric fans behind the grill. Factory setting is for these to cut in a bit below 100C.

In regard to oil temp, the oil cooler does not have a thermostat on it so it is putting the oil through cold water in the radiator all the time. During colder months my oil temp won't get above 50C. In the warmer months it will sit around 70C but can go above 90C when working the motor.

It should also be noted that based on the location of temp senders, the water temp is taken at its hottest just before it goes to the radiator and the oil temp is taken after its left the sump but before it goes through the cooler and then the motor. So the water temp in the majority of the motor is likely to be less that the temp stated and the oil temp could be hotter or colder in the actual motor.

Link to comment
Share on other sites

If you are out on the open road the temp that a fan cuts in will have little effect.

Of course not, but then the engine should never get up to 105C unless it is working EXTREMELY hard on the road, these temps are far more likely manouvering trailers or sustained off road, where the fans will come into their own.

With adequate airflow (i.e. 40mph+) if you are getting to 105C (and running an 83/88C stat) there is something wrong with your radiator/cooling system!

Link to comment
Share on other sites

I realise this is a tad pedantic but...

p76's comment that you shouldn't run cooler on EFI to avoid overfuelling is not applicable to MSEFI as you have control of the ECU's warmup map.

Also I'd worry about running cold oil, I'm sure there's a happy temperature range for engine oil (hence the purpose of oilstats for remote coolers) and 50c sounds very cool to me.

As for the OP's issue of fitting a cooler stat: If you're saying it runs too hot and hence overheats quickly in summer, then by fitting a cooler stat all you're doing is buying a little bit of extra time in an inadequate cooling system. You need overhead in your system's cooling capacity, not in thermostat temperature.

Link to comment
Share on other sites

Other thing I meant to say was... with some re-plumbing of hoses you can do away with the silly spherical stat (replace with a T-piece with two large and one small outlet) and fit a 'normal' stat in the inlet manifold of even the very late Serp V8s, then you have a greater choice of temperatures.

Link to comment
Share on other sites

  • 1 month later...

OK, I think I've worked it out - you want the PEL500110 if you need your HVAC heater to work in a cold climate and PEM101020 if you live in the tropics and the HVAC's heater is rarely used.

Both the PEL500110 and the PEM101020 have a main valve that opens earlier than the standard PEM100990, but the difference is that the PEL500110 has a softer spring for the by-pass flow valve than PEM101020.

Thought I should report back that I fitted the PEL500110 and it works a treat. Engine temp now sits at just under 90degC on my VDO gauge whereas before it was sitting just above 100degC.

Thanks for that info tempestV8!

Link to comment
Share on other sites

My LSE has an interesting tweak by the tuning company that fitted the engine. The coolant temp sensor had another resistor fitted in parallel with it. By adding a second resister you can fool the ECU into thinking the engine is hotter than it really is (or cooler, not entirely sure) and access the leaner fel map earlier.

IIRC the Lucas 14CUx system has either 6 or 8 fuelling points as the engine warms up, the highest is around 80 degress (82 springs to mind) below which it is still "choking" or over-fuelling.

The V8 is most efficient at around 75 degrees IIRC, the higher temp of late engines is indeed an economy/emissions issue

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy