Hi, I bought an after market thermostat from AB. It is identical to the ones sold by the LR dealer and failed the same when installed. They are made by the same vendor every marking and part number are the same. I have bypassed the thermostat temporarily waiting the parts needed to install the inline thermostat conversion Ijdiscovery has suggested in the next post. I'll let you know how it goes as soon as I have the results.

 

2001SE7, thanks for the updates. It is amazing that LR felt the need to design such a funky thermostat. The tried and true style has worked for decades without a hitch. Have you considered installing the retro style thermostat conversion that is outlined in a thread on the forum? It may be ther ulitmate way to go, especially with the defective thermostat issues. I just put a different fan clutch in to see if that made a difference, it didn't. thanks again. keep us posted. Phil

 

It is of my opinion that it is not a thermostat issue guys, it is a clogged/restricted heater core.
In your owners manual LR states why they have this funky cooling system set up, it is to reduce engine warm up times as well as increase passenger comfort in the winter.
At lower engine RPM the coolant it routed away from the radiator and to the heater, so its going to run hotter at idle because the heater cannot remove as much heat as the radiator can.
Is it stupid? Yes.
But the point is your truck will run "hotter" at idle, and as long as the temp gauge is in the normal range you are fine.

 

I didn't know about the thermostat conversion, I am going to start hunting for it. Do you know the title; just incase I can't find it? Thanks.

And 2nd; I believe Spike is on to something that the problem might not be the thermostat but I very much think there is nothing wrong with the heater core; I have flow checked mine and there is no restriction. Also there is so much heat generation at the core I cannot hold my hand to the vents for more than just a few seconds without actually burning; believe me the water is flowing just not enough through the radiator.

Mr. Spike; is it normal for the cooling system on these to build up so much pressure the hoses feel like they are going to explode? Mine does but the pressure does not release at the expansion tank cap. I bought a new cap; no change. I have ordered a new expansion tank just cause nothing else seems to have helped.

The system acts like the thermostat never opens; the lower hoses stays at ambient temperature. If it does open then for sure something is restricting the flow through the radiator and my radiator is brand new. When I updated my bypass gizmo by blocking the inlet from the manifold gooseneck it does force flow through the radiator but I do not believe the flow is enough too cool properly. A lot of people are experiencing these same symptoms; if someone fixes theirs with a new heater core; I'll try it but I am convinced at this point there is nothing wrong with mine as if it were clogged I would have little to no heat in the cabin.

I am not sure I agree the truck runs hotter at idle as DiscoMike warns when over heating to pull over and let the engine idle as it will remove heat quicker than just shutting it off. Also I do see my temperature gauge drop at idle; this may not be a valid argument as there is definitely something haywire with my Disco.

Please let me know if it is normal to have so much pressure build up and if you know why the cap doesn't release that pressure. As soon as I get the new expansion installed and tested I'll post the results. Thanks guys.

 

Hi all; I found the thread(s) on the conventional inline thermostat conversion mentioned several posts up.
It is my opinion that conversion is superior to anything I have read/seen so far.
It turns my bypass setup into an embarrassment exposing my neanderthal like mentality. My temporary bypass unit at best should only be used if you need to get your Disco back on the road while you are acquiring the parts needed for the inline thermostat conversion.
I highly recommend you don't mess with at all unless you absolutely need to drive your LR.
I will be going through my subscriptions and purge my bypass posts ASAP. So if you are wondering what the heck I am talking about chances are I have already edited them out.
I am sorry for all the headaches and confusion I may have caused.

 

If a engine is overheating while driving then yes, pulling over and letting it idle will cool it quicker than shutting it off. Once you shut it off the coolant stops flowing and just sits in one spot, letting the engine idle keep the coolant flowing through the radiator to cool the engine, but this only works if there is coolant in the system and you are overheating because you were overworking the engine.
Climbing a big hill in 100+* heat with the a/c on and pulling a trailer and you overheat, pull over, turn the a/c off, the heater on and let the engine idle.

No your hoses should not be that hard.
Rent a cooling system pressure tester and install it, then start the truck and let it idle and watch the gauge on the tester, it should not go over 16psi.

 

Geez, I am having over heating problems. I can find the thermostat. Pics anyone?

 

http://www.roverparts.com/Parts/PEM100990.cfm
That is what the thermostat on the D2 looks like.

 

I agree with most of this, however after studying the manuals and diagrams for a while... the system really was a little too ambitious for them IMHO.

For example at idle, my aux fan is ALWAYS running - even when it's freezing outside. The bypass spring shuts and re-routes coolant away from the radiator at a temp which causes my aux fan to run constantly. I've read the temps and they're not alarming or anything, but the second I rev the engine 200-300rpm above idle - the fan shuts off (once that bypass spring opens and allows coolant through the radiator again).

There's a certain percentage of coolant which is supposed to remain flowing through the thermostat loop when bypassed, so that it can "sense" when the heater can no longer dissipate enough heat - I think this is the problem personally, as MANY variables can prevent an adequate "hot" coolant % from getting to the tstat before mixing or losing flow rate.

Once you're at any RPM above idle, that bypass spring releases to relieve pressure (quickly giving the tstat accurate temps) and bam, problems are solved.

Is something wrong with my system? ..probably - but the fact that it goes away above idle means it's obviously related to the over-complicated cooling system. A tstat is the only variable I can think of which would cause -slightly- higher temps at idle only (I'm thinking bypass spring, or a slow-to-open tstat that needs more than a trickle to begin opening).

A while ago I did some research into the bypass with the inline tstat, and (don't quote me on this, it was a while ago) I believe my gripe with the solution was that in a closed tstat state, 100% of the coolant volume/pressure is redirected through the heater core loop which is a BAD thing. Yeah usually it'll be at least slightly open, but that's still not how the heater core or hoses were designed - and when your engine is cold and you've gotta go somewhere before letting it warm up to opening temp, you'll be at RPM above idle while still forcing all the coolant through that loop.

I'll let you know if the tstat solves my issue, but as I stated above.. the nature of the bypass system and it's reliance on a sketchy percentage/trickle of coolant to begin opening (when in a bypass state) is what I believe to be the problem.