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How to change Thermostat..


In Third Gear
Hello all

Could anyone advise or point me in the direction of any threads/diagrams on changing thermostat on my 1995 300TDI auto.

Is it something that appears simple yet has pitfalls ??

Thanks in advance...

This should be pretty straight forward.

Remove coolant hoses, remove bolts, remove housing cover.

Then take out thermostat, replace with new one, making sure sealing ring gets replaced (might want to swap for new one).

Refit the housing, hoses.
Thanks very much for your help, if any one has got a diagram or step by step then I'd be grateful as I am the bloke who needs one believe me !!
Follow the big hose from the top (right as you look under the bonnet) of the radiator to the block. It goes in to a sort of triangular-looking bit. That's the thermostat housing. There should also be a smaller (and I mean tiddly by comparison) hose coming off this which goes straight back to the header tank (I seem to recall, not got the bonnet open at the moment!).
Undo the jubilee clips that hold each of the hoses to the themostat housing and gently pull the hoses off. Depending on how old/dirty you car is they make take quite a tug. You might get a little dribble of coolant come out but nothing serious.
Now undo the three bolts that hold the thermostat housing in the block, and gently pull the housing out, maybe using a little leverage with something like an instrument screwdriver.
Pop the old 'stat out, again with a little persuasion, insert new 'stat making sure the little vent hole is at the top or 12o'clock position in the housing.
Reassemble. (which according to Haynes is the reverse of removal!)
hi lee
as mentioned before straight forward change but try this site lr4x4.com under landrover technical archives
I do not agree on some of the steps Les pointed on lr4x4: "remove the top radiator hose"?!? - what for? / no need to disconnect the plugs / the thermostat needs to be seated in the thermostat housing, not the elbow.

So here it is another link (i did it the same way): in french or roughly translated into english
You can click on the pictures to see them in a better resolution.

Some personal advice:
- like previous said, do it on cold (like in the morning) - this way you increase the chances to unscrew the two 10mm bolts (spray some penetrating oil the night before - it doesn't hurt);
- use the best, newest and toughest 10mm socket/drive/ratchet you have; you may not have a second chance on the bottom bolt if you "screw" it;
- when removing the old thermostat check it to see if has all the bits and pieces (compare it to the new one); if something is missing, check if you can find it in the thermostat housing, you might be lucky as I was;
- don't forget to place the valve of the thermostat in the upper position when fitting it to the housing;
- use some grease on the bolts before putting them back (just a touch) to make your life easier next time;
- don't forget to bleed the system and top up the coolant level.

Nothing to worry on the whole job except unscrewing the bottom bolt.
I do not agree on some of the steps Les pointed on lr4x4: "remove the top radiator hose"?!? - what for?

I think it means disconnect it from the 'stat housing, not remove it all together. Depending on condition, some hoses may not have the flexibility to allow the housing off whilst still attached to the hose.
Yes, this is what he means, disconnect it from the elbow, but there's no need for that. If the hose isn't flexible enough to allow the couple of inches needed for the thermostat replacement, then it has to go the same place as the old thermostat (the trash can). Otherwise the next thing to go is the radiator.
I did the job on -5 deg C and the hose was quite flexible. I don't recall the elbow beeing in my way, not at all.
Well, both methods do work and will lead to the same achievement, so it's for lee1 to choose which one suits him best.
The threads I post are to supply the best information to anyone - regardless of their abilities. Leaving wiring connected or the radiator hose in place, risks damage to them. The electrical connections are fragile enough without twisting them to provide sufiicient room to replace the thermostat. How much easier is it to carefully disconnect a couple of wires and remove a hose?
Better than a risk of unexpected damage I would have thought. The thermostat valve has to go in the housing, rather than than the elbow becuase it has to sit correctly with the bleed valve at the top. Try to just put it in any old way and see the results.
A little bit of care because of a little more work than you feel is neccessary is no recommendation at all.

Why? Well, why do you think a hose is used on any motor vehicle to connect the engine to the radiator or the engine to any other thing/part that's not bolted to it? Why don't they use a simple steel/alloy/plastic pipe? If that hose loses its flexibility in such a degree that it can't be bent a couple of inches then it becomes nothing more than a simple rigid pipe. Or why does the engine have rubber/hydraulic mounts on the chassis?

How? It cracks. Especially where it is soldered. Most likely where the hose connects to the radiator (this can be repaired) or where the center rad tiny pipes are soldered to the caps (u can get unlucky here).
If that hose loses its flexibility in such a degree that it can't be bent a couple of inches then it becomes nothing more than a simple rigid pipe.

What?! Loosing enough flexibility to remove the 'stat housing with the hose still attached is one thing, a hose so solid and hard it's actually affecting the structural integrity of the radiator is way off the other end of the scale. Even an old hose still has some give in it, just not enough to genuinely flex to the extent decribed in the above job.
just not enough to genuinely flex to the extent decribed in the above job.
This means it needs to be replaced. That is what I was saying in the first place. Or do we have to wait until it gets rock solid?:p

Les, as for the "abilities", if someone has two left hands it will screw things up regardless of any method, tutorial, pictures etc. In this case, one can brake the wires when removing plugs, drop the elbow down and brake the "legs" of the sensors, overtight the hose to the elbow when refiting or forget it loose or God knows what else.
There's nothing wrong with the way you did/do it. I just did it and will do it a different way. It took me 5 mins to change the thermostat, no coolant mess on the engine or on the floor (a piece of cloth underneath the elbow was enough), no need to bleed the radiator, didn't even need to start the engine to bleed the housing 'cause I used another method (10 secs to do that - an extra cheat is that i replaced the plastic cap with a metal one) and didn't even need to top up the coolant on the spot as I lost only about 4-5 mm of coolant level (in the exp. tank) and I was about 2 mm over before anyway (and I was in a bit of a hurry). That's all. If someone wants or cares to do it this way its fine, if not, its fine too.
Indeed, you can do it your way, but you are taking the greater risk of further damage. Bending a rubber hose as much as would be necessary to replace the thermostat is risking damage to the carcass of the hose. If you have bought the thermostat and then as a result of bending the hose, you split it, don't you think it would be:
1) annoying and inconvenient to then have to go and buy a new hose
2) easier to have just undone the jubilee clip and disconnect or remove the pipe.
Just because a pipe is old or weak doesn't mean that it's failure is imminent - it may last a while yet. You putting unnecessary force on it will more likely cause it to fail.

Les, as for the "abilities", if someone has two left hands it will screw things up regardless of any method, tutorial, pictures etc.

What qualifies you to make such a rude statement about people that may not have the same mechanical abilities as yourself?

If that hose loses its flexibility in such a degree that it can't be bent a couple of inches then it becomes nothing more than a simple rigid pipe.

Are you expert in the flexible abilities of rubber hoses.

overtight the hose to the elbow when refiting or forget it loose or God knows what else

You are assuming somene will do the job wrong, why is that?

There's nothing wrong with the way you did/do it

So why are you flaming people in this thread, and why the aggressive nature of your posts?
This means it needs to be replaced. That is what I was saying in the first place. Or do we have to wait until it gets rock solid?:p

Last time I looked the hoses on my 300TDi were rubber and the radiator was something tougher, probably a metal of some kind, but hey, I'm fick and know nuffink.
My guess is the weaker part will give way first, so although the flex between rad and hose may be lost, I'm sticking to the idea that a brittle hose will give way before a robust radiator.
To say the hose will damage the radiator is a bit like saying a flat tyre will damage the rim it's on more than it damages itself.
I'm not saying a hardened hose can be ignored, but at the same time, just because it's not quite flexibile enough to allow removal of the thermostat housing is no need for panic just yet.
Maybe you've been buying cheap radiators? :(
Bob, i never had to replace no radiator on any of my vehicles 'cause none broked/leaked. But i recall replacing about 2 or 3 top hoses on different vehicles (not LR) when i thought they hardened to much for the job (specially when cold). It's not an expensive part compared to the radiator and it's not difficult to replace.
But i've seen a large amount of radiators leaking around the pipe the hose connects to right where it is soldered. Solderings are aging with time and get weak because of the thermal stress (repeated heting/cooling cycles), so the hose needs to be as flexible and elastic as it can be without deforming under pressure/temperature.
The radiator won't get damaged by the hose itself (like when fitting a hose to the radiator and place them on a shelf somewhere) but from forces/vibrations transmitted from the engine to the radiator by the means of the hose.
And yes, it's like driving with a flat tyre. It's not the tyre that damages the rim by itself but the gravel track or the pothole u drive through 'cause the tyre isn't able to dampen and spread the shocks if completely deflated. Otherwise we would be using just a thin layer of rubber on the rims as it would be almost for free compared to a set of tyres.
I say again: if the hose is in such a state that it cannot withstand such a small bend then it needs a replacement. If it won't stand such a bend without damaging, how it will withstand a significant number of engine stops for example (lets say the engine doesn't move/vibrate when running/starting), when everything's shaking like coming apart?

Les, I believe you never had the experience of a stuck hose on its metal connection when the rubber inside "glues" to the metal and gets torn (inside) when removing it despite the precautions you take. So there's a risk in this too.
And what about fitting it back? Which way to do it? Fit it dry, wet, greased, oiled? These are the 4 methods i've seen people doing it. Should it be placed on the very position it was before dismantling, slighly more in or out? The jubilee clip should be placed in the very position it was, rotated or on a different path? I think it would be nice for you to tell people the proper way to put the same hose back 'cause i've seen to many weird ways to do it (by "qualified" mechanics, not mentioning others).

1) better to have to go and buy a new hose than have it split after a while in the middle of nowhere; i think it's better to replace the parts before they brake or at first sign that they don't work as they should do, not to sqeeze every drop of their life or to wait for them to brake apart; this is the way i like to do it; in 23 years of motor vehicle ownership, 11 vehicles and more than 500k miles driven no car broke on me in middle of the road, not even close on braking; and i intent to keep that way; i got this Disco 3 mo ago (not for everyday use) and it will take me another 4-6 mo before i will consider it fully road worthy and dependable; despite the fact it has recently passed the MOT, it still has to pass my checkings;
2) that is for everyone to decide for himself; i did it some time ago the same way you do it (and like the manual says) and i noticed it can be done simpler; then i did it the way i described, it looks easier to me this way and i do not consider that it involves any dangerous unnecessary stress to anything; this is my opinion, good or wrong, and i stick to it.

How about a qualified mechanic from a dealer shop that "forgot" to switch the state (to service state) of an antitheft device that he had to remove in order to replace another part on a different vehicle that i have (job done under warranty) so he thrashed a 200 quid part (replaced "under warranty" too) although everything was stated in the workshop manual? Or what about another fully qualified mechanic that "forgot" how to screw a simple nut so that the steering developed a dangerous play after 2 miles driving (on the drop arm ball joint - on this disco i have - previous owner had the ball joint replaced)? Do these two examples qualify me to say that there are people in this world with two left hands or two right brain halfs? I think they do.
What i meant is that there's no way for nobody to do a full 100% fail safe tutorial or workshop manual. But what u could say was that disconnecting the hose is the method in the manual, so nobody could beat that :p
But it seems you missinterpreted my words like i was refering to the people that posted on this thread or the users of this or that forum. Please read again my post, there's nothing of this kind. I didn't even exclude myself from the "lefties" group :p

As for aggressiveness, i'm sorry, it was beyond my intention to be agresive to anyone. If my posts say otherwise i apologize.

Flaming? I believe you're kidding. I simply said i don't agree with something and there's no need to do other things. What flaming is that? All i did next is to answer questions.
On the other hand, the obvious sign of a flaming message on a forum/bulletin board is when people start to "disassemble" someone's post and ask/answer/missinterpret phrase by phrase. Guess who did that?

Les, please don't get me wrong. I'm 99.99% fond of doing things as the manuals say, using the proper tools and devices, screwing the bolts on the proper torque etc. I also do apreciate the time and effort you took to make many howto's as I did quite a few myself and I know what a pita this involves. By the way, i'm not the author of the howto i gave the link to. It just happend to step onto it while looking for something else regarding the injection pump after about 3 weeks from when i changed my thermostat.

As from my part, I think that i answered the topic initiator's question. But you or anybody else is welcome to criticize, thrash or say anything about the method i use or even delete my posts.
Again, i apologize if i offended anyone in anyway. I'm sorry but I won't spend any more time on this subject, sorry for the long post and i'll end all of this right about HERE.
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