changing the thermostat - how to

the good news first - it is a DIY job and can be done through the engine inspection grill, no need to remove the inlet manifold.
The engine cover needs to be removed only to reach the bleeding point in the engine bay to bleed the cooling system afterwards.

This is the part we need to access - the thermostat housing:



To get access I removed two elements, the coolant expansion tank and the oil neck.
The oil neck is fixed with one 10mm bolt only to the inlet manifold.
The expansion tank is bolted on with two 8mm bolts, two rubber hoses are fixed with clamps. Of course you will lose some coolant when removing the lower hose but it can be caught easily with a little bowl and reused later:



And this is the area we need to access:



The thermostat housing is bolted to the engine with a single 10mm bolt, quite easy to reach (but hard to photograph).
One rubber hose is clamped to it, also easy to reach and remove. Here you will lose about 3ltr coolant, catch it with a bigger bowl under the car.



Now the funny part starts - to remove the thermostat housing a coolant hose needs to be moved that is bolted to the engine.
It's not rubber but steel and the bolts cannot be seen from above. The area is really narrow with several hoses and cables, small hands and several extensions for a ratchet are an advantage...
That's the part that needs to be moved:



It's bolted to the engine block with two 10mm bolts you need to find with your fingertips...



That's the hardest job!
When the bolts are lose the hose can be moved to the left and the thermostat housing removed.
To open the housing simply open three 8mm bolts and remove the thermostat:



The thermostat did not look too bad but when tested in boiling and cold water it did not open/close.



Rebuild in reverse order, refill the coolant system and bleed afterwards.

Great job Bertl. :broon:

The more guides the merrier. :yesnod:

Thermostat (PRT) Pressure Relief - Replacement guide.
Thermostat replacement guide - Replacement guide.
Thermostat replacement pre 2002. - Thermostat replacement, older type, pre 2002.

Excellent work! :broon:

Well done notes.
The only additions I have to help, is if you put a small mirror placed on the cross member you can see the bolts to undo on the pipes.
Also when re-installing the thermostat housing put a cable tie just behind the "O" ring that goes into the pipe, so that it does not get displaced out of its groove.

Excellent how to topic, clear instructions, clear pictures and diagrams. Thank you for sharing.

Thank you for this Rob, I've spent two afternoons trying to remove the steel coolant pipe and thermostat housing so that I can check and replace/reseat the seals as I have discovered a leak here at one side of the thermostat or the other.

Your guide has re-assured me that I'm following the correct procedure, as I've failed to remove the steel coolant pipes and thermostat so far. I guess I need more gorilla wrestling practice.

The time that you've put into the community over the years is always really appreciated.

Thanks ...my MGTF overheated last week after being sat for a few months I have replaced the under floor coolant pipes as it had a rusted and was leaking badly But still overheating.. no heat from heaters so I am suspecting it’s this job .. and not the water pump 🤞

No heat from the heater will be air in the heater loop. Bleed the heater matrix.

Thanks David will take a look 👍

Definitely helped thank you. Now just need a hose they stopped making for the mgtf auto .

You could probably make one up using tee pieces and some bits of hose, if you take the offending hose into your friendly local ports shop they may be able to match up the bends in the hose you need with hoses from other cars, then it just a matter of cutting out the pieces you need and joining them together with the tee pieces to make up your new hose.

That hose was replaced on the later MGTFs with several component hoses. No reason why you shouldn't update yours.