THERMOSTAT ?????

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WELSHVIKING
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THERMOSTAT ?????

Post by WELSHVIKING »

Hi The temp gauge on my Xantia estate 1.9td 1996 stays around 70 degrees and the heater is only warm at its best, will it be the thermostat that will need replacing, and if so how easy / hard is it to replace the thermostat. i have also checked for air locks in the cooling system but none found ...any advice will be appreciated...thanks Colin

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AndersDK
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Post by AndersDK »

How did you check for airlocks ?

I mean : you cant see or otherwise diagnose airlocks. The only way is to vent the cooling system. This is done by the homemade expansion tank trick ensuring you have a topped up expansion tank located higher than the cooling system.

The thermostat itself is rather easy to check - not dismantling anyting or using any tools :
From cold run the engine up to working temperature. Use your hand as temp sensor on the large top hose running to the radiator. The hose should stay cold until the thermostat opens. Then the hose should rather abruptly raise in temp to the scalding point - when engine reaches working temp. Its very clear to feel with your hand on the top hose.
Remember to close off the heater while testing.

If the top hose temp constantly raises slooowly over the engine warm up time - then the thermostat is defective.
I've just replaced the thermostat on my BX TD using precisely this method to diagnose a defective thermostat. And now the engine is much faster to reach a useful temp for the windscreen demister.

Peter.N.
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Post by Peter.N. »

If your gauge is accurate, even 70C should give you a good heat output. Have you tried bleeding the heater by disconnecting the heater inlet hose, the top one, then filling the header tank until water flows from both ends. If you have had both hoses off, have you put them back the right way round?

8304
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Post by 8304 »

if theres any doubt i would just change it, they only cost about a tenner.....

then you wil know its fine for the summer (when it finaly arrives :roll: )

cheers

alastair

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WELSHVIKING
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Post by WELSHVIKING »

as i have misplaced my haynes book of lies, can anyone give me the procedure for replacing the thermostat....XANTIA 1.9TD 1996

8304
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Post by 8304 »

my car is a zx td so i surpose its the same.....:


the thermostat is situated below the fuel filter behind a triangular plastic plate held onto the cylinder head casting with 3 bolts - i think they are about 11mm or so....

undo the top rad hose which goes into the plastic casing, some coolant will be spilt.

Remove the bolts from the triagular plastic thermostat cover and gently pull it away from the head., the thermostat should now be visible, along with the rubber seal around its outside which will also need replacing. The thermostat just pulls out of the housing, it might be a bit firm in there but just grip the top with some pliers and tug gently and it will come out. - some more coolant will be lost.

as the haynes states - refit is oposite process....

just remember to refill and bleed the coolant system and put antifreeze in etc. also make sure the new seal which will be supplied with the ne stat is located properly to prevent leaks, and do the work when the engine is dead cold!!!!!....

have fun!!

alastair

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WELSHVIKING
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Post by WELSHVIKING »

Thanks alastair will have a go at it next week as i am in work for the next 4 days...cheers Colin