The thermostat on my '04 1.9JTD seems to be jammed open.
The output hose is warm minutes after starting and it's very rare the car will get above 2 bars.
I've done a couple of OBD logging runs graphing engine temperature to road speed, and the temp never gets above 79c and will drop off with increased road speed. Hence the radiator appears to be in play.


So after getting a thermostat on offer for a very reasonable price I read all the relevant forum posts.
Ignoring the advice not to bother (I want to bother) I see many people complaining this is a pain of a job.



So the question is, what am I missing here? It looks like a very accessible bolt, a similarly accessible nut and a bunch of hose clips.

IIRC there is a bolt into the side of the block that is shared between stat and egr cooler. You need to unbolt cooler to get at bolt... it has rigid pipework with flimsy gaskets that are totally inaccessibile. Search for my thread on this I'm pretty sure I left some hindsight on it that might improve your experience!!marty.

REplacing 1.9JTD stat
https://www.fiatforum.com/multipla/446743-thermostat-replacement.html?p=4235131

Sorry Marty but oddly I can't access that post for some reason.

I've just had a look at the lower stud and it is indeed shared, but only with a thin bracket. I can even get a socket on it with out removing anything.

Is this normal?

Ok just search forum for Replacing 1.9jtd stat. Should pull it up.
My recollection is that the stud is shared by egr cooler and stat. To get to the stat you have to remove the cooler... to remove the cooler you need to remove the egr....

Try find that thread above... it's all in it!!

Ok I see what the problem may be, the EGR cooler bracket blocks socket access to the inner nut. I've got a plan.

Socket to remove the outer nut then slip a ratchet ring spanner over the stud behind the bracket to get the thermostat nut off. Looks like easyish (around 15 degree swing) spanner access from the front.


I'll take some photos.

Funnily enough I have a very similar issue with mine. I've owned it for almost a year now, and in that time I have only seen the temp go to 3 bars on a handful of times, all in very hot weather and with the car under load.

It's only since the weather has turned much colder that I've noticed that the interior fan doesn't blow as hot as I believe it should do, so would that be indicative of a stuck thermostat also ?

Anyone know how many hours labour a thermostat replacement books in at a garage, as I doubt I'll get a chance this side of Easter to do the job myself ?

3 bars used to be the norm for me, but since the weather got colder I've got this problem.
However... The thermostat output hose gets hot, but the return hose on the offside is remaining coolish. So either the radiator is very efficient or maybe my water pump isn't working!
Still, I'm off away for the end of the week and it's going in to have the water pump and cambelt done. I'll keep you all posted.

Tubthumper73 said:

Funnily enough I have a very similar issue with mine. I've owned it for almost a year now, and in that time I have only seen the temp go to 3 bars on a handful of times, all in very hot weather and with the car under load.

It's only since the weather has turned much colder that I've noticed that the interior fan doesn't blow as hot as I believe it should do, so would that be indicative of a stuck thermostat also ?

Anyone know how many hours labour a thermostat replacement books in at a garage, as I doubt I'll get a chance this side of Easter to do the job myself ?

Click to expand...

Am cold in my car never warms up . Am allways wearing to coats . Nice to hear that it not just me[emoji63]

REplacing 1.9JTD stat
https://www.fiatforum.com/showthread.php?t=429714

So I guess we're not going to find out if I've sussed how to easily do the thermostat.
Just got the car back from it's cam belt/water pump change and the cooling problems have fixed themselves.
Nothing obviously wrong with the water pump, but now my thermostat output hose runs initially cool and the radiator output hose runs warm.
Car runs at 3 bars and the thermostat cycles properly.


I'm guessing I had air in the cooling loop.

Hi guys, I need help

After replace of old thermostat with new one, problem is still here.

Only in driving over 110 kmh, I can reach the working temperature (90 degrees). With any reduction in speed(or RPM), the temperature goes down.

This is checked with delphi diagnostic, so i am sure that display in cabin is showing real values.

I'm guessing you've already checked the hoses?
Start the car from cold and leave it running for 10 minutes.
The output hose from the thermostat to the radiator should be cold and the input hose from the radiator to the water pump should be warming up.