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hi

1.9d n reg non turbo.

my old thermostat i am convinced is stuck open, got a new one 87 deg. fit that and the van runs up to 3/4 temp (not happy).

with the old one in, it runs 1/4, also when sat on the drive the fans kick in at half (when it eventually gets there), also the fins on the back of the rad open and close. it will go upto half but hardly ever and only when really giving the engine some beans!

with the new thermostat the fans don't kick on untill almost 3/4 temp. :(

not sure how the thermostat can effect when the cooling fans kick on, unless it has something to do with how much flow is going past the fan senser.

the aux water pump works (when power applied) but cant really test if it is coming on when the engine is running. can this have such an effect on running temp?

so is the temp senser for the aux pump knackered? is the fan sensor knackered? they are one and the same sensor??

so i am going to try replacing the sensors and putting back in a 87 deg thermostat, which opens at that measured with a thermometer in a pan of water. (the old one looks open all the time). to see if the aux pump comes on and if this has an effect.

at least i am glad only done a couple of miles at 3/4 temp, the compression and coolant seem ok, so hopefully not cooked the head :)

i have read others have had this same problem did changing the sensors fix it?
 

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I fitted a new thermostat to mine and the temp. gauge went off the scale. The new thermostat was stuck shut so i've removed it completely for now.
 

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Hi,

Have you checked the radiator thermo switch, located left/middle (when looking into bay)?

This could be the fault, i.e when water is passed through this switch, providing its the right temp - the fans should come on, also providing fans and fuses are not at fault.

I changed my Temp Sender switch, which is located on the Water Flange, but GSF gave me a newer or wrong type i.e the new one has a nipple on it, where as my old one (which works fine) didn't and the reason why I changed - the temp gauge wasn't working :( which is now sorted A: .

New Temp Sender - For a Petrol 2.5 AAF (apparently)


With the nipple on the new Temp Sender sent the gauge through the roof which meant the engine and water was not getting to the temp required to open the Thermostate or to turn the fans on.

So if any one needs a Temp Sender (green and 4 pins with a nipple) let me know.
 

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Sounds like your new stat is not right to me.

Maybe its not opening fully.

If the fans came on at half before then they should come on a half after. inless its restricting flow in the engine.

The stat is in the engine - and the cooling fan switch is in the rad. so the engine can be too hot and the rad not hot enough.

Am I making sense - New parts can still be faulty.
 

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Aux pump only opperates when the engine is hot and switched off,its opperated by the two pin switch in the water take of housing on the cylinder head next to the 4-pin sender for the gauge,and ecu if it is not 1.9.
Where did you buy the new stat from? If its not a genuine one then try a genuine one and see if its any different.
Gauge on the dash shouldnt move more than half way if all is ok,diesels are heat efficient and rarely reach more than 90degrees.T:
 

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Did you manage to resolve this problem in the end? I've got a similar problem. I posted above that the stat i got from ECP was dodgy and stuck shut so i removed it. I've only just got round to fitting a new one (genuine VW part) and all seemed well, running at exactly 90c around town. I took it for a run on the motorway yesterday and noticed it was running at slightly over 100c. I'm guessing this is too hot. Again, fans don't cut in because rad temp. isn't high enough but head temp. is too hot. Anybody got any ideas? I also fitted the 87-102 stat.
The one thing that may be my problem is that i fitted a Golf 1Y diesel into my T4. Practically the same but on the 1X the head has a small coolant outlet cast into the head that has a pipe running to the expansion tank. This isn't on the 1Y, the 1Y has the small outlet on one of the flanges that runs back to the expansion tank but i couldn't use this on my conversion. The small pipe into the tank is currentlyy blocked off. Does the engine need the small pipe from the head direct to the expansion tank (obviuosly does or it wouldn't have been designed like that) but do you think this could be a cause of my problem? Maybe restricting flows in the system? Thanks.
 

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My 1.9 d runs at a quarter in the summer and the fan comes in at just over a quarter,(what ever that temp is) .Now its colder and if i sit at 60 all day it sits inbetween 0 and a quarter but i can get it up to the quarter if i take it over 70 on a run. Last winter i fitted a new water pump and flushed the cooling system out and new coolant and the running temp is the same.The heaters work fine the cooling fans cut in and work fine,and it dont lose any water, so this being my first VW im just taking that this is the norm for a 1.9 non turbo and not bothering about it.
 
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