Diesel Auto inline thermostat overheating

[Don.Hasi]

I have read many topics but couldn't find one which describes my problem. So here it is:

My Diesel was way too cool. In the winter the coolant gauge didn't climb over the first quarter. So I installed the inline thermostat from Dmgr. Voila, cabin was toasty, mpg improved, more power and we had a happy driver with the indicator just a width of itself under half of the gauge

Now, with temperatures rising (yes, they do ) and giving it more load on the autobahn and/or with just little climbing, the gauge rises to 3rd quarter and there is, where the drama begins... If it is just under the 3rd mark, the car rolls fine, if it passes the mark, the ignition retards andthe engine slows down to limp mode

The power will come back, when the temperatures goes back, it goes downhill or, when I push the throttle to kick down and force more psi through the turbo. It feels like, the coolant flow is some kind of blocked, then forced to get open and presto, the needle goes back to half and the power is there.

The car has got just a fresh service with oils, filters incl Pcv, vitons, samco intercooler tubes and a quick clean of the EGR (which should be deleted next time, because the was many gunk found). It has warm start issues which are a little bit improved with injector cleaners, but no good at all.

So, what do you think? Is the inline thermostat not capable continuously autobahn speeds? Another fault to be checked?

Thanks for your help in advance.

[another_clean_sheet]

It would be a good idea to switch on the OBD (On Board Diagnostics) and see what is actually happening to the water temperature. The gauge is notoriously inaccurate.
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[Don.Hasi]

will do it next time. But there is no doubt about the heat, because of the lack of power. I know the gauge is just a beautyful indicator, but in the extreme values is a constant reproducible behaviour.

[klarzy]

Perhaps when I am in Ittersbach in July I can take a look for you..

[Don.Hasi]

Oh, yes, what a fine idea. Please drop me a note, when you are around! I hope, I have this sorted until then...

[Don.Hasi]

Some more infos: I have also a FBH. Haven't seen the proper bleeding how to before. So I have checked now the bleeding screw... I have demounted it and found, that there is no water in the tube. Even when squeezing the tube, no water to be seen. The level in the buff is on top of the max... That doesn't sound right?

[75driver]

Undo the securing screw holding the coolant tank.
Undo the bleeding screw a bit.
Slowly raise the coolant tank until the water level in it is above the level of the bleed screw, whereby some coolant should come out of the bleed screw. Then tighten the bleed screw.
Not exactly as per proper bleeding procedure, but should shift an air bubble if there is one.


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[Hootbleet]

Don, I had the exact same issue you're describing just last week. The inline stat I had fitted had failed, I've now removed it and the car is running fine again all be it a little bit cooler due to not having the inline stat.

My advice to you, before doing anything else is to remove the inline stat, reconnect the hose and take the car back out on a run. It will not overheat this time.

Good luck
Graham


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[trikey]

If the diesel overheats, the engine will lose power dramatically, try not to run with excessive temperature.

[Don.Hasi]

Changed yesterday the inline thermostat with a gates one. Indeed, it was a broken thermostat. The brass piece was broken off and flew back in the engine and was stuck at the first bent. Luckily I could get it out after a painful time…

Now the new Gates one does a phenomenal job! Car warm, engine cool. Job done.

I have a new “tool” for getting it quick in: a water installation tube with DN40 diameter aka 40mm outer diameter which doesn’t damage the rubber tube nor the thermostat.

Thank you all for your help. This could have been a serious damage…