Round 6 Thermostat

[Johann2.7t]

Hello far more intelligent mechanics than I...

Following my saga of breaking down mid trans america relocation, I'm attempting to correct my thermostat issues once and for all.

Following an overheating issues I've narrowed down the issue to the thermostat not opening/operating correctly. I currently have a gutted thermostat in the car and it runs and drives perfectly apart from a bit cold any time the ambient temps are below 80 or Im not driving like a lunatic (albiet hard autotragic).

I was hoping my thermostat issues were related to the non OEM brand and have since attempted to fit a brand new OEM unit with the same issue; overheating.

The car has all the traditional symptoms, hot upper hose, cold lower, rising coolant level in reservoir etc. Using a chemical reaction tester hopefully eliminated the possibility of a leaking head/head gasket as all of my tests were negative for mixing of combustion gases.

I have tried boiling water to test the second new thermostat but for the life of me cannot get it to open. For those that have, what are you doing to prove its functionality on a stove top?

I've been told and read the sensor is purely a warm up function and the thermostat itself is an old school mechanical unit?

Lastly where and when does the signal to the sensor originate from? Id like to throw a meter on the wires and see if there is indeed power running to the unit as it should be.

Thanks everyone, really appreciate the time and effort.

[old guy]

The thermostat is a mechanical device with a built in heater that allows the ECM to force the thermostat open earlier under specific conditions. There is a lot of information in this thread that will hopefully give you enough information to properly diagnose your problem: Clicky click®

[Kevin C]

FYI, your local altitude is 5000 ft (NM), so water will boil at about 202°F. That might be close enough to the T stats opening temp that it doesn't happen during the stove test.

[old guy]

Wow Kevin! Great observation. Totally missed that one.

[Johann2.7t]

FYI, your local altitude is 5000 ft (NM), so water will boil at about 202°F. That might be close enough to the T stats opening temp that it doesn't happen during the stove test.

Wow interesting! How else can i test the thermostat assembly without ruining it?

[old guy]

Use the information in the thread I linked. If you don't want to invest in something like VCDS you can get the same information with a hand held IR temperature scanner for less than $20.

[Kevin C]

Wow Kevin! Great observation. Totally missed that one.

Thanks Considering how much you contribute, I feel happy to add to any thread.

Wow interesting! How else can i test the thermostat assembly without ruining it?

A 50 / 50 mix of antifreeze will boil at about 265°F, more than enough. A cooking thermometer might help as well.

[Johann2.7t]

Use the information in the thread I linked. If you don't want to invest in something like VCDS you can get the same information with a hand held IR temperature scanner for less than $20.

Thanks for the link! I'll certainly see what I can figure out with vag com. Thanks!


Sent from my iPhone using Tapatalk

[a1rh3adSz]

any updates on this?

[Johann2.7t]

Use the information in the thread I linked. If you don't want to invest in something like VCDS you can get the same information with a hand held IR temperature scanner for less than $20.

Update after reinstalling OEM thermostat.

VCDS seems to show a functioning system with thermostat cycle increasing as engine actual temp increases. Once the radiator temp increases and engine actual decreases the thermostat cycle decreases.

This all occurs from 102-97 C and seems to hover 100c as specified.

Im still not convinced the system is functioning correctly. I have refilled the coolant and am trying to bleed my new heater core. With the reservoir cap off I can get coolant to bleed from the top pipe but as soon as i reinstall the screw the fluid level rises in the reservoir and will overflow if I let it. I cannot seem to get fluid out of the return hose (upper) from the heater core. With the reservoir cap installed fluid seems to backfill the heater core and eventually does bleed out of the hole.

Its almost as if the hoses are swapped but they dont appear to be.

If i remove the reservoir cap fluid wants to overflow the reservoir unless i remove it very slowly.

Any thoughts on my random rant?

[kosmo38]

Use an airlift coolant fill tool to avoid air pockets