[bderoziere]

UPDATE
Heard back from shop... they said they had to dig deeper and found codes stored prior to me bringing it in. So unfortuntely its on me. They are saying stuck thermostat. Quoted me $775 (which includes misc. wiring/connector, 2.2 gallons of coolant & 3 hours of labor)

Local VW has the Thermostat for $115 and the gasket is $18 (Do I need this?). Coolant is $32/gallon

DIY seems pretty straightforward...

 

[TRespect]

Yes you need the coolant. Go diy.


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[TRespect]

And the gasket if not part of the thermostat package.

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[bderoziere]

On the diagnostic report from the shop it also states:

"Scanned vehicle for faults, found faults related to customers concern for short to
ground on the electronic controlled thermostat.
Pressure tested cooling system and found no leaks, checked fan operation and fan are running, checked time stamps on the coolant faults and found vehicle had set a pending fault for the thermostat on 5/29/20, and then set a hard fault on 6/6/20 causing the vehicles thermostat to stick closed, Removed the thermostat temp sensor harness and found corrosion in both the harness and the temp sensor/thermostat housing"

"Thermostat sticking closed and Found corrosion on Both the harness and the
thermostat connections, harness will need to be repaired at this time as well"

So is the Thermostat the issue or the Sensor/Connector/Wiring???

 

[bderoziere]

I guess my question is, will replacing just the thermostat resolve my issue? OR do I also need to replace the thermostat temp sensor & harness???

 

[mtnride]

You will need the coolant if you replace the thermostat and housing (one unit) mine also came with gasket included. The electrical connection is easy to get to, maybe you start with a can of electrical cleaner in a spray can and clean thermostat housing side and wiring side. Clear codes and see if thermostat if the hard fault sticks after cleaning electrical connections. It will depend on how bad the "corrosion" is. You should be able to look at the wiring side for evidence of corrosion on the connector. Connection point on thermostat housing probably couldn't be inspected without removing at which point you might as well replace it. If it were me I'd replace housing first before replacing electrical wiring harness.

 

[TRespect]

The thermostat is certainly the issue. Now when you do the work check the wiring and do some some cleaning if the corrosion is not advanced. Then you decide wether you change the sensor plug or the sensor itself. Get that treg back and inspect for yourself. 700$ for a thermostat replacement is not a fair price.


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[nickyt]

"Thermostat sticking closed and Found corrosion on Both the harness and the
thermostat connections, harness will need to be repaired at this time as well"

So is the Thermostat the issue or the Sensor/Connector/Wiring???

This appears to be install a new thermostat and repair via replacing the electrical connector.

As above, you might be able to get by with cleaning the electrical connector and covering in in de-ox if the corrosion is not advanced.

 

[bderoziere]

So what actually causes the codes/faults and causes the Thermostat to stick? (The Thermostat being bad OR the sensor/wiring being bad)

 

[bderoziere]

Just worried changing out JUST the Thermostat won't resolve issue!

 

[nickyt]

It sounds like you have two faults.

The mechanical thermostats are a wear item, just like the water pump. Given enough time, both of them will fail and have to be replaced.

You have some corrosion on the temp sensor. If it was mine, I would clean it, cover it in electrical de-ox grease, and see if the problem goes away. If not, replace the sensor. See if the problem goes away. If not, buy a new electoral connector plus the pins and replace the connector. You will need to get some picks to release the electrical connector, but it is fixable.

Odds of success: 40% chance cleaning it will fix it, 50% chance that new sensor will fix it. 10% chance you will have to work on the connector.

 

[mtnride]

As NickyT states above thermostat is a wear item, I replaced mine at 125,000 and the wife's Saturday at 152,000, both times had sudden overheating issues and both times new thermostat fixed issue.

 

[nickyt]

Here is a basic how to clean an electrical connector. Honestly I usually just put a little light sandpaper on the contacts of the sensor, wipe it clean, put some de-ox on it and hope for the best. But if you are restoring old parts and want to do the best job possible, this guy has got you covered.

 

[mtnride]

Here is the old thermostat and housing and as you can see the pins for the electrical connection are tiny and could easily be damaged by corrosion. This unit doesn’t appear to be damaged in any way but justoutlived is useful life

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[bderoziere]

Guys, thanks so much this is awesome! I am starting to feel confident about this!

I think I will try to replace sensor as well, easy DIY? is it in the same location? Attached to the Thermostat? Anyone know a part #

 

[nickyt]

See pic above. It looks like the sensor comes along for the ride.

You will need the coolant if you replace the thermostat and housing (one unit) mine also came with gasket included.

On your engine, it looks like you will be replacing both at the same time.

 

[bderoziere]

Oh, so the sensor "is attached" or "attaches" to the actual thermostat housing?

 

[TRespect]

There is no temp sensor on the thermostat housing or ETKA is lying to me
That plug is what makes the thermostat be called map-controlled engine cooling thermostat.
The temp sensors are on the radiators and on the hoses. Two of them.
So they just noticed that the connector and harness of that plug which the ecu uses to control the thermostat is corroded which remains to be verified.
Temp sensors can be changed later if you want and are easy to do.

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[bderoziere]

Ok. I am getting ready to order parts at tackle this DIY.. how does this sound...?

Thermostat Replacement
Parts to order:
Thermostat w/housing & gasket - PART# 079121115BF (now# 079121115BK)
Sensor - PART# 06A919501A
Coolant
#1 – locate thermostat on driver’s side directly below air filter box
#2 - remove belly pans, air filter cover and air filter
#3 - clamp both hoses going into thermostat housing and remove hoses OR drain into a bucket
#4 - disconnect electrical connection on thermostat, you can also unplug the brown electrical connection in front of radiator to allow for extra room to work (optional)
#5 - remove 5 bolts securing thermostat housing to water pump
#6 – install new thermostat
#7 – reattach 5 bolts securing thermostat housing to water pump
#8 - refill with coolant, start car and shut down, add more coolant as needed, start again and check for leaks
#9 – while car is on, turn heat up & on full blast to remove air bubbles in coolant line. If no heat comes out, rev engine a couple of times till heat comes on
#10 - reinstall belly pans

Couople Questions:
-Can this repair be performed from above the car (under the hood)? Or do you need to be under the car?
-Drain into a bucket? Who? what? where?

Please add anything I may have missed!

 

[TRespect]

Here you go:
Don’t be frightened by the tools there. You can do without. But there is a very helpful hose clamp tool for 10$ I guess which makes stuff easier.
You don’t need all the drain procedure. It’s there so you have the full picture.