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Failed Thermostat Housing/Coolant Loss Info Gathering

Subliminal

Autocross Champion
Location
Vegas
Car(s)
Slow FWD VW Hatch
Ya this issue goes back to at least the mk5 generation as far as I know
 

shovelhd

Autocross Champion
Location
Western MA
My MkV had a total water pump failure, not a slow leak, but I'm sure there were leakers, too. There's currently a class action lawsuit for MkVI cars for the same issue.
 

ReadTheBook

Autocross Newbie
Location
Bay Area Smoke Hell
Car(s)
DVP Spektrm, MK4 R32
Ya this issue goes back to at least the mk5 generation as far as I know

That would be incorrect! Much older problem that started with the MK1 :)

They initially had cast aluminum thermostat housing flanges on the older MK1s, but at some point switched to polymer. We have a '90 Cabriolet that I have sourced the 2 different aluminum flanges and 1 thermostat housing flange for to put a stop to leaks from those due to warping or cracking.

I know some of the MKV/MKVI cars had issues with water pumps and the MK4s also leak.
 

Subliminal

Autocross Champion
Location
Vegas
Car(s)
Slow FWD VW Hatch
That would be incorrect! Much older problem that started with the MK1 :)

They initially had cast aluminum thermostat housing flanges on the older MK1s, but at some point switched to polymer. We have a '90 Cabriolet that I have sourced the 2 different aluminum flanges and 1 thermostat housing flange for to put a stop to leaks from those due to warping or cracking.

I know some of the MKV/MKVI cars had issues with water pumps and the MK4s also leak.
Re-read my post and please explain to me how it's incorrect
 

shovelhd

Autocross Champion
Location
Western MA
Agree but you would think that VW would care because of all the warranty cost they have incurred.

If they fixed all of them sure, but they don't. You see it here on the forum all the time. Customer complains of coolant smell. Tech pressure tests the system, it passes, NPF. The thing finally blows and it's out of warranty. Customer pays all or part of the cost.

That's the definition of not giving a f*ck.

If the customer is smart, and takes the time to remove the belly pan and take a picture of the small leak before it blows, it gets fixed. How many owners do that? This is the cost/benefit game that they are playing.

Mine has just started to leak. The reservoir is down about 1/4". 30K miles.
 

ReadTheBook

Autocross Newbie
Location
Bay Area Smoke Hell
Car(s)
DVP Spektrm, MK4 R32
If they fixed all of them sure, but they don't. You see it here on the forum all the time. Customer complains of coolant smell. Tech pressure tests the system, it passes, NPF. The thing finally blows and it's out of warranty. Customer pays all or part of the cost.

That's the definition of not giving a f*ck.

If the customer is smart, and takes the time to remove the belly pan and take a picture of the small leak before it blows, it gets fixed. How many owners do that? This is the cost/benefit game that they are playing.

Mine has just started to leak. The reservoir is down about 1/4". 30K miles.

Yep. This just went on with my in-laws car. The dealer even acknowledged it is a common problem but they aren't seeing a leak at all. Told them to keep an eye on the tank and bring it in if it starts to drop again.
 

jimlloyd40

Autocross Champion
Location
Phoenix
Car(s)
2018 SE DSG
If they fixed all of them sure, but they don't. You see it here on the forum all the time. Customer complains of coolant smell. Tech pressure tests the system, it passes, NPF. The thing finally blows and it's out of warranty. Customer pays all or part of the cost.

That's the definition of not giving a f*ck.

If the customer is smart, and takes the time to remove the belly pan and take a picture of the small leak before it blows, it gets fixed. How many owners do that? This is the cost/benefit game that they are playing.

Mine has just started to leak. The reservoir is down about 1/4". 30K miles.

The reservoir is down 1/4 of an inch in 30,000 miles. You must have a massive leak. ?
 

LB_724

New member
Location
PGH
Edit 12/6/2019: Please file a complaint with the NHTSA for this issue using the following link, this would initiate the process for a recall.
https://www-odi.nhtsa.dot.gov/VehicleComplaint/?

For those interested, a thread has been started on the r/GolfGTI subreddit on Reddit.com asking for info about when your thermostat housing failed.

https://www.reddit.com/r/GolfGTI/comments/drna5m
Thought I'd put it here if folks want to contribute since so many of us have had this issue.

If you are not a Reddit user and wish to add your info, post it here I am happy to add it to the post for you. It would be tagged with your forum username and a link to your post here.
I’ll have to check my paperwork. I had mine replaced after getting the run around from the dealer back in October, and the car dead on the road the next morning from a “failed” injector. Just had oil change on Thursday and the mechanic (not dealer) said that he could smell coolant again. I don’t think that they replaced anything except the housing.
 

ReadTheBook

Autocross Newbie
Location
Bay Area Smoke Hell
Car(s)
DVP Spektrm, MK4 R32
I’ll have to check my paperwork. I had mine replaced after getting the run around from the dealer back in October, and the car dead on the road the next morning from a “failed” injector. Just had oil change on Thursday and the mechanic (not dealer) said that he could smell coolant again. I don’t think that they replaced anything except the housing.
They do the seal the housing and the union pipe, typically.
 

Boltsfan17

New member
Location
Tampa, FL
Checked my coolant level after a week of driving and noticed a loss close to midway between full and minimum. To top it off, today I noticed a small pinkish puddle in my garage.

I know for sure there’s a leak. I guess the next question is from where. I’ve heard about the faulty water pumps. Regardless, I’m due for service in 700 miles and thankfully this is part of the powertrain warranty as I’ve just eclipsed the 39k mark.
 

jimlloyd40

Autocross Champion
Location
Phoenix
Car(s)
2018 SE DSG
Checked my coolant level after a week of driving and noticed a loss close to midway between full and minimum. To top it off, today I noticed a small pinkish puddle in my garage.

I know for sure there’s a leak. I guess the next question is from where. I’ve heard about the faulty water pumps. Regardless, I’m due for service in 700 miles and thankfully this is part of the powertrain warranty as I’ve just eclipsed the 39k mark.

Almost surely the thermostat housing.
 

Judas

Go Kart Newbie
Location
Tempe az
not on reddit

2015 vw gti s dsg non pp
bought new

replaced waterpump around 25k under warranty
replaced thermostat and housing at 59k (just before warranty ran out, wouldve cost me 1100)
also had to replace top timing belt cover at the same time as thermostat for 450 not under warranty
when replacing the thermostat and housting they found 3 leaks i think as well

long story short

bought this car brand new

every single day i can smell a faint bit of coolant after driving it
and coolant was always getting lower and lower
had two dealers check multiple time kept saying they couldnt find anything
until my car shit on me with a dashboard full of error codes, turned out to be waterpump
after the waterpump it kept smelling like hot coolant
both dealers said it was normal for vw to smell that way
iv drivien cars a long time and never had any smell of coolant unless it was leaking
i had them check probly 5 times over four years and could never find a leak apparently
after replacing thermostat housing i hoped thatd fix me smelling it, but no its still there
of course dealer cant smell it,

has me very worried especially having to fix an oil leak from the top cover of the timing chain,
cars too young to have leaks,



edit/////

now i have to replace secondary coolant pump, and car has more leaks in tubing
 
Last edited:

theDoktor

Go Kart Champion
Location
Buffalo, NY area
Car(s)
2017 GTI Sport
Looks like I get to join this party. No sign of any coolant leakage in early Sept. when I had an oil change & 30K service at the dealer. Shortly after that service I noticed that the perpetually wet spot in my driveway where the nose of the car sits when parked had a reddish tint to it. Then a week or so ago I noticed a puff of steam from under the hood about 15-20 seconds after I shut the car off. This has happened several times since the first observation. Looked under the hood- no obvious signs of a coolant leak except for an overflow tank with coolant at the Min mark when hot. I now have an appointment at the dealership for next week to look at, & hopefully fix this problem.
Thank you all for all the helpful information on this issue. If suspicions are confirmed, I plan on filing an NHSTA complaint. Hopefully enough of these complaints to NHSTA will turn our complaints into a recall.
 

jimlloyd40

Autocross Champion
Location
Phoenix
Car(s)
2018 SE DSG
Looks like I get to join this party. No sign of any coolant leakage in early Sept. when I had an oil change & 30K service at the dealer. Shortly after that service I noticed that the perpetually wet spot in my driveway where the nose of the car sits when parked had a reddish tint to it. Then a week or so ago I noticed a puff of steam from under the hood about 15-20 seconds after I shut the car off. This has happened several times since the first observation. Looked under the hood- no obvious signs of a coolant leak except for an overflow tank with coolant at the Min mark when hot. I now have an appointment at the dealership for next week to look at, & hopefully fix this problem.
Thank you all for all the helpful information on this issue. If suspicions are confirmed, I plan on filing an NHSTA complaint. Hopefully enough of these complaints to NHSTA will turn our complaints into a recall.

That could be the biggest recall in history. ?
 
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