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Issues with coolant expansion tank?

amsr

Ready to race!
Location
Michigan
Has anyone had issues with their coolant expansion tank leaking? Or with cap or the gasket?

I ask because even though my thermostat was fixed after it was found to be leaking by Volkswagen under warranty, I still smell antifreeze. The smell is strongest around the passenger side near the firewall. This is right where the expansion tank is. However I don’t see any coolant residue. I’m wondering if it’s venting for some reason and I’m smelling it?
 

jimlloyd40

Autocross Champion
Location
Phoenix
Car(s)
2018 SE DSG
Has anyone had issues with their coolant expansion tank leaking? Or with cap or the gasket?

I ask because even though my thermostat was fixed after it was found to be leaking by Volkswagen under warranty, I still smell antifreeze. The smell is strongest around the passenger side near the firewall. This is right where the expansion tank is. However I don’t see any coolant residue. I’m wondering if it’s venting for some reason and I’m smelling it?

The coolant overflow tank isn't that close to the firewall. Are you having to add coolant?
 

Carlosfandang0

Autocross Newbie
Location
UK
Car(s)
2016 3Dr GTi DSG CSG
How long ago was the thermostat housing changed? I smelt coolant for a while after having it done, which appeared to be due to some coolant having splashed onto the engine during the swap.
 

Strange Mud

Autocross Champion
Location
Small Town CT
Car(s)
Assorted
keep an eye on the level....if it stays up I would guess just some spillage. You can rinse under hood warm stopped engine lightly rinse with water. Don't soak electrical
 

jimlloyd40

Autocross Champion
Location
Phoenix
Car(s)
2018 SE DSG
Not saying that this is the case with you but sometimes when you've had a leak in the past your senses can get tricked into thinking you still smell it. If you're not having to add coolant it's not leaking.
 

stuntnuts

Go Kart Newbie
Location
Maine
Your overflow cap is releasing vapor. That's what you are smelling. Have the dealership PRESSURE TEST THE OVERFLOW CAP. Look for a trail of dirt that starts below the coolant bottle and travels down to the front of the vehicle, along the frame rail, like in this pic:

01.jpg


I've had two Mk7's and they both demonstrated this.
 

Golfs everyday

Autocross Newbie
Location
USA
As others have noted, I would keep a close eye on the coolant level and rinse the area with water. You don’t have to baby the engine bay like it’s going to melt. You can wash it with a garden hose and use a blower to rid the water. Be mindful not to drench the electronics and intake filter. I wash the engine bays on my daily drivers including my GTI all the time come Spring to rid road salt. I’ve never had an issue.
 

amsr

Ready to race!
Location
Michigan
Your overflow cap is releasing vapor. That's what you are smelling. Have the dealership PRESSURE TEST THE OVERFLOW CAP. Look for a trail of dirt that starts below the coolant bottle and travels down to the front of the vehicle, along the frame rail, like in this pic:

View attachment 165069

I've had two Mk7's and they both demonstrated this.

Thanks I’ll check it out. What was the fix for your two cars that did this? Replace the cap? The tank? Both? Also, why would it be doing this in the first place?
 

stuntnuts

Go Kart Newbie
Location
Maine
Thanks I’ll check it out. What was the fix for your two cars that did this? Replace the cap? The tank? Both? Also, why would it be doing this in the first place?

The cap controls the pressure that coolant is released at. It is malfunctioning and releasing pressure at way too low of a pressure, intermittently

My first Mk7 that did this got bought back by VW before I addressed it. The current Mk7.5 just started doing it and I haven't replaced the cap yet.
 

The Fed

Old Guys Rule
Location
Florida
The cap controls the pressure that coolant is released at. It is malfunctioning and releasing pressure at way too low of a pressure, intermittently

My first Mk7 that did this got bought back by VW before I addressed it. The current Mk7.5 just started doing it and I haven't replaced the cap yet.
What he said. It's not really a sealed system. If that were the case, you would blow a hose as soon as the coolant got hot. You also could have a leaking hose on the heater core, but you usually would smell coolant coming out the vents. If you have a leaking heater core you often can check it by turning up the defroster full blast and looking for fog coming out the defroster vents.

I should check my cap.
 

amsr

Ready to race!
Location
Michigan
What he said. It's not really a sealed system. If that were the case, you would blow a hose as soon as the coolant got hot. You also could have a leaking hose on the heater core, but you usually would smell coolant coming out the vents. If you have a leaking heater core you often can check it by turning up the defroster full blast and looking for fog coming out the defroster vents.

I should check my cap.

OK but under “normal” driving conditions it shouldn’t be venting, right?
 

MCoulombe

New member
Location
So Cal
I've always thought I've smelled coolant, around 20-30k noticed that the coolant resevoir was getting low. Topped it off, another few thousand miles it was low again. Thought it might be the waterpump or thermostat, took it to the dealer and they couldnt find a leak. They topped it off and coolant level has been pretty consistent since. I still smell coolant every once in a while, but still see no signs off leaks, no over heating.
 
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