Intermittent Coolant Light in 2004 BEW, Shop Says No Leak

kennethsime

Veteran Member
Joined
Oct 29, 2010
Location
California
TDI
2004 Jetta Wagon GL TDI 5-Speed Baltic Green
Hey all,

I've got a 2004 BEW that is sometimes a bit slow to warm up, and has a coolant light come on about 50% of the time I'm driving. It seems to me that these two things are related, and often occur when starting on a cold morning. I bought the car about a year ago, but hadn't really taken it anywhere due to COVID. I think I've topped off the coolant reservoir once or twice in the past year. The previous owner mentioned a shop thought it might be the EGR cooler, but I don't have any paperwork to that effect.

I had the car into the shop this week to look at a few things, and they pressurized the coolant system but found no leaks.

Does this sound familiar to anyone? To me the behavior is kind of like a thermostat that's getting sticky. Any other reason the coolant light would come on sometimes?
 

Tdijarhead

Top Post Dawg
Joined
Nov 10, 2013
Location
Lawrenceville PA
TDI
2003 TDI Jetta Daughters Car, 2001 TDI Beetle, Daughters car, 2005 Golf TDI Mine, all 5 spds
A new coolant ball is about $25 at idparts. They are fairly easy to replace. I had a sensor go bad on me once the two wire probes down inside the ball got gunked or dirty or whatever and a new coolant ball solved my problem.

However if you’re adding fluid, then you have a leak somewhere. I had a very slow leak from the coolant flange which is mounted to the drivers side of the end of the head over top of the transmission. The telltale sign was dampness that just never seemed to dry out on top of my transmission. A new O ring on the coolant temperature sensor solved my problem.
 

kennethsime

Veteran Member
Joined
Oct 29, 2010
Location
California
TDI
2004 Jetta Wagon GL TDI 5-Speed Baltic Green
Hopefully picking up the car today. If the shop doesn't have anything else to say, I'll probably pickup a new Coolant Ball and maybe the EGR Cooler Bypass kit from ID Parts. Those sound like two very likely culprits, and pretty easy to rule stuff out. Thanks guys!
 

PakProtector

Veteran Member
Joined
Jan 5, 2014
Location
AnnArbor, MI
TDI
Mk.4 and the Cummins-es
First watch the level when it is cold and parked in the same spot for a wee bit. Ov course, if the light comes on and the ball is dry, that is indeed another thing entirely. It does sound like the level is never low, and there is a false positive on coolant loss...
cheers,
Douglas
 

kennethsime

Veteran Member
Joined
Oct 29, 2010
Location
California
TDI
2004 Jetta Wagon GL TDI 5-Speed Baltic Green
First watch the level when it is cold and parked in the same spot for a wee bit. Ov course, if the light comes on and the ball is dry, that is indeed another thing entirely. It does sound like the level is never low, and there is a false positive on coolant loss...
cheers,
Douglas
Honestly I just don't think I've paid attention to it enough. I've definitely topped it off once or twice in the past year, so there may just be a leak they couldn't find. I've heard the EGR Cooler sometimes fails and leaks coolant into the exhaust, and frankly I feel like I might've smelled that in the past - especially on cold mornings.

Perhaps there's a rubber seal or gasket involved, and when the rubber is cold and contracted it leaks a bit, and when the engine warms up the rubber expands and stops the leak? This might help explain why it's a very, very slow leak, and why the shop isn't seeing it when they pressure-test the coolant system.
 

kennethsime

Veteran Member
Joined
Oct 29, 2010
Location
California
TDI
2004 Jetta Wagon GL TDI 5-Speed Baltic Green
You could also simply have a bad cap. And since that is off when the system is pressure tested....
Hmm... would a bad cap be leaking coolant very slowly, and/or causing the coolant light to come on?

Mechanics did say they found a bit of dried coolant on the timing belt cover but this could also have been from me topping off the coolant.

Sure would be nice if we still had a TDI expert in the East Bay.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
Hmm... would a bad cap be leaking coolant very slowly, and/or causing the coolant light to come on?

Mechanics did say they found a bit of dried coolant on the timing belt cover but this could also have been from me topping off the coolant.

Sure would be nice if we still had a TDI expert in the East Bay.
Oh yea it could. I think what OH is saying is when they pressure test, they connect to the coolant bottle, so you'd never know if it was simply a bad cap.
 

kennethsime

Veteran Member
Joined
Oct 29, 2010
Location
California
TDI
2004 Jetta Wagon GL TDI 5-Speed Baltic Green
Oh ok that totally makes sense - thank you! I have a couple of things to try for sure, and will report back if I find the solution.
 
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