Water Level Sensor False Reading

vwfern

Member
Joined
Dec 29, 2005
I've got an '02 jetta wagon 5spd with about 184k miles on it. For the past several winters I've been getting a water level alarm as soon as I start the car when the engine is cold. Once it warms up a little and I turn it off and re-start the light doesn't come back on. The light does not come on when the engine is warm.

I've replaced the temp sensor and thermostat and flushed the coolant. The coolant level is good.

Thoughts?
 

Rxfire

Veteran Member
Joined
Dec 29, 2006
Location
Dripperley-Blanco Triangle, TX
TDI
2 each 03 5 speed Jetta wagons, 1 NA Isuzu P'up (a keeper)
Yep, common with ours when cold, too. Same deal, drive to end of driveway, turn off, turn back on, all is well. I slightly overfill coolant during winter, seems to help
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
Replace the expansion bottle. The probes get gunked up, are nearly impossible to clean successfully, and the bottle is cheap. Mine did this as well and a new bottle stopped it.
 

Seatman

Top Post Dawg
Joined
Apr 23, 2010
Location
Scotland
TDI
2014 Skoda rapid elegance 1.6 cr tdi
Or if you're tight clean it with an old toothbrush, that seems to have worked well for a number of people but I think the tank is cheap anyway.
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
I tried that and it helped for a little while but you can only get to part of the probes with the brush (not the bottom half) and the problem comes back.
 

MT204

Well-known member
Joined
Dec 7, 2009
Location
Montana
TDI
05 JETTA
Funny thing.
A couple of days ago the wife said she started the car (first really cold morning) and the low fluid light came on. She turned it off to look in the owners manual to be sure but when she started it up all was, and has been fine.
About an hour later got a call from the kid. He wants to know what the one warning light was (same year TDI). He shut the car off, when he started it all was well again.
Both had correct amount of antifreeze in them:rolleyes:.
 

halocline

Veteran Member
Joined
Aug 13, 2009
Location
San Antonio
TDI
04 Jetta Wagon
Mine does the same thing, I tried cleaning the sensor probes, didn't work, someday soon I'll replace the coolant expansion tank.
 

jeallen

Member
Joined
Jan 13, 2007
Location
London
TDI
57 plate Octavia II Estate, 2.0l TDI (was 140bhp but now a bit more!)
Late to the thread, but getting the same "issue" and the same short term "solution" (i.e. ony happens when totally cold, and "cured" by switching it off and then on again) on my European spec 2l TDI Octavia II.

May get around to changing the tank in the longer term.
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
Yeah just buy another tank. They're pretty cheap. I've tried cleaning the probes with various items (e.g. toothbrush, etc) but it doesn't really solve the problem.
 

jeallen

Member
Joined
Jan 13, 2007
Location
London
TDI
57 plate Octavia II Estate, 2.0l TDI (was 140bhp but now a bit more!)
Yeah just buy another tank. They're pretty cheap. I've tried cleaning the probes with various items (e.g. toothbrush, etc) but it doesn't really solve the problem.
Will be doing that sometime soon, and, Yes, they are mostly pretty cheap (around £40-50UK /$60-70US new, or about half that "used") - but some like these ones (if you select "Highest Price" first) are not!:eek:
 

jmodge

Top Post Dawg
Joined
Jun 18, 2015
Location
Greenville, MI
TDI
2001 alh Jetta, RC2 w/.205's 5speed daily summer commuter and 2000 alh Jetta 5spd swap, 2" lift, hitch, stage 3 TDtuning w/.216's winter cruiser, 1996 Tacoma ALh
Another common issue is coolant migration up the wires and towards the ecu . Cutting the wires and putting in butt connectors is a recommended mod
 

jeallen

Member
Joined
Jan 13, 2007
Location
London
TDI
57 plate Octavia II Estate, 2.0l TDI (was 140bhp but now a bit more!)
Another common issue is coolant migration up the wires and towards the ecu . Cutting the wires and putting in butt connectors is a recommended mod
Thanks for the tip - I don't think that is the issue on this occasion, but I'll check and do the mod if it does look to be the case.
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
The other alternative is to remove the seal on the plug. IMHO this is highly recommended because if the seal on that connection leaks, and the plug has the seals on it the coolant will be forced up the wires. If you remove the seal it will both harmlessly leak out there at the plug and in addition you'll know there's a problem because it will get wet where you can see it.
 

jmodge

Top Post Dawg
Joined
Jun 18, 2015
Location
Greenville, MI
TDI
2001 alh Jetta, RC2 w/.205's 5speed daily summer commuter and 2000 alh Jetta 5spd swap, 2" lift, hitch, stage 3 TDtuning w/.216's winter cruiser, 1996 Tacoma ALh
I’ve run across trucks that would do this by oil or coolant, wether by migration or force, it would damage ecu’s. Apparently this was common on Mk4’s, so I did this as preventative measure on both our cars
 

TornadoRed

Top Post Dawg
Joined
Aug 3, 2003
Location
West Des Moines (formerly St Paul)
TDI
2003 Jetta TDI wagon, silver; 2003 Jetta TDI wagon, indigo blue; 2003 Golf GL 5-spd, red (PARTED); 2003 Golf GLS 5-spd, indigo blue (SOLD); 2003 Jetta TDI wagon, Candy White (SOLD)
Another common issue is coolant migration up the wires and towards the ecu . Cutting the wires and putting in butt connectors is a recommended mod
I remember hearing of some instances of this back in the early 2000s. But I would not describe it as "common."
 

Rob Mayercik

Veteran Member
Joined
Dec 19, 2001
Location
NJ, U.S.A.
TDI
2002 Jetta GLS, Baltic Green/Beige
Common enough that there was a 26-page TSB on it. I had it happen to me years ago, but I got off with only a need to replace the coolant ball and have the instrument cluster pulled and its connectors cleaned.

I not only removed the seal, but I also drilled a drain hole in the connector boss on the ball so if any coolant did come out it'd weep out and not just pool up around the contacts where it could possibly cause a short. Got the idea from a post on here.
 

irvingj

Veteran Member
Joined
Nov 28, 2006
Location
Etna,NH
TDI
2005 Jetta Wagon TDI (PD/BEW)
Mine does the same thing; I just add a bit more fluid (50-50 VW A-F) to the ball and it's fine. After a year or two, with very minor losses, it starts up again. Add a bit more fluid -- not more than 1 cup at most.

Otherwise, yeah, wait til it warms up a bit, shut off, then re-start. No problem. I just live with it.
 
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