Coolant was low, then magically wasn't

Sappington

Veteran Member
Joined
Jul 10, 2003
Location
Manassas, VA
TDI
2017 Chevy Volt now -- sold '03 Jetta Wagon :-(
Maybe my understanding of how the coolant system is a bit off, but here's what I just experienced this morning:

I turned my Jetta on and started to pull out of the parking lot when the red Coolant light beeped at me and started flashing. So, I pulled back into the lot, turned the car off, and popped the hood to take a look. Sure enough, the coolant level in my reservoir was about a half inch below the Min line.

I drove 4 miles to the dealer and bought a jug of coolant since I didn't have any. I popped my hood, unscrewed the reservoir cap (which gave a long hiss), and then looked at the measurement again to guage how much I needed to add. Lo! and behold, the coolant level was now a good deal above the Min line! I put the cap back on, drove to work, and the light didn't come back on.

What happened??
 

mrGutWrench

Top Post Dawg
Joined
Aug 29, 2002
Location
Carrboro, NC
TDI
'03 Jetta Wagon, 5-speed, 563K Miles (July '23)
Sappington said:
Maybe my understanding of how the coolant system is a bit off, but here's what I just experienced this morning:

I turned my Jetta on and started to pull out of the parking lot when the red Coolant light beeped at me and started flashing. So, I pulled back into the lot, turned the car off, and popped the hood to take a look. Sure enough, the coolant level in my reservoir was about a half inch below the Min line.

I drove 4 miles to the dealer and bought a jug of coolant since I didn't have any. I popped my hood, unscrewed the reservoir cap (which gave a long hiss), and then looked at the measurement again to guage how much I needed to add. Lo! and behold, the coolant level was now a good deal above the Min line! I put the cap back on, drove to work, and the light didn't come back on.

What happened??
__. OK, first you see the level way above the line and then it magically comes back down. That's easy to explain -- you had a bubble of air in the system that forced a bit of coolant into the reservoir and when the air got burped out (the reservoir set up is good for this). But the scenario that you described is a bafflement to me.
 

Joe_Meehan

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Joined
Sep 3, 2005
Location
Ohio USA
TDI
NB TDI, 2002.5, Silver
Well I guess it could be things warming up.

Next morning before you drive check the level and then check it again when warm.
 

boraTDI04

Veteran Member
Joined
Apr 9, 2007
Location
Indianapolis
TDI
2004 Jetta TDI
well the system is under pressure while the engine is running, which would explain why it is lower while running. but i would assume level is low
 

Sappington

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Joined
Jul 10, 2003
Location
Manassas, VA
TDI
2017 Chevy Volt now -- sold '03 Jetta Wagon :-(
It's happened again the past 2 mornings. On both days my car spent the night parked slightly inclined. When the light came on, I checked my reservoir and the fluid level was right at the Min line. This time I watched as I unscrewed the cap, and right when the seal broke and release the pressure, the fluid in the reservoir shot up to about a 1/2 centimeter below the Max line.

Do you still think I should add fluid?
 

Sappington

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Joined
Jul 10, 2003
Location
Manassas, VA
TDI
2017 Chevy Volt now -- sold '03 Jetta Wagon :-(
Here's what a TDI Club member and mechanic told me regarding this:

Apparently, too much pressure is being held in the system (evident from the long hiss when I loosen the reservoir cap), and the lines are holding the fluid instead of running off into the reservoir when I turn the car off.

If I let the car warm up, turn it off, then back on, the light goes off. He suggested switching my coolant cap with my other TDI, but that had no effect.

What would happen if I didn't completely screw the cap on, but left it at the point where I hear the hiss? Would pressure build up and blow it off?
 

todriver

New member
Joined
Oct 28, 2007
Location
Toronto
TDI
2005 Jetta TDI Auto
Hi there,

This exact same thing happened to me (2005 jetta TDI) 3 mornings in past two weeks. The light will come on then it will go away. I only checked the level this morning though - it was below minimum.

I'm going to check in the afternoon to see if the coolant level will go back up like you described.

I guess if there are no change in coolant level after warm up, I should add fluid. Do I need to buy the fluid from a dealer or can I get one from Wal mart? I couldn't really find any thread on what is the correct spec on engine coolant. Please recommend what I should look for.

Btw, thanks for writing such a good thread with play by play narrative. Your shared experienced is much appreciated by newbies like me. ;)
 

ymz

Top Post Dawg
Joined
May 12, 2003
Location
Between Toronto & Montreal
TDI
2003 Jetta TDI Wagon, 2003 Jetta TDI Wagon
todriver said:
Do I need to buy the fluid from a dealer or can I get one from Wal mart?
You don't need to buy it from a dealer, but you DO need to use the correct fluid, and you won't find it at WalMart !!!!!!!!!!

I believe your car uses VW G-12 (or G-12-Plus), and unless you have an extremely well stocked foreign car parts store nearby, the closest place to find it would be at the dealer's... (since you're in Toronto, try Precision Tuning to see if they carry it... www.precisiontuning.ca )

Of course, if you only need a tiny bit, some distilled, demineralized water will do... just make sure not to overfill the system.

Yuri.
 

Sappington

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Joined
Jul 10, 2003
Location
Manassas, VA
TDI
2017 Chevy Volt now -- sold '03 Jetta Wagon :-(
I've been keeping tabs on my coolant level, and now when I remove the cap, it just barely makes it back to the "Min" line, so I think I'm gradually losing fluid somehow. I have some G12 I got from the dealer that I'll use to add to the tank. 50/50 mixed with distilled water, right?
 

jimnms

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Joined
Jan 19, 2005
Location
Vicksburg, MS
TDI
2005 Jetta GLS Wagon 5-speed Tiptronic
Mine has been doing the same thing since October. It only does it when it's below 60°F, and only for the first start. When it first did it, the coolant level was about half way between the hatch marks, and when I opened the cap, it released pressure and the level rose to the full mark. However the next day, the light came on again, the coolant was about 1/3 up from the bottom of the hatched area, but it did not release any pressure when I opened the cap.

I've just been ignoring it because we've had a warm spell, and it's only dipped below 60°F a few times in the past few weeks. I decided to check this past weekend anyway. The temp was about 65°F when I started it so the light didn't come on. I ran some errands and when I got home that afternoon, I checked the coolant. It was right on the Min. line. I added some G12 to it to bring it up to the max, but now I wish I hadn't done that.

My car is still under warranty for another 7000 miles, and last October when I did my 20k oil change I noticed the coolant was on the bottom of the hatch mark, but I never had a warning light. I bought some G12 and topped it off then, so I don't think I should be losing any coolant like that. I may siphon some out so it's back on the min. line and take it to the dealer.
 

d2305

Veteran Member
Joined
Jun 26, 2004
Location
Pensacola FL
TDI
14 Ram EcoDiesel
jimnms said:
Mine has been doing the same thing since October. It only does it when it's below 60°F, and only for the first start. When it first did it, the coolant level was about half way between the hatch marks, and when I opened the cap, it released pressure and the level rose to the full mark. However the next day, the light came on again, the coolant was about 1/3 up from the bottom of the hatched area, but it did not release any pressure when I opened the cap.

I've just been ignoring it because we've had a warm spell, and it's only dipped below 60°F a few times in the past few weeks. I decided to check this past weekend anyway. The temp was about 65°F when I started it so the light didn't come on. I ran some errands and when I got home that afternoon, I checked the coolant. It was right on the Min. line. I added some G12 to it to bring it up to the max, but now I wish I hadn't done that.

My car is still under warranty for another 7000 miles, and last October when I did my 20k oil change I noticed the coolant was on the bottom of the hatch mark, but I never had a warning light. I bought some G12 and topped it off then, so I don't think I should be losing any coolant like that. I may siphon some out so it's back on the min. line and take it to the dealer.
You may have a faulty EGR cooler.
 

Cosmobug

Veteran Member
Joined
Jul 1, 2004
Location
Colorado, USA
TDI
2004 Jetta, Black on Black Leather
I'm having a similar problem. It has been very cold here the last week and I've had to park the car outside in the cold several nights while traveling. First start I get low coolant indicator and the level is right at the min line. I've had the EGR recall done.

If I had a leak, would this likely be covered by the powertrain warranty? I am at 50500, just outside of the bumper to bumper...of course! I assume if it was the EGR then that would be covered by the recall even though I have the "new" one. BTW, this EGR makes a lot more noise (whistling) than the old one...has ever since they put it on. :(
 

jimnms

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Vicksburg, MS
TDI
2005 Jetta GLS Wagon 5-speed Tiptronic
I didn't get an EGR recall notice. I have an '05 Wagon, should I have gotten one?
 

I KNOOOW

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Joined
Oct 23, 2007
Location
Brooklin
TDI
2003, 1986 (Sold)
I have had this problem with the low coolant and i needed to add more, with out thinking becuase i was late for work i added about 1/4 cup of tap water to the resivor. is this a really bad problem or not? what is going to happen?
 

mrGutWrench

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Joined
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Location
Carrboro, NC
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'03 Jetta Wagon, 5-speed, 563K Miles (July '23)
I KNOOOW said:
I have had this problem with the low coolant and i needed to add more, with out thinking becuase i was late for work i added about 1/4 cup of tap water to the resivor. is this a really bad problem or not? what is going to happen?
__. It's best to use distilled, especially if you're going to mix up a full batch (like when changing the timing belt and water pump) but I don't think that 1/4 cup of tap water will hurt anything. I keep a gallon of distilled water ($.79 at the grocery store) in my garage.
 

Sappington

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2017 Chevy Volt now -- sold '03 Jetta Wagon :-(
jimnms said:
I didn't get an EGR recall notice. I have an '05 Wagon, should I have gotten one?
Yeah, I haven't heard about this notice, either. I'm still having this issue. I guess it's time to take it to a shop to get checked out....
 

mrGutWrench

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'03 Jetta Wagon, 5-speed, 563K Miles (July '23)
Sappington said:
Yeah, I haven't heard about this notice, either. I'm still having this issue. I guess it's time to take it to a shop to get checked out....
__. Mine (over Halloween weekend so we're talking about 7 weeks ago) seems to have been a one-time thing. Sorry yours has recurred.
 

jimnms

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Vicksburg, MS
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2005 Jetta GLS Wagon 5-speed Tiptronic
This morning it was about 50°F, and when I started it up, beep beep, and the light came on. I had to stop and fill up before heading out anyway, and when I checked the coolant level, it was right about half way between the hatch marks. I just topped it off last week! No beep or light when I restarted it.
 

vgmnstr

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Lake Worth, FL (33467)
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2001 New Bettle TDI
Did anyone even stop and consider this could just be simple thermal expansion of the coolant while heating? The fluid is does expand to a certain extent, either staying in liquid form, or expanding through steam. It could be possible?!? The air bubble theory sounds probable too.
 

asauer

Member
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Apr 16, 2007
Location
Decatur, IN
TDI
2000 VW Jetta GLS TDI
vgmsntr- you stole my thunder. If your coolant level was on the minimum, then proceeded to drive it up to temperature, shut it off, and check the coolant level of course it will register alot higher. This very reason is why the coolant overflow tank is also known as the "coolant expansion tank"...
But, I am right along the same lines as you guys- I have had to add about a cup of coolant to my car every week or so. It's really bothering me- I hope my head gasket isn't going south...
 

Sappington

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2017 Chevy Volt now -- sold '03 Jetta Wagon :-(
But would that be the case when the car has sat in the cold over night? For instance, last night got down to about 40 F. This morning the coolant light came on. I drove for about 5 miles and stopped to get haircut. When I came back out and started the car, the coolant light didn't come on.

The previous 4 days we had that warm spell (60 F highs, 50 F lows). The light never came on during that time. It only seems to do it when it's been cold outside and the car has sat for a while.
 

merlin53716

New member
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Jan 9, 2008
Location
USA
TDI
98 Jetta
just my opinion here~

top it up, keep an eye on it.

take a cold fluid, warm it up, and it expands. don't overthink it too much.

if it keeps losing coolant, look for a leak.
 

professor

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Jan 8, 2001
Location
Edina, Mn USA
So try filling it to the max line when cold, and quit looking at it if the indicator light is not on. Another problem might be the contacts in the sensor need cleaning, probably a couple of prongs inside the jug. Try brushing with a metalic toothbrush.
 

jimnms

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Location
Vicksburg, MS
TDI
2005 Jetta GLS Wagon 5-speed Tiptronic
Sappington said:
But would that be the case when the car has sat in the cold over night? For instance, last night got down to about 40 F. This morning the coolant light came on. I drove for about 5 miles and stopped to get haircut. When I came back out and started the car, the coolant light didn't come on.

The previous 4 days we had that warm spell (60 F highs, 50 F lows). The light never came on during that time. It only seems to do it when it's been cold outside and the car has sat for a while.
That's exactly what mine does. I also got in the car on a cold morning, drove to get a haircut, except I only drove about a mile. When restarting the car afterwards, no light. As short of a distance that I drove, the engine didn't have enough time to warm up and open the thermostat, so the coolant could not have expanded.

We've had a warm spell here too, so it hasn't done it in a few weeks.
 

MayorDJQ

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Williamstown, Mass
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'10 Golf 2dr 6m, sold.
Sappington said:
But would that be the case when the car has sat in the cold over night? For instance, last night got down to about 40 F. This morning the coolant light came on. I drove for about 5 miles and stopped to get haircut. When I came back out and started the car, the coolant light didn't come on.

The previous 4 days we had that warm spell (60 F highs, 50 F lows). The light never came on during that time. It only seems to do it when it's been cold outside and the car has sat for a while.
The car doesn't need to sit overnight for the coolant to reach ambient.

I reread your posts, have you actually added any coolant yet?

As far as the coolant level rising when the pressure is released, that's normal. Any car will do this. Back in the days before presurized expansion bottles, if you opened your radiator cap when hot, all that hot coolant would come shooting out.

On an '03, I'd be surprised if you hoses are at the point that they're ballooning enough to be "holding" coolant. But it might be a good idea to check them.
 

asauer

Member
Joined
Apr 16, 2007
Location
Decatur, IN
TDI
2000 VW Jetta GLS TDI
As an update to my similar problem...I suspected the water pump as per the FAQ section (heater core inop, lower radiator hose still good), and the cheap OEM plastic impeller had fallen off the water pump. I am still putting it back together (doing the whole timing belt update kit), but I'm sure this is the source of my coolant loss due to overheating.
What amazes me is it has never overheated, unless I got on the interstate going 70+. I drive 1/2hr to work everyday going 60, and it has never gotten too hot. I've pretty much been driving an aircooled motor for awhile now...
 

Sappington

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Manassas, VA
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2017 Chevy Volt now -- sold '03 Jetta Wagon :-(
MayorDJQ said:
The car doesn't need to sit overnight for the coolant to reach ambient.

I reread your posts, have you actually added any coolant yet?
I did. I added about 8 oz a month ago or so.
 
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