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misterdecibel
12-05-2008, 01:54 AM
My 2007 VW GTI w/12,400 miles on it, gave me a "CHECK COOLANT" warning this morning. The level was down even with the "MINIMUM" mark on the expansion tank, so I topped it up with 50/50 and all is fine.

But in a closed system, where does coolant go?

DonTom
12-05-2008, 03:26 AM
My 2007 VW GTI w/12,400 miles on it, gave me a "CHECK COOLANT" warning this morning. The level was down even with the "MINIMUM" mark on the expansion tank, so I topped it up with 50/50 and all is fine.

But in a closed system, where does coolant go?

Fill it to correct line in recovery tank only when cold. If you fill it up when hot, it can be normal to lose some out of the recovery tank. Otherwise you should not lose any and it might have a slow leak, such as a water pump or very small leak in a hose (sometimes a small leak from a hose is not obvious).

Another sign of a leak is a smell of coolant, often from inside the vehicle. If a strong smell, it could be a leaking heater core.

Coolant leaks can be intermittent, so you may find sometimes it leaks and sometimes it doesn't. The most common problem causing an intermittent leak is the water pump, but sometimes even a pinhole in a hose or a loose hose clamp can cause an intermittent leak. I assume even the heater core and radiator can have intermittent leaks too, but I have not yet ran into that.

BTW, I am dealing with an intermittent leak problem in my 1999 Dodge Ram Truck. It lost a lot of coolant a couple of times. But when I keep an eye on it, it seems to stop leaking. I assume it's the water pump, but I want to see it leak at least a little before I change it. It won't leak a drop when I check with a hot engine, both engine running and just stopped.

It has no low coolant warning and the the first symptom I get is that the heater works fine when the coolant gauge is low but the heater won't work at all when the coolant temperate reads high. Just the opposite of what one would expect.

BTW, can somebody here explain why that happens?


-Don-

MikeHalloran
12-05-2008, 04:56 AM
It's overheating, badly. Check for backwards/ wrong/ old thermostat, clogged radiator, inoperative radiator fan.

DonTom
12-05-2008, 05:38 AM
It's overheating, badly. Check for backwards/ wrong/ old thermostat, clogged radiator, inoperative radiator fan.

I was making the assumption that the 2007 VW GTI has some type of overheating warning. Doesn't it?


-Don-

Eric
12-05-2008, 07:05 AM
My 2007 VW GTI w/12,400 miles on it, gave me a "CHECK COOLANT" warning this morning. The level was down even with the "MINIMUM" mark on the expansion tank, so I topped it up with 50/50 and all is fine.

But in a closed system, where does coolant go?

I agree with Mike; I'd be a little worried - especially since your car is near-new.

Do you see any signs of visible leakage externally?

Ken
12-05-2008, 11:28 AM
It's overheating, badly. Check for backwards/ wrong/ old thermostat, clogged radiator, inoperative radiator fan.

Could be a stuck thermostat or even, in the worst case scenario a leaking head gasket - possibly water jacket to cylinder if there are no visible external leaks. The cylinder gases will pressurise the water jacket and pump water through the reservoir tank and out through the vent pipe. As the engine cools it will suck a large amount of water back into the depleted water jacket - no visible leaks but a significant loss of water. For a quick check feed the overflow pipe into a catch tank.

Ken.

Eric
12-05-2008, 12:41 PM
Could be a stuck thermostat or even, in the worst case scenario a leaking head gasket - possibly water jacket to cylinder if there are no visible external leaks. The cylinder gases will pressurise the water jacket and pump water through the reservoir tank and out through the vent pipe. As the engine cools it will suck a large amount of water back into the depleted water jacket - no visible leaks but a significant loss of water. For a quick check feed the overflow pipe into a catch tank.

Ken.

Hopefully he is still under the full factory warranty.

I would take it back to VW, pronto - and not take it back until it stopped consuming coolant.

misterdecibel
12-05-2008, 01:58 PM
It's overheating, badly. Check for backwards/ wrong/ old thermostat, clogged radiator, inoperative radiator fan.

It's not overheating, at least not according to the water temperature gauge, and it's not throwing any engine codes on the computer.

The distance between the "Max" and "Min" lines on the expansion tank is about 3/4".

For now I'll keep observing the level, and see if it continues to change.

I haven't seen, or smelt, any signs of external coolant leakage.

dom
12-05-2008, 02:12 PM
In a closed system, if not out the bleed on the reservoir, the only two places to go would be:

a. in the oil pan (resulting in milkshake oil when checking on the dipstick)

b. into the combustion chamber (resulting in some clean piston tops and nice white smoke out the tail pipe, maybe not too noticeable at first, the catalytic converter can clean a small amount)

chiph
12-05-2008, 02:15 PM
Since you're under warranty, get it checked out by the dealer.
If they don't find anything, make sure they enter it into the computer that you suspect an internal coolant leak, so that if there's a major problem later, you'll have some records to back you up.

Chip H.

DonTom
12-06-2008, 05:56 AM
It's not overheating, at least not according to the water temperature gauge, and it's not throwing any engine codes on the computer.

The distance between the "Max" and "Min" lines on the expansion tank is about 3/4".

For now I'll keep observing the level, and see if it continues to change.

I haven't seen, or smelt, any signs of external coolant leakage.

Is it possible that it was low on coolant to start with? I know in some cars, such as my 96 Saturn. the recovery tank only has to be a little bit low to have the coolant warning come on. Did yours come on when the engine was still cold, such as within a few minutes after starting? That's happened to me too.


-Don-

Eric
12-06-2008, 06:42 AM
It's not overheating, at least not according to the water temperature gauge, and it's not throwing any engine codes on the computer.

The distance between the "Max" and "Min" lines on the expansion tank is about 3/4".

For now I'll keep observing the level, and see if it continues to change.

I haven't seen, or smelt, any signs of external coolant leakage.

For your protection, I would take the car to the VW store and have them check it over. At the very least, this will establish a "paper trail" in the event you need to make a warranty claim in the future. Especially if you have to make one after the powertrain coverage's mileage/time limits have been exceeded. Evidence of a problem prior to that can sometimes get full or partial coverage even if the warranty is technically no longer in effect.

Be certain that the specific complaint - coolant loss - is noted on the repair order.

Dave Brand
12-06-2008, 06:49 AM
Just down to the 'low' mark in 12,000 miles doesn't look to me like a serious coolant leak - unless it's suddenly dropped. Have you had cold weather recently? Coolant levels are to a certain extent temperature-dependent, so on a very cold morning the level will be down - my Alfa was right down on the 'low' mark when I checked earlier this week, but with an outside temperature of 1 I saw no cause for concern.

In your situation I would just keep an eye on the level; if it drops again, see the dealer.

misterdecibel
12-06-2008, 01:03 PM
Just down to the 'low' mark in 12,000 miles doesn't look to me like a serious coolant leak - unless it's suddenly dropped. Have you had cold weather recently? Coolant levels are to a certain extent temperature-dependent, so on a very cold morning the level will be down - my Alfa was right down on the 'low' mark when I checked earlier this week, but with an outside temperature of 1 I saw no cause for concern.

In your situation I would just keep an eye on the level; if it drops again, see the dealer.

It was indeed a cold morning.

I had not previously been monitoring the level, so I don't know whether it's been slowly going down or if it was a sudden decrease.

I got to Auto Zone before the car was warmed up, it takes a couple of miles before the temp gauge gets up to working temperature. I don't know if the thermostat had even opened yet. I topped it up to the "MAX" line, and drove off. The warning went away, so I was satisfied.

Today the system appears overfilled, by about the amount I added...

...which appears to be about 1 pint either way.

DonTom
12-06-2008, 05:27 PM
"Today the system appears overfilled, by about the amount I added..."

Then I would forget about it.

Only compare when the engine is at the same temperature each time. Best to check when completely cold.

-Don-

misterdecibel
12-06-2008, 08:06 PM
Is it possible that it was low on coolant to start with? I know in some cars, such as my 96 Saturn. the recovery tank only has to be a little bit low to have the coolant warning come on. Did yours come on when the engine was still cold, such as within a few minutes after starting? That's happened to me too.


-Don-


On the VW, the warning appears to come on as soon as the level drops even to the "MIN" marker on the expansion tank. I saw the warning as soon as I started the car that morning, and it didn't go away until I added coolant. Literally as soon as the engine fired a text message popped up on the trip computer/nag screen, after a few seconds the text was replaced by a flashing icon.

DonTom
12-06-2008, 11:20 PM
On the VW, the warning appears to come on as soon as the level drops even to the "MIN" marker on the expansion tank. I saw the warning as soon as I started the car that morning, and it didn't go away until I added coolant. Literally as soon as the engine fired a text message popped up on the trip computer/nag screen, after a few seconds the text was replaced by a flashing icon.

Sounds like you might have a very small coolant leak. They type that's very difficult to find. I had that problem once from a pinhole leak in a hose. You might not see or hear anything. I felt it on my hand and that's how I found it, when checking for something else.


-Don-

Eric
12-07-2008, 07:01 AM
Sounds like you might have a very small coolant leak. They type that's very difficult to find. I had that problem once from a pinhole leak in a hose. You might not see or hear anything. I felt it on my hand and that's how I found it, when checking for something else.


-Don-





Yep - and while the car is under warranty (if it were me) I would get the dealer to find and fix it.

Leaks almost always tend to get worse over time. And that will probably be just after his warranty expires.

DonTom
12-07-2008, 07:28 PM
Yep - and while the car is under warranty (if it were me) I would get the dealer to find and fix it.

Leaks almost always tend to get worse over time. And that will probably be just after his warranty expires.

Yes, it could be something small, such as a loose hose clamp OR something big, such as an internal engine coolant leak. If new and still under warranty and cannot find the problem in a quick look, I would bring it back in too. But small things I will fix myself if I can do so without voiding the warranty.


-Don-