Disappearing coolant

I own two of these cars, and it seems like one acts up once the other gets fixed. The one I drive myself does this:

2 weeks ago I heard gurgling in the dash, didn't have that before.

Today after work, started up, got the STOP sign, looked, coolant tank empty!

Filled it, drove home, turned motor off, coolant dripping out overflow hole.

Coolant looks clean, tank clean, oil looks same as always.

I had Susan rev it to 2000rpm, not sure I see coolant moving in tank, but tank is hot. Vagcom-no codes, temp is 90C.

By the way, it's 92K since timing belt/water pump change.


So, is it time for new water pump?

Is there a way to prove/disprove head gasket bad?

Thanks for any ideas.

It quite could be the water pump. I had the same type of thing happen to me when my water pump had almost 75k on it. It would leak over a day or so. In retrospect, this is how you might be able to discern that it is the water pump. Pull the timing belt cover and look for whitish dried wisps of coolant that has a slight pink overtone. Put the cover back on of course and then fill your coolant recovery tank to proper level with the proper VW pink coolant, take your belly pan off and warm up the car to operating temperature. Then park it and observe. If indeed it IS your water pump, the coolant will drip off the oil pan on the passenger side at the front (at least it did for me). Do not mix coolant. Stick with the VW formula.

Check also your coolant flange at the back the cylinder head (it is in a 'lovely' location). If that leaks, make sure you replace your temp sensor while you are in there. YOU DON'T want to monkey with that twice.

I hope it is NOT your head gasket. Is your tank clear of black gunk or oily residue? That may bode in your favor if it is a lovely clean pink. Good luck and let us know what gives.

OK, I feel like I am on the (defunct) Silk Road asking this, but if it could be a month before I can do a timing belt and water pump changeout, can I drill a hole in the reservoir cap? I accept any flames without rancor.

OK eh, it was the thermostat. I paid a local shop to do a coolant pressure test and sniff for combustion products; both normal. He said the temp stayed between 194-197F, a narrow range, and that was the reason the coolant pressure got too high.

So I replaced the OEM stat with another OEM stat, and it's been fine! No coolant loss. Seems like it warms up a little slower than before, but it's been cold.

I'm not yet understanding this, any good explanations?

That temperature range isn't too hot.

If you have VW coolant in it then you should find a pink residue from wherever the coolant leaks out. That would include the coolant bottle builtin overflow tube, around the water pump, thermostat housing, coolant hose with a leak, etc. The only place you wouldn't find it is internal to the exhaust gas cooler.

Drilling a hole in the cap prevents the system from reaching pressure and increases the likelihood of coolant boiling. Pressurized coolant has a higher boiling point.

Right, there has been no measurable overheating, according to the dash and VAG-COM. Also no leaking seen anywhere but the overflow hole; when it was happening, it was coming out fast.

Now with new stat, driving every day, no coolant loss. Maybe my car is the only one this has ever happened to? A thermostat that keeps to a three degree range is almost like a closed stat. Could have been pockets of overheated coolant that got into the reservoir?

That's all I got on this one. Mostly, I think about Audi A6s and MB Sprinters...haha

OK, just finished a 1000 mile holiday round trip, took a gallon of 50/50 with me, laptop, VAG-COM, and toolbox. Kinda superstitious now.

I did not have to add any coolant! Coolant is bright pink. The car ran great. Temp stayed normal.

If a new stat has been the fix, that's very good for me; I'm nervous because of the skepticism from the board here. I'm interested to see how the similar current threads turn out. Guru input is welcome.

auntulna said:

So, is it time for new water pump?

Is there a way to prove/disprove head gasket bad?

Click to expand...

92K seems quite premature for needed a new water pump.

Look, if you have a coolant leak of any significance, you are going to see coolant somewhere; whether on the ground after you parked it of a while, or on the floorboard inside the car.

If you see no visible leak, it has to be going out the exhaust, due to head gasket issue. It could be perfectly fine to just keep adding coolant if that is the case, or at least try a stop leak, the kind with copper in it.

IF THINGS ARE TOO GOOD TO BE TRUE, THEY ARE!

This car ran great(RC2) for another two months, then dumped the coolant well after 1000 mile trip went great.

So, Frank found leaking water pump, it was time for timing belt, he did all that.

It dumped coolant again, so head gasket it was--obviously! Water/coolant evidence both cylinders 2&3. This work was done, head thoroughly inspected, compression upper 400s all four.

AFTER head gasket replacement-- no power....

What it did and still does now, is can't go uphill in the driveway in the morning, cannot deliver with a load. Have to run the motor two minutes to get up driveway, then limp mode before I'm out of the neighborhood. Starts with no problem, always. Has given the underboost code every day, goes into limp mode with very ordinary driving variation. Some parts of the RPM span seem pretty peppy though, like it has a tune.

Things I or we have done:

Replaced N75, fuel filter, coolant temp sensor, fuel injectors! Tried an immobilizer free ECU from Jeff R. (No difference)

torsion value -.5

Frank has inspected the turbo, feels it is OK. Said tandem pump pumps great.


So amigos, we are both open to your thoughts here

And in VCDS, group 1, injection quantity, it shows 9 at idle. A normal car reads 6. This I think means not enough fueling, not sure.

Does the in-tank fuel pump run?

Fuel filter clogged?

Split hose or loose hose connection? These hoses are the large intake hoses and their snap together connections.

Bad vacuum hose connections at the vacuum pump, N75 or turbo?

I think the book can be closed on this episode. After all of the above (it was cool to take a turbo apart, see how it works and reset it), finally putting the correct BHW injectors in has made this car run good. Faster than before the head gasket problem no question about it. RC2 tune, it's a blast!

It seems, but cannot yet be proven, that PD injectors have such tight tolerances that their function may degrade with time; then if they sit over most of a winter, that could be the last straw, no effing power at all. To this point in time, there is nowhere in the US where these can be rebuilt, only replaced. Accept no substitutes.

With VCDS, Group 1, injection quantity should be about 6. Mine was running 9-10, and mileage was crap. That was the only software clue. Now normal again. What a puzzle. In hindsight, it could have been figured out in a week, but you had to have been there. I now know head gaskets can be real sneaky, and nobody wants to take the head off as the first step!

I have spent over 50% of the purchase price on this unit so far. I guess I better keep it, because there is lots of tread left on the tires. I just might buy one of Hans' turbos, and move to Montana.

I meant Frans. He used to partner with Hans