Tell me I'm just being paranoid!

[ScottArizona]

O.k., so I recently replaced the coolant tank and cap (updated to the '01 cap) in my 99 C2. This was a few months back. I have religously watched the coolant level in the tank since then and all has been fine, until recently. I had previously makred the EXACT coolant level on the tank with a sharpie, and monitored the level that way. Recently I noticed that the level, when completely cold, is a few milimeters below my mark. Now, I know this is not alot, but as you can imagine, with a 99 I fear the dreaded porous block issue. The car runs great, and is just below 60k miles. I eecently changed the oil and the oil did not appear to be "watered down" or to have any hint of coolant (should I have it tested?). So, what could be the cause of this loss. It has been very hot lately in Arizona (Phoenix). I've heard, however, that the coolant system is "closed," and that a properly operating system should not therefore lose ANY coolant. Please tell me I'm wrong. I can handle tank replacements, busted hoses, or bad tank caps, but please tell me an engine replacement is not in my future. Any comments would be appreciated. Scott.

[jlb532]

Scott,

I have the EXACT same situation you described, and have gone through many a sleepless night because of it. I've got about 70K, car runs beautifully...and no coolant in oil. Talked to numerous mechanics.

One thing I've observed is that the coolant level can be a tricky beast. Sometimes you'll check it and it will be several mm above the min...while other days it might be below the min. I've even seen it below the min first thing in the morning, and then ABOVE the min by afternoon...without even starting the car!

I think ambient temps and humidity play a role...and on top of that, you might have had some excess air in your system from replacing the tank. It's probably worked itself out, and hence you're a little low.

IMHO (or at least what I've learned to do)...is stop worrying about it until you see the coolant light come on. If that ever happens, add more coolant and watch it. IF it comes on a second time, then you can worry. Maybe. Could still be air bleeding off.

Check the level once a week max (not every day like you're probably doing currently-like I was)...and don't add any more coolant at this point. For now, keep that engine lid closed and enjoy the car.

[ScottArizona]

Thanks for that thoughtful reply. I suspect you are right, as I too have seen the level fluctuate a bit, even without driving the car. Also, good point about air still escaping the system and causing the levels to fluctuate. After I replaced the tank I don't think I properly "burped" the system as I recall feeling frustrated that I couldn't get the car hot enough (mostly because I was unwilling to "free rev" the engine per the instructions) to get all the radiators opened up completely and all the fans to come on. This suspicion was confirmed a few months ago, on the first real hot day of the year, when I had the coolant level drop enough to get my light to come on on a very hot and humid day filled with a bunch of stop and go driving. When that happened I stopped the car, checked the level, gave it enough coolant to take it back above the min. line, and it has been holding fairly steady since (in hot weather no less). Given that my car actually runs pretty cool (I have never seen it run much past the 180 mark), I chalked this episode up to the fact that I had probably not burped the system properly and it was very hot that day. I think I'll stop checking the coolant level everyday.

[1999Porsche911]

It can take several drive cycles to fully bleed the system when coolant is added. Once bled, your should never lose any fluid. Keep ading in the mornings until you no longer need to.

[Izzy]

Scott, Tiptronic or manual? If it is Tip, I have some suggestions where to look. I had the same problem and found the leak in the ATF cooling area, a small valve had a leak so small I never saw or smelled it. But coolant will dissapear very slowly. Changed the valve and situation resolved.

[ScottArizona]

Izzy,

Wouldn't you know it, I have a tiptronic too. I'd be very interested in hearing about your experience!

[Izzy]

Izzy,

Wouldn't you know it, I have a tiptronic too. I'd be very interested in hearing about your experience!

Could be the same culprit. It is the valve that lets coolant to the ATF cooling unit. It is a plastic body under the car, and the only way I found out it leaked was by compressing the coolant hoses in and out of the valve, then I saw some bubbles escaping, and rubbing my finger on it was wet with coolant.

To get to it, get the car up on stands, and remove the rear most under body plastic panel. You will need a flashlight to see under there, but the valve is located in the middle, right were the coolant hoses come through from the tunnel where the gas filter is.

Looks like this. The pictures are sideways, the floor is to the right of the picture. The crossmember seen in the top pic can give you a reference point:

This is a closer up. You can't see the leak, but if you squeeze the hoses, the edge between the white and black parts ooze coolant.

And it is part 14 in the diagram below.

The valve comes off easily enough, two hoses -one in, one out. I clamped the hoses to prevent coolant drip, just used a couple of small "c" clamps and some old pieces of a garden hose cut to about 1 inch lenght, and then in half to form a U channel. Placed the rubber hose cutouts against the coolant hoses and then the "c" clamps compressing on the outside. Makes a nice seal.

I think the valve is only held in place by a single phillips screw. Also, the air hose on the top simply pulls out. It is a vaccum hose that opens and closes the valve.

Hope that is it for you, from memory it was about a $30 part, no more than an hour of work including getting the car off the ground. I reused all the clamps.

Izzy

[PTEC]

I say paranoia. As the coolant gets hot and cold its losing small amounts in the form of vapor.

[ScottArizona]

Thanks for all the responses guys. And a special thanks to Izzy for going out of his way to alert me to a possible source of my coolant loss. What a great board. Scott.

[1999Porsche911]

I say paranoia. As the coolant gets hot and cold its losing small amounts in the form of vapor.

Under NO circumstances should you lose ANY coolant if the system is functioning properly. It is a sealed system and short of a leak or substantial overheating, no coolant will ever be lossed. Evaporation cannot occur in a vacuum.

Edited July 21, 2006 by 1999Porsche911

[PeterC4]

Like PTEC I say paranoia is taking over. Be careful if the warning light does not come on, but otherwise keep the car maintained properly and let things work the way they will.

[GOB]

The head tech at the local dealer told me to make sure to let the car rest on an incline (nose down) for a few hours with the coolant tank lid off to make sure that all air bubbles get out. I was having the itermittent low coolant light and fluctuating levels, but after topping it off and bleeding it many times as suggested (even a few overnight resting periods), I am happy to say no more issues.

Anyone have the part number for the updated cap?

Thanks

[Ubermensch]

I say paranoia. As the coolant gets hot and cold its losing small amounts in the form of vapor.

Under NO circumstances should you lose ANY coolant if the system is functioning properly. It is a sealed system and short of a leak or substantial overheating, no coolant will ever be lossed. Evaporation cannot occur in a vacuum.

The first part of your statement is correct, but please don't tell people that evaporation cannot occur in a vacuum. That's just plain wrong. Lower pressure (vacuum) actually helps fluids vaporize. Of course I'm not sure what that has to do with this conversation since the coolant system isn't under vacuum, it's either at atmospheric pressure or it's pressurized.

My guess is that you either have a small leak in your system as described by others, or you're seeing the natural expansion and contraction of the fluid due to temperature variations. That's the whole point of the expansion tank (to coolant excess fluid the system can't handle when it warms up).

Shawn

[1999Porsche911]

I say paranoia. As the coolant gets hot and cold its losing small amounts in the form of vapor.

Under NO circumstances should you lose ANY coolant if the system is functioning properly. It is a sealed system and short of a leak or substantial overheating, no coolant will ever be lossed. Evaporation cannot occur in a vacuum.

The first part of your statement is correct, but please don't tell people that evaporation cannot occur in a vacuum. That's just plain wrong. Lower pressure (vacuum) actually helps fluids vaporize. Of course I'm not sure what that has to do with this conversation since the coolant system isn't under vacuum, it's either at atmospheric pressure or it's pressurized.

My guess is that you either have a small leak in your system as described by others, or you're seeing the natural expansion and contraction of the fluid due to temperature variations. That's the whole point of the expansion tank (to coolant excess fluid the system can't handle when it warms up).

Shawn

In order to have a static vacuum, you must have a completely leak free environment. You cannot leak, or otherwise loose substance in a system that is air tight. This has absolutely nothing to do with vaporization which does not result in an unrecoverable loss of coolant in a closed system.

Edited July 24, 2006 by 1999Porsche911

[Ubermensch]

I say paranoia. As the coolant gets hot and cold its losing small amounts in the form of vapor.

Under NO circumstances should you lose ANY coolant if the system is functioning properly. It is a sealed system and short of a leak or substantial overheating, no coolant will ever be lossed. Evaporation cannot occur in a vacuum.

The first part of your statement is correct, but please don't tell people that evaporation cannot occur in a vacuum. That's just plain wrong. Lower pressure (vacuum) actually helps fluids vaporize. Of course I'm not sure what that has to do with this conversation since the coolant system isn't under vacuum, it's either at atmospheric pressure or it's pressurized.

My guess is that you either have a small leak in your system as described by others, or you're seeing the natural expansion and contraction of the fluid due to temperature variations. That's the whole point of the expansion tank (to coolant excess fluid the system can't handle when it warms up).

Shawn

In order to have a static vacuum, you must have a completely leak free environment. You cannot leak, or otherwise loose substance in a system that is air tight. This has absolutely nothing to do with vaporization which does not result in an unrecoverable loss of coolant in a closed system.

Sounds like we agree.

S.