My indie topped off my coolant when I changed my oil 800 miles (1 mo) ago. Today my car was looked over for other issues and when they did a general checkup, they found that the coolant needed another top off. Alarms of course went off because of recent stories about.... well, you know what. What's the normal rate of coolant loss in a 996? What should be diagnosed to rule out possibilities?

I am going to quantify how much coolant was lost tomorrow, but my spidey senses are telling me that in 800 miles I should've lost almost no coolant.

 

Your level can fall because of air in the system (that's what the bleeder is for,) or because of a leak which is common in the reservoir. The system can be pressure tested at a mechanic, the caps fail a lot too and should be checked.

 

In a properly operating cooling system, you will not loose any coolant. Not even a drop, assuming it is bled completely.

 

When I had my coolant cap replaced at Foreign cars Europa the service manager told me some coolant loss is normal (a little...not a lot!).

 

Two things One:cap leaking or two: leaking reservoir look for crusty stuff under reservoir both are usually small amts that evaporate quickly. Third, head gasket, check oil.
Any sweet smells near the rear of the car? check one and two.

 

He is wrong.

 

So my first order of business tomorrow will be to ask the shop to run a compression test on the cooling system. Is this a quick and easy check?

 

I don't think that will tell you if you have a bad cap.

 

Run your car up to operating temperature and then park it for the night. Remove the coolant cap in the morning. If you hear vacuum being released as you remove the cap, chances are that the system has no leaks.

 

It is quick and easy. They hook up a compressor to an adapter and plug it in to the reservoir. Next, a different adapter is connected to the cap and it is tested.
5 minutes when I watched it done on my car.
I am not sure what the dealer will tell you though.

 

Coolant reservoirs have a habit of cracking and leaking (historically) so that's a good place to start looking. They often crack at the back (where you can't see the crack) and only leak under pressure (at running temps) - they often leak onto the exhaust and evaporate before they hit the ground, so you may not see any puddles of coolant.

Also, coolant tank caps have historically had leakage issues - and there have been a number of replacement caps produced with different model numbers to designate them.

Also - there is a pressure release vent on the coolant system which is designed to allow a significant pressure build up to vent safely - this valve can go faulty and allow excessive leakage. (less common)

All of these are possibilities before you look at block issues.

 

Thanks everyone! Will diagnose this ASAP.

 

Just had my water pump replaced (CPO) this week. They wanted to keep it over night after the pump was in to make sure ALL the air was out of the system. It's like a baby, sometimes you burp them and they still have a tad more deep down inside and then you get the big air release bubble.

+1 (If your car is working properly you will NOT lose any coolant - ever) completely sealed system. As stated above, check tank, cap, hoses (bottom hose on water pump ) water pump itself which will be noisy...good luck.

 

When I bought my car it had a new coolant reservoir, when I asked the tech why, he said that because of a lot of heat in the engine bay they tend to develop cracks. I bought the car at 44K, now has 54K a year later and no issues. I drive it year round, and outside temperatures vary from 100F to -30F in Minnesota.

 

+1000 on it being difficult to fully "burp" the system. I had minimal coolant loss for months after I changed my tank, even though I tried to follow the factory burping procedure. I finally took it to get pressure tested (out of paranoia) at a porsche tech, who said there were no leaks in the sytem and then used the porsche tester to assist in burping. Absolutely NO coolant loss at all since then.