Coolant overflow, ideas?
 

After driving my 2000 Boxster S uphill rather spiritedly, I parked in my driveway and turned my car off only to find a few gallons worth of coolant spilling out from behind the rear right tire. The dash temp gauge read just a tick over 180, which is what i've come to expect as normal. I haven't noticed any puddles or drips prior to this, and my coolant level has stayed constant in the past. Looks like the spill came from an overflow drain, likey after boiling out of the expansion tank. There was condensation on the trunk lid, but no wet carpet or puddling (already experienced that one).

Has anyone had an experience similar to this? I've narrowed it down to a few plausible causes, and was looking for some input.

- reservoir cap (i have version 00, not 04)
- water pump (original, nearly 70k miles)
- small leak/air pocket
- something very bad

additional info: 60F outside, ~30 min drive (uphill), 4k to 5.5k rpm. engine still starts/runs, but not driving it.

Had this exact thing happen. I had topped up the coolant reservoir to the full mark while the engine was cold.

After a drive and getting out of the car, the coolant proceeded to barf out by the rear passenger tire.

Its the location of the overflow tube.

Verdict was over filled the coolant. Now I only go to half way on the reservoir when the engine is cold. Issue never recurred after the excess overflowing incident.

If you remove both the OIL and COOLANT caps you can remove the plastic shield, and underneath you will see the pressure release/Burp valve and the overflow drain. You will then be able to cycle the valve to make sure it is resealing properly and burp out any extra air when the engine is hot. (Don't Burn your hand)

Also make sure the coolant cap is on properly as its easy to put the cap on improperly, which prevents it from sealing and allows coolant to escape as well.

1) Replace the coolant cap.
2) Inspect the pressure relief valve for leakage (crud around the seal) replace if required.
3) Lift relief valve D ring for at least 3-4 complete heat cycles to eradicate air in system - engine to running temp & then cool down.
4) Top up with (correct) coolant mix as level will drop if air was in the system, check the level daily until stable.

If the system won't hold pressure it will overheat. The cap is a likely suspect.

Had a similar experience. Ends up it was the coolant cap. I had the original one that ended in .01 and replaced it with the latest one ending in .04.

Dripping at overflow tube
 

Thought I would validate that I'm on track. Small stream suddenly appeared. Thought the worse. Removed undercar plastic shield only to discover dribbling out of overflow tube. See photo: some condensation, none on carpet. Cap says Germany, no part number. So I need a cap, should I replace bleeder valve too?



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Why overflow when the engine is shut off?
 

I had the same problem, but hadn't touched the coolant level in weeks. It leaked a gallon or more within a couple minutes of parking. I refilled the tank the next day to troubleshoot and once it reached operating temp, it leaked from the fill cap. After observing the leak for a few seconds, I shut down the engine and within a minut, another half gallon or so of coolant rapidly leaked from the fill cap. I have a replacement cap on the way, but why does it gush only AFTER the engine is shut down?

Heat soaking of the system without air moving through the radiators.

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And less heat dissipation becuse of the lack of coolant circulation.

I replaced the coolant bleeder valve recently. I went Porsche, and the question is what I should torque it to. I am a little concerned with overtightening, due to the piece being plastic on plastic. And is there a sealant that I can seat the screws with?

There's still a little coolant condensation on the trunk coming from this valve, so I am pretty sure it just needs to be tightened more.

So my questions are:
- What should I torque the screws to, and
- What, if anything, should I seat these with?

Thx

Been dealing with leak

1. Changed the cap - still leaks
2. Changed the bleeder valve - still leaks
3. Took it to mechanic and found very small crack at the base of the reservoir

I thought it was from overflow as well

Pressure tests reveal a lot very quickly and are cheaper than throwing good $ after bad on parts with your fingers crossed.

Good luck :)

100% agree - I switched mechanics cause original mechanic could not find the leak. Said pressure test was good. Hope benster figures out his issue.

Just a suggestion...if you have to change the coolant tank take a look at Oil Filler Tube when everything is taken apart. Mine had a leak and was swapped.