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Old 03-09-2016, 08:16 AM   #1
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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.
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Old 03-09-2016, 11:07 AM   #2
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Quote:
Originally Posted by benster View Post
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.
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Last edited by jb92563; 03-09-2016 at 11:11 AM.
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Old 03-09-2016, 01:12 PM   #3
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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.
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Old 03-09-2016, 01:29 PM   #4
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If the system won't hold pressure it will overheat. The cap is a likely suspect.
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Old 03-09-2016, 06:53 PM   #5
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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.
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Old 12-18-2018, 09:54 AM   #6
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Dripping at overflow tube

Quote:
Originally Posted by Chuck W. View Post
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.
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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