Intermittent Coolant Leak - any ideas?
 

I have been having an intermittent coolant leak that I have not been able to figure out:

It only leaks about 1/2 quart at the right rear wheel after hard high RPM autocross runs.

I replaced the water pump with a new OEM unit thinking maybe this was the first sign of the pump bearings going, but same results after replacing. I had already changed the thermostat to a low temp unit some years ago, so I left the thermostat as is.

I replaced the coolant cap with the newer version, but no change in problem.

I pulled out rear carpet and checked tank for any leaks with engine at maximum operating temperature with the fans running, but no leak there.

It is definitely not an inter-mix issue as oil looks fine, and I'm only finding coolant on the ground after autocross runs. Driving around on the street will not cause any leakage.

Anyone else ever experience such an intermittent leak?

Thanks for any info, and Happy New Year!

My guess would be that under the conditions you describe that the coolant temp is reaching a level where pressure and expansion are forcing the coolant out the overflow. the overflow tube is above and in front of the right rear tire.

Possibly small cracks in the expansion tank. Mine leaks intermittently, usually after I drive it hard, there is a small amount on the garage floor.

Have a look at your coolant pressure relief valve. Mine was dumping coolant when hot due to a bad o-ring in the valve.

For what it's worth, my 20 year old (98') coolant tank developed "spider cracks" on the underside that were impossible to see when the tank was in the car.....but what would happen is, as the car warmed up the pressure in the tank builds up (totally normal) ..... as the pressure would build, the "spider cracks" would open up enough to (for lack of a better word) "weep". Eventually there would be enough weeping that a decent amount of coolant would collect under the trunk raised floorboards that the fluid would find it's way out a seam or hole and leak on my garage floor.

You might be having the same issue......mine was fixed with a new tank install (and $800 in parts and labor)

OK. Am I missing something here?

OP says:

It only leaks about 1/2 quart at the right rear wheel after hard high RPM autocross runs.

I replaced the coolant cap with the newer version, but no change in problem.

I pulled out rear carpet and checked tank for any leaks with engine at maximum operating temperature with the fans running, but no leak there.

I'm only finding coolant on the ground after autocross runs. Driving around on the street will not cause any leakage.


That wouldn't give me the impression of any spider leaks or whatever.

I'm going to guess that OP drives his car hard... perhaps there's an air bubble... needs to properly be bled out... and back to normal.

Does not the coolant leaking at the passenger rear wheel provide at all a clue? Doesn't a leak follow the path of least reistance?

I'm not trying to be schmuky, it comes natural. ;)

I drove my Boxster home from Vegas, a couple weeks after purchasing it in 2017, like a ****************stain on a new pair of undewear and when I, literally, hit my driveway it dumped like a transient on a San Francisco boardwalk.

A new coolant cap... some distilled water... and letting the relief valve do it's job for a few days.

However, OP should follow Rob's adviice... check under that piece of wood on the trunk floor board... although my guess is that when the OP "pulled" the carpet the wood was evidentr and begged to be lifted up, checking underneath.

Good day, gentlemen.

I just ordred a new tank with a new bleeder valve and will proceed with that. I probably won't know for sure if it is fixed until 90 F temps and autocross season are back again.

Thanks to all you gentlemen for the input, but I'm not sure I know what to make of this:

[QUOTE=Starter986;609257]
...when I, literally, hit my driveway it dumped like a transient on a San Francisco boardwalk.
QUOTE]

Sounds like a California thing, although we have some homeless that urinate in the streets during the summer months so I have been told

California is a liberal ****************hole. Literally.

SnapCrap.

https://www.govtech.com/civic/Snapcrap-creator-provides-visual-tool-to-help-SF-clean-up-its-sidewalks.html

I do have a 10 year plan. :cheers: