[MLB]

or, crazy coolant conundrum, for the search engine...

Long post explaining my saga, sorry:

 

So for a whole season, maybe 2, before I got the supercharger, I had this periodic problem where I would drive the car, not necessarily hard but fully warmed up and when I shut off the car, or when I started slowing down into my neighborhood after a several hour cross country drive, the expansion tank would overflow spilling 100-200 mL or more of coolant on the ground. Always air then behind bleeder screw, top of engine (as determined after cool down). In June, on our drive to Vermont, it had even sucked the expansion tank dry once when I checked after overnite in Rochester NY.  I was scared we were screwed, but I refilled and bled the system best I could in the O'Reillys parking lot, and soldiered on.

 

This has continued even since replacing the HG and expansion tank when I installed the SC last winter. Even brought our return trip from Porsche Parade to a halt on the highway as the car temp gauge instantly pegged when I reached highway speed again after a brief stop for fuel on a pretty hot day. Only steam hissing from the bleeder screw when I cracked it open to check. The car was flatbedded to Eric Steinel's shop in Twinsburg (great experience there by the way, but unfortunately no long term fix) where the recently replaced thermostat and expansion tank pressure cap were replaced again with new after re-bleed of the system. Eric also drilled the thermostat (four 3/16" holes), but I'm not convinced thats a great idea, even though I will rarely drive the car in really cold weather.

 

Anyway, I have been dreading testing for exhaust gases in the coolant, but finally bought NAPAs blue/yellow liquid test kit tonite, and warmed up the engine. Even waited for the fans to run indicating thermostat open. Using the bubbler device to draw a vacuum on the air above the coolant level in the expansion tank resulted in no color change whatsoever. So thats good, suggests I dont have a cracked block or HG failure. But what then? How is AIR getting INTO a pressurized system? I let the car cool down and can use a syringe to add about 300-350 mL of fresh coolant thru the bleeder screw until the neck fills to overflowing.

 

Radiator and WP are original to the car, as far as I know, and they are on the short list for replacement, but can a partially plugged radiator perhaps cause these symptoms?

I dont know what else to do or replace? The "thrill is gone" until I can get this figured out and fixed. Actually had momentary lapse and thought of selling the car, but I've put too much blood and sweat and CASH into this car to give up now...  ;0)

--Michael

Partial Post: Please Login or Register to read the full post.

[Bulti]

Are you 100% sure you got a fully functional and correct 150 Kpa coolant cap? Are there any coolant droplets hanging from the overflow tube?


I know, you probably checked it more than once..

Partial Post: Please Login or Register to read the full post.

[MLB]

Yep, cap is correct 150 behr, replaced twice, no 3 times now since i bought the car, always bought thru porsche channel, such as sunset, or SSF my indie mechanic's source. Replaced "just because" when i first bought the car in 2013, then again when i got the new expansion tank and hoses last winter, and again at Steinel's in June.


And blowoff line works. But there was only the one time in Rochester when i has lost enough coolant over multiple stops on a long day's driving that the expansion tank was sucked dry overnight.

Every other time there is stil plenty of coolant in the tank to stay above the MIN line


So even if a cap was letting coolant pass at less than 1.5 bar, how can that explain the massive introduction of air in the top of the system?


Dumb question: am i correct in believing that once a system is properly and fully bled, there should no air, only coolant, at the bleeder screw even after driving?

Partial Post: Please Login or Register to read the full post.

[flash]

when the system was bled, was the heater on max temp and fan on high?

 

failing that, sticky thermostat would be my guess.  

 

either that, or somebody replaced the fiber sealing washer underneath the bleed screw with a regular washer, or replaced the bleed screw with a regular screw.

Partial Post: Please Login or Register to read the full post.

[MLB]

Hmm fiber washer you say!?

I thought i ordered replacements from sunset and they are aluminum. Bleeder screw appears to be the correct banjo type. I even sanded and polished the neck where the washer and screw head seat, in an effort to ensure a good flat seal because i was concerned about that.

But if its supposed to be a fiber washer...crap. Hope the solution is that simple after all ive been thru

And yes i always bleed system with front of car slightly higher than rear, heat on high, full power

Partial Post: Please Login or Register to read the full post.

[MLB]

Just talked to my indie mechanic who said no, its an aluminum washer from Porsche. Anyone else using a fiber washer?

Partial Post: Please Login or Register to read the full post.

[flash]

just like the fan temp switch, it should be fiber, not aluminum.  i have seen mechanics use the wrong thing though, and it would weep as a result.  if it isn't weeping there, don't worry about it.

 

interestingly, the PET does not seem to show what it is at all

Partial Post: Please Login or Register to read the full post.

[MLB]

Yeah i couldnt find in PET either with a quick look. Sometimes items are listed but not shown in the drawings. Will dig a little more for descrip and part # later, maybe call sunset also. But its never weeped, at around 7 ft lbs

And i tend to trust a mechanic with an encyclopedic knowledge of the cars, who has worked on them for decades and never seen a fiber washer there.

Partial Post: Please Login or Register to read the full post.

[flash]

every car i have ever had in here for a supercharger installation, had a fiber washer.  i haven't checked all of the other cars, but i have checked a few others, and almost all had fiber.  if you think about it, it makes sense.  it's under pressure, and a metal washer would not seal as well.  everywhere else in the coolant system they use a fiber washer.

Partial Post: Please Login or Register to read the full post.

[MLB]

At this point im certainly interested in trying a fiber washer. Will continue looking for part number, and source.

Anyone got that info?

Thanks!

Partial Post: Please Login or Register to read the full post.

[flash]

if you don't see orange coolant (assuming you are using the prestone phosphate free orange coolant), then the chances of that being an issue are nil.

 

more than likely it is a stuck thermostat.

 

however, pull the spark plugs and look for signs of coolant first.

 

then, if nothing shows up there, check the inlet and outlet coolant hose temps.  they should be about 40 degrees apart, not 100.

Partial Post: Please Login or Register to read the full post.

[MLB]

I use blue Pentosin pentofrost NF, phosphate free


Can easily check or replace thermostat, but that would make 3 in as many years with same prob


Will check plugs and IR temps tonite

Thanks

Partial Post: Please Login or Register to read the full post.

[MLB]

Close inspection: this looks like a helicoil, no?

Hmm... plot thickens


   

Partial Post: Please Login or Register to read the full post.

[Bulti]

Mine got a helicoil too since I bought it. I use a copper washer. It leaks nada. But I will definitely use a different washer next time if the oem one is a fiber one.


If the pressure builds up too high -above 1.5 bar- it will overflow through the cap and the hose, obviously. And IF that is the case, maybe there isn't a leak but some reason why the pressure gets too high for the cap.


Like Bob said, check the plugs.


I have no clue why the air gets inside there, presumed that it was all out in the first place.


I'm quite curious to know what's going on. I hope it's nothing bad.


FYI - today I just sealed a coolant leak on mine. It was the block off cap on the radiator, the clamping ring got a bit loose.

Partial Post: Please Login or Register to read the full post.

[MCL968]

Have you used a sniffer to see if there are exhaust gasses in the overflow tank? A miniscule head gasket leak could produce those symptoms.

Partial Post: Please Login or Register to read the full post.

[MLB]

@MCL

I used NAPAs "blue to yellow" liquid color change kit if thats what u mean. No color change at expansion tank, and i even tried it at the bleed screw. Stays cobalt blue, suggesting no combust gases in coolant passages

Partial Post: Please Login or Register to read the full post.

[kwikt]

Mine is heli coiled as well. I've been using aluminum washers for years with no problems of leakage. Waterpump??

Partial Post: Please Login or Register to read the full post.

[MLB]

Hi kwikt,

i am considering replacing the WP now @ 100k miles, "just because" but can you explain a scenario by which a failing WP could allow air into a pressurized system? keep in mind i have no coolant leaks, with the exception of when the expansion tank overflows. So the WP isnt leaking coolant out anywhere that Ive ever seen. And I keep things very clean in there :0)

Personally, I'm leaning toward a partially plugged radiator, where a passage in the radiator gets very little flow, that coolant overheats to boiling, creating steam which then ruins my life, and my chances for taking the car on the track. Road America is in my proverbial backyard and I cant run on that track til I solve this effing bugger of a problem!

Partial Post: Please Login or Register to read the full post.

[MCL968]

That could be the problem. Radiators are pretty available for these cars. I have one with a leak in one of the tubes that the shop said they would weld up for around 30 bucks if you are in a jam.

Partial Post: Please Login or Register to read the full post.

[MLB]

Thanks MCL.

I have no problem buying a new rad, but it would be nice to get an actual 968 rad where I dont have to plug the 951 turbo port, and worry about it leaking which a number of people have complained about if you get Porsche's crappy plug. I would plug it using a short section of rad hose just big enuf to take a hose clamp and a stout metal cap/plug.

My understanding is the 951 is the defacto substitute for actual 968 rads nowadays.

Anyone know of a surefire way to get the right one, or maybe those are much more expensive?

 

Thanks for all the replies everyone!

Partial Post: Please Login or Register to read the full post.