washington951

hi folks!

recurring problem. cooling system gets bled, is fine, then develops air bubbles again.

have changed the cap (will double-check - may have one that is of lower than adequate pressure) with slight improvement, tho.

car runs at or just above the first white mark at highway speed, but will quickly rise to the 2nd white mark upon exiting/stopping unless engine is revved. when its revved, temp immediately drops - consistent with air in the system - along with that gurgling sound under the dash!

car runs great - feels like full power - AFM dithers/reacts properly. no white smoke (that i can see) and only exhibits a bit of black smoke with WOT/full boost condition...which is fine - just means i'm not going lean...22-25 mpg on extended runs (just did 2 days/1200 miles with 80mph moving avg)

not dropping any coolant while parked and the system seemed to pick up air into the cooling system while recently sitting in storage for 2 months. it does shoot some small black 'dots' of liquid from the exhaust upon startup sometimes, but i think this is due to the test pipe and running a bit rich...

plan to do the following:
check the cap to make sure i have the correct one.

get a pressurizer and pressurize the system to ck for any leaks. (any specific places to check - tips on pressurizing??)

inspect spark plugs - what should i look for to indicate a head gasket failure or is this out of the question given the way its running - or how can rule in/out a head gasket failure???

i'm a bit confused here (obviously) and the only related condition that i can even come close to thinking of is the fact that my A/C drain seems to have a partial obstruction which causes the a/c to gradually lose its efficiency over a very long run. after parking the car (even for 10 mins) i get full cooling back - for a time...the a/c continues to drain for a LONG time when i finally park it. it dribbles out over night. i plan to attack this by removing the center console and going in that way - i've already tried numerous times over the last couple years to clear the drain tube from the bottom - i guess i've only been partially successful!! time to get serious (but i doubt this is related by my coolant/air issues...) i guess the reservoir just gets full due to the partial obstruction and it just can't move as much air....it starts out REALLY cold - i just want to keep it this way! i think that the ONLY way this could be related is thru the heater valve - maybe...doubtful, tho.

thanks tons everyone!!

ERAU-944

check your oil! my roommate developed bubbles in his tank in his 951, turns out his coolant was going into his oil... yikes! cooler seals... no fun! he did a head gasket too for fun

-Michael-

washington951

ok - i'm due for a change, anyway - i guess it'll be obvious, right?!

ERAU-944

yep open the filler, if you have chocolate mousse in there, happy cleaning, and have fun with the oil seals... we found out a few weeks after his started... at a gas station. he checked his oil and found chocolate milk, then drove it home and that was that.

-Michael-

washington951

ah - just topped up the oil today (was on it pretty hard during a few stretches the past couple o days!) dry as a bone and clean on the inside of the filler, but i didn't look down IN it, but i'm assuming it would foam up and i'd notice it. i DID notice that it was 'normal' tho...
thanks for the notes michael - keep em comin!!
oh- btw..on our way back this aft, noticed a porsche factory hauler, an alex job hauler and a mercedes hauler - was there testing at sebring?? they were all on the FL turnpike headed north...

ERAU-944

yeah, we noticed after he turned his car off he was getting bubbles in his brand new coolant tank, and disappearing coolant. didnt figure out for awhile where it was going. this was after installing autothority chips, and driving the car hard at an autocross. as for just plain bubbles in the coolant, i'm not sure best i can say is raise the front of the car on ramps or something, open the heater fully, and run it for awhile. then bleed the system. seems to work most times. the temp your car runs at seems to be normal. have you noticed any disappearing coolant? or just bubbles as you say from an unbled system?

-Michael-

washington951

hhhmmm - not seeing any loss of coolant that i can detect. but honestly, its hard to tell for sure as the air in system plays havoc in the indicated level in the overflow tank, ya know? but no...i don't think i'm losing any coolant - just gaining bubbles! but i'm inclined to think that if air is getting in, that means that coolant is getting out!!! i'm gettin' good at bleeding - or i thought i was!!

ERAU-944

to bleed you need to make sure at the very least that the heater is full open. if not you'll always have bubbles in the heater core. helps immensely to have the front of the car raised too. if you aren't losing coolant then dont worry about it. the only thing i could think of really is that your head gasket might be *slightly* blown leading to air going into the coolant system that way. do a compression check, see what you come up with.

-Michael-

Charlotte944

Check your plugs! I had a leaking head gasket on my '84, and #3 plug was consistantly cleaner than the other plugs were. When the head gasktet finally failed, it failed at #3 cylinder.

washington951

cliff - thanks - i'll add it to the list!

Mike S

GROUNDS!!! Check your grounds!!! I had what appeared to be air bubbles entering my cooling system. I'd bleed it out and everything would be fine, then after a brief bit of driving the temp gauge would start bouncing and going up. What was actually happening was that my grounds were bad and when the cooling fans went on the load got too much for the crappy grounds to handle. Go down to the store and buy a $5 ground. Add it from the engine near the wastegate to the rear control arm mounting point. You could also run one from the motor to the drivers side headlight area. It's a cheap and easy test.

crushingday

Checking the grounds is a good Idea to make sure the teperature reads accuratly. But could the ground have anything to do with actual coolant loss?

I ask because I am having the same problem.

C5Driver951

This sounds an awful lot like a failing headgasket. I had similar symptoms in my first car. It would only do it under boost, however.

I think you really need to pressure check your cooling system. You can also pull the cap off of the reservoir and check for bubbles. This is another sign of a blown headgasket.

Autothority chips have a history of causing blown headgaskets, especially with manual boost controllers that don't tail off the boost.

washington951

interesting joel. pressure checking is first on the list this week when i get time. i appreciate all the input and help - when i get time to track this down, i want to be able to blast thru a bunch of different tests all at once. i REALLLLLY hope its not a head gasket (obviously)...

mike s - i'm good on the ground dept. - i've got the ice shark supplemental ground (along with the full-boat headlight kit) and don't seem to have any other ground-related problems...i wish it were that easy!!

thanks

C5Driver951

Brian,

I hope it's not your headgasket too. BTDT three times. If you do have to do it, get new headstuds preferably Raceware or an equivalent.

It looks like you have the capability to look at you fuel/air ratios. Are you running lean?