So the other day after driving around, i pulled in the driveway, shut the car off and it started pouring coolant all over. It eventually the stopped and i opened the overflow tank under the hood and it was full to the top. Soit was overfilled, no big deal. I took it to the shop and they drained the fluid and put in new coolant in the right amount. After that it seemed ok except for when i stored the car a day later, i noticed a small puddle of coolant under the motor, after 5 days of being parked, but it leaked out then stopped, same as before. So i took it back again, they pressure tested it and it turned out fine. I got it back today and parked it and again a small puddle, but then it stops after a little bit. Anyone know whats going on?

Thanks

 

fresh fill, its possible its just pushing out a small amount. I would keep a very close watch on the coolent tank and watch its level. Let the car cool totally and see where it is, see if it goes down. If its just slightly to much or overfull any it will stop leaving a spot and the level will stabilize. Unfortnatlly the Northstars are known to have headgasket problems and you may have one, it wont alwasy show up on a presure test. But if your lucky it will stop and it was just not filled quite right. you may even have a hose connected oorly, when its cold and the hose isnt as soft as when its hot it wont leak and then when it all warms up it will.

keep an eye on temp, coolant tank, and watch oil level.

 

The temp gauge stays at half and the car runs fine, no signs of overheating.The oil seems to go down a little bit over a while but not bad, although I heard the northstar goes through oil faster than a different motor.

 

I am not undrstanding the highlighted part.
how can one overfill past the top?

Did the mechanic "burped" the system after servicing?

 

it was over filled and when pressure built up it came out the cap or some place. i dont kno how there was still to much in the tank but there was after i opened it so im guessingthere was to much to begin with.

 

By your login name I'm guessing a 99 STS, right? If so, this sounds like a ridiculously simple problem that resulted in hideous failure and my purchase of a beautiful car for $2000 with leaking radiator, bad water pump and blown head gasket.

It's the darned reservoir neck and cap! Remove the cap and patientlypolish the neck with 500 grit THOROUGHLY WET sandpaper wrapped around a block of wood or similar. Then replace the cap. The cap is the ONLY part I've found in stock at the local Cadillac dealerwhen I said, "I bet you buy them by the case" I got a smile...

 

Ok thanks for the help. But does it make sense that there was a puddle under the center of the motor? I just want to make sure I dont hav a bigger problem like a head gasket. But it sounds like the cap thing will fix it.

Btw what does polishing the neck do?

 

Polishing the neck ensures that you get a good, tight seal. Unlike every other car I've owned, the coolant reservoir is pressurized with its cap serving as the "radiator cap" as well. GM issued a service release for this very issue, including polishing the filler neck. Even after my water pump, radiator and head gasket were repaired, I'd get occasional coolant leaksalmost always after a long drive but for the life of me I couldn't find the source. After a good highway drive I instantly opened the hood after shutting off the car and saw quite a lot of coolant spurt from the cap to drain away almost instantly. Found the service relase, polished the neck and replaced the cap and the problem has not reappeared with the coolant level staying perfect for over six months. My best guess is that pressure would rise suddenly after shutting down the car with a fully heated engine causing the leak.

 

additionally, a dab of silicon grease on the seal will really make that seal tight.




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