1997 Pontiac Grand Prix Loosing Coolant

MLBPLAYA513

MEMBER
1997 PONTIAC GRAND PRIX
6 CYL
FWD
AUTOMATIC
120,000 MILES

Hi, my 1997 Grand Prix Gt had its upper intake plenum replaced at Pontiac Dealership about a year ago for the simple fact I heard it was a good idea to do so becuase of being know for its notorious failure and gasket wearing issues. Now my grand prix is loosing quite a bit of coolant and its not leaking anywhere. I checked my oil and it doesn't seem as if coolant is mixed. After researching, many people state they have had similar problems but said that if it was the lower intake plenum in which I have not replaced usually you would be able to see it leak from underneath somewhere and that it usually leaks internally if it is the upper intake plenum. I am now lost. My question is, could it be the upper intake plenum even after getting it changed a year and less then 12,000 miles ago? Could it still be the lower intake Plenum, even though I don't see any fluid underneath? And finally, could it possible be a head gasket leak? What could it be?

1 Reply

JAMES W.

MECHANIC
2,395 POSTS

Yes, yes and yes to all your questions. It could be a head gasket, but let's not blame them yet. These engines are notorious for coolant leaks between the intake manifold and the heads. Most times the leak isn't to the outside where you can see it. It's to the intake port of the head and is burned up in the engine and if the leak is small enough, you won't see it smoking out the tailpipe. I would have the cooling system pressure tested for leakdown. If leakdown is detected, the mechanic may have to pull the spark plugs to determine which cylinder(s) is leaking. Hope this helps.