94 Gran Prix Cooling Issue

[MoDoggie]

I have a 94 Grand Prix with a 3.4 DOHC motor and the tempeature gauge fluxuates while driving. I just had the heater core line replaced and since then the temperature will go up to 210 or so then drop to 155 then gradually rise to 210 or so then right back down to 155 and this cycle just keeps going. Before I had the line replaced it would heat up and stay between 190 and 210 unless at an idle.

Any ideas?


Thanks

Mo'

[auxbar]

Did you bleed the air out of the system after you changed out the heater core pipe? Just a suggestion. I've heard that air in the system will make them act crazy.

[richtazz]

yep, it's either air in the system, or an intake gasket leak, both common issues on the 3.4 DOHC.

[jstower]

Originally Posted by richtazz

yep, it's either air in the system, or an intake gasket leak, both common issues on the 3.4 DOHC.

Same problem, I replaced the water pump and thermostat and tried to bleed the system with no luck, going to check the intake manifold gasket even though I replaced it 50k ago.

[MoDoggie]

Originally Posted by jstower

Same problem, I replaced the water pump and thermostat and tried to bleed the system with no luck, going to check the intake manifold gasket even though I replaced it 50k ago.

I also just replaced the intake gaskets less than 1k miles ago. I took it in to the shop and they checked it out and could not find anything. Mechanic though it may just be the gauge? He said they are built with a buffer in them and after a while they will go bad (216,000 miles on car now), so what I am seeing is the actual coooant temp as with the buffer it will hold the high temp so you don't see the gauge flucuate like it is now.

?????