My 98 Venture redlined one day at -8 outside. I had the thermostat replaced (wishful thinking) and the temp gauge continued to rise and fall. I took it back to the mechanic and they said that it needed to be bled. After doing so the temp gauge still rises and falls, but doesn't redline anymore. I read that if it's the intake manifold gasket that I would have oil in the coolant. I don't, nor am I leaking anywhere. Another mechanic told me it was the intake manifold gasket and quoted me 1800.00. He claimed that combustion was being injected into the cooling system and the cause of the rise and fall was an air pocket. A third claimed the same thing, though neither mechanic even looked at the vehicle. I have driven it accross town and it never overheated. I parked it of course hoping to do the repair myself as the vehicle has 145,000 miles and hardly warrants an 1800.00 repair. Could this be caused by anything else? Could it be that the thermostat was bad and they simply didn't bleed it enough? I am not looking foward to working on this thing, it looks awfuly cramped in there.

Intake gaskets are a prone to leaking, but especially on a van I wouldn't rule out head gaskets either

I have found the magic nummber to be 153,000 k but hey, you never know. Do you have a gasket issue, hell yes, GM never built a 3.1 or 3.4 that didn't have a gasket issue. $1800.00 ? I'll give you a hell of a deal,I'll do it for $1700.00. J/K No dought you need it. Shop it out REAL GOOD!

I've seen the problem with the intake gaskets start around 60,000 miles,( mine was at 62,000 miles) and I've seen some close to 200,000 miles with the original gasket still intact. If you shop around, you'll find the price can vary greatly and is generally less expensive. Prices at independent shops are around $600 to $1000 generally,depending on what else needs to be done.

definetly intake gaskets . not head gaskets yet. don't take it to a gm dealer to get them put in.they will eat you alive on the labor. erratic temp gauge a dead give a way for blown intake gaskets. fair price for just intake gaskets put in $600.00 as it takes 6 hours to get to them and 6 hours to come back out of the motor.