1997 Pontiac Transport Overheating

[quote:792548bd0a="moneyman64"]I have a 1997 Pontiac Transport minivan with 161K miles on it. I have replaced the radiator, radiator cap, intake gasket, and heater core. The engine overheats after 15-20 minutes of driving. Someone told me that they removed the thermostat from their car and the overheating problem was solved.

Please help!

Ryan
El Paso, Texas[/quote:792548bd0a]

Are your cooling fans running when it overheats? Here are some of the things that can cause overheating.
Loss of coolant
Loss of system pressure
Low coolant protection
Incorrect belt tension
Timing retarded by malfuntioning PCM
Radiator fins obstructed
Cooling system passages blocked by rust or scale
resevoir hose pinched
cooling fans inop
Loose or damaged deflector
Thermostat stuck in closed position
Faulty water pump
Incorrect radiator
As for removing the thermostat, that will not eliminate your problem unless the problem is with the thermostat. The maximum coolant temp is not set by the thermostat, it is set by the cooling fans. Removing the thermostat will just make it take longer to reach its peak temperature. If you have a problem other than the thermostst, it will eventually get just as hot.

1997 Pontiac Transport 161,000 miles plus

I took the van to a mechanic. He tod me the fans were okay. He said he fixed something called a relay. I was on the road back home when the van started overheating again. The temperature gauge flucuated from one extreme to the other. The needle would climb to 210 degrees, then back down below 210, then back over 210. I can feel something slip as I accelerate...could that be a belt or is there something internal (drivetrain, transmission) that is causing the engine to overheat?

Loss of coolant - no

Loss of system pressure - don't know

Low coolant protection - don't know

Incorrect belt tension - maybe

Timing retarded by malfunctioning PCM - maybe

Radiator fins obstructed - don't think so...radiator is new

Cooling system passges blocked by rust or scale- maybe

Reservoir hose pinched - no

Cooling fans inop - don't think so...fans spin at a high rate of speed when engine is running...slow down after the engine is turned off and spin slowly, eventually stopping

Loose or damaged deflector - don't know

Thermostat stuck in closed position - don't know

Faulty water pump - don't know

Incorrect radiator - no

I am going to give my mechanic a list of the items listed above that I am not sure about.

Your thoughts? Thanks much.

Ryan
El Paso, TX

[quote:4f0784e3ff="moneyman64"]1997 Pontiac Transport 161,000 miles plus

I took the van to a mechanic. He tod me the fans were okay. He said he fixed something called a relay. I was on the road back home when the van started overheating again. The temperature gauge flucuated from one extreme to the other. The needle would climb to 210 degrees, then back down below 210, then back over 210. I can feel something slip as I accelerate...could that be a belt or is there something internal (drivetrain, transmission) that is causing the engine to overheat?

Loss of coolant - no

Loss of system pressure - don't know

Low coolant protection - don't know

Incorrect belt tension - maybe

Timing retarded by malfunctioning PCM - maybe

Radiator fins obstructed - don't think so...radiator is new

Cooling system passges blocked by rust or scale- maybe

Reservoir hose pinched - no

Cooling fans inop - don't think so...fans spin at a high rate of speed when engine is running...slow down after the engine is turned off and spin slowly, eventually stopping

Loose or damaged deflector - don't know

Thermostat stuck in closed position - don't know

Faulty water pump - don't know

Incorrect radiator - no

I am going to give my mechanic a list of the items listed above that I am not sure about.

Your thoughts? Thanks much.

Ryan
El Paso, TX[/quote:4f0784e3ff]

Usually the cycling you describe is caused by air in your intake. Of course this is usually associated with fluid loss. So, with no fluid loss, it may be the thermostat. Not holding my breath for that as a solution, but possible.
I would check to see if the water pump is pumping. If the water pump is pumping, and the fans are running, and the thermostat is open, then you are starting to look at an obstruction, or possible radiator has just become so ineffecient that it cant handle the cooling needs.
As for the slipping, that almost sounds totally unrelated. Unless the engine gets so hot that you have a loss of power, you shouldnt feel anything out of the norm.
Good luck

I had the same problem, replaced thermostat and water pump, and rad cap but still runs warmer than usual. I heard minivans and these in particular love to over heat. As well, I heard this problem is due to a dirty throttle body. I will clean it and see how it goes.