The last few days our '02 venture has been running hot off and on. I've made sure the system is full of dextron and bled out. The reservoir is full when hot.This morning I let it idle in the yard. After 15 minutes the temp had climbed to 3/4 mark and the fans kicked into high. The hoses were both warm with the upper being a little warmer but not so much I couldn't hold onto it. That dropped the temp momentarily but then it continued to climb to the last mark before the red. Then I took it for a short drive. As soon as I accelerated down the road the temp dropped to what I would consider a normal range for driving and stayed in a range of 1/2 or lower as long as I drove. When I returned to idle the temp climbed again to the upper mark before the red. all this time I didn't get any heat out of the heater or defroster.
The intake gasket was replaced about 15,000 miles back and I don't see any obvious signs of leakage.
I've read alot about problems with this engine, but I'm not sure where to start looking for the problem on this one and I don't want to break the bank by just replacing things until I get the right one.
Any ideas?

 

Well first check your thermostat you can take it out and test it in a boiling pan of water make sure it is opening and closing properly. it should open when you drop it into the pot of hot water and close once it cools down when you take it out if this is not occurring then replace. Have you burped the coolant System? (letting it run with out the radiator cap on and letting thermostat open and close several times). is it possible that your heater core could be clogged?

Hopefully this gives you a hand im not very familiar with the 3.4 motor but plan on learning as i just bought a chevy venture. I'm coming from www.probetalk.com. That is a very good community and i will try to bring that experiance with me because i dont see people getting allot of help good luck