Guys, im having some trouble and its really beginning to annoy me. some background, I had to replace the water pump when I got the motor from a junkyard, because the pulley was bent. its a 6L LQ9. I got an aftermarket water pump from ebay, dont exactly remember which brand it was.

Problem Im having, is that when the car is warmed up, and im sititng idling, the temperature gauge starts to climb, if let sit long enough all the way up to the red zone on the gauge. The car doesnt overheat when its doing this, the 15 PSI pressure cap doesnt blow. One interesting thing, when the gauge goes up, lets say its at the 3/4 mark on the gauge. I can rev the car to 2000rpm for 2-3 secods, and the temperature gauge will come down instantly, to its normal operating temperature.

This leads me to believe that somehow the water pump isnt pumping enough at idle, letting the temperature in the head climb up and heatsoak the sensor, and flow at and above 2000 rpm is enough.

Also, it has done this identically with the stock thermostat, an autoparts replacement, without the thermostat, and with the hypertech 160 that I have now.

Does anyone have any suggestions? Does this sound like a bad waterpump / can a waterpump be bad like that? what else can it be? I called the dealer and ordered a GM water pump, should be here by the end of the week i hope... Also, I have the steam pipe going to the upper radiator hose...

 

ttt..

 

Sounds like a water pump to me. I had the same problems when towing w/ my silverado, the dealer said it was overloaded and that caused it however about 6 months down the road it got hot while idling in traffic, throttled it up and good to go. I'd do a water pump if it was me. Are you using a clutch driven fan? If so it could be that as well.

 

just to close this thread up, swapped in a acdelco waterpump today, and all is well. thanks guys, weird problem that nobody seen before, but the pump wasnt pumping enough at idle.