Cooling system problem (searched)

[book-ends]

Hello all,

I did a search for water pump related posts, but I didn't quite see what I was looking for. Over the last few days I have replaced both upper and lower radiator hoses, thermostat and radiator (just did that today). The car was overheating at idle and coolant was going everywhere from a crack in the radiator.

So now that everything is together, the car is still overheating at idle!! If you rev the motor to about 4000 PRM, the coolant temp drops immediately which leads me to believe that it's the water pump......

Can that be right? If the water pump is failing, why would it just be at idle? Blasting down the highway at speed isn't a problem at all so I can assume the fluid is moving through the system......

Any insight by early tomorrow morning would be greatly appreciated!

P.S. - I have a 91 240 KA24DE

[loco240sx]

when is cool before you start the engine .open the air relief plug located at the end of the upper radiator hose (10mm)on the intake manifold then open the radiator cap and fill with coolant .bounce the car by pushing it down until you see the coolant coming out from the relief plug .fill the reservoir tank to max level .install radiator cap ,relief plug ,reservoir cap and start the engine .race engine 2 or 3 times under no load.stop engine and cool it down then add coolant as necesary.

[book-ends]

Uh,

Thanks, I guess. I know how to flush and fill the coolant system. It's not that it's empty, it's a broken pump......I assume. I just don't understand why it overheats at idle and a simple rev gets it to cool down........

I can only assume that the pump is sticking at sub-1000 rpm levels.

[eddiec]

sounds like you want to replace the pump. then do it. if not then take it off and look inside. any corrosion? does the impeller look to be in good shape? replace as neccessary. could be you have corrosion and buildup else where in the system. or maybe you still have air in the system as well.

[book-ends]

Okay,

First of all, thank you both very much for the info. I pulled the old pump out and it was in top shape. The bearing hadn't seized nor was there any build up that I could see. Of note was that the NAPA pump, while cheap, just wasn't up to spec with the OEM unit.

I put everything back together and it didn't overheat at all. It really must have been a bubble in the system........or else a mystery. The thing is, usually a bubble in the system results in cool air when set to hot in the cab. I was getting very hot air when I asked for it........hence I threw out the air bubble cause.

Oh well. Thanks again.

[Ubernoober]

The air bubble may have been trapped at the thermostat. The heater core is fed from the block, so a closed thermostat would not have clued you into the bubble.

[xero1]

hook up a scan tool and look at how much degree the ecu is reading, if its not the same as your gauge is reading replace the gauge or you could have a wire problem