I just replaced water pump on engine after snaping water punp shaft. Now truck runs hot 250degreesunder load. When at a idle and easy driving runs normal or slightly hot about210 degrees .Under load, lower hose on rad to pump will colapse alittle.New rad and hoses installed and thermostat. Fan and pump rotates counter clockwise. I put on a normal pump. Looks just like old one. I don't need a reverse rotation on by any chance? Or could it be something else like head gasket? Dosen't seem to use water and none in oil either.

 

I don't quite understand the colapsing of the new lower heater hose... But it sounds like you may have a problem with the fan clutch not working properly. When cold, the fan should turn with little resistance. When hot, the fan should be engaged to pull air through the radiator and as such should resist turning to a certain extent.

 

I also have that same engine and replaced the water pump you may need to put a spring in lower hose to keep it from callapsing as far as the temp goes mine does the samething runs alittle hotter than it should.did you put an oe replacement thermistat back in it ?I recal it should take a 192/5 themistat..good luck..

 

I just woke up, so here's possibly a silly question. Is it possible to route the serpentine belt incorrectly and have the pump running in the wrong direction?

 

Clutch fan is working, air rushing in as normal when it engauges. belt is routed correctly and new belt.

 

Then I'm leaning towards the possibility of air in the system... I still don't understand the collapsing lower hose unless it doesn't have the internal spring as john has suggested.

As for the tstat, stock should be a 195*F stat which should result in a temperature in the range of 205-210*F under normal operating conditions.

Do you get nice hot air out of the heater when turned on?

 

It calls for a 195 thermostat, but sometimes its better to put in a 165.

Close to all the Chevys I have owned the Thermostat did not really kick in til the gage read 210 (delay for the t-stat to open and flow to start to cool). I have not tried on newer Chevys yet, but on my older ones (pre 95's) I core out the t-stat and run it open flow.

When you refilled the collent did you have your heater running too? (this helps in getting some of the air pockets out of the heater core area)

 

For the older engines, it is ok to run a 165 stat. On the newer engines, if the coolant temp doesn't go over 175*F in a preset amount of time, it will never go out of fuel enrichment mode and your mileage will tank. For the newer ones (96+), a 180*F stat would be as low as I would ever suggest going.

Most of the reason for the higher temp reading on the gauge is due to the location of the temperature sender. My Bravada will read 210*F on the gauge, but through my OBD2 scan tool, I see 193-198*F at the temperature sensor for the PCM.

As for coring the stat out, this may actually hurt the cooling efficiency of the engine and over time will result in an overheating engine if the outside temperature is not sufficiently cool enough to fully cool the water in the radiator. The reason is because the water in the radiator is not meant to be continuously circulating. If the hole you open up in the stat is too large, you may have overheating troubles on long distance drives in higher ambient temps.

On my '01 Bonneville SSEi, I run a 180*F stat with 3 1/16" holes drilled in the tstat valve. This allows a certain amount of coolant to be continuously flowing as well as increasing the wide open flow rate of the stat. But I also have my fan trigger points set to optimize this mod.

 

I don't have a spring in the hose. I will try. Thermostat is a 195 and working. I'm Leaning towards a flow problem could be air trap in system. Is this motor prone to air pockets being traped in motor?

 

I believe that you would need a reverse rotation pump if you are using a serpentine belt system...the older v-belt pumps were normal rotation pumps...