73-87 Chevy _ GMC Trucks > Diesel Engine Discussion

issues with cooling system

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Irish_Alley:
So my 91 v3500 cummins has been acting up. i was spewing coolant to the overflow jug, thought this might have been from a bad radiator cap. replaced the cap and still have issues, then i still had issues with they system. replaced the old broken radiator and i still have issues.

the issue is i can drive to work (about an hour) with no issues as long as i dont stop. if i stop it will start to over heat, i can control this by moving. Ok this sounds like a fan clutch issue, but if i keep the rpms up (stay in second gear) and going 25 mph ill have no issues. after i noticed what i had to do to keep it cool i made it home with no overheating issues but half my coolant was in the overflow jug. also after it cools the radiator will suck all the coolant from the jug back to the radiator.

to me this kind of eliminated a cracked head/gasket/block cause if exhaust gases were present in the radiator it wouldnt suck back all of what was displaced. also when controlling the temp by keeping the rpms up the gauge would never read above 160 (about normal for this cummins). and if i sit still for 10 seconds without keeping the rpms up ill lose hot air in the cab defrosters.

monday ill probably get a coolant tester but the idea of the water pump going out keeps crossing my mind but anyone got any other ideas?

AZ4X4SQBDY:
In my years as a mechanic, I have seen 2 water pump impellers spinning on it shaft causing over heating issues so don't rule it out.

The first was a brand new water pump that made it overheat right after installation, it was obvious once we took it back apart. The second was a Japanese industrial engine with a ton of hours, it was found after we exhausted every other resource and days of screwing around with it. It acted exactly the same way as you described, it would run off idle for hours, when idling it would begin pushing coolant out.

Take an hour and pull the pump off.

Irish_Alley:
Took the pump off didn't see anything wrong everything was still together. Took the thermostat off and tested it and it was ok. I did notice the thermostat housing was somewhat dry. Thinking maybe there's an air pocket trapped.

Refilled the system and it seams like it's better IDK.

Irish_Alley:
well still have the same issue. i have a set of electrical fans that im going to try and see what happens.

1967KaiserM715:
Sounds like a head gasket still.

Could be a blockage somewhere to though...

Oils and coolant all clean, no sign of contaminants or mixing?

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