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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Diesel Engine Discussion => Topic started by: Irish_Alley on September 30, 2017, 09:47:51 PM
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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?
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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.
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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.
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well still have the same issue. i have a set of electrical fans that im going to try and see what happens.
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Sounds like a head gasket still.
Could be a blockage somewhere to though...
Oils and coolant all clean, no sign of contaminants or mixing?
Sent from my SM-S920L using Tapatalk
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I'm sorry I made you pull the pump, it is part of troubleshooting it though. At least it wasn't expensive.
Ok, so sitting there idling from a cold start up, will it push coolant out of the radiator with the cap off? Can you observe the flow in the radiator or does it violently spray at you?
The thing that gets me is you lose heat at the defroster in 10 seconds of idling. That's either a flow issue, a hot spot that is boiling the coolant away from that area, or a crack/blown head gasket pushing the coolant out of the area. But you have said it will pull all the coolant it pushed out back in the engine once cooled.
Was this a fresh rebuild or used engine? Any plates or baffles in the intake, turbo, or block that could have failed and is letting coolant bypass an area?
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Can't really see flow due to how the hoses are setup. The heater core hoses don't return to the radiatorfan just back to the water pump. Not upset about the water pump, needed to eliminate it anyway. I've let it ideal for half hour without it overheating.
There's no coolant going to the turbo and it's an old motor. Don't think anything could be letting coolant bypass.
The supply line to the heater core is the last opening before the radiator return.
I'll check the oil for contamination again but I know right before I had this issue it was good.
I ordered a fan clutch but not sure if it will fit. The one that's on it kind of resembles a gm fan clutch. If it is I have a flex fan I can toss on it.
If I start the motor cold it can sit there without the cap on for sometime before coolant is pushed back out. Never timed it.
This thing is very confusing.
Loosing defrosters after sitting for 10 seconds is what getting me but it might be because a gallon or so is sitting in the overflow. I think this is the first time ive had the overflow working but there is bubbles coming to the overflow tank even after shutoff.
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instead of pulling the water pump, pull the hose off the bypass port and put them into a container
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when you say bypass port, you mean the where i have the heater core connected at? i have a couple other ports but those are the only ones with hoses on them and no plugs
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just a small update, finally got around to getting the cummins from my moms to my house. unhooked the turbo so it was pushing 0 PSI and no overheating issues. hopefully this week ill get a chance to pull the head and replace the head gasket. have an OEM gasket sitting on my shelf in the garage
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so replaced the head gasket and been driving her again for the past few days with no issues. also finally got around to putting the cowl hood on. i know it would look better with a paint job but that will come soon enough. it almost seams as if something on the roof is missing. vile you have any suggestions? ;)
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It's all you man
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lol, perfect. now to find a place that sells them
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Just steal it off the Napa truck. I've done it lol
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i think theyve caught on to that around here, cause napa doesnt sport them anymore. i think the last straw was the guy who every year has one on his demo derby car. granted its free advertisement but i think it also led to more people wanting one for themselves
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Guy pulls up to deliver parts, leaves, comes back 20 minutes later, "Did you guys steal my hat again?" lol
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Classic lol. Love the part about "again" cause one is never enough