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Alright, I’m heavily suspecting the water pump at this point, I just want to see if you guys can confirm.
So the truck is running hot but not overheating now. It stays around the middle of the gauge at idle, then gets to and stays about halfway between normal and hot when driving. It moves around a bit depending on how hard I’m driving as well. Also after it’s warmed up the heat will work for a few seconds when I turn it on then it blows cool. If I turn it back off and wait a minute or two it’ll do the same thing.
So I’m thinking the impeller is corroded, at idle it works okay, but when the engine spins it faster it’s not able to move as much water as needed. Opening the heater core circuit just adds to the problem. This would, to me at least, explain why it was overheating so slowly before and why it’s usually okay at idle.
I should mention that I recently put in a 160 degree thermostat, this is probably why it’s running warm instead of overheating now. It’s a band-aid fix and will be corrected once I have the real issue fixed.
Let me know if this makes sense. Thanks.
Nodak, There was tons of rust in the coolant to be honest. I’ve flushed it out several times and there’s still a bit in there. I suspected the impeller may have rusted out as well. But the pulley on it feels tight, there’s no leaks from it, and from what I can tell I seem to have good pressure and flow. I tried pulling the water pump to inspect it but ran into some snags, I need specialty tools and more patience than I have left I think.
Interesting thought on the reversed belt set up, I’ll pull up a diagram and double check it in the morning but no one has touched the truck since we bought it and it’s ran fine until now. Still, never hurts to rule out something easy.
I’ve been burping it on my terrible Mt. Everest style driveway so I’ve got the uphill aspect covered. Must have been an air pocket though as after some more burping and driving it’s gone. And it doesn’t seem to be overheating now, it will keep a fine temperature while it’s in the driveway idling, but now when I take it out it warms up to about %75 of the gauge and just stays there the whole time.
So I’ve put in a new, verified working, thermostat today. Burped it some more. Will do it a few more times.
After more research I’ve discovered something… weird. On level ground and when pointed up hill the temperature is fine. When I go downhill the gauge starts climbing almost instantly. Around 15 seconds of significant downhill will bring the gauge from normal almost all of the way to hot. Go back up hill or level out and it stops climbing. Park it up hill and leave it running and the temperature starts falling within a minute or so.
I have zero clue why going downhill would be causing an overheat? Air pockets maybe, I’ve burped it again and again and I’ll do it some more. Any one have some ideas, I’m stumped?
Well the thermostat is brand new but there’s always a chance I suppose. I’ve got another one lying around, I’ll swap them out and see where we stand.
Radiator and heater core both flow water through them great. The heater core hoses feel even in temperature and pressure.
Bulging may have been the wrong word, the hose is in good enough shape, but there is a visible change between when it has very little pressure in it and quite a bit. It swells a bit but doesn’t inflate or anything like that.
By hand inspection the radiator feels even from top to bottom and left to right. The lower radiator hose is pretty warm and doesn’t collapse. And as mentioned when I pull the drain plug and force water through it flows very well. Nothing is blocking the radiators air flow either, there’s a condenser and tranny cooler in front but no obstructions.
I’ve been fiddling with it some more and I can confirm that it holds temperature just fine sitting still, I’ve even held the revs up for a few minutes and the temperature stayed put. It’s only when driving it that the temperature starts to climb. It blew the upper radiator hose off last time i took it out which surprised me, I’ve pressure tested the cooling system and found no leaks and the cap functioned as it should.
I’ve burped the cooling system on a pretty significant uphill slope several times now so I’m confident no air is in there. The first time it “over heated” it didn’t completely overheat, the temperature got to the upper end of the gauge and overflow boiled over. Every time since I’ve rested and cooled the engine before it got too hot. And it’s a big, old cast iron block. I’m not saying a warped head is impossible, I just don’t think it likely. Not ruling it out though.
Do these symptoms seem in line with a failing water pump? I feel like if it was going out it would be overheating at idle as well. I’ll try to pull it off tomorrow and inspect. From playing with the fan and pulley things feel okay and it isn’t leaking.