Been trying to figure this thing out for a couple of weeks. It's overheating at high RPM's.
Last week I messed with it and had it idling in my driveway for 4 hours with no overheating. There was some air in the system and I was bleeding it out. I was pretty sure I had all the air out of it. He drove it 2 miles to his house and said it pegged the gauge and was puking water when he got home.
It acts like it's not getting enough coolant flow. We've replaced the thermostat, waterpump, bypassed the heater core and replaced the radiator. Lower hose was replaced a few weeks ago.
I had him do a compression check the other day while I was at work. Came back with 90 to 95 on all of them. I'm not sure what to make of those numbers. All low... but equally crappy. The car is a wore out POS... But unless both head gaskets are leaking on all cylinders I'm thinking the head gaskets are good. Well, there is some oil leakage in spots but as far as the overheating is concerned I don't think head gaskets are the problem.... hoping....
No coolant in the oil. No coolant smoke from the exhaust. I asked him if there was a spring in the lower hose he put on and he said no. I tried revving it up to see if it was collapsing and it didn't. But that was just sitting in the driveway at 3000-4000 RPM for less than a minute, don't know how to check that on the highway.
Through this whole process we've been constantly bleeding air out of the system... and it never ends! I don't think we've ever opened up the bleeder and got a steady stream of coolant.. well, water. I think maybe we aren't purging it correctly or something.
I know the system has to pressurize to cool properly... and it can't pressurize if you're constantly opening it up to bleed air or add water.
That 4 hours in my driveway last week... literally nothing but adding water and bleeding air out. and I'm still not sure there wasn't air in it. And no leaks. One of the small hoses under the throttle body was leaking a few weeks ago but we replaced both of those hoses and the lower radiator hose then. No leaks since then.
Crap. Just remembered an article I read the other day about head gasket leaks that allow exhaust to be pumped into the water jackets.... Wouldn't that still show as a drop on one cylinder in a compression check though? Is the compression just so crappy that a leak in a head gasket goes unnoticed?
I don't think that car is worth the effort of changing the gaskets... but it's the only one he has... hell, it's not worth the money I fronted on parts today. I'd tell him to get a bicycle but I remember how many tubes I replaced when he was a kid.. wouldn't be much cheaper.
2004 Pontiac Grand Prix GTP
1990 Trooper 2.8 V6 Auto (Wrecked... sent to the crusher)
1993 Shortbed, regular cab Z71 (Donated to step-son #2)(deceased, parted out)(Forums for GM and fullsize 4X4s suck... so I'm still hanging out here)
1965 Ford Fairlane 500 Sports Coupe 289 & 4 speed (some assembly required)
1968 Kaiser M715, Chevy 350/700r4, stock NP200 and 5.87 gears... prepping for Ford 390/T-18/divorced NP205 transplant.. .just because.