PlatonicSolid
OBS Enthusiast
89 GMC C3500 454 7.4L
The leaking heater core a year ago was the beginning of the end as the truck was driven with little coolant. Temp gage did not indicate a problem.
I flushed the system when I replaced the heater core and it seemed to run OK. It doesn’t get used much as it’s primarily a dump run – Home Depo run – pick up a ton of gravel vehicle. Maybe 1K miles per year.
Last September it started to stall at idle when warmed up. After my son borrowed it to pick up a ton of gravel it was stalling at idle constantly. To the point that I had to put one foot on the gas and the other on the brakes at every stop. On the highway it felt like it had a governor on it. I limped it home and it hasn’t left the driveway since.
It’s also leaking oil from somewhere and I saw white smoke coming from the left exhaust flange leak at startup.
The more I work in it, the worse it gets. It currently only starts and runs (erratically) when the engine is cold. Here’s a video: Link
What I’ve done so far:
• Replaced the alternator (actually took 4 alternators from Advance Auto before I got one that didn't fall apart. I now carry a spare in the truck at all times)
• Replaced transmission pan gasket + filter + fluid
• Replaced vacuum lines
• Replaced Throttle body with rebuilt + TPS + IAC
• Replaced gas tank and fuel pump
• Replaced distributor, coil, plugs and wires
• Changed oil and filter
• Fixed exhaust manifold flange leak by filling it with JB weld muffler cement (attempt to do a proper fix will break the manifold flange studs which leads to bigger projects than I want to tackle outside in the cold)
• Replaced O2 sensor
• Replaced coolant temp sensor
• Replaced left valve cover gasket (there was nothing wrong with it = not the oil leak source)
• Ran “Steel Seal” through the coolant system which solved the white smoke at startup problem. This process involved thoroughly flushing the cooling system yet again.
No visible coolant in oil. No visible oil in coolant.
Oil pressure gauge in this truck has always read very high = the gauge is always near max reading.
Only thing I can think of now is head gasket cylinder to cylinder breach. My next plan is to do a compression test to see if that tells me anything.
At this point it feels like I’m fixing the truck to death. Probably time to cut my losses as the truck is not worth installing another rebuilt engine in it. That would lead me down the path of replacing the entire exhaust system, all rubber bushings, all suspension components, …
The leaking heater core a year ago was the beginning of the end as the truck was driven with little coolant. Temp gage did not indicate a problem.
I flushed the system when I replaced the heater core and it seemed to run OK. It doesn’t get used much as it’s primarily a dump run – Home Depo run – pick up a ton of gravel vehicle. Maybe 1K miles per year.
Last September it started to stall at idle when warmed up. After my son borrowed it to pick up a ton of gravel it was stalling at idle constantly. To the point that I had to put one foot on the gas and the other on the brakes at every stop. On the highway it felt like it had a governor on it. I limped it home and it hasn’t left the driveway since.
It’s also leaking oil from somewhere and I saw white smoke coming from the left exhaust flange leak at startup.
The more I work in it, the worse it gets. It currently only starts and runs (erratically) when the engine is cold. Here’s a video: Link
What I’ve done so far:
• Replaced the alternator (actually took 4 alternators from Advance Auto before I got one that didn't fall apart. I now carry a spare in the truck at all times)
• Replaced transmission pan gasket + filter + fluid
• Replaced vacuum lines
• Replaced Throttle body with rebuilt + TPS + IAC
• Replaced gas tank and fuel pump
• Replaced distributor, coil, plugs and wires
• Changed oil and filter
• Fixed exhaust manifold flange leak by filling it with JB weld muffler cement (attempt to do a proper fix will break the manifold flange studs which leads to bigger projects than I want to tackle outside in the cold)
• Replaced O2 sensor
• Replaced coolant temp sensor
• Replaced left valve cover gasket (there was nothing wrong with it = not the oil leak source)
• Ran “Steel Seal” through the coolant system which solved the white smoke at startup problem. This process involved thoroughly flushing the cooling system yet again.
No visible coolant in oil. No visible oil in coolant.
Oil pressure gauge in this truck has always read very high = the gauge is always near max reading.
Only thing I can think of now is head gasket cylinder to cylinder breach. My next plan is to do a compression test to see if that tells me anything.
At this point it feels like I’m fixing the truck to death. Probably time to cut my losses as the truck is not worth installing another rebuilt engine in it. That would lead me down the path of replacing the entire exhaust system, all rubber bushings, all suspension components, …
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