88 350 TBI cold start stumble.

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Steven Petersen

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I just warmed it up again to operating temp/thermostat open with the radiator cap off. The coolant dropped like normal, but it goes into a surging cycle. Every ten seconds or so it will purge out about a pint of coolant. I let it run for about 20 minutes with the thermostat open and cap off. This air purge never stops. Is this an indication of blown head gasket, or a faulty thermostat?
 

Schurkey

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I'd think compression is leaking into the cooling system. I don't suspect the thermostat if the scan tool is showing relatively stable temperature.

Pull the plugs. If compression is getting out, coolant may be getting in. That should show up on the plugs. You'd know for sure which cylinder head to remove.

'Course, I'd do both heads just to assure that the other side didn't pop a month from now.

Most likely a head gasket--but it could be a cracked casting.
 

Steven Petersen

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I'd think compression is leaking into the cooling system. I don't suspect the thermostat if the scan tool is showing relatively stable temperature.

Pull the plugs. If compression is getting out, coolant may be getting in. That should show up on the plugs. You'd know for sure which cylinder head to remove.

'Course, I'd do both heads just to assure that the other side didn't pop a month from now.

Most likely a head gasket--but it could be a cracked casting.
I’m noticing now that it does seem to smoke white excessively. I thought it was just the cold weather but now that I look closer it does seem excessive. But no sweet smell. And no milky oil on dipstick or under oil cap. I just changed the oil about 2 months ago and there was no water in the pan. I will pull the plugs tomorrow and take a look. Could it be intake manifold gasket?
 

Steven Petersen

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I’m really suspecting intake manifold gasket on the back side. There have been a couple times I thought I smelled coolant in the cab. Enough so that I pulled back the carpet by the heater core to make sure it wasn’t going bad. Never found anything. This could explain things.
 

Steven Petersen

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Leaking intake manifold doesn't pressurize the radiator.

Pulled the plugs cold.
 

DavidAlan

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I decided not to follow all these treads ,but will ask a simple question, if it stumbles and you have done everything humanly possible, now I will ask, have changed the fuel filter? or there could be bad fuel in your tank, dirt may have gotten into your fuel line, rust can be what cause your truck to stumble.
 

Steven Petersen

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I decided not to follow all these treads ,but will ask a simple question, if it stumbles and you have done everything humanly possible, now I will ask, have changed the fuel filter? or there could be bad fuel in your tank, dirt may have gotten into your fuel line, rust can be what cause your truck to stumble.

I changed it right after I purchased it a year ago. I still have a new EGR valve and MAP sensor ordered. If neither of those fixes it I will try another fuel filter. It’s possible the tank is full of crap. The vehicle was hardly used the last 30 years.
 
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