Need advice on a 6.9 purchase

SamSuhl

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Hey everybody I'm new here and in need of some guidance. I found an '87 6.9idi with 180K miles on it. The owner says that it has been bubbling coolant in the reservoir tank. He says it doesn't matter how long the truck runs for (meaning hot or cold it will do this) and says that the pressure only lasts 10 to 20 seconds then stops.

He is guessing head gasket or head. I am guessing head gasket, but my knowledge is limited.

I'm just concerned that it could be cavitation. How likely do you guys think that would be? I know the 7.3 was prone to cavitation, but was always under the impression it was less likely with the 6.9.

Please let me know what you think!

Thanks,
Sam
 

Philip1

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The 6.9 didn't have the cavitation issues unless it was bored out. The most likely cause of the bubbling coolant would be the head gasket. I know there was a point during the transition between the 6.9 and 7.3 where it was labeled a 6.9 but was bored out to the 7.3 bore. The easiest way to determine if this is the case would be if it has 7.3 parts such as the ip gear cover and glowplug controller. The bored out 6.9 would have the possibility of cavitation similar to the 7.3
 

Knuckledragger

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Your information is correct, the 6.9 had little reported cavitation. A head gasket job is probably in order.
 

SamSuhl

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The 6.9 didn't have the cavitation issues unless it was bored out. The most likely cause of the bubbling coolant would be the head gasket. I know there was a point during the transition between the 6.9 and 7.3 where it was labeled a 6.9 but was bored out to the 7.3 bore. The easiest way to determine if this is the case would be if it has 7.3 parts such as the ip gear cover and glowplug controller. The bored out 6.9 would have the possibility of cavitation similar to the 7.3

Would this transition period likely have been '87? I think '88 was the start of 7.3 (not positive)

Your information is correct, the 6.9 had little reported cavitation. A head gasket job is probably in order.

Any ideas on how I could confirm head gasket over a possible cavitation issue on-site without a teardown?
 

lotzagoodstuff

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You could pressurize the coolant system and see if you can see how fast and where the pressure goes. If it hasn't put any coolant in the oil, it's probably a head gasket.

Good luck
 

SamSuhl

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You could pressurize the coolant system and see if you can see how fast and where the pressure goes. If it hasn't put any coolant in the oil, it's probably a head gasket.

Good luck

He did say the oil was free of coolant and coolant was free of oil. Seemed like some good signs to me? How do you mean pressurize the coolant system? Just run the truck or are you talking some sort of pressure test. Sorry I'm limited on knowledge here, I just pretend to be a mechanic on my own stuff lol
 

Philip1

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Would this transition period likely have been '87? I think '88 was the start of 7.3 (not positive)



Any ideas on how I could confirm head gasket over a possible cavitation issue on-site without a teardown?

'87 is the transition year that has the modified 6.9. If there is no coolant in the oil, chances are slim of there being a cavitation issue.
 
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