hey everyone,trying to help my buddy with a problem. He just picked up a 5.2 1500.long story short, shortly after truck over heated and was shooting coolant out of the exhaust.took motor apart and one of the heads was cracked. But there was also about a half a dozen knicks on the piston from the plug and the plug was bent so there was no clearance. he said there was no washer on the plug but i dont think that would bring it down far enough to hit the piston and other plugs are same kind and no other nad ones. im thinkin its maybe the rod bearing or something? not really sure but thats the only thing that would make sense to me. also wondering if by the piston hitting the plug multiple times the impact is what cracked the head? otherwise i dont see a conncectionbetween the both. What are your thoughts?

 

Heads on these trucks were prone to cracking in any event. **** poor castings.

Verify that the plugs that are installed are the correct plugs for the motor. Also check bearing clearances on that rod....... see what you find.

 

yea i know the heads crack easily or commonly on these but maybe its just a coincidence it happened at the same time?also the plug being too long is the first thing i thought of but if the other plugs are the same i would assume more than one piston would be damaged

 

The missing washer may be the only difference that it needed.

Where was the piston hitting the plug? On the threaded portion sticking into the cylinder?

 

yes the tip was bent into the threads so the clearance was negative. i didnt think that the washer would bring it that close to the piston but maybe. Also i would assume that it woulda been hitting since day one when the plug was installed without the washer. He has driven it about 1500 miles and it was runnin prestine before this.

 

Some of the clearances are pretty tight, so, that washer may have made the difference. Check the rod bearings...... see if they are sloppy. Was the engine knocking at all? (aside from the piston hitting the plug?