[jpm53]

Hello everyone,
Just joined the forum and am hoping someone can help me with some info regarding 7.3 head cracks.

I am working on an 88 7.3 in an E-350 chassis which is a trash truck that I am trying to get running for my son's trash company. While replacing the injectors and glow plugs, I broke a pick while attempting to extract the injector washers and the broken piece went into the cylinder. Had thought about removing the heads anyway since it seemed to be getting air in the cooling system. Thought that the pulsating coolant with the radiator cap off might have just been caused by the cylinders expanding and contracting. Didn't seem to be a lot of air, just coolant pulsating so was going to do the injectors and glow plugs first and see how it went. But the broken pick in the cylinder made the choice to remove the heads for me.

I got the head off the side with the broken pick off (no small feat in that *!!!!## van chassis) and took it in to get magnafluxed in case a cracked head was causing the coolant issue. Magnafluxing showed two cracks, one in each of the two center combustion chambers starting in the intake port and running up through the valve seat of the intake valve. Had a spare motor that my son had recently purchased, so took the head off of it and took it in to be magnafluxed just to be safe. This head also showed two cracks in almost the exact same place as the other head.

Anyone know if this is a common problem with these engines, or is just my usual luck?

Have attached a picture of the second head. Don't know if yo will be able to see the cracks. Just pulled the other head off the spare motor and don't need to have it magnafluxed can see the cracks and took a look with a magnifying glass just to be sure. Cracks are virtually the same, two center cylinders in the intake seats

Sorry for the lengthy first post.

Thanks for any help.
Jon

 

[LMJD]

Anyone know if this is a common problem with these engines, or is just my usual luck?

No it's not a common problem with these engines unless the engine has been badly overheated. That's an odd one, 90% of the time a crack will be at the web between the intake and exhaust valves. (For better or worse, I'm somewhat of an authority on cracked heads, I used to work on a LOT of 53 & 71 series Detroit Diesels )

 

[oldrebuiltdodge]

No it's not a common problem with these engines unless the engine has been badly overheated. That's an odd one, 90% of the time a crack will be at the web between the intake and exhaust valves. (For better or worse, I'm somewhat of an authority on cracked heads, I used to work on a LOT of 53 & 71 series Detroit Diesels )

I have seen the cracks in the intake, but like you said, it came from a severely overheated engine. Even the natural gas fired engines I used to work on usually cracked in the exhaust, or between the two seats, like you describe. The hot fuel like natural gas was harder on heads, and valves than any Detroit I ever saw. We were doing good to get 1,000 hours out of a set of heads without rebuilding (valves, and seats). That hot exhaust would hammer the seats right out, and with solid lifters, the guides would go as well. When there wasn't any more adjustment, we would sometimes put washers under the rocker stands to get a little more run time. I've seen rocker stands so high up that the intake valve adjustment bolts weren't long enough any more.