First some history on the machine. I bought it 5 years ago. It had a blown head gasket when I bought it. I did not discover it till I had it shipped here to my home. The previous owner wrote in a log book the work he did to replace it and that it blew. He said nothing about it. I missed it as I had driven 10 hours one way to look at it and I was tired. My fault there. The dozer sat idle 7 years in his possesion after his repair and failure. I bought it, found the issue and repaired the head gasket and replaced a ton of stuff. Injectors, lines, had the head very lightly surfaced, corrected valve height, pressure checked, some welding on the radiator frame etc. The head gasket blew again in 20 minutes from start up. I do not recall retorquing the head bolts.
Fast forward to Yesterday and another head removal. While the first head gasket showed multiple grooves from pressure pushing it's way to the water jacket, this head gasket yesterday showed nothing obvious for where it blew. I found the head gasket was not centered on block as one of the guide pins is severly erroded and allows the gasket to shift on the cylinder liner. The fire ring had drifted off the liner land and was partially on the deck of the block. The manual states the head gasket should be centered on the liner to within .040 I am sure it was way out at this point.
Today looking closer and measuring I found the liner on number 4 was .006 low like the liner was tilted in the block. Please see the picture.
![Image](https://img.photobucket.com/albums/v201/Kaiserjeeps/JD450/DSCF5895_zpsqyedkcok.jpg)
The rear guide pin damage.
![Image](https://img.photobucket.com/albums/v201/Kaiserjeeps/JD450/DSCF5896_zpselsjrtn6.jpg)
My main questions are...
Could this mean my block might be cracked where the liner packing land is under the head gasket fire ring? and that the liner land might be broken away and in the oil pan?
The fact that the head gasket fire ring drifted out of position on to the block deck where the liner was .006 low, could this be the cause of the head gasket failure?
I have ordered new JD guide pins. This will help keep the head gasket where it is supposed to be.
One pin is fine and intact up forward. The rear one is badly erroded from coolant or water contact long term.. It is tapered, any advice on how to extract this? How tight are they in the block? I was thinking about welding a big nut on it and prying up with two prybars at the same time. It looks like a one shot deal.
The liner top ridge is .027 higher than the liner fire ring. A new head gasket is .055 thick. the liner is .006 low only between the black marker marks. If I keep the head gasket in the proper place, does the .006 low matter?
I also bought all new head bolts. I was told by two people that is why it would not hold a seal. Both of them heavy equipment mechanic's.
Any advice, thoughts, or ribbing???
EDIT: I forgot to add I put a precision straight edge on the deck of the block and was not able to get a .0015 feeler gauge under any part of it. So the block deck looks to be OK. The cylinder head also checked out good for warpage.