Leak Down with Head OFF
 

I recently pulled the head off my 5.9 12v and I was hoping to find a bad valve or bad head gasket well no surprise my My bucking I have doesn't look like it is coming from there. Gasket looked good. No bent valves. So a mechanic told me dump diesel in the cylinders and see if it holds. Well lets say cylinder 2/4 went down in about 2 hours 1/3/6 next day 24 hours and 5 48hrs. Any insight. Obviously it is not a scientific experiment but sounds like my rings are shot. The cylinder walls still have hatch marks in them and it is std bore. What you think. I also noticed that 4 out of 6 injectors that are new 1 month were covered in black crap 2 were as clean as the day i put them in.

if it were me.

replace pistons, rings and bearings
(check and make sure your cylinders are not out of round)

put marine pistons in, I would also put marine cooling nozzles in.

The leak down test is an old trick, you could put the head back on and do a compression check to really be sure what it is.

if you need parts, you can give Brice at BBD Performance a call or send him a pm.

Good luck

whats the mileage on the motor?

Can you elaborate? Why?

those pistons are .20 shaved eliminating the need to run a .20 over "marine" gasket = lower compression = more air = lower EGTS = more room for more fuel = MORE POWER :lol: and the marine nozzles flow more oil to the pistons

Leak Down
 

155,000 to answer your question. Doesn't seem like many but it was a construction vehicle and i'm not sure if it was left idle a lot. I bought 2 off them in a KILLER DEAL 700.00 for both trucks. 1 has a locked up motor with 350 on the clock regular cab. The other I put lower control arms on it and drove it home. It is an 2500 95 extended cab. Both are 4X4 Auto 2500 cummins Turbos. The other is a 94. Rotted pretty bad. I did find a broken valve spring before I pulled the head. I fixed that and still had a miss. When I pulled the head and checked the valves the exhaust valves are pretty nasty looking with deposit's on them PITS under that. But nothing bent. So since I have it apart I am thinking about putting rings in it.

when we pull a head off here, we have it decked and always run a cummins .020 marine head gasket.

Ok update. Took it to my buddy all my valves where leaking. Redid the valves hopefully it will help alot.... We will See....LOL

liquid test the head before you put it back on