On a recent trip I fubared my motor, lots of white smoke, engine missing and blowby.

Pulling the head off showed a loose valve seat which in turn held open the valve and kissed the piston on #5. Also the turbo was shot, impeller moves in and out over 1/4 inch but no side to side play.

Pulling the #5 piston showed some scuffing on the piston. Cylinder wall still shows cross hatch but there are some vertical streaks that I can see but not catch a nail on or feel. Rings were ok.

Trying to decide if I can do a light hone and just replace the piston, rings and head and turbo.

Could a bad turbo cause boost pressure to escape past the seals and into the crank case?

 

You're not describing anything unusual about the piston or cylinder wall. I wouldn't hesitate to hone it and install a new piston.

 

No on the turbo seals. It sounds as if you just dropped a valve seat and took out the piston. Hone it out, through in a new piston, and replace the head. The turbo may be O.K. if the turbine is in good shape. From memory, some in and out play is normal, up and down is bad. Check the compressor housing and see if the compressor wheel has made any contact. Try to put an 06 head on it. Much better flowing head and better seats.

 

There is WAY to much in and out movement on the impeller. Over a 1/4 inch. Some wear on the impeller fins as well.

Already have a new head from Cummins from another project that didn't pan out. It should have the better seats.

I'm pretty tempted to just put in another piston. Just wish I had an explanation of where the blowby was coming from.

 

Clay.

The hone job should work fine, as long as the cylinder is in otherwise good shape. Check the condition of the rod, and replace the valve seat and valve, or the head if required, piston, rings and rod bearing shells in that hole.

Excessive blowby can be caused by a bad compressor seal, and/or excessive shaft play in the turbo. It lets compressed air into the oil return, and shows up as blow-by gases. To the point I have seen engine oil coming out of the vent tube full stream on some larger engines. There are people who will tell you it isn't possible, I am here to tell you it is.

Good luck with the rebuild man, engine trouble sucks

On edit, turbo radial play is normal when there is no oil pressure present, but axial play ( in and out) is a BAD thing. That is when the wheels start hitting the housings, and it really goes downhill from there. In and out play is a sign of a bad thrust bearing in the turbo, a small amount of radial ( up and down ) is normal when not running, due to pressurized oil being used as a liquid "bearing" as such.

 

Thanks for your comment, make me feel much better.

I'm going to try a new piston and rings. I already have a new head here from another project so the cost is fairly minimal, mostly just my time.

 

+1. Your assessment is spot on. End play in and out on the turbo shaft should be non existant. Side play is ok. The turbo shaft bearing is a floating bushing that spins in the housing and spins on the shaft as well. This means there is an oil film clearance on both sides of the bearing which is why it feels loose when not running. Once oil pressure is there the bearing centers itself in the housing and centers the shaft in the bearing . Bad turbo seal can be a cause of blowby, it is not unheard of.

 

Oops, i typed it backwards. In and out play on the turbo shaft is bad and some up and down play is O.K.

 

I have to disagree. The new rings in the cylinder will never seal properly unless the block is rebored. Your cylinder hone on the end of a drill is NOT a reboring machine. Worn piston bores tend to have ovality and this can be confirmed with a an inside micrometer. Just honing is a very small bandaid fix to a large problem and it will fail real fast. As for blow by, the scuffed cylinder is increasing your blowby by leaps and bounds. That cylinder which has around 350psi per piston stroke and is leaking about 150 psi per second to your crankcase is causing the blowby. Think of inflating of a tire with a major hole in it (scuffing). As you put the air hose to the tire valve, you can feel, hear and maybe see the air leaking from the tire. This is what is happening from your motor except at a lot faster pace. Check a manual for turbo end play. A 1/4'' feels like that but upon checking with a dial indicator, may only be 40-50 thousandths and with in limits.

 

I don't think the bore is worn. I'm not trying to do do a re-bore with the hone, just take off the glaze so that the rings will seat. Its a pretty common practice but you are tight, you'll never correct a ovaled bore with just a hone.

For the turbo its definatly got atleast 1/4" of in and out play. I'm HD mechanic by trade and do tons of diff setups. I know what 1/4" of slop feels like and this definitely has it. The impeller show wear.

The engine went back together yesterday with a new piston and rings, honing of the cylinder, new head, new gaskets, used turbo(this one is tight in/out and side to side).

Hopefully I'll be able to get running in the next few days.

 

Fired the truck up last night. Sounds good no weird noises, blowby is back to normal from what I can tell. Didn't get on it hard as there is a problem with the fuel system. Engine starts to bog and cut out with I get past about 1/3 throttle.

Any thoughts? No loose lines that I can see. Usually if there is it makes a big mess. I didn't undo the supply line to to filter bowl or injection pump so it shouldn't be sucking air.

I wish my Edge gave fuel pressure like it did on my old '01.

 

My bad, the plug on the FCA wasn't seated all the way. Running good now.

How many kms do you think that new piston needs to seat in before I start to turn the Edge up again?

 

The turbo seal, if leaking, can put pressure in the crankcase.
Drive pressure--maybe 30-50 psi.