Blow by and Low Mileage Tare Down Questions

[ChevellRCR]

I have an engine that has less than 2500 miles on it since rebuild. The engine was doing great but developed a lot of blow by around the 1800 mile mark. The It is a factory turbo engine. The CDR was new when this started but since then I have installed a catch can system from CDD and the problem has not gotten any better. It's bad. Pushing oil out every possible location and even lifting the dipstick. I figured it was a cracked ring and since my only regret from the engine build was not using total seal rings I decided to go ahead and pull the engine to investigate. What I found was disheartening... All piston rings were in tact and no cracked pistons that I have found yet. The only problem I have found so far is bearing, cylinder and piston scratching on number 7. Everything else looks perfect. It looks like something came through the oil system as there is rod bearing scratching, the piston skirt is scratched in a couple places and the cylinder wall has a couple scratches also. Please see the pictures. My question is... Where is the blow by coming from. I don't see ring damage but is the scratching enough to let compression of this magnitude by and if not where should I look next? Heads were rebuilt also but maybe a guide has developed a problem?

 

[ChevellRCR]

One last pic

 

[ROCK HARVEY]

First off, this sucks and I’m sorry it happened to you. I would check the cylinders to verify roundness and lack of taper, starting with #7. If the machine shop used on old worn out boring bar, it might be the right diameter at the top but a lot bigger at the bottom. That’s just the first thing that came to my mind, but hopefully others will chime in with more experience.

 

[ChevellRCR]

Thank you. Will do. I trust the shop but always good to check.

 

[IDIBRONCO]

The first picture looks like a lot of wear on the bearing for only 2500 miles. The next thing that jumped out at me was the spot in your 5th picture that shows a spot where the crosshatch has been worn off completely. That's not normal for an engine with 2500 miles. The scratching in the piston looks minor to me, but the scratches in the cylinder wall would have me concerned. Those look to be pretty deep compared to the ones on the piston. At this point, I don't really have any suggestions other than to check everything over very closely.

 

[ChevellRCR]

I agree with you. I am very concerned. The crosshatch is still there but the flash with the phone I was taking the picture with makes it look like it isn't. I am going over everything with a fine tooth comb. I think a piece of trash may have been in the oil galley after boring and cleaning the block as I am very keen on filtration. I even have bypass filtration on this truck. I hoping honing will take the scratch out of the cylinder wall. I dont want to have to sleeve or bore the block again.

 

[IDIBRONCO]

I wish you the best of luck.

 

[Cant Write]

It’s prolly my eyes, but the piston rings look like they are full of grit? That isn’t build up on the pistons already is it? I assume a simple brake clean spray would remove all that.....

I’m sorry to hear about your luck!! That really sucks, and I hope it’s salvageable and back together for a modest price.

 

[IDIBRONCO]

It’s prolly my eyes, but the piston rings look like they are full of grit? That isn’t build up on the pistons already is it?

You're right. I missed that earlier. I'd like to hear what that is.

 

[Nero]

Looking at the piston rings, the compression ring looks worn, and the second ring has uneven wear. I'd chock it up to dirt intrusion. The vertical lines on the hone marks also tell me this.

 

[Old Goat]

The 3rd picture looks like a used Piston that
wasn`t cleaned up. Like carbon deposits or?


Goat

 

[IDIBRONCO]

. I'd chock it up to dirt intrusion.

That's where I was leaning too, but wasn't sure enough to say it.

 

[Lumberjackchuck]

Did you consider maybe it was fuel knock? I had a leaky injector and it was causing me to have a ton of blow by. Not as bad as you are describing though.

Also I’ve heard that using PSD rings on these pistons can cause a ton of blow by. Hopefully you didn’t use those. Best of luck.

 

[ChevellRCR]

Yes I agree dirt or something got into the cylinder. I think it must have come from the oil system as the rod bearing has the scratching also. I think it may have been injected into the cylinder with the oiler that cools the piston. The dirt you're seeing on the pistons is from the teardown process. Everything in the engine was very clean until I got my grubby hands on it. lol The grime you're seeing around the rings is washed away easily with brake cleaner.

Now... The ring wear issue... I see and have not noticed the wear pattern on the rings. That I agree is very interesting. Thank you for bringing that up. I noticed the scratching and the rings are not nicked but that is a strange wear line. Looking back on the invoice the machine shop has a part number S42105 on these rings. I cant seem to find that part number. Looks like S42104 looks to be the correct number. Could have been a mistyping when the invoice was made.

All parts were new when assembled. Nothing other than the crank, rods, and block were reused. There is a lot of carbon in the chambers because my turbo up pipe was leaking and I wasnt getting the desired boost. The injectors are new also and I have observed no fuel knock.

 

[ChevellRCR]

ok... Update. I called the machine shop and talked to them for about 30 min. This engine even though its low mileage has been a forever project and it's been a few years since the machine work was done. After talking to the shop they want me to bring the block back in and let them rehone the cylinders. They said the block was done with their old methods and have since switched to a computerized diamond honing process that they measure the depth of the hone marks and print a report on each engine. They found that their old process wasn't always getting a depth that was optimal for especially high compression force fed engines. No matter what I'm glad that they are going to look it over.