Oil Consumption

[schoelta]

I was just wondering what are the main reasons for oil consumption in the old 6.9L engines. Obviously they have fixed most of them as the diesel engines got newer. I am going to be rebuilding mine in the near future, and I am wondering what I can do when I rebuild it to stop a lot of oil consumption. To me what Ford says is normal is excessive.

Thanks

Tim

 

[Diesel JD]

What I've heard is that it was usually a combination of a bad oil scraper ring design and the old umbrella valve stem seals. I suspect a new set of pistons, newer rings and a good break in procedure would keep the oil consumption very low for awhile at least. I've heard of people upgrading to 7.3 valve stem seals as they are a more positive seal and using gapless piston rings. I would not use 7.3 valve seals if I could get the old ones, but I know nothing about the ring upgrades or gapless rings. Maybe some of these guys do.

 

[icanfixall]

A few years back DAS in Canada "thought" the gapless rings were the new great thing for these motors. I talked this with Paul and he told me they found the gapless rings were worse than what the first motors had and didn't recommend them any longer. Now this is someone that has his hand on the pluse so I wont be trying them "just to see". I run the Mahle pistons 14418 with the hard anadised tops. They have the big pin and plasma coated rings. Yes, they take longer to breakin but thats what the diesel is all about. The pistons with rings cost me $550.00 from Diesel Direct. the second set did. The first set the chicken #hit machine shop that ruined my motor sold me the same set for $1200.00..... I should have gone down the road then. But I gave them several other chances and sure enough they screwed me everytime.... A person would think I kinda liked getting screwed by all the trouble I went thru with these motor rebuilds...

 

[schoelta]

What's wrong with going to the 7.3L valve seals? Also, how long would a typical break in period be. I've heard that it's longer for diesels than gas motors.

Tim

 

[icanfixall]

Breakin done wrong can last almost forever like 30,000 to 50,000 miles. This happens when the cylinders are not hot enough to burn off the oil and they varnish up. This will happen to the rings also. Search for Breakin. Its tells how to properly do this. Think about the big rigs. They get put to work and never really stop. They get broken in doing the job they were designed to do. The important thing is don't drive at a steady rate for long periods. Find a large parking lot. Be in first gear and speed up, then let off and use the motor on back compression. This heats up the cylinders and rings. Do this till your bored. I know it sounds crazy but these motors are designed to work and not to be babied like running on the streets without a load on them. That wont break them in. They need a load on them and some heat in the cylinders. Motors that have the oil varnish on the cylinders sometimes need it machined or honed off. Plus this happens near the top of the cylinders and makes the cylinders wear differantly because this area has less friction and ring contact to the bore. Makes for high oil usage too.

 

[FordGuy100]

What's wrong with going to the 7.3L valve seals? Also, how long would a typical break in period be. I've heard that it's longer for diesels than gas motors.

Tim

I guess the desiegn was good in that it caused the 7.3's to not burn as much oil as the 6.9's, but it also caused the valves to fail and cause some major damage to the engine.

 

[Diesel JD]

Those #s you gave for Mahle pistons are not going to be right for a 6.9 are they Gary? Do you know if Mahle still makes the big pin pistons for the 6.9? If so I might go over there and get a set this summer from Diesel Direct when I actually have some cash in my bank account.