The Source of Excessive Blowby

[Glennman]

First, I would like to thank everyone for their help with my air compressor change out. I did it mainly because it may be the cause of excessive blowby, but it was leaking oil all over it, it was old and rusty looking and I just never did trust it very much anyway.

I'll be test driving it this weekend over some fairly steep hills between Yakima and Ellensburg to see if the blowby has at least been reduced. When I idle it in the driveway, the blowby seems pretty neglegible. I've heard that the turbo can also create blowby, and if it's neither of those, it can be an internal engine issue. I've also heard that a leaking compressor can cause problems with the head gasket (?)

That being said, suppose it is an internal engine issue. Just what is it that takes place in the engine that causes it, or what kinds of things in the engine can cause blowby?

Thank you in advance.

[luvrbus]

Blow by is caused by compression leaking it could be from the head or compression rings in the engine, or the liner sinking in the block, series 60 are going to have blowby with miles on the engine. Run a compression test it could be just the head gasket or a broken head bolt that happens on a series 60.Only thing you need to watch is for coolant in oil, and the extra use of coolant ,if your coolant starts to get gray in color then shut it down and get the check book out ,you probably needed the compressor but I never saw one cause blowby on a series 60

[Jim Blackwood]

All piston engines have blowby. Less when new, more when old. Less at idle, more under load. It's a matter of how much is too much.

Jim

[Glennman]

I don't know if mine is actually "excessive", but when it blows the oil up the turbo drain tube, it is certainly suspicious.

I was under the impression that the local Frieghtliner outfit might be willing to work on the bus, but I was recently told otherwise. I'm not afraid of doing a moderate rebuild of the engine. I have the place and the resources, I only wish I had more time, at least to get it done in time for the upcoming travel season. My concern is that if I need to pull the head off, I may as well keep going once I have the engine out of the bus anyway.

[Jim Blackwood]

My older brother recently rebuilt the S60 in his Peterbilt, he started out by buying a wrecked truck that had a good engine, had it towed to a local shop and traded them that truck to swap engines. Not long after that he found out the crank in that engine wasn't so great, brought the truck home and tore it down himself. Got a crank sent up from Texas and did a complete rebuild. Seems to be a pretty nice engine to work on, he farmed out the head work but did the rest himself. Took him several years to finish it, and ended up having to look for a new ECM for it to clear all the error messages and I think that cost him over a thousand after a long time spent shopping for a bargain. He took as long to get that done as he did on the rebuild itself, maybe even longer. In the meantime he contracted with a local company to drive one of their trucks.

I guess the moral of the story is that the timeline tends to stretch out once you get into something like that, so it's a good idea to get as many ducks lined up beforehand as possible. If the problem can be solved some other way that may be better.

Jim

[Glennman]

A agree Jim. The last thing I want is to spend the rest of my days fixing the engine and not driving it around!

I heard that a test that can be performed is to disconnect the turbo drain, drop it in a bucket and run the bus and see if that changes the blowby pressure. I suppose that they are implying that the turbo can mess up and drive air into the pan through the turbo drain (?) However, it appeared that the pressure was pushing the air up the turbo drain enough to drive the draining oil up the tube. Since then, I changed the gasket on the drain and now it's not leaking, so I may have been misdiagnosing that whole thing (the oil only appeared to go up the tube).

At any rate, I'll find out what's happening this weekend after my test drive!