When I designed the rear floor relief for the valve cover of the ISM to slide in far enough I did not leave enough room for the last valve cover bolt to be put on. When I first started running the bus I didn't worry about not having that bolt. However, after a period of time I was getting oil seapage down the back of the valve cover where the bolt was missing. So, I designed a little bracket to apply the equivalent of the bolt pressure. This bracket was able to be accessed through the rear floor engine access hatch. While the bolt down was missing I never had any problems with exhaust smoking during throttle at idle conditions. However, after I put the bolt down bracket on the valve cover I started having problems with significant quantities of smoke coming out the exhaust during power off conditions like slowing down a freeway exit ramp. The very first drive after I put the bracket on was our Labor day weekend. As you might recall we ended up canceling the trip and coming home because it was smoking SO bad I thought the turbo had failed. We put a new turbo on and a significant portion of the smoke went away. However, not all of it dissapeared. I even brought it in to Cummins and they could not find anything wrong. Their theory was possibly an injector hanging up every so often. However, I had my doubts about that since the smoke would be blue with the jake brakes off and white with the jake brakes on.
Well, over the last 2 months I've been trying to figure out what would cause this problem to come on all of a sudden when it wasn't doing it before. Finally I put the pieces together and realized that the problem started only after I put the bolt down bracket on the valve cover. So, I developed a working theory about the problem and decided what might be happening was the valve cover breather was not allowing crank pressure out to atmosphere and therefore on throttle lift off the pressure on the inside of the turbo oil galleries exceeded the pressure on the exhaust side thereby forcing the oil through the oil control rings and out into the exhaust stream. Today I took the valve cover vent off and found out my theory was correct. Inside the vent was a bunch of metal mesh designed to catch large "chunks", etc and to filter the air going out the vent. This mesh was completely CLOGGED up with 600,000+ miles of GUNCK. YUCK. I pulled it all out and put the vent back together.
I am now happy to report a smoke free driving experience. So, sometimes it is the simple things that are necessary to solve a problem. I am very glad to be able to come off the freeway and not be embarassed about the smoke coming out the tail pipe. After all, part of the benefit I saw in the electronic 4 stroke was the clean exhaust. The entire time I drove on my 20 mile test trip earlier today I had not a bit of color at any time! Yeah! What a relief!
Good analytic process Brian and your right some of the simplest problems take the most thought to resolve.
Ron
That's probably why it was smoking the day you ran it for while still on the truck chassis.
Awesome job of figuring that one out.
Way cool!
Brian,
Congrads and thanks for the info.
John
Quote from: gumpy on October 13, 2007, 04:49:41 PM
That's probably why it was smoking the day you ran it for while still on the truck chassis.
Craig, I think that it was definitely part of the problem. The other part of the problem was the bad #1 injector that got replaced. You should have seen how much smoke would show up in the exhaust when they turned the injector back on after it had been disabled!