Cummins ISL 400hp engine

usersmanual wrote:

passingthru; then you probably know torquing bolts is stretching them to almost breaking.

strange statement can you explain your thoughts on this statement?

Depending on the torque spec, bolts are stretched to just under their yield strength.

Years ago I had some training on these squirt washers. They were (probably still are?) used extensively in build and bridge construction to ensure the bolts were properly torqued but not over torqued into the yield strength area.

kb5ujs wrote:
Ended up having the manifold replaced. Old was warped beyond grinding, etc. No additional information as to why. Talked to Cummins and all they said was they would have to look at it. Apparently not a lot of this problem reported.

One suggestion is to always let it cool some before shutting it off. After you've stopped let it idle for a few minutes before shutting it down. This is beneficial to both your manifolds and your turbo. By letting it idle it cools slower than just shutting it down, and a slow, steady cool is better for everything.

passingthru; then you probably know torquing bolts is stretching them to almost breaking.

strange statement can you explain your thoughts on this statement?

Ended up having the manifold replaced. Old was warped beyond grinding, etc. No additional information as to why. Talked to Cummins and all they said was they would have to look at it. Apparently not a lot of this problem reported.

The JB Weld idea is to provide more support for the gasket. The gaskets are very thin stainless steel and #3 without a totally solid mating surface just eventually burns through that weak spot. Very poor design...guaranteed to fail.

I use the exhaust brake a lot but do not run with it on all the time. I have talked to local (Houston) cummins and they can't tell me anything without looking at it, or won't. I am trying to get some feedback before putting in shop to have an idea of what to inspect or do to keep from happening again. One of you suggested JB weld and I got that from a mechanic in Ohio that I use as well. Thanks for all replies. ap

If you are replacing, do all. DIY isn't that hard but do it according to the torque specs, use new bolts and a Torque wrench that has been calibrated and you know how to operate. If you do have an airwrench to remove it and new bolts then you probably know torquing bolts is stretching them to almost breaking. Some you tighten down, loosen and re tighten. They should last 300-400,000 miles without trouble but shutting it down hot, startup and running full throttle before full warmup can cause damage. Usually driving it hard stretches head bolts on Cummins. Have owned trucks for years and did my own overhauls.

why not call Cummins and talk to someone there?

Same on mine...55k and starting again at 111k. The edge of #3 flange overlaps a small freeze plug... less surface toque area... the unsupported gasket burns through... design flaw.

I'm thinking about filling that little cup with JB weld this time. ???

Ivylog wrote:
The smaller of the two haves often cracks. Good luck. If it is cracked, there are some after market manifolds that look to be better built.

Have only seen the "larger (cylinders 3-6) cracked between 3 and 4. Would appreciate info on cracks on cylinders 1 and 2 manifold.

Also, a suggestion on a "better design" for the exhaust manifold. There are LOT of ISL's in RV's out there.

Thanks.