A salesman noted a bit of a noise from my engine that I had not detected before or after he told me nor had service technicians when doing the annual maintenance. The service people did then investigate and conclude the slight noise was probably an exhaust manifold leak. For those not familiar with this topic, I will review what I have found and learned and hope that others with more expertise add to this topic. You do need to know about this threat to your engine.
The exhaust manifold obviously carries exhaust away from the engine compartment. When the manifold fails to completely perform that function, fumes can enter the coach. This was not detected however in my coach so that telltale signal was missing.
The manifold if leaking can reportedly injure the engine. And exhaust gases are used by the turbo system. If that is not performed well, you will notice a loss of boost (power) and mpg.
If left unattended (repaired) the leak can also leak hot gasses into equipment and areas where it does not belong. several sources said one should not drive if the loss is very significant though there were reports of fairly major exhaust leaks that did not cause damage.
Why does the manifold system fail? The gasket can develop a leak and, or the manifold itself can develop a crack. The heating and cooling of the manifold, over time, stress the system and can in time cause the failure. One technician observed that they are seeing an increase in these failures and it seems primarily related to the age of the coach (he did not say miles but that may be more important?).
How to repair it? You might undertake this but you may take the coach to a professional. It is not unusual for one or more bolts to break off and pose a particularly difficult removal. Also if the manifold can be reused, it may or probably needs resurfacing. Replacing the gasket requires dismantling the turbo system. A Cummins repair shop estimated 11 hours for this work.
So, what was wrong with ours? No gasket! No explanation, Tyler Truck only speculates that someone left it out on prior work. Cummins told me that they never built this engine without the gasket.
How to check for a leak? I will try to listen better to the engine. Look for signs of a leak with the engine running using a flashlight? Note any loss in boost could be a reason to check for this. Look for bent manifold bolts. Mike 2001 U320 40′
I had a cracked manifold when I bought the coach (did not know) but noticed black exhaust type marks on it then checked the gasket joint. It was also leaking a bit. Took it all apart (first time ever) and broke 1 bolt in the hardest place to do it, and that was because I feel that even though I heated the block up around the bolts with an oxy/acet torch I could not get this one as hot and all except this one came out fine. I drilled the bolt and used a stud remover after giving the head a good heat up (easier now as manifold was off) and out it came. Luckily the seating area was good and I put on the newer 2 port manifold which Cummins said was part of the reason the first one cracked (stress??) Anyway all worked out fine.
Friends a few weeks later arrived in their Monaco and guess what He had been carrying a spare manifold he got in Costa Rica as he too was leaking. We set about doing that one with some confidence now. We also broke a bolt-on his but not to worry it came out after drilling too.
I had a tough time in some awkward positions but we managed it. Not a hard fix as long as you have a few tools. John Haygarth 2000 U295 36′
Aside from all the items listed above, extended operation with a missing gasket or crack in the manifold adjacent to the cylinder head may, if not repaired, cause erosion in the exhaust port mating surface as the hot gases to travel from the port to the outside. In extreme cases, this could require removal of the cylinder head to surface the entire exhaust port area on the side of the cylinder head so the exhaust manifold gaskets will seal completely. Pierce Stewart 1993 U300 36′
Any exhaust leak on diesel will leave a black “soot trail”. When inspecting motorhomes, I go over them with a good flashlight: head to the exhaust manifold, joints in exhaust manifold (most are 3 pieces), manifold to the turbo, turbo to exhaust brake (if present) and exhaust brake or turbo to exhaust. It would have to be pretty bad to be able to hear a leak at idle on a large diesel. Brett Wolfe 1993 U240
I had a horrible exhaust leak that was caused by some backyard mechanic, no not mechanic, only an idiot would replace a broken head bolt with a drilled through-hole a use a common bolt, nut, and washer, in addition to using common SAE bolts to ” secure” the manifold. In any case, the Cummins mechanic told me that exhaust manifold leaks are not uncommon on diesel pushers and easily fixed if addressed early on. Such was not the case with my exhaust leak. Cummins took care of it and everything is good…..for now.
Roland 1993 U280