We have a 2005 Holiday Rambler Ambassador with a 330 ISL Cummins engine. 105K miles but well maintained.When I checked the oil before shoving off this morning, after sitting for a week, I was a bit surprised to see it down 1.5-2 quarts. I don't check it every morning, but when I do, it's normally pretty close to full.When I drive next to a highway divider which reflects the sound, I hear what I can best describe as "engine noise": a repetitive mechanical sound which does vary with the amount of gas I give it. To say that there is a "tapping" noise would be too much, but I do hear a repetitive mechanical engine sound which I've not heard before. If I didn't know better I'd just say there was a hole in the muffler; I don't even know if diesel engines can develop those as cars can.Inside, all systems are normal. Oil pressure 60 as I drive, less if I let off the gas. Water and oil temps normal, the Allison electronic-check of the trans fluid good.If I'm not driving next to a divider I don't hear anything unless I park and idle it and walk to the rear of the coach.I was considering just staying put today and going to a shop tomorrow, but with everything operating ok, I thought I'd get on the road.Any thoughts?Thanks-DaveUPDATEI drove about 30 miles, stopped for a half hour, and checked the oil. Near full.

Broken/Craked exhaust manifolds, and leaky manifold gaskets are a regular occurrence on some Cummins engines. Have it checked by a Cummins service center.

What sch911 said. I am getting mine out of the shop tomorrow for the exact same thing. My symptoms were exactly as you described. Look at your engine probably from where your air filter is. Look at the bottom half of the engine you should see the manifold. Also look for soot around the engine area if the manifold is cracked you should be able to detect the area of the crack. I have a Cummins 300hp ISB. BTW, an LED flash light works best. Good Luck, Bill.

Ah, followup. 2B, how much was the repair bill? I'm getting nervous.....

dshinnick wrote:Ah, followup. 2B, how much was the repair bill? I'm getting nervous.....???.?? covered by my GS insurance, just paying my deductible of $250.00. I will have that info tomorrow and will PM you if you like.

Hole in muffler? | Good Sam Community

sch911
Explorer
Jun 05, 2016
Broken/Craked exhaust manifolds, and leaky manifold gaskets are a regular occurrence on some Cummins engines. Have it checked by a Cummins service center.
2BNOT2B
Explorer
Jun 05, 2016
What sch911 said. I am getting mine out of the shop tomorrow for the exact same thing. My symptoms were exactly as you described.

Look at your engine probably from where your air filter is. Look at the bottom half of the engine you should see the manifold. Also look for soot around the engine area if the manifold is cracked you should be able to detect the area of the crack.

I have a Cummins 300hp ISB. BTW, an LED flash light works best.

Good Luck, Bill.
dshinnick
Explorer
Jun 05, 2016
Got it. Thanks much.
dshinnick
Explorer
Jun 05, 2016
Ah, followup. 2B, how much was the repair bill? I'm getting nervous.....
2BNOT2B
Explorer
Jun 05, 2016
dshinnick wrote:
Ah, followup. 2B, how much was the repair bill? I'm getting nervous.....

???.?? covered by my GS insurance, just paying my deductible of $250.00. I will have that info tomorrow and will PM you if you like.
dshinnick
Explorer
Jun 06, 2016
Ouch. That means it'll be more than $250. Oh well.

Also, does driving with this condition cause any damage? I don't mind sounding like a 32,000 pound go kart, but if it's doing any kind of damage, I need to head straight to the nearest shop.
Executive45
Explorer III
Jun 06, 2016
dshinnick wrote:
Ouch. That means it'll be more than $250. Oh well.

Also, does driving with this condition cause any damage? I don't mind sounding like a 32,000 pound go kart, but if it's doing any kind of damage, I need to head straight to the nearest shop.

Question #1. Did you inspect the manifold for soot? You'll see where the leak is simply by the excess soot around the manifold.

Question #2. Assuming you've completed #1 above, have you tried tightening the manifold bolts?

Question #3. Inspecting the manifold for cracks? Look closely around the leakage especially the bolt holes.

Get it fixed ASAP.....Dennis
rgatijnet1
Explorer III
Jun 06, 2016
If you take it to a shop, try to find one that will actually troubleshoot the problem and not just throw parts at it that you are paying for. Have them show you the exhaust leak before they start replacing items and have them explain the whole process with you before they actually start work.
If you don't they will have things apart and you will be at their mercy with a non-running RV.
crasster
Explorer II
Jun 06, 2016
Before you go to a shop TRY to find the problem yourself. It's always better to walk in showing the mechanics what is wrong. (unless it is a very trustworthy mechanic).
hipower
Explorer
Jun 06, 2016
Common to find cracked exhaust manifolds on diesels as well as pipes coming from the turbo outlet rotting away. Both of those need inspected carefully and addressed as needed since they are in the upper areas of the engine compartment and pose a risk of starting a fire in the enclosure under the bed in most cases. While you are inspecting under the hood, so to speak, open up your interior access and check from above also. You may find something you couldn't see from ground level.

I recently replaced the manifold on my ISC-350 Cummins at a flat rate shop and if I recall the price it was about $800 for that part of the job. I had some other things done at the same time and don't have the bill in front of me so I can't be positive, but it's pretty close.

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