Wednesday, December 24, 2008

Cummins Engine Repair - Camshaft Gear Noise

Here's an email I received from Jonah Barnes, Lead Mechanic for the School District in Sierra Vista, Arizona. He noticed a noise coming from the front end of a Cummins C Diesel Engine. It turned out to be the camshaft gear. The photos tell the story and I'm amazed how long this gear lasted. It just goes to show how durable a quality metal casting can be and how long it can take a pounding without blowing apart. This gear would have made a huge mess if it exploded inside the timing cover.


Hello John,
It really wasn't too noisy actually. When the compressor placed an added load on the cam gear it would actually rock the gear back and forth and "knock" against the front cover. It almost really did sound like a " bongo drum".

According to the other mechanics who have worked here longer than I the previous attempts of replacing the compressor would cause it to be quiet for about a week or so then it would go back to the intermittent drum beat. They were adament that it was the compressor again and they were just getting bad ones.

They even went as far as replacing the fan hub and alternator a few times with no luck. I used redneck diagnosis and used a piece of fuel line and placed one end in my ear and the other end I listened around until I was sure it was in the front timing cover.

It actually made the sound faintly using the hose when the compressor governor unloaded but it was not as pronounced as when the compressor was running. I have only been with the school district here just a few months but have been a mechanic most of my life.

I have run into a lot of different broken things but this gear being broken like this and the engine still running down the road and running routes without missing a beat (literally) is pretty amazing I think.

They said it has been doing this almost 3 years but no one really thought it was that serious. I contacted cummins here and they know of no recalls on the gear but they are available from cummins for about $350.00 US.

I am originally from Indiana and my dad was an engineer for cummins for several years and he was pretty amazed too that it was still running. I don't think it would have much longer though. I will be sure to keep you informed of other mysterious problems I encounter on my end.

The more information out there the more it can help other people who are sitting there scratching there head. We tend to get a lot of life out of a bus out here because of not having to deal with rust issues so there are several high mileage buses just waiting to keep me employed!

Thanks again for your help.

Jonah Barnes
Lead Mechanic
Sierra Vista, Arizona


Thanks to Jonah for sharing!

I love to receive emails with Mechanic Information sharing experiences of real life repairs & troubleshooting. This is helpful for Mechanics & Truck Owners who always have new and interesting problems to solve.

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