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DA_BUS 09-27-2011 08:14 PM

We are on our second diesel pusher and been around trucks all my life - still have 5 tractor trailers in our fleet.....engines that are made to run over a half a million miles before any work on them needs to be performed are going to survive a lot longer than the everyday issues the other parts of the coach will bring up. Make sure the coach drive train has been mantained regularly and focus more on the rest of the coach. Cummins and Allison (and the other brands) are made for the long haul and are built to take it - these manufacturers are not slouches....if the motor and transmission has been developed in over the road tractors that pull 80,000 pounds day in and day out - the drive train would be the last of my concerns. Make sure the drive train has some consistent activity - not high mileage - but started and used enough on a regular basis to keep things lubed and in working are never going to be able to second guess if you have bought a "bad" driveline until it happens or previous service records reveal "buy one" and enjoy!

RVNeophytes2 10-02-2011 08:11 PM

Chemical Aspect of Oil Change Interval

Originally Posted by Pairajays (Post 963117)

Annual oil changes, without substantial milage, is not required, IMO.

Is this true in diesels? As an airplane mechanic, I stress annual oil changes as the very least; six months is often preferable. The reason is that your oil protects in two ways: mechanically, by definition; and, chemically by maintaining a protective coating on surfaces inside your engine. With the introduction of moisture, acids form, the protective role is compromised, and engine life is shortened.

Cummins, in their bulletin entitled CumminsŪ Engine Oil and Oil Analysis Recommendations, says the same thing: Oil provides a protective barrier, isolating non-like metals to prevent corrosion. Corrosion, like wear, results in the removal of metal from engine parts. Corrosion works like a slow acting wear mechanism. These are the engineers who built your engines, who gain nothing if you shorten your oil change interval. But, they don't quantify the amount of wear nor do they address environmental variables.

Now, in jumps the State of California, which says you can optimize wear by using premium oil and high efficiency filters, coupled with extended change intervals. Their findings are HERE. Does the same thing apply in Ohio, Florida or Michigan? I have no idea.

What do our professional diesel mechanics think?

phredsee 10-03-2011 12:03 AM

We found a specific model motor home we were looking for but it had 10,000 on the motor with 410 hours on the generator, go figure. No service records as this was a bank repo bought by the dealer at a lower price. We also realized that tires would have to be replaced and all systems tested, including liquid analysis, outside Cat dealer verified the motor, including the Alison transmission. No service codes and some work done to brackets for safety underneath.
We set aside about $10,000 for any repairs we might have that didn't show at time of purchase, excluding tires and shocks.

After we purchased, we had all fluids replaced on the engine, transmission and radiator. Most hoses replaced. We had no service records so I felt we needed a starting point for current usage and future service requirements.

Things that have already gone wrong were (2) coach batteries needed replacing, roof sealant brokedown on trip with entire left side lifting up but luckily repaired, (2) leaking windows I corrected and some other minor problems that were easily fixed. The jacks need to be serviced and plan on doing that shortly.

Bottom line is depending on how far back in years you go and as others have said, buying used is an unknown factor unless you have reputable service records, plan on spending some bucks along the way.

So far we are happy with our decision on buying a higher end coach and with continuing preventive maintenance, we have expectations it will last a long time.

Good luck in your search and get what you want but practice the caveat emptor thing.

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