How to determine your engine and transmissions health?

[Barney]

Hello Amigos,

I've been preparing myself to purchase my first Prevost, so lately I made a few calls to some local DD service people.

In general, the info I received was to bring it in and for $800 to $1000 they would give it a good look over, connect to the computer,
test drive etc. Hmmm? ( $113.00 per hour)

One guy said the only real valid test is to dyno it ($350). That unless you put it under a heavy load you really don't
get a good test of health.
However, he said that with coaches there is a very high risk of ruining the tires due to the extreme heat build up doing a dyno.
Not a problem on tractors cause the open rear wheels get lots more cooling air. Hmmm?

What's been your experiences on the above and what's your advice for me?


Thanks,

Barney

[Fogsrv]

Barney, Here is what I just did on the purchase of my 07 in December... first thing was I had oil test on both the drive engine oil and transmission... when the results of that came back satisfactory... I had a full Dyno done at a DD dealer. I spoke directly to the tech than ran it and was emailed the report for the files... Everything checked out fine but for my two cents it's worth the time to get it checked out... In my case the seller paid for all of it as part of the deal we worked out. Good luck Bill

[Barney]

Thanks Bill,

Couple questions.
Did you extract the samples yourself and mail them off or the DD guy do it? How long does it take to get a result?
Did they say anything about tire damage doing the dyno and were you present when they did it?
Do the allusions have a drain plug ( unlike most autos)?

I use to to do oil analysis on my airplane, capture a few onces during a change then mail it off, this took two to three weeks
for results.

[Gil_J]

Barney,

CAT had to dyno my last coach to evaluate a problem. The dyno operator said that they limit the dyno test on motorhomes for the reason cited. I don't recall if they limit speed or time or both, but they did do a limited dyno. I have no idea how thios limited dyno may impact the resulkts, but I do know they were able to run the coach up to maximum RPM.

If the coach you decide on needs new tires, this may be moot. The tire could be replaced by the same service center or one likely just down the road.

I had the local Detroit shop check ECM data, SM revision, inspect what they could without opening anything up and doing a complete service. FWIW, I did this post purchase. If you have more patience than me, have this done pre purchase. You should also have a DOT inspection done pre purchase. A DOT inspection isn't required, but is a good way to have the brake system, lights, and a few other things inspected. It's only $100, so noit a big investment.

The Oil Analysis labs I've used in the past would post the results within 24 hours of receipt of the sample. So, send the sample next day and you're only talking 2 days for results. Keep in mind oil analysis is most valuable in looking at trends. So, a single analysis will have limited value. Also keep in mind if the oil was recently changed the analysis will be of even less value.

[Fogsrv]

Barney I had the Prevost shop that was doing the PDI for me gather the samples. Nobody said anything about tire damage to me... Based on the report that was provided it's a pretty quick test. good luck

Thanks Bill,

Couple questions.
Did you extract the samples yourself and mail them off or the DD guy do it? How long does it take to get a result?
Did they say anything about tire damage doing the dyno and were you present when they did it?
Do the allusions have a drain plug ( unlike most autos)?

I use to to do oil analysis on my airplane, capture a few onces during a change then mail it off, this took two to three weeks
for results.

[BrianE]

Barney,
There is an Article on doing a dyno test: http://forum.prevostownersgroup.com/...namometer-Test

The tech who did this test was a very experienced mechanic. The test facility was Pacific Power Products who are located just down the road from the Marathon plant in Eugene, OR. Pacific Power consequently does frequent dynos on Prevost motor homes. They didn't say a word about over-heating the tires. They did say that if a tire were to let go during the test, it would probably cause some damage to the bus. They consequently asked my verbal agreement that any damage would be my responsibility. The tech said he had never seen a tire come apart. All in all I found the test to be very informative. I'm sure that any significant power loss either via tranny or engine would have been discovered during the test.

[Barney]

To all,

After many posts and lots of replies I finally feel like I am armed with a plan of what to do in order to buy a coach
with some confidence I won't totally screw up. And it all came from joining this site, making some new ( soon to meet) friends.
Still got a 100 questions on operations, systems etc, but the major money issues at purchase are covered.
Maybe after 10 years of ownership, I'll be one of you guys answering the newbie's questions.

Thanks so much, now if I can just find that "perfect" coach for the Queen and I.

Barney

[Joe Camper]

Brian that is the first time I have seen that and was very interested by it all. In all the years I was trucking I couldnt think of any other owner opporators who had that done I never did.

So I called around and I ended up were I often do in my Dago buddy Frankie Galuchios ear.

Here is his take on dyno and I thought Id pass it along.

I asked if he ever did this with any of his tractors and he did. With a Mac Superliner some years back he bought new he said it was way off on power and they did find low #s did something with the pump and fixed it.

He also suggested when motors were mechanical dyno was much more prevelant and nessessary and this truck was a mechanical non computer. He also mentioned u will get a much closer estimate of HP to the wheels doing a dyno on a computer motor but it is not nessessary with a computer controled engine.He went on to explain if his Pete he has now has a problem he will get the DD tech in the pass seat with the laptop hooked up and go for a ride theres your dyno. Thats going to give u the same info as a dyno for the most part, for our purposes.

I asked then what advantage that a dyno would provide with a computer motor if this is the case. He said if your having a motor built and want to verify an exact # because the builder is charging for that increase or if it needs a specific rating for an industrial application of some kind that is where the dyno is nessessary. If a tech and his laptop is plugged in and u go out and drive it that would be in his opinion more than sufficiant to answer questions. If something bad or wrong is happening the computer and laptop will find it just the same.

[BrianE]

Thanks Joe. Due to the fact that Petervans outclimbed me on a convoy we made together, it made me wonder if I had lost power due to a valve adjustment that was done on our coach about a month previously. Hence I visited the local DD dealer for a dyno check. I was told by DD the only way a true evaluation of power could be accomplished was via the dyno. Due to the fact that rolling resistance, tire slippage, transmission and drive line loss were known values, the true output from the engine could be calculated and compared to DD acceptable limits. The dyno that was used unfortunately was an 800 hp unit that split its capacity to two rollers since trucks have two drive axles. Consequently the test wasn't able to go to the rated power of my engine (470hp). The torque curves that were generated however could be extended assuming the engine didn't blowup during the last 70hp or so of rolling resistance. In order for a dyno test to be absolutely accurate it would need to be able to generate 500 hp of rolling resistance as a bare minimum since it would be a very bad thing if the test actually stalled the roller.

[Joe Camper]

Our bus had an 8-V and only 200,000 and at that point i felt no need for a valve adjustment everything ran great.

The 3406 Cat I had in the pete went to 550,000 before ever having the valve cover off of it. At that point I had new injectors and the the valves checked not because it was down on power or something was amiss just for insurance after 1/2 a million miles+.

It pulled better before I did it lost about 50 rpm down to 1900rpm max from 1950. It was mechanical so I adjusted the throttle stop back to where it was previously and drove it another 500,000 without the nessessity like that again for a second half a million miles.