My brother stopped by with his new motor home. He asked if I wanted to see his engine. I asked if it was a gaser or diesel. He said that the engine was in the front. He mentioned that if it was a diesel the engine would be in the back.

I have noticed that on large vehicles (busses) the diesel engine is in the rear. Is there a reason why gasoline engines are in the front and the diesels are in the rear?

Thanks.

Tim

 

I think it's because of the weight of the diesel over the gas engine.
The motorhomes are already pretty heavy on the (only 2) steer axle tires, so moving the diesel engine to the rear (4 tires) compensates for it.

JMHO

 

There are diesel motorhomes with the motor in the front. I can't remember seeing a front diesel that was over 36'. The real biggies are rear.

The interesting thing is how much it costs to service a diesel motor the minute they put it in a MH. My ISC (rear engine) cost me $325 to be serviced. Absolutely stupid, but when you are on the road you don't have much choice.

 

Could be just a issue of convenience.
Many modern diesel pusher motor homes are built on a bus frame.
Im guessing buses have the engine in the back due to the full length, center walkway and under belly storage arrangements.
Many early luxury coaches were just bus conversions.
Today, many coach makers build their own bodies on existing bus frames because the rear engine adapted very well for luxury motor homes that needed room for water, plumbing, storage, generators, etc, and still provided the length, strength, and power needed for modern luxury coaches.
However, there is currently a trend that is going beyond the motor coaches built on a bus frame.
The new luxury coaches are being built on semi truck frames. Thus, the engines of some of the top line luxury coaches are going up front.

 

I was in the Cummins shop this week and they have a top line motor coach in there with the new ISC Cummins engine that blew a head gasket.
Because this is this families "Home away from home", they are living in the coach while the mechanics are replacing the head gasket.
This means that all work must be done from the engine bay. (Easiest access is from inside the coach).
The mechanics are having to remove a lot of stuff that wouldnt normally be touched, but because they have to work in such small area, a lot of stuff has to come out for access.
This is all warranty work, but would costs thousands outside of warranty!


Rich

 

On a lot of the rear engine buses the whole drive axle, tranny and engine rolls out the back as one unit. Slip a rebuilt one in and the bus is ready to roll again in an hour.

 

On forward engine units, the drive shaft is too long (over 34ft), that's why they put them in the rear. I think Bluebird & Newmar made them for a while.

Forward engines are much easier to work on and cheaper too. Oil changes were $149 vs $325 with a rear-engine unit.

But I wish the builders would put in a full (4 wh) axle instead of just a tag (2 wh).

 

Dang! Is that semi-RV Bill Gates' vacation wagon or something???

 

The main reason for rear engines in buses is space efficiency. Passengers can sit over the engine. It works out well for motorhomes too, keeps the floor in the driving area open and keeps it quiet too.

 

As others have said, its because of the access to the engine. Just changing a VP44 on a B5.9 in a motorhome can take 4 hours more than what it would on a truck because your laying on top of the engine.

Take the intercooler for instance, if you blow a turbo and need the intercooler cleaned. You can just about bet your looking at 15-20 hours for the job that includes removing the whole back skin of the RV, radiator etc. Its a tough job to do.

A couple of months ago, the Excursion pusher motorhomes with the ISC developed a BAD oil leak problem. The oil leak was so bad that it was blowing it up on to the backup camera. Turned out that the casting hole for the blowby tube was not big enough and was letting crankcase pressure build up to high. This consisted of digging your way into the side of the RV and drilling a 1/2" hole into the casting hole to allow pressure to get out correctly. This wouldnt be a very bad job on a truck, but with a motorhome, it is a PIA.

Speaking from a mechanics point of view, myself or any other person I know of wouldnt even think about working on RV's for the same amount of money as trucks.

The way I see it, if you can afford to drive them, you can afford to service them.

 

Man, I was thinking the same thing - what a palace!

Bill

 

Blue Bird still makes front engine and rear engine buses. Its more user prefence. Yes, rear engines are a hell of lot easier than front engine. Rear engine may use a bigger engine like ISC, N14, M11and ISM. Front engines use a Cat C7

 

I think if you look at the distance in the front engine and rear engine buses, you will find that the wheel base is shorter on the front engine models.

 

True but only by 41 inches . A front engine is 232 where as a rear engine is 273