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Old 12-01-2008, 12:26 PM   #1
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Pusher problems? Engine layout, parts, cooling...?

I'm "giving lessons" about skoolies over on the Burning Man forum, and a question has come up that I need help with. Here is what the man asked:

I've been told that pusher buses can be hard to find replacement parts for-- that there is no standardization. I am not clear on what is different from bus model to bus model on them. It might be the drive train or something about the engines...? Also, I have heard that, being in the back, cooling is problematic for pushers. Have you heard anything like this?
Having no experience with pushers, I need your help! What is the engine and tranny layout in the common skoolies? The ones I have seen had everything simply backwards compared to a front engine bus. I'm thinking that the differensial would have to be "up-side-down" and that would be it. I know there are buses out there with the engine sideways -- but mostly highway coaches like MCI, maybe???
And what's your experience with cooling?

I think I may have found a couple of potensial converts over there. One of them is an old co-worker of Jason's. Jason, you "sold him" on Burning Man!

I'll relay your answers, but you are of course also welcome to join the frey over there yourself:
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Old 12-01-2008, 02:07 PM   #2
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Re: Pusher problems? Engine layout, parts, cooling...?

I've got a 1980 Gillig 636 pusher, CAT 3208 and Allison MT643. Thermostatic/hydro controlled fan (no belt). It crawled/struggled over the Cascades at 15-20 MPH, and the gauge NEVER climbed over 140. In fact it has never been over 140. This pusher actually runs TOO cool. The Gillig pushers I've seen have several different cooling system layouts. Pushers have been used in school, transit and inter-city busses forever, at least since the '40s. If this layout is a problem, it would have been discontinued decades ago. My understanding is that Gillig and Crown used standard medium duty truck parts for their drive trains. I imagine this is true for newer skoolies as well- why would a school bus maker use specialized parts that would make their product overly expensive??
Pusher gives a better ride, better visibility, and more usable room both inside and under the bus.
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Old 12-01-2008, 03:03 PM   #3
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Rear engine cooling problems.....None

Engineers who build/design rear engine buses are very good at that task. Most of my history of buses have been rear pushers. Some methodology used for driving the fans is not great for long term use but very substantial. My Thomas bus has a Cat/Kitty 3208 with an Allison trans. This bus has a belt drive with a short drive shaft and a gear box to turn the fan. Lots of maintence, and spendy but works good. Almost all heat problems are because of a bad radiator. Frank
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Old 12-02-2008, 10:23 AM   #4
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Re: Pusher problems? Engine layout, parts, cooling...?

component mfgs. use a standard list of options and specs., the vehicle mfgs. then pick and choose the "right" parts for their package and then accessorize the total pakage to do the job required.

prioritize your needs, top speed, max weight, gradability, acceleration, etc then choose an engine with enough power to do the job, match up a transmission that is capable of handleing the power that the engine develops, both torque and hp, and then match up the cooling system. radiator and fan requirements are specified by the engine and transmission manufacturers as heat rejection numbers/ amount of btu capacity needed to keep temps within specs at max power/load. size a radiator that can remove that amount of btu's and then design a fan drive and plumbing system to connect everything.

it sounds easy, and most of the components are off the shelf items the fan drive sytems get kind of rube goldberg looking sometimes, but the parts are usually standard "industrial supply" parts(bearings,pulleys, shafts and belts, temp switches etc)

cooling system issues are most likely caused by marginal radiators and trans coolers followed by missing/damaged fan shrouds/shutters and then fan drive problems. it is also imperative to have a an operating thermostat in the engine, removing the t-stat will prevent the coolant from absorbing the heat generated in the engine properly and delivering it to the radiator.
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Old 12-02-2008, 09:19 PM   #5
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Re: Pusher problems? Engine layout, parts, cooling...?

Mine also has the Cat 3208, which was the primary work motor from Caterpillar for many many years. They put these things in trucks, bulldozers, buses, and a number of other construction equipement. Parts are very easy to get. The new buses are using new engines, the same engines that are going into trucks. BTW, I work for a heavy truck dealer, we sell Caterpillar, Cummins, Detroit, & Allison parts etc. The Thomas pusher is built on Freightliner Chassis, all the chassis parts are easily obtainable, Thomas has it's own dealer network out there too!

As for over heating, I'd like to see an example of that problem. How many pushers are out there? Schoolies, Hiway buses, Hi-End RV's... if they had cooling problems nobody would be buying them. My Thomas moves massive amounts of air, it goes from one side to the other. Going down the road you still get plenty of extra air, just try opening the drivers window on your car as you go down the hiway and see how much air is going in...

Who ever asked that question doesn't have a clue!!

You just might be a Redneck if...
...your motor home used to be a school bus!
...Your living room has a steering wheel!
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Old 12-02-2008, 10:37 PM   #6
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Rated Cap: 84
Re: Pusher problems? Engine layout, parts, cooling...?

I'm pretty sure that's why he asked, which I feel was a smart thing for him to do.
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Old 08-25-2015, 02:23 PM   #7
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I was thinking of adding some air scoops that are used on vw buses, would it help to keep engine cooler?

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Old 08-25-2015, 02:35 PM   #8
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I don't know anything about pushers, but here's an excerpt from Porkchopsandwiches recent adventure:

Originally Posted by porkchopsandwiches View Post
We headed out of Roswell in the afternoon, and headed to Colorado Springs. My dad has a friend there, who's house we parked near for a night. Then we went to my friend's aunt's house, also in Colo Spgs, then back to the first spot. The drive out of Roswell We headed through some very remote areas on old US highways, which was interesting, but also nerve wracking, as the bus started to run quite hot. We were climbing in elevation most of the drive, and it was also about 100 degrees out. The engine eventually hit 220 degrees, which is 10 degrees before the engine warning light and buzzer come on, and the computer derates the power of the engine by about 50%. Since I didn't want that, I pulled over and high-idled it back to 195, which takes about 10 minutes. It kept getting hot, so I decided to remove the cover door over the radiator:

This door was pretty restrictive for airflow, it didn't let a whole lot in, and there wasn't much area for the hot air from the fan to go. So this seemed to help some, it kept the engine in a temp range where I was comfortable to continue driving.

Bear in mind, this is with a perfectly functional cooling system. The radiator is new and I had recently flushed the dirt from the fins, the water pump and belts were good. These buses were just not designed for sustained highway cruising in high temps. The radiator is just not big enough, and doesn't have particularly good air flow. If I were to do this trip again, I would have to put in some sort of aux radiator, or at least hook up the heater loop.
With that being said, air scoops might be something worth playing with.
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Old 08-25-2015, 02:53 PM   #9
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I think a lot of it depends on the design of the pusher. I know on my Amtran RE, I've got huge intakes on either side, up along the window line-

Driver's side

And a huge @$$ radiator in the back-

I'll have to get you the curbside after work
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Old 08-25-2015, 03:20 PM   #10
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Am trans rear engine buses are build better than any Bluebird or Thomas.

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Old 08-25-2015, 04:00 PM   #11
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Originally Posted by nat_ster View Post
Am trans rear engine buses are build better than any Bluebird or Thomas.

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