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Belts — Warning
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Talking about belts and tension, had my coach serviced last year at Prevost Houston and heading home (100 miles west) thing started heating up. 65 or 70 degree day. Pulling a Ford Edge. Pulled over a couple times and temp would go down to 175 degrees. Get her up to 65 MPH and would heat up. Called service manager back and he said might be radiator time. Took it to house and was gonna make appointment for next week for check. Had my Guru come down on another house electric issue and he found somebody had shut the valve in motor compartment that keep tension on belts. Flipped valve and have run it another 10,000 miles and stays under 195 in this 100 degree weather. Show you how smart i was, didn’t even know vavle was under there to flip and change belts. Thanks Justin Griffith, Granger Texas. If valve is completely shut in for belt change at idle will still cool just not up to speed. Belt will do the watusi but not bad.
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Same with me Buddy, the single 3 belt was way too shakey for me.
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I had the 3 wide belt on my 87 coach and I much prefer the three individual belts not because of the shaking and flopping issue but that three wide belt seemed like it was always getting torn up with stones that got between the belt and the pulley. I think the three individual belts give stones a chance to slip out harmlessly most of the time.
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I never put the engine to high idle unless the air pressure in shown 60 psi to make sure the belt tensioner bag is fully pressurized.
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A mechanic here told me to be sure and not leave the Prevost over the road air turned on when parked for a long period. He said the compressor would kick in before the belts aired up and would throw them off as well.
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Tom,
It isn’t good practice to leave it on when we shut down anyway, but what I cannot understand is the attention everyone is giving loose belts.
We are vastly out numbered by seated coaches yet I have not seen any provision for those guys to tighten their belts before starting. I can also imagine a lot of drivers just don’t give a damn so I imagine a lot of starts take place with the bus in high idle with the OTR on.
There’s no downside to having the belts tight when we start the engine, but so what if we forget or choose to not do that?
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Jon,
I can’t find any wording in the manuals requiring it, but then again I suppose not everything is reflected in the manuals. All I can find is this:
PA-1164 2003 DDEC IV:
“Special precautions are necessary with turbocharged engines to avoid possible turbine damage. After starting, run the engine at normal idle for two minutes to allow lubricating oil to reach the turbocharger. Then run the engine at fast idle. Let oil pressure reach normal operating range before driving”.
I exercise my bus every three weeks and so far the accessory air system always has at least 90 psi in it before I start the engine – it never leaks down in the 3 week interval. I never dump air at the fan belt air-bellow so loose belts aren’t an issue for me. I have minimal house systems on acc air; the only addition over standard Prevost chassis stuff is the air slide for the entryway stairs. All this is probably true for your typical seated bus; i.e., they drive them periodically, accessory air is always aired up, they may follow the above 2 minute rule, with the result that the belts are almost always under tension prior to coming off idle.
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Prevost told me you could run the OTR air when on High Idle all day long if you want to. Doesn’t hurt anything but fuel consumption.
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That’s true,
But I think the post was to indicate you don’t want to start the engine with the OTR “on” as is possible with XL coaches. XLII coaches and late model H3 automatically shut off AC when the bus is shut off.
David,
Yours is a rare coach that holds aux air as long as you describe. As coaches age they all leak due to the fittings losing their seal.
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I always turn my bus air off before shutting down. I do not run the bus air when on low idle as a rule and I always switch to low idle for a minute of so before shutting down the engine. Of course I still let mine idle for 10-15 minutes after running hard any way. It usually takes that long to figure out where I am going to park.
Davy
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On MCI buses, the OTR comes on automatically every time we start the engine, set for 72 degrees. I can shut it off before the compressor kicks in, but that has to be done manually, as does changing the set temp and fan speed. MCI conversion shells share more DNA with seated coaches than do Prevost conversion shells, and this is plainly a carry-over from the seated coaches. As John noted, having the OTR switched off while starting is probably a good idea, but it is not likely practiced by seated coach drivers. The MCI manual recommends leaving the OTR on full auto all the time, so I suspect the OTR is rarely shut off.
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Yesterday was the second time in 2 years I lost the 50DN serpentine belt on start-up.
On our S60 model, the serpentine belt uses a mechanical adjuster and requires 200+lbs of tension. We were boon docking for 5 days, so I assume there was a big load on the alternator right after start-up. The belt moved sideways on the pulleys and got cut. Lost about a third of the belt width. Interestingly, the shredded belt took only 30 seconds to UNSCREW the transmission dip stick.
I’m thinking about upgrading to the newer automatic serpentine belt tensioner style. Has anyone done this?
Gerald
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I converted to the new setup and had no further problems.
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Do you remember what was involved in the upgrade?
It seems I could just move the engine oil fill access cover to the left access cover and get a new cover with the bolt hole for the tensioner plus the automatic tensioner. The old idler pulleys and bracket could stay. Is that what you did?
Gerald
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Gerald, I do a lot of dry camping and I always run my generator before starting up. Letting the generator bring up the batteries prevent the sudden loading of the alternator on starting the coach.
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