83 mc9 cooling fan air ram question

tombuchanan · March 20, 2021, 02:12:10 PM

I started my mc9 for the first time since rebuilding the air ram that tightens the cooling fan belt and noticed that as air pressure started to build the ram pulled in loosening the belt. Is this normal at low engine temps or did I put it together backwards? I didn't want to to keep running it and see what happens when the engine is warm as i'm afraid the belt would come off being this loose.

Raymond smith · March 20, 2021, 03:14:58 PM

Sounds like you have the hoses reversed.

tombuchanan · March 20, 2021, 04:23:25 PM

that was my first thought, but i thought maybe it was designed to loosen the belt on startup so the engine warmed up faster then switched to tighten when it was warm enough

tombuchanan · March 20, 2021, 05:12:42 PM

i switched the hoses around and there's no way that's the way it was based on how awkward they have to bent. I also replaced the air valve at the same time so maybe that's where i messed up. i have the air supply coming in the top of the valve, the right goes to the regulator, and the left to the ram front.

Busted Knuckle · March 20, 2021, 08:11:32 PM

I don't remember if that vintage MCI did or not, but a lot of the valves were a dual action where in one position they pushed out the cylinder and in the other position they sucked the cylinder in to make it easier to change the belts.

BK

buswarrior · March 21, 2021, 05:36:49 AM

WhatBK said.

It sucks in to change the belt, pushes out for normal operation.

Valve in opposite position, or the lines to the valve are in wrong holes?

Nice to hear someone fixing the useful stock tensioner, and not just replacing it with a fixed bar.

Happy coaching!
Buswarrior

tombuchanan · March 21, 2021, 05:49:04 AM

in one position my valve loosens the belt and in the other it dumps air out one of the open valve holes which i guess is for loosening the belt. so i guess i messed up when replacing the valve. as for fixing it, if i had known i could get away with a straight bar, i would have gone with that since i'm in more than 200 on the fix so far.

buswarrior · March 21, 2021, 05:54:03 AM

Try changing that belt with the @$# of the bus hanging in the active lane in the rain...

Every penny of returning the ram to operation will be well spent, you'll have the new belt on in about 10 seconds...

lesson taught to the crowd, mark everything for re-assembly!

Good job!

Happy coaching!
Buswarrior