air leak question

travelingfools · March 18, 2011, 10:17:53 AM

On my 87 MC9 w/6v92, on the valve (?) that feeds the piston that creates tension on the belt, there is a brass body that feeds the piston and what appears to poss be a regulator. The brass body has a open orifice on the top that leaks air in wholesale fashion. It appears to be threaded, and poss missing a plug. before I cap it off, I thought Id better make sure thats not supposed to be open. The part in question is the brass block next to the silver thing (technically speaking)

bevans6 · March 18, 2011, 10:42:53 AM

On mine that is a three way valve, one position applies air to the tension cylinder, the other way opens it up to exhaust so that you can dump the air to change the belt real easy. Mine does leak a little when in 'closed' position and there is quite low air pressure. it seals up over about 40 psi.

Brian

travelingfools · March 18, 2011, 11:11:01 AM

ok...it does have a stem like a valve. Im guessing now it just needs to be turned to close. Ill try that. Thanks Brian

wildbob24 · March 18, 2011, 11:52:47 AM

Fool,

The best thing you can do is remove all that stuff and install a manual adjuster in place of the tension cylinder. Eliminates several air leak sources.

Bob

rcbeam · March 18, 2011, 06:05:08 PM

Finally I may be able to actually contribute something to 'the board'. My MC8 leaks a little out the little weep hole at the back of the same air valve (if I am following you correctly)... the valve that regulates the air to the tensioner for the blower belt. I was at the local tour bus garage just the other day talking to the head mechanic there about some stuff and that was one of them. I figured the valve was bad... he said he changed three of them once before he finally figured out that it wasn't the valve that is bad it is the power cylinder that is actually leaking back through the weep hole in the valve... You rebuild the power cylinder and the leak stops. However, he said it was a PITB to do because of the spring inside, but doable. For no more than mine leaks I'll let it go. I figure I probably have more air leaking out other places than to worry about this small one.

Russell
MC8
Lexingon KY

Joe Camper · March 19, 2011, 04:57:51 AM

If it is leaking out the exhaust port on the valve the air cylinder itself is leaking, pushing air out thru there.

Rebuild the tensioning cyl itself and the leak at the regulator valve will stop.

Joe Camper · March 19, 2011, 05:07:42 AM

Don't plug it. If you turn the red pointer about 1/2 way back you can stop the leak and still get "reasonable tension on the belts.

The pnewmatic tensioner has a large internal spring that will keep some tension on the belt if air goes away.

Joe Camper · March 19, 2011, 06:38:10 AM

On a side note. Our bus has probably easily 1000 dollars worth of components that make up those pneumatic belt tensioner assemblies and if you are into seeing 100 PSI on the gauges when you get up in the morn it could become an expensive proposition.

Another issue is the "aux air compressor" and its frequent cycling when camping due to those aux air leaks.

How does a poor grease monkey like me solve the issue.

Well.............. while underway that very very slight loss is IMO insignificant and "manageable" so I live with it.

When we get stopped and camping I put an air toggle to the air feed to the engine bay and shut it off.

I also added one for the air wipers that seep and are kinda pricey and that same toggle also shuts off the air seats stopping my dog from bleeding off the air and getting the aux air compressor to run frequently by jumping in and out of the drivers seat every 2 min.

Cost of the rfix less than 10 bucks