Compressor - It maybe time. :(

Chaz · March 07, 2011, 09:55:02 AM

'Nother Air question:
It takes my bus quite awhile for the air to build. It always did so I just figured for the time.
Dallas told me that it was getting weak when he rebuilt the motor and it's probably time I bite the bullet and address it. Is it better to rebuild it or replace it?? And, where is the best place for such stuff??
Oh, this is on my 4108. (I forgot to put that in my last thread.

)
Thanx again!
Chaz

bevans6 · March 07, 2011, 10:19:09 AM

It's good to have a benchmark rather than "a long time". I use the DOT standard test for compressor recovery. That's really easy to do - get the bus completely aired up and stable. Do the leak test - no more than 1 psi drop in one minute, engine off. Next, engine at high idle or 1,000 rpm, fan the brakes to lower the pressure down to 80 psi, watch the governor cut in, and time the rise from 85 psi to 100 psi. That is the standard test. DOT failure in Ontario is 2 minutes, I have read that it is 45 seconds in some states. My bus takes 18 seconds. I would say that if you are less than 30 to 40 seconds, you do have a problem. It's hard to judge between time it takes to air up the bus, time it takes to fill the suspension, air loss from leaking, etc, which is why there is a standard test.

Brian

Just Dallas · March 07, 2011, 10:40:58 AM

Brian....

Chaz's bus doesn't even come close.

Brake pressure drop test was 12 -15 psi/minute of full application.

Recovery was slow enough that after 3 minutes I gave up.

Most of this is caused from the compressor leaking oil over time.

I didn't go farther than that. I let Chaz know he needed a new compressor, and that many of his air problems would be fixed by cleaning out the oil in the system and replacing stuff that couldn't be cleaned or rebuilt.

Good Luck,

Dallas

luvrbus · March 07, 2011, 11:10:10 AM

I don't know what compressor you have now but if you have the 500 or 600 upgrade to a 700 big difference in recovery time and recovery time depends on the cfm of the compressor

good luck

Barn Owl · March 07, 2011, 12:29:36 PM

Price good used takeouts from NIMCO. They had all sizes the last time I talked with them. Put the biggest one on you can without doing any modifications.

Chaz · March 07, 2011, 02:37:16 PM

Thanx for the info guys. Upgrading would be nice - I guess - but do you know what I can upgrade to without a lot of fab work?? I seen a 600, 700 and a 750. Are there benefits to different ones?

JackConrad · March 07, 2011, 04:12:08 PM

Quote from: Chaz on March 07, 2011, 02:37:16 PM
Thanx for the info guys. Upgrading would be nice - I guess - but do you know what I can upgrade to without a lot of fab work?? I seen a 600, 700 and a 750. Are there benefits to different ones?

The larger the model number, the more CFM/faster fill. I do not know if compressors are rotation specific (RH or LH rotation) Jack

Chaz · March 08, 2011, 06:21:29 AM

Thanx Jack. Good point. I guess I will just have to make sure they know exactly what I have and don't assume.
Thanx again,
Chaz

bevans6 · March 08, 2011, 07:19:44 AM

There are about a zillion variations and permutations of air compressors. the Bendix web site has a big chart. I just got the model number off the tag on mine to order a new one.

Brian

TomC · March 08, 2011, 12:36:53 PM

There are also air compressors for turbocharged and non turbocharged engines. On the turbocharged engines, the air compressor is fed on the pressure side of the turbocharger so when the compressor does kick in and if you're pulling a hill with full boost, you can watch the air gauge go back up to 120psi in a very few seconds.

Chaz-get an exchange rebuilt. It is the easiest and usually have a warranty on them too! If you don't have one, also consider an air/water separator like the Bendix AD-9. Good Luck, TomC

bevans6 · March 08, 2011, 12:40:58 PM

seriously? The compressor is fed from the hot side of the turbo? I wouldn't have thought that at all. I was planning to feed mine from the air cleaner same as it is now, after I install my turbo engine.

Where is your air compressor fed from on your turbo 8V71?

Brian

Jriddle · March 08, 2011, 02:37:39 PM

Chaz

Take the inlet off your compressor and check that these valves are not sticking on your compressor. I found my bus was slow to air and in the link below I have some pictures of what I did to remove and clean the valves. Might be worth a try. When the compressor was building air I was loosing air at these valves until I cleaned them. I can air the bus up to meet all the regulation pressure tests with no problem now.

http://www.busconversions.com/bbs/index.php?topic=17357.0

John

Lin · March 08, 2011, 03:42:07 PM

If you end up wanting a rebuilt. REI (Rebuilders Enterprise Industries) had the best price when we needed one. Speak to JR at 800 489-9860.

TomC · March 08, 2011, 04:15:14 PM

I had recently exchanged my air compressor for a rebuilt, so when I turbocharged my engine, I just put its' own small (really cute looking) air filter on it, rather then buying a new turbocharger capable air compressor. I can tell you, on my truck, it is really fast when you have turbo boost when the air compressor does cycle. Good Luck, TomC

Chaz · March 10, 2011, 07:05:20 AM

Thanx guys. I wonder if the leaking wiper valves have anything to do with my air issues??

Working on rectifying that on another thread.

Anyway, my compressor is a Bendix ___Flo. PC no# 289925 and Ser. no#M1986R
At least that's what the tag looks like. Some of the stamps are lightly stamped.

I guess I'll check REI and the Detroit shop Dallas recommended in Cincy. Any other ideas?
Thanx for all the help. It sure will be good to have good air again!

Chaz