compressor dilemma

David Anderson · November 09, 2009, 02:38:50 PM

Just returned from a 500 mile trip. I noticed a change in the air up time of my brake system. It is taking a lonnnng time to air up, about 7 minutes from 0-120 and about 4 mins from 90psi (cut in) to 120. It used to be about 1 min from cut in to 120. The leak down is the same, about 36 hours back to zero when parked. I removed my air cleaner and checked the inlet pipe and I could feel suction on my fingers. When the dryer sneezed suction would cease. The coach loses about 10psi on a hard brake application. No noticable leak down holding the brakes with the engine off.

Something has changed and can't be good. The Eagle manual says I have a BW700 compressor with a D-2 governor. I don't know the age or time. However, I've had the coach since 2000 and put on 56k miles. Dryer desicant was changed about 20k miles ago.

I'm thinking a new compressor and governor may be in order just for the peace of mind.

Help.

David

bevans6 · November 09, 2009, 03:47:31 PM

The DOT test for compressor function is, with engine running, to fan the brakes down to below 85 PSI, and measure the time it takes the compressor to recover between 85 psi and 100 psi. The test fails if the compressor takes over 2 minutes and the vehicle must be taken out of service immediately (per the DOT). Normal time for the test is between 20 and 40 seconds. B
Vehicles with dual service air tank systems tend towards 40 seconds, my bus with a DD3 single service tank system takes 18 to 20 seconds. FWIW my bus takes close to 10 minutes from dead flat to 120.

There are various valves and shuttles inside the compressor and governor, you may get away with servicing what you have rather than just replacing, but it does sound like you have a problem somewhere. The key is that something changed. If it's working right it's the same every time.

Brian

luvrbus · November 09, 2009, 03:58:49 PM

David, check your auto drains on the tanks up front and the rear if the compressor is not pumping a lot of oil it is probably ok.
FWIW David the Bendix 700 is getting hard to find for a Eagle ,Jefferson is about the only show in town for that compressor

good luck

gumpy · November 09, 2009, 06:57:19 PM

You have a leak in your aux air system (wipers, belts, shutters, etc). Get out the spray bottle and start spraying soapy water on all the components. Regulators, air valves, tanks, bleeders, tensioner cylinders, throttle cylinders, etc. Eventually you'll find a bubbler or two.

After I reread the original post, I agree that this is probably not a correct diagnosis.

bevans6 · November 09, 2009, 07:10:07 PM

if Gumpy is right and there is a leak in the aux system, then you should see the pressure leak down to about 60 psi quite quickly, then the pressure protection valve will kick in and the service tank would then leak down quite slowly. David said that over all leak down from full pressure was unchanged at 36 hours. If the bus leaks down at a reasonably steady state to zero, then there isn't a new and dangerous leak in the aux system.

you could probably hear a leak that caused the compressor recovery to increase from one minute to 4 minutes 90 to 120 psi, as soon as you turned the bus off and started snooping around, too.

David Anderson · November 09, 2009, 07:37:23 PM

Quote from: luvrbus on November 09, 2009, 03:58:49 PM

FWIW David the Bendix 700 is getting hard to find for a Eagle ,Jefferson is about the only show in town for that compressor

good luck

Do I have to replace it with a 700 or is there an alternate compressor that will bolt on to the 6v92?

David Anderson · November 10, 2009, 08:51:09 AM

Also, what price range am I looking at for parts? I can install myself.

David

luvrbus · November 10, 2009, 09:04:02 AM

David, I have never seen a replacment air compressor for a Eagle other than the Bendix Tu Flo 700 you can use a truck type but it requires new piping.
Jefferson charges around 500 bucks,and if you do change replace the compressor drive also buy it from DD.
It is not hard to do if you can still get into the engine hatch at the rear, you do have antifreeze and oil to contend with.

good luck and do you still have my number if you need help

RickB · November 10, 2009, 09:33:55 AM

I believe there is a new 700 on ebay for around $300 after shipping. It may be a 500 but it's worth checking out. keyword detroit diesel in the search and press newly listed. it just came on in the last day.

RB

Len Silva · November 10, 2009, 09:40:26 AM

I would do some more trouble shooting before springing for a new compressor. Perhaps a problem with the dryer causing some restriction in the line.

luvrbus · November 10, 2009, 09:47:04 AM

Rick, Eagle uses a different 700 compressors from most buses and trucks only the one for a Eagle will work without a lot of new piping I never understood Eagles reasoning for doing that way.

good luck

bevans6 · November 10, 2009, 11:30:55 AM

Could also be problems with the check valves between the air dryer and the wet tank, and the wet tank and the dry tank.

Brian

gus · November 10, 2009, 01:05:09 PM

Since governors are so cheap($20+-), if yours uses the common type in use now, it is far better to start with replacing that before replacing the comp. The gov should be replaced anyway if you replace the comp.

bottomacher · November 11, 2009, 06:15:38 AM

I have a reman Bendix Tuflo 700 that I bought for my mc9, but it won't fit. A friend told me that he thinks it is for an Eagle. If you send me some photos or other identifying info, I'll see if it's what you need.

David Anderson · November 11, 2009, 07:02:02 AM

I pulled the compressor off. The coupling seems to be steel, not carbon fiber. I noticed there was no cotter pin in the slotted nut. Hmmm, could be bad. I also noticed the circle around the nut is rubbed clean. What does that mean? See the pictures:
The first and second and 3rd pictures are of the compressor with the drive cog slipped in

The 4th has the pencil pointing to the area around the slotted nut that is rubbed clean.

See next post below this one