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Engine compressor unloader rebuld
#1

Hello all,
  Has anyone ever rebuilt the unloader valve on a DD60 Bendix compressor.  The actual rebuild looks very simple but getting to it not so much.  Was wondering it it would be easier to pull the compressor and do it on the bench or pull the alternator and do it in place.

Jack and Dianna Hunt
Coach #663
2003 - 45' triple slide
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#2

Well, I finally got around to pulling the compressor and rebuilding the unloader valves.  That thing is a pain to get out, it weighs almost 100 lbs with that pump on the back and you have to climb back into the little access area on the curb side to get to it.  Word of advice should anyone be contemplating doing this, the bolts in the back are very difficult to see (you will need a mirror on a stick) and get to and they are not all the same.  Looking at the photo, the bolts at the 6, 8 & 10 positions are 15mm bolts and easy to get to, the one at 12 is a 15mm nut and in close quarters but accessible but the 15mm bolt at 2 is tough and requires a fairly long extension and the one at 4 surprises you and is an 8mm socket head bolt and the most difficult of the bunch.     Once out the actual job of rebuilding is very easy, just pull the plate from the top of the compressor,      remove the valve pistons, drop in the new ones and put it back together. I tested it with the rig I had built to check it in the first place      prior to reinstalling it and unlike before it held pressure.  After installation the system came up to pressure near what it had usually maintained though not quiet there.  I installed a gauge in the line between the wet tank and the governor     so that I could check the cutout on it. fired up the engine and the cutout was set at 115 so I adjusted the governor to between 125 and 130.  Starting with the tanks at atmospheric pressure I reach cutout in about 11 minutes.  I still have a leak somewhere but the bus builds and maintains pressure very well so it is once again derivable.  Now I just have to chase down the last of the leaks.  Here is the kit you need.     

Jack and Dianna Hunt
Coach #663
2003 - 45' triple slide
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#3

nice writeup. thanks. all that work for a 15 dollar rebuild kit. saves a ton doing it yourself

tom

2002 45'8" Newell Coach 608  Series 60 DDEC4/Allison World 6 Speed HD4000MH

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#4

I didn't even price it out to see what it would cost to have it done, after doing it I'm sure it would have been more than I would have wanted to spend.  I included the part number for the kit but not the actual compressor spec, that wasn't very complete info.  The compressor is a Bendix Tu-flo 750.     

Jack and Dianna Hunt
Coach #663
2003 - 45' triple slide
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