air brake fail ideas anyone

[laurencen]

on a freightliner truck the compressor failed, rebuilt using a kit but its a little slow building air, there are 2 small lines maybe 1/8 dia going into the air govenor, thinking I may have them backward, if I trace them back where should they go, one for sure goes to the bottom of the drier, anyone have a idea where these go

Laurence

 

[DieselPower]

It sounds like the unloader valves were not properly installed. The two lines going to the govoner (which is probably a D2 govoner) are the sense line that goes to the primary air tank and the other is the unloader line that goes to the air dryer. The sense line let's the govoner know when to turn on and off and the line to the air dryer tells the purge valve in the air dryer to pop off after the end of a compression cycle. I would pull the head off and check to make sure the valves are properly installed and seated. What type of compressor is it, a Holset, Caterpillar, Bendix?

 

[laurencen]

hi, its a holset, single on a cummins, the initial issue was eratic pressure, it worked then quit, took the hose off the drier and it worked, finally quit, took the head apart and found the outlet valve (thin ring with a weight above it) there is or was a steel gasket with 3 dimples, these dimples keep the disk from riding up over the seal face and thus stopped pumping when the dimples disintigrated, got a re build kit, replaced both inlet, outlet and governer, well it will not pump at idle, at 1200 to 1500 works but slower than the good days, when the pressure line was removed at the drier it pumps but if you put your finger over you can hold the unit from pumping.
Today took the head off, think the inlet ring was off center, its held by a washer that is slightly deformed and it fits into the head above the cylinder, I think the bevel was the wrong way allowing the seal disk to off center, put it back the other way and will see how it works tomorrow, the kit came with 2 wavey washers, cummins say install both washers, they go into a groove on the outlet weight, with them both in the compressor could not put out any pressure, with both removed it will pump up at 1200 rpm but slow ihave one in now, new compressor is 1300 dollars, not cheap so have to figure how to make this one work, did put 15 weight oil in the cylinders last week when the head was off to see if the rings leak, overnight no oil was lost.

 

[KICK]

on your basic bendix D type governor ( probably the most common governor)

there is a port on the governor called RES, the air line from the tanks goes there. it is the sensing line.

the other line is UNLOADER, goes from the unloader port on the governor to the unloaser port on the compressor.

if you disconnect the unloader line from the compressor and it still has problems pumping, the problem is in the compressor because with the unloader disconnected it should pump all the time.

you dont have a restriction somewhere else in the air system, do you?

foreign matter can clog the air dryer if truck is so equipped.

 

[laurencen]

Kick, after many dis assembly the issue seems to be the intake valve plate, it sits on top of the head above the cylinder, I did not work in this area but the disc is held in place by a bevel washer, it was upside down and the bevel would allow the disc to get trapped thus not sealing when the poston came up, figure with me removing the compressor many times it slid into this position and the second issur emerged, maybe the exhaust rebuild I initially found was never the issue but as it was damaged figured I had it beat, the funny thing both Cummins and Freightliner who sold the kit had no idea or diagrams on how to locate the plates and discs, say thet never re build them, find it hard to believe as a kit was $150.00 and replace the compressor was $1700, trucking companies must make too much money, now I have a leak and air goes down to 0 from 125 in 20 mins, this may be sloppy pipe fittings being taken off too many times, soapy water should find them later this week


Thanks for the asssistance and ideas