Mbe engine air brake compressor ?

[tknight]

Has anyone had any issues with their air compressors on the mbe motors I have a m2 with the mbe and I'm hearing a slight knocking sound that stops when the purge valve spits thi all started right after I had the steel air line changed to air dryer
Pressure I around 135 all times and everything cycles fine so I'm hoping it's something simple as getting into change this is gonna be a tight fit and since it's winter I'm not looking forward to to it
currently 500k miles on it
Thanks

 

[paullud]

with the mbe

I found your problem. ;-)

Where is the sound actually coming from? Are you sure it's not the air dryer?

 

[tknight]

Air dryer is on opposite side of truck it's coming drivers side rear of motor and it's rhythmic when your holding the steel line at first I thought it was just transferring the noise through where the line run into the metal and amplifying it

 

[tknight]

Wow 1800.00 + labor for a new compressor the mb curse continues!
Never again will I buy a truck with the mbe and drive train".........

 

[usafk9]

Is it broken? Is that the price someone quoted you after looking at it?

If it's producing air at the proper rate, my question would be what is wrong with it? Ours has almost a million miles on it is why I ask. Also, you may be able to find the compressor cheaper at a place like Fleetpride or Ryder Fleet products. I avoid FL dealerships or Detroit shops, if I can.


Edit: Maybe a PM to DaveKC or Greasytshirt might be in order.

 

[davekc]

I believe those have a Bendix so 1800 sounds high. As suggested, I would shop that part and figure 5 to 6 hours on the labor. If it is keeping the air up, just might need one of the valves or governor replaced? Whole lot cheaper. I would start there since it was fine until you changed one of the lines.
A lot of places will say just replace it (professional parts changers) and that will fix it, but there may be some inexpensive options before you do that.

 

[tknight]

I havn't shopped it totally yet, but I'm thinking it's got a bad bearing on one of the pistons, because it's sounding just like a mini rod knock, I did find a used one, for 350 but they can't give me the miles on it. The head rebuild hit is like 275 or so, but till it's off it's no telling what, but my educated guess is it's an expensive noise

 

[davekc]

That is true. You will know more at that point, but I think even with that, you should be able to stay well under 1800. Good luck.

 

[tknight]

Well it's a Rockwell, and in stock at Detroit diesel canton oh 874.87 for remanufactured unit, parts guy says its common to spin a bearing just like a vw did in the 60's 5 hrs labor, it's a ***** to get it out apparently since it's only 4 bolts and a hose, so I guess I'll get it in the shop in a few days

 

[Slo-Ride]

Knight did ya use a stethoscope to try and pin point the knock? Taking a fast look at mine it does look tight coming out and going back in... Extra set of hands for sure would be needed.. Seems to me a bearing noise would be there all the time not just under a load... Once the AC stops pumping those bearings are still running..
I'm with Dave, Check out that head and unloader valve before condemning the air compressor. I have seen them so full of carbon they couldn't work properly..
The replaced line was replaced with the correct hose correct? Meaning exact match... Nothing kinked, bent, all fittings where checked for carbon build up all the way to the air dryer.

 

[tknight]

All is clean and tight the only difference is the length of the hose,as that is what then had .
Detroit diesel looked at it this mornin and they said under pressure the rod knocks and when it unloads it lessens but if you put your hand on the compressor you can really feel it being unhappy it builds fine and there is no problem in the head or valves involved it's define tilt a rod knock
Might last a year might last a week ! I'm in agreement with them and they really hate doing that repair so I'm not thinking they're just out for the money

 

[tknight]

Great news problem is finally fixed !! 10.00 for a 1/4 in coupler and 5 min time although I too 5 weeks to become apparent to the 4th mechanic. It was a leak under the radiator on the air line going to the governor on the compress it wasn't allowing the gov to do its job hence the 140lbs of air in the tanks the excess was causing a knock in the comp driving me nuts
You could barely hear it while the motor was running

 

[Greg]

That is good news. Air problems are nothing to play with.

 

[ttruck]

ive got a cat c9 with a knock or loud tic at the compressor 4 yrs now been told there are spring loaded cups of some sort inside springs a getting weak,waiting for total failure then ill replace it still runs at 135 lbs.

 

[gandrimp]

Glad it's fixed and was cheap.Someone brought up " stethoscope " I have a tip that may save a few $$ for someone. I have a few pieces of 1/2 x 1 3/4 plywood in lengths from 2 ft to 5 ft. One end has a taper about 4in that ends with a blunt point, the other is just squared. To use, put tapered end in/on the area to listen to, the other end into your ear (not q-tip deep). Stick cant touch anything else due to picking up other sounds.Ever wonder what your valvetrain sounds like? Is your alternator making a noise? Air compressor knocking? I work around some slow turning ball bearings that with this contraption you can hear the ball fall in a dry bearing, seriously. I once held this above a mouse hole and heard it say excuse me after farting,,,,,,, not seriously.I have been told a wooden dowel will work the same.