Air Compressor for an Cummins ISX question

I did this today on both the Primary and Secondary tanks, and here is what I got from this.

I could hold pressure at the cut off as long as it was hooked to the shop compressor, I found one small leak and repaired it as well as installed new drain valves on all the tanks, after I made that repair I found no other leaks, but the truck still will not hold or build air past 75 lbs. Any new ideas?

 

Remove the compressor air intake piping and check for air leaking into the intake side of the compressor.

 

Ok... So when you charge your air tanks with air from a shop air compressor the tanks will fill to 120 -130 Psi? But when you remove the shop air the tanks drain quickly or over a period of time? Do you lose air pres. at highway speeds? The reason I ask this is because about 2 weeks ago I had 2 problems with this truck. It had a bad trans. oil leak and a loss of air too. I installed a pres gauge at the vent on the trans. and sure enough when the range select was in high it pressurized the transmission and leaked oil out of the vent. I would check what Bender stated in his post and if you do not find a fault there I would replace the compressor head. I have the Pn# for it at work and the kit has the instructions in the box.

 

tanks filled to 125psi, i didnt try removing the air lines from the shop to the truck tanks so ill try that and let you know what happens, yes the truck looses pressure at hwy speed if i am not underload under stress, ie. Going up an incline, how hard is it to replace the compressor head, and where is the tras vent?

I will be honest, i use to own a peterbuilt and i did all the work on that truck, i traded it in for this volvo (the worse choice i made buying a volvo) and i am trying to do all the repairs on this truck. So if you can help me out with photos or detailed instructions that would be greatly appreciated. I am trying to get this fixed before i get stopped and inspected and put out of service.

 

Did you eve r isolate the problem?

 

how do you fix that . that might b my problem bcause i just change my turbo ,,, . but my is not building air pressure a all

 

I'll have to admit i'm a little lost as to what the problem is exactly. I had the initial interpretation that air pressure was able to be built but is being lost due to the test that was performed where the tanks were filled by the air compressor, unit shut down then keyed on and when driver returned to dash cluster air pressure has already diminished. Personally i'd start by removing air discharge line from air compressor, couple 2 #10 fittings together with a 1/4 turn shut off valve in between the fittings. Use shop air to fill the system from where the air compressor would be connected. Use the 1/4 valve to shut off the air pressure to lock the air pressure in the system once the in dash gauges read 120 psi. Then let the system sit and monitor the in dash gauges if they drop at all with key on or key off (engine off) you definately still have an air leak that should be audilble. Fix this issue first, you will have to crawl all over the unit to listen. If there is no leak like this and pressure does not fall, move to chocking the wheel and release the brakes. Check all over the unit again. Now have someone apply the foot brake and hold it while you crawl all over the unit again. Have person holding the brakes watch the gauges they should drop immediately then settle at a point. If they continue to drop you have a problem in the braking system. If all is still ok then you have an issue youll probably need to have checked out by someone. Finding an air leak when the unit is operating can be VERY tricky. Lastly air compressor could have an issue where it cant keep up with the demand needed but again from what i've read I am having troubles fully understanding your problem. Have you tried operating the unit with out the trailer? Do you pull the same trailer all the time?

 

You sound like you have a blue line air leaking. I eould sa build pressure, block wheels, then somehow hold down trolley lever, then go out snd listen. If blue air line is leaking that is the only way I know of to find it.

 

Check the westgate- the boost controller arm on the turbo. Get a soap water and spray on that arm with truck running and look for bubbles.
Sometimes air dryer may be preventing air to pass thru
You can remove air supply line going from air compressor to air dryer and check air flow and do the same thing on the air lane pass air dryer. Pressure should be about the same.
If it builds up to 85 only it could be bad air governor.

 

So, did you figure this out yet??? Enquiring Volve owners need to know.