Cummins isx ,engine brake and air loose problem

A air driven engine brake? ERM.... I don't know enough to answer that.

Jacobs Brake sure. Oil pressure based.

Now....

Air pressure supply lost. Did you lose that from your Prmary tank or the secondary tank? Remember there are two needles in your air supply gauge. One green and one Red. Both of those gauges need to maintain at least 65 psi for your truck to be in running and driving sitaution. Most people are not happy until the gauges are at least 115 psi, 125 ideal.

A second thought is if you sit still, take your tractor and trailer dump valves off and then put your foot on the service brake to hold the truck in it's spot, you should lose a certain amount of air (There is a brake pressure application gauge which should tell you how much air you are placing on the service brake pressure) which should match very close to what your air supply is remaining. You need to lose a certain amount of air intitally and then hold a level or better yet improve on that level via your air compressor.

A third thought is that air compressor. Is it turning over and doing work making air for your entire rig? Thump thump thump thump with a occasional FART from your automatic Bendix air drying. PFFFFTH... thump thump thump... alls well then?

If that air supply line from your compressor to the wet tank is not warm or hot, you may not have a working compressor. I had one quit and burned out quietly while I was parked at the Doswell North Petro in my 1983 freightliner big cam 4 288 I think it was. I come back to truck and lo and behold the brakes wont come off. The springs had set. And the air supply line from the compressor which was no longer making working noises was cold to the touch ergo, dead compressor call company to get me a spare tractor and tow this one to Frederick and I will be along at some point in the future with the spare tractor.

A 4th point.

Are you losing air during braking? This is very important. If you are on the freeway coming up say on a ramp that requires you to reduce speed from 60 down to 25 for a 30 mph marked exit ramp.. you are braking with the service brake and then see and hear the warning tone as your have lost from 125 psi all the way down to 45 and bleeding at a enormous rate what little air you have left while increasing your application pressure to try to maintain the desired rate of deceleration.

That.... sir is caused when your rubber diaphragm between your air chamber that takes air and the chamber that contains the maxi spring that expands and makes you unable to go anywhere without that air in the brake chamber by your wheel. The rubber diaphragm has been eaten through by the grease, oils, condenstation etc that has been accumulating in your wet tank (If you have no air cleaner) or has gotten several gallons of the sludge into your wet tank which then punches through your air cleaning, filter system which no longer works anymore being itself full of sludge that finally made it into at least one of your 10 brake chambers aboard that rig.

You do drain your tanks at night when asleep right? Right... RIIIIGHHT? Don't ######## me.

A 5th point. Your pads have been abused on a mountain and no longer are in adjustment. If you are not a qualified card holding brake adjusting mechanic, find a shop or call the company shop who will assign someone to find the bad pads and replace and adjust for you.

The fastest way to find the bad pads is to park the truck with your tractor and trailer parking dump valves (The yellow and red ones in a 1974 or later cab, the black, white and blue ones for the older pre 1974 1,2,3 braking systems) with the parking brakes on. Chock two of the tractor wheels, get underneath tractor with ball peen hammer. You want to hear the thuk thuk thuk thuk sound when you rap a drum lightly near the bads on the bottom inside.

If you hear a ding ding ding, get a peice of school yard white chalk and X that wheel on the inside. You do not have adequate contact with that brake pad set to the wheel drum.

Repeat process for your trailer.

Im about to bury you in more brake stuff. But suspect your eyes are glazing over so I'll stop here.

 

I haven't seen a jake brake that is tied into the air system before. I'm not familiar with the ISX but I'd say no jake on 3rd stage is likely electrical (most likely the switch) since if it was a fault with the 3rd stage cylinders you should at least have 4/6 cylinders working on 3rd stage I would think. Someone with ISX experience will probably come along and clarify things.

Does the air system leak down with truck running, off and engine off with key on?

 

Presuming Oil driven jake.

Either electical as mentioned, or it's going to be oil pressure with the computer denying you full jake power.

If that is the case maybe it threw a code. Did it?

If you got a older rig, my thought would be to pull the dipstick and see what oil you got in that there engine.

 

Nope, not connected.

Air leak, could be anywhere on the truck, you'll have to hunt it down or have it done for you.

Jake brake is a 2/4/6 cylinder, step 3 is all cylinders. Low oil pressure can effect Jakes low oil or thin oil. Fresh oil change fixes this. Otherwise most likely cause is electronic, the ECM runs the Jakes, it needs input from you (Jake switch) and sends signal to Jake controller which directs oil pressure to the Jake rockers. If any of these aren't working correctly you may have a engine code. If it's the switch you will not have a code as the ECM doesn't know that you've engaged step 3.

Happy hunting!

 

Check with soapwater the airmanifault on the firewall
The the main airline from the airpressur to the dryer
Check the airtanks by them self
Airbags from the cape like to leak im the base.....