Truck#1 Posted September 10, 2007 Share Posted September 10, 2007 I installed a new air dryer on my 98 CH. Right after it spits it sounds like air is leaking from the compressor but only for a few seconds. Why does it do this??? There doesnt seem to be any leaks around the compressor. Also the compressor charges my system up to 130PSI. Is there a way to dial it down???? Is there any special way to install the air dryer besides mounting it and connecting the 3 air lines and plug.? It was pretty simple...but almost too simple.Thanks for your help.Rob w. Quote Link to comment https://www.bigmacktrucks.com/topic/2844-air-dryercompressor-questions/ Share on other sites More sharing options...
ThaddeusW Posted September 10, 2007 Share Posted September 10, 2007 Rob,The three lines and plug are all thats needed. As for the air leaking sound, the governor sends out positive pressure to hold the unloader valve in the compressor open. This stops the charge cycle and that same air signal also triggers the purge cycle of the air dryer. The governor does have an exhaust port, that might be the leaking sound but thats normal. 130 PSI sounds normal as the pressure relief valves in the brake system are set at 150 PSI. Turning that pressure down is possible by adjusting the governor cut out pressure via a screw on one end. But some governors are not adjustable like the D2-A from Bendix. Here are the instructions for the D2 from the Bendix website: To raise the pressure settings, turn the adjusting screwcounter-clockwise. To lower the pressure settings,turn the adjusting screw clockwise. Note: Be carefulnot to overadjust. Each 1/4 turn of the adjusting screwraises or lowers the pressure setting approximately 4psi. Quote -Thad What America needs is less bull and more Bulldog! Link to comment https://www.bigmacktrucks.com/topic/2844-air-dryercompressor-questions/#findComment-13858 Share on other sites More sharing options...
Truck#1 Posted September 10, 2007 Author Share Posted September 10, 2007 Thanks for the help Thad!! Quote Link to comment https://www.bigmacktrucks.com/topic/2844-air-dryercompressor-questions/#findComment-13864 Share on other sites More sharing options...
HK Trucking Posted September 10, 2007 Share Posted September 10, 2007 I'd leave it at 130.That extra 10 lbs. pressure isn't going to hurt anything, and it will give you an extra reserve of air. Quote "If You Can't Shift It Smoothly, You Shouldn't Be Driving It" Link to comment https://www.bigmacktrucks.com/topic/2844-air-dryercompressor-questions/#findComment-13865 Share on other sites More sharing options...
CML Service Posted September 12, 2007 Share Posted September 12, 2007 Some of the newer air driers like the Bendix AD-SP have a longer purge that will sound like a air leak from the bottom valve, but only for 10 seconds or so. Chuck Quote Link to comment https://www.bigmacktrucks.com/topic/2844-air-dryercompressor-questions/#findComment-13917 Share on other sites More sharing options...
Noid93 Posted September 13, 2007 Share Posted September 13, 2007 Unless the destroking process on the air compressor takes longer than the purge, It will continue to pump air untill the destroking valve hold the valves open on the air compressor. Just had a 3176 cat in a t600 KW (part of Maxvilles fleet) that would continue to pump all day long. The culprit, a collapsed line from a governor to the compressor, but if your mack is like mine, the gov is bolted to the comp. Also, The o rings on the destroking valves could be old and cracked, I just ordered a "destroking kit" for the bendix tf 550 air compressor on that cat(the same as on my truck) that consists of a gasket and push rods with new o rings for a whole 15 dollars. Those valves are just under the cover on the head of the comp(right on top). If you need i can get a part #. Let me know. Quote There Is No Replacement, For Displacement!!!!! Link to comment https://www.bigmacktrucks.com/topic/2844-air-dryercompressor-questions/#findComment-13939 Share on other sites More sharing options...
Truck#1 Posted October 13, 2007 Author Share Posted October 13, 2007 OK gang i still need your help. I installed a new unloader kit in my 98 CH. It didn't really make much difference but my air dryer is doing silly shit. It is a new dryer from the Mack dealer....When i start the truck with 0psi its fine until the dryer spits at about 125 (sometimes 130) then it ticks like a bomb for 5 seconds then it hiss's air until the red needle is down to 100. Air builds back up (dryer still hissing air) until it hits 125/130 again. Then it starts over. It seems to hiss air all the time and the compresor is just doing it's normal thing. Is the new dryer bad?? The parts guy at Mack said they are really never bad out of the box. thanks for the helpRob W. Quote Link to comment https://www.bigmacktrucks.com/topic/2844-air-dryercompressor-questions/#findComment-14434 Share on other sites More sharing options...
theakerstwo Posted October 13, 2007 Share Posted October 13, 2007 OK gang i still need your help. I installed a new unloader kit in my 98 CH. It didn't really make much difference but my air dryer is doing silly shit. It is a new dryer from the Mack dealer....When i start the truck with 0psi its fine until the dryer spits at about 125 (sometimes 130) then it ticks like a bomb for 5 seconds then it hiss's air until the red needle is down to 100. Air builds back up (dryer still hissing air) until it hits 125/130 again. Then it starts over. It seems to hiss air all the time and the compresor is just doing it's normal thing. Is the new dryer bad?? The parts guy at Mack said they are really never bad out of the box. thanks for the helpRob W.Where does the air leak fromand what kind of drier is it? glenn Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/2844-air-dryercompressor-questions/#findComment-14441 Share on other sites More sharing options...
fjh Posted October 13, 2007 Share Posted October 13, 2007 Unless the destroking process on the air compressor takes longer than the purge, It will continue to pump air untill the destroking valve hold the valves open on the air compressor. Just had a 3176 cat in a t600 KW (part of Maxvilles fleet) that would continue to pump all day long. The culprit, a collapsed line from a governor to the compressor, but if your mack is like mine, the gov is bolted to the comp. Also, The o rings on the destroking valves could be old and cracked, I just ordered a "destroking kit" for the bendix tf 550 air compressor on that cat(the same as on my truck) that consists of a gasket and push rods with new o rings for a whole 15 dollars. Those valves are just under the cover on the head of the comp(right on top). If you need i can get a part #. Let me know.You may have bad unloder orings in the compressor head depending on your compressor they can be easy or hard to change!If you have a 700 bendix its easy if you have a 500 bendix its dificult!take the small line off the air drier while the compressor is pumping between 90 and 130 if there is air coming out the line the problem is in the unloader ! Quote Link to comment https://www.bigmacktrucks.com/topic/2844-air-dryercompressor-questions/#findComment-14443 Share on other sites More sharing options...
Truck#1 Posted October 14, 2007 Author Share Posted October 14, 2007 Where does the air leak fromand what kind of drier is it? glennThe air is coming from the valve or hole at the bottom of the dryer. I dont recall what model Bendix it is. Quote Link to comment https://www.bigmacktrucks.com/topic/2844-air-dryercompressor-questions/#findComment-14446 Share on other sites More sharing options...
Truck#1 Posted October 14, 2007 Author Share Posted October 14, 2007 There is one thing i forgot to mention...when i put the new unloader kit in I had a problem with the gasket leaking and took the cover off again. I did notice the piston on the left side popped up with the new spring and the right one (the one to the front of the truck) didn't pop up and almost seemed stuck in the hole. I did grease the new ones up with the grease in the kit before i put them in.. Was it supposed to pop up when i took the cover off???? Quote Link to comment https://www.bigmacktrucks.com/topic/2844-air-dryercompressor-questions/#findComment-14447 Share on other sites More sharing options...
theakerstwo Posted October 14, 2007 Share Posted October 14, 2007 There is one thing i forgot to mention...when i put the new unloader kit in I had a problem with the gasket leaking and took the cover off again. I did notice the piston on the left side popped up with the new spring and the right one (the one to the front of the truck) didn't pop up and almost seemed stuck in the hole. I did grease the new ones up with the grease in the kit before i put them in.. Was it supposed to pop up when i took the cover off????If it drains the air tank down till the governor kicks back in and it is a ad4 or a ad9 bendix you have a check valve in the drier draining the 1st tank back in to the drier and out of the purge valve. The ad 4 has a plastic flapper for a check valve inside and you have to tear down to replace and the ad9 will have a screw in check valve on the bottom on the inlet port of the dier and can be changed from the bottom. glenn Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/2844-air-dryercompressor-questions/#findComment-14448 Share on other sites More sharing options...
Truck#1 Posted October 14, 2007 Author Share Posted October 14, 2007 The part # on the box is 745 800887 it says AP-SA Bendix air dryer it doesnt have a number after AP. I'll look on the air dryer itself on Monday. The old one doesnt say either. The new one does have a plastic flapper on the bottom. So what you guys are telling me the air dryer is probably the problem and not the compressor or unloader?? It's still under warranty. Also the Mack dealership said I can bring it in and they'll test it.thanks againRob W. Quote Link to comment https://www.bigmacktrucks.com/topic/2844-air-dryercompressor-questions/#findComment-14451 Share on other sites More sharing options...
Truck#1 Posted October 14, 2007 Author Share Posted October 14, 2007 My bad ...it's AD-SP Quote Link to comment https://www.bigmacktrucks.com/topic/2844-air-dryercompressor-questions/#findComment-14452 Share on other sites More sharing options...
theakerstwo Posted October 14, 2007 Share Posted October 14, 2007 My bad ...it's AD-SPI sorry but i cant help you on the ad sp i know what it is but have never wored on it but if the dier is draining the wet tank it sounds like the deir is defective. glenn Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/2844-air-dryercompressor-questions/#findComment-14454 Share on other sites More sharing options...
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