jeffl1107

Because I am a rookie when it comes to working on Mack trucks, I cant seem to locate the pressure relief valve to see if it is faulty. There is somekind of valve where the line comes into the main tank. It has a small cylinder coming off it coming towards the ground with a hole in the bottom. I am wondering if that might be it. If anyone could lead me in the right direction I would appreciate it. Jeff

Thanks for the info. I am going to check it out today. Yeah, I hear no bleed off of air at any time. I have had it just past 150 psi and then I shut it down. I drove it home after I bought it around 10 miles and when I shut it down instantly heard an air leak. After fixing I built up air pressure and realized it was not being regulated. So I will check and see where the governer is.

Hey all. I just bought a 1997 Mack RD688 tri axle dump truck. Been fixing some things on it and not being familiar where stuff is on this, have a question. The truck is, I am sure, building up to much pressure in the air system. The guage in the truck goes up to 150 psi. I have had it just past the 150, probably up to 160 and I hear not bleed off of the air to keep it from building up to much. Can someone help me with finding the bleed off valve because I would assume it needs replacing. I know on a Ford truck I had, that bleeder valve use to pop at around 130psi.

Hey all, I am new to the forum by not new to Mack trucks. I use to drive dumps in my earlier year's, the old DM800. Anyway, getting back into dump trucking on my own as owner operator now. I just purchased a 97 Mack RD with 350 engine. The question I have is I never worked on one that had a jake brake on it. The other owner stated that he disconnected it because a couple places he worked for did not allow the use of it when in there quarries and his guys kept forgetting to turn it off, so he just disconnected it. My question is where is it located on the engine? I looked at the switch on the dash and it is plugged in. I guess I need to trace it from the engine to see where he disconnected it. I cant get him to return my call, although it has only been a little over 24 hours. Did not know if there might be somekind of fuse he removed. Just want the option to use it if I need it as I know if would save on brake wear. No hills as I live in Southern NJ. Thanks for the help.