jeffl1107

thanks joe, I will check that out tomorrow.

Yeah, both you guys make sense with regards to the lift axle. I have already taken each valve off, cleaned it good with brake cleaner and then shot in some WD40 and still the same. I know when I push the valve in, you instantly hear air and the axle goes right down. But when I push it in to raise it up, there is about a 6-10 second delay before you start hearing air and then it takes forever for it to go up. So I guess I will try and replace them. Only reason I asked is it seems impossible to find these things. I even called Hendrickson and they were having a problem figuring out what I needed. But a local parts store found what I needed and they are ordering them. As regards to the low air alarm, finding the switch will be a challenge since I dont know where that would be. Jeff

Hey guys, This is two questions in 1 post. Have been doing alot of work on my truck and have now pretty much got it in good condition. Replaced all wheel seals, bearings and brakes. Some brake cans and slack adjuster and some other odds and ends. Anyway, need your help as I cant seem to troubleshoot these two things. First, my low air alarm stays on constantly, even after it has built up to operating pressure, around 125psi. The guy had it unplugged, so I plugged back in. Stays on all the time. Bought a new alarm and plugged it in and it still stays on. Not sure where to go from here with it. Second, with my lift axle. The axle, when I pull the quick air release valve, goes down in under 10 seconds, but when I go to lift it up, it takes almost 90 seconds. It is a non steerable hendrickson axle. I replaced the in cab Velvac quick release air valve and still does it. The little valves mounted on top of each air bag release air but I guess not fast enough. If I go out after I push the valve to bring the axle up, while it is releasing, if I stick a screw driver in the end of valve above air bag and push in slightly, it releases with a vengeance and comes right up. Do you think it is as simple as needing to replace those valves with new. Thanks for any help. Jeff

No dirt built up under pedal. So I will check the two switches. Thanks

Hey guys, Another question for you. Got be picking my hair out. Anyway, my brake lights are constantly on. I traded out the stop light relay with 3 others and it is still staying on. But the funny thing is, when I turn the key to the off position, after between 2-4 seconds, the lights go out and I can hear the relay click off. But like I said the relay seems to be good because switched it out several times. Where else could I look to troubleshoot this. Thanks for the help. Jeff 97 Mack RD688S

By the way rhasler, is there an easy way to tell what size rears these are or do you have to cross ref. the numbers on the rears?

Ok cool. I will check them today. Thanks

Wondering if someone out there can tell me where the normal problem area's are with the camelback rears for leaking. have a 97 rd688s tri axle dump i just got. worried about the rear leaking. I know mack's leak but just a little concerned that some companies might not let me into there quarry with this leak. Wondering if someone could tell me where the normal area's are for leaks and what is the best fix. I have not really cleaned it and kept an eye on it to see where it is coming from. Bare with me as I dont know all the part names. But I cannot tell if it is coming from where the carrier bolts into the rear housing itself or it is coming from a plate that is on the side of the carrier. But I am going to have to address this soon. If I had a diagram I am sure my mechanic friend and I could do something with it, but cannot find any diagrams. Any help appreciated.

I check the air cleaner. I also agree you guys about the Mack and smoke issues as I have driven them in the past. But this was definitely more than would be expected. I just found an exhaust leak where the turbo hooks to exhaust so I will have to fix that.

Hey All, Posted on other area's with some issues that I was able to fix on my own with help from the guys here. Hoping you could help with one more issue. Finally got tags for truck and is on the road now. 97 mack rd688s tri axle dump with e7 350. I was driving it over to a guy to have some spots welded on the body and my wife was following me. She said that it seemed like most every time I shifted gears but always on intially taking off from start, that it was puffing some dark smoke. I really could not see much as stack is on passenger side above mirror. before i bought it, i saw it come in to yard a couple times while someone else was driving it and i did not notice much smoke at all, but she is saying that it was definately puffing out smoke. It was dark smoke she said which has me a little concerned. The truck only says 379,000 but and the engine looks in good condition. I know this could be a fuel issue or possibly injectors. What do you guys think could be the culprit here. I definately dont want to hear the big "O" word, not yet atleast until I get this thing making some money. Any help is appreciated.

Hey guys thanks for all the info. I had to get an authority about 7 years ago when I was running a Toter truck hauling mobile office trailers. But it seems to have changed a little. First, I was told I would have to wait up to 20 days after applying for MC# before I can start running, not good for me. Also, somekind of payments with the IRP, which I dont remember when I did this before. I just dont want to go the easy route with the tags for just Jersey and then in fall or winter be screwed because I cant go to other states for work. Hey Bullhusk, I am going to email you to see what you might be able to do here. I just want to start running.

Yep, your correct. Thought about it when I was out there racking my brain and switched the ground over to the Norm Open post and WAH LAH! it works correct now. So all is well now. Appreciate everyones help!

Ok this is where I am stuck. Maybe you could tell me if I am just a derlick or what. Electrical is definetly not my strong suit. But, it seems as though I have figured out the wiring, or maybe not. I took the hot wire I found that is attached to the clutch switch and connected that to the common on the fuel pump micro switch. I took a ground and hooked that to the Norm Closed terminal on the switch. All seems to be working like it is suppose to. I have not re mounted the switch yet, but when I have the Jake dash switch on either low or high, and I physically push in the micro switch, the Jake is disengaged. When I let off the switch, within about 1 second the Jake engages. But my question is now, when I physically let off the micro switch like when the acclerator arm would do, and rev the engine up, it sounds like the Jake is engaged as I am reving it up and I know that cant be right. So is there something that I did wrong, or something that is not working? Thought I had figured it out but does not seem like it. Jeff

Thanks for that but I am not, by far, an electrical wiz. My switch has 3 holes in the back of it. first is marked "Common" 2nd "Norm Open" 3rd "Norm Closed". I was assuming that the hot wire I found goes to one of them and then a ground comes off another. But I dont know what goes where. So if I cannot figure it out I will just have to get someone to wire it for me.

Oh and the business in her name is an LLC

Mark, You must be a mind reader. That is exactly how we are going to do this. The company we will run truck under is in my wifes name and I would be driving it as an employee. But is there any difference with it the company being owned by my wife. Does she then have to do everything. Only reason I am asking is because the guy I got the truck from has 4 trucks of his own. He is saying, NO, you do not need an MC#. He said just get your DOT number, go to Trenton to the IRP and get your apportioned tags telling them we would be running in NJ and PA. But when I go online to try and get my DOT number, one of the questions is are you a For Hire company. And having to answer yes to this, it tells me I need an MC#. Just seems like a royal mess to get involved in the MC#. Have to pay for the number, have to get a processing agent for BOC-3 filing, have to pay the IRP money, how much I dont know, and who the hell else money. And I heard it can take up to 20 days before my numbers are even approved before I can start running. But if I just go up and get regular tags for NJ only, dont need any of this crap. But being new, I dont want to cut myself off from work, expecially when winter comes around. I dont know what the frig to do.

Didnt know where to post this, hope it is ok. I am in Southern NJ. Just bought a tri axle dump truck and I want to get the tags for it in the next day or so. But have a question. I have talked to a couple other owner operators in my area. I am thinking of getting apportioned tags to run in NJ PA and Del. vs. getting the Code 11 to just run NJ because I have been offered work in PA. But I am wondering if anyone out there knows if I do get the Apportioned tags to run in multiple states, being a dump truck, do I also have to get an MC Authority? The guys I have asked say, NO, just get your DOT #, go up to DMV and get the Apportioned tags. But when I go online at FMCSA to fill out the questions of what I need, it says I DO need an Authority. I am a For Hire driver, my wife owns the company and I will be driving the truck. DMV is saying since I am not directly employed by any company I might work for, and I will be running for them hauling their materials, sand, stone, asphalt and such, that I have to get the Authority. Does anyone know? Are these other dump drivers wrong when they tell me I dont need it. I dont want to get stopped by DOT and get a huge fine if in fact I do need it. Thanks for any help!

Ok maybe you could humor me one more time. Sorry for the step by step. I found the wire, he had it wired tied up, hard to see. But I took the tester, and it is hot with the clutch out. When it is depressed, it cuts power off so it looks like the clutch switch is working. Also, when switch to jake brake is in either low or high, it has power with clutch out and no power with clutch depressed. So, my question is, I see where the diagram shows that 1 wire I found goes to pump switch, but it seems as though all the wires are in place to the switch in dash, where it shows another wire from the pump switch is suppose to go. Am I missing something here???

Do you think it is 2 wires encased in brown. If so, I saw a plug with 2 wires that is encased in brown casing wired tied up on the pump side of the firewall. That is the only thing I see on that side that is not pluged into something. I will look at the diagram you linked to. The only thing that may make me believe they are not the wires is the plug I am talking about has round holes and everything that I have looked at from Jacobs seems to have blades on the switch. Hopefully I can figure it out from what you sent. Tried to follow wires from switch on dash but they all seem to go into the main wire harness.

Ok, I found the switch on the fuel pump that the guy was talking about and there are not wires going to it. I dont see any terminals on it, just 3 holes in the back, bottom, middle and top. So, does anyone know what wires are suppose to go there???

Hello, Tried this about 2 weeks ago but go no response, so thought I would try it again since I got a little more info. I have a 1997 Mack RD 688 dump truck with E7 350. The guy I got it from said he disconnected it. He told me that he disconnected 2 wires from behind the pump. I have never owned a truck with a Jake Brake so I was wondering if anyone might know what he is talking about. Any help would be appreciated.

You were right on the money, Dave. It was the air governer. Replaced it and WALAH!!!!!!!!!!! Fixed! Thanks a million for your help! Jeff

Ok I just got back in from trying to adjust it. I went as much as 2 full turns which by my calculations was equal to decreasing the pressure by 32 psi. Started truck and still went over 150psi before I shut it down. I guess I will get a new one tomorrow.

Ok I found it. It is mounted right on the passenger side firewall. Should I attempt to adjust it. I found on Bendix site that after losening the lock nut, 1/4 turn clockwise is equal to lowering the pressure 4psi. I dont want to screw anything up. My guess is that it is probably bad, but I dont know. Sorry if this is an inexperienced question, but if I do attempt to adjust it, does the governer just not let anymore air build up after a certain point or am I suppose to hear the air discharge. And when I do hear most trucks discharge the air every once in a while, is that the valve you were telling me to look for on the reservoir? Just asking because my 94 Ford L9000 use to do that everytime it reached 125psi, but this Mack has not done it at all.

Ok thanks for the info. Did not see it until I just came in from installing the relief valve which of course from your explanation did no good, which it didnt. I will look for the part that you have pictured, but where would the governer be. I am thinking I might see it under the cab, could that be where it is? If so, I dont know how I am going to get to it. If so, looks like the cab will pivot up, but dont know what I have to go threw to get that up if that is what I have to do. Thanks