Ricky Beals

Did the Mack RD 686 come with the informer on the side of the air cleaner? I have one and don’t have a clue if it is even working or working correctly. After reading a little on it they advise to use a vacuum pump to check it. Any other way to check one? I can’t think of anything I would need a vacuum pump for. I’m going change the air filter because I don’t have a clue how old that one is. The informer is showing very little restriction but don’t know if it even is working.

Thanks guys a lot of good advice. I didn’t prefill the oil filters but will in the future. I will prefill the fuel filters, I have a transfer tank that has a filter that I can get diesel from and know it’s clean. Ok I’m guessing I can get a test kit and check my coolant. What do you want your ph at? Never really thought about coolant ph. I just check to see how cold it can go without freezing.

67RModel that’s sound advice. My RD686 does not have a coolant filter that I can find. Mackpro I ordered a belt wrench this morning that was used for those specs. one more question guys. I’m changing the fuel filters and was wondering if I need to fill them with something? Some say Lucas fuel injector cleaner, some say diesel and some say mystery oil. I have never changed a fuel filter on a truck. A little knowledge here would help. Like what do you guys add or not add. I’m trying to start out on the right foot and I’m a big believer in maintenance. Got her all greased up, oil changed and now going change fuel filters.

No I don’t have a operating manual and was just needing for future use. Thanks

Mechohaulic you stated proper filter wrench and I was wondering what you were referring to? Onyx610 what do you use to remove the metal canister?

Well today was the first time I have ever changed the oil on a big rig and what I thought would take an hour took all day. I didn’t have anything to take the centrifugal filter housing off with. Drove 45 minutes one way to get a strap wrench and it wasn’t big enough. Drove back and got what looks like a big set of pliers and they wouldn’t work. Waited on a friend to get off work and borrowed his 25 year old snap on strap wrench that would take 3/8 or 1/2 ratchet. Finally after some torque and 1/2 breaker bar got it off. I put it back on hand tight but those big pliers seemed they would crush or dent it? I’m thinking of trying to find a metal strap wrench that will fit filter and metal canister? what filter wrench do you guys use? What filters do you guys run? I bought mack since I was at dealership but don’t want to drive down just to get them. May look for Wix filters that replace them. also didn’t see a crush washer on drain plug. Nothing but a bolt. Should there have been one?

Onyx610 would you happen to have something that shows what those numbers are to. 1 through 29

Thanks Onyx610

Can someone post the schematic of a 2000 rd fuse panel. Thanks Ricky

I got a question about the dump bed part. I was told at dealership the main cylinder needed repacked. We are expecting a lot of rain so I raised the bed. The bed is still up and hadn’t leaked down at all which I felt like it would. Which brings me to another question on how does the bed raise and lower. I understand when I engage the pto it starts the pump which raises the bed thru hydraulic fluid. Does the pump also drain the fluid out of cylinder to lower it? I guess I don’t know what is keeping it up with truck shut off and if the cylinder needs repacked wouldn’t the bed leak down.

Ok when I turn the control to Ac Max,Norm,Vent,Heat I can hear air. If I turn it to Off or Deff I can’t hear air. So is there one of those items that ONYX610 posted or multiple? Thanks

Didn’t really understand your answer. The ac system is off, fan is off. When I kill the truck I can hear air in that area and hear it best from the bottom vents below the AC controls. I’m thinking it’s something behind that ac box but have no idea what it is. What solenoid are you thinking is malfunctioning?

When bringing the 2000 rd688 home yesterday I was watching the air gauge and the red and green would peg 120. The green would stay at 120 but the red would move down to 100 then bounce back to 120 just to start back down to 100. when shutting truck off I can hear a lot of air coming out of the ac vent in middle of truck. Any idea where this is coming from and how to access it? Thanks Ricky

Posted a new photo in the original post with new question. Trying to see if the single psi gauge came standard on this truck or if it was an add on. It hasn’t moved showing any air so not sure what it’s for. this may be a boost gauge. I read where it doesn’t show boost unless there is a load on truck so may be why I have seen it move.

Good call Mark that turned the light off. I’m guessing when this light comes on you need to respect it and find the problem. second problem!! Did this gauge come with truck or was it an add on. It’s a psi gauge but not working or i have yet seen gauge move? its not letting me add the photo and same phone I took the first photo with. I may have to start another thread

I have no idea what coolant it has in it. Or what it should have in it. I’m going get ALL MAKES ALL MODELS and put it in there for now.

Ok thanks Mark, no coolant in reservoir or near cap on radiator. I’m going put distilled water in and find the leak before adding antifreeze.

Ok when that light comes on I should definitely figure out why it’s on.

Got my truck yesterday and going change the Trunnion bushings out at the end of month. In process of moving household down to my birthplace. At this time I’m not getting to work on truck but building cabinets for shop building. The parking brake light on left side of truck stays on. What parking brake light is this? It’s not the one that’s goes off when air pressure hits 70. Anybody got any idea on what to check. I took both wires off the switch on outside of firewall below fuse box, took wires off switch below ignition (key switch) light stayed on. Just taking one problem at a time.

Thanks guys, I think those low gears are pretty low can’t imagine what lower than low would be like. Probably will only use it in LoLo hole. We don’t have many hills but could see where it would come in handy starting out on a hill.

JoeH thanks for the replies. Here is a question. I’m stopped and gear shift is in Lo. I move deep reduction switch in (forward). Lo gear becomes lolo gear. What happens if I still have deep reduction in and move to 1st or 2nd. Are these gears now lower than they would be if I didn’t have deep reduction switch in? Do I have lolo first, lolo second, lolo third?

My first mack had a mack 9 speed so it had a high/low switch. I understood how it worked. The RD 688 I’m getting has a Eaton fuller 8ll. It has the high/low switch in front of shifter knob but then has a reduction switch on left of shifter knob. When do I use the reduction switch? What’s the sequence?

I bought the truck Monday. After the salesman explained to me they just took the truck in on trade and have done nothing to it. General Manager wanted to fix it up and sale it so wasn’t coming off one penny. Salesman told me if I wanted anything done to truck it would cost me 145 an hour. They are putting in windshield for purchase price. I asked parts guy was it heavy frame and he said it was. Truck was bought by county new and they have owned it roughly 21 years. It’s a one owner truck. It’s a little rough on inside but I should be able to fix it up. It has cable controls to raise and lower bed. I’m going have some questions for you guys. Thanks for all the information. I truly think this is one of the best forums I’m a member of.

The frame was solid and no rust. Been a south Arkansas truck all it’s life. Not a double frame but the big thick one. I’m thinking I will probably be sitting in sales office Monday morning. I will get better photos if I buy it. Of course I will have a lot of questions for you guys.