RS Disposal

The hydraulics kinda got put on hold for a bit while doing rear brakes. I did get a new "cab tilt" pump. Just haven't had a chance to install it though. Just about everybody I have talked with has said that the two way pump I was using should work. It does work the ram both directions when just hooked up but not dealing with the weight of the cab when the cab goes over center and and finishes its travel with just the weight of the cab. I did notice in reading the spec sheet that came with the pump that a certain hydraulic fluid MUST be used or issues with the system could arise. MIL H-5606 What I used was a hydraulic jack oil. In researching what this specific oil to be used was and why it might be different it appears that it is a bit thinner than regular jack oil being what is used in aircraft due to the colder temps that those hydraulics encounter. As we all know, hydraulics don't like the cold as I am reminded every morning I run the packer on my truck up canyon all winter. in my thinking of trying to remember when my issue became an issue it was early winter here and even though it wasn't the bitter cold I get up canyon, it was colder than back when I can recall the system was working with the old ram before I thought that ram had just worn out. So I did pickup some aviation MIL H-5606 spec fluid to refill system after I flush it out of the old. My thinking, if that is the case, the fluids being thicker may of been causing the safety valves in the ram to close. My weekends are tuesday-wednesday so next week I guess I will find out if my new plan of attack is going to work.

This was grey gasket maker and I used very little being it was a metal to metal seal. Like I mentioned earlier, I will watch to see if it leaks and if necessary pull back off and and make a gasket.

I was pretty much just going on the previous axle removal and replace where there was just evidence of silicone and no gasket. I did make sure that the cones were clean. I do know that the last time the axle was pulled was 30+ years ago due to a pinion gear break. This truck sees ALOT of salt in the winter being it works up canyon at the local ski resorts. I had no problem getting axle out. Two quick hits with a hammer and the axle popped right out. If the axle ends up showing signs of leaking I will just op it back out and make a gasket. Previous heavy work was all done by my dad who is no longer with us. I have been keeping up on the lighter pm maintenance work. But as far as the more intense work I am pretty much a newbie to heavy trucks, as those of you that followed me on my engine breakdown last summer will attest to. I asked ALOT of questions. I am a light truck/automotive mechanic so I do understand the basics of mechanic work. Shop manuals are great for alot of things, but I highly value real world experience. Particularly on older trucks

there wasn't a gasket when I took it apart so I didn't use one putting back together. I went with what the nut and bolt industry google search for grade "C" nuts using a mid range torque of 100 ftlbs. The studs do have the tapered cone on them anyway.

I was able to find wheel bearing nut torques on a previous thread here on this site. Followed that recommendation and I felt comfortable with it. My question actually deals with the axle flange nuts where the axle is bolted back to the drive hub

Ok guys, this one is totally off topic here, but didn't want to start a whole new thread. Doing rear brakes on this truck and unfortunately this truck requires the drive hub to be removed to replace shoes. Can't find anywhere in my factory service manual as to what the axle flange nuts need to be torqued to when putting axle back in. Any help as to what I should be torquing them to.

Yes. the cab raises to a center point then fully tilts under its own weight. To lower, the pump tilts cab back to its center point and then it lowers under its own weight. That was my thinking when I bought the pump. It was alot cheaper than a true "cab tilt" pump. But I did get the new pump today so in the next day or so I will get a chance to see it it works.

update on what is happening Like I stated previously the cylinder got to the point it would move after sitting a couple of weeks on the bench. Hooked up to the lines and bleed multiple times. Was able to extend and retract the cylinder with the pump multiple time. hooked up to the truck and locks up with the weight when trying to lower cab. unhooked from truck and again was able to extend and retract the cylinder. Only thing I can think of is, even though the pump is new, it is a 2 way pump and worked for a while, it is not specifically a cab tilt pump. So I ordered a cab tilt pump from PAI. Maybe something specific about a cab tilt pump that this pump isn't compatible with my system pump

This ram has a c clip type on the end

The hydraulic guy said he hooked it up to his test bench and wasn't able to get it to move either direction. There is no debris in the screens that are in the in ports. His theory was that even though new the internal checks valve malfunctioned. I know when I first put it on and bleed the lines the fluid came thru nice and clean with no debris to indicate hose failure I guess I try hooking it back up tomorrow and see if I can work it without the weight of the cab

Ok, after the ram just sitting on the bench for a couple of weeks cause I got frustrated. I can now by hand move the piston all the way in and out with no problem. Mu questions is now , how would be the proper way to bleed if there is an other way from the normal of just cracking the respective line and working the pump until all air is expelled. Should I be using something other than regular jack hydraulic oil?

This is a single cylinder setup. The pump was replaced a while back and worked quite awhile with the old ram before the same thing happened. I just assumed the old ram had dies being over 40 yrs old. I never did try working ram with the ram un installed but still hooked up. I did take it to my hydraulic guy and he wasn't able to do anything. Pretty sure there is something that I can do being i'm sure i'm not the only one that has had this problem. I just need to find the correct solution. As far a hydraulic oil, i used just regular jack oil. Didn't consult the factory manual.

I haven't been able to locate a bleed procedure in the factory trk shop manual. Haven't had alot of time to research on the internet yet.

Did a quick search and didn't really find an answer. Hopefully someone here has some hydraulic knowledge. While doing some major engine work (long story in another thread) my tilt ram stopped working. It just locked up solid Would collapse or extend, even with external pressure. Just figured it had gone bad being the truck is older. A new pump was installed and it worked for quite awhile before this happened. My hydraulic guy wanted almost $800 to rebuild and I was able to get a new one thru Mack for $900 so I went that route. Installed it and it worked for just one cycle and the it also locked up. My understanding of a hydraulic ram is very limited, but I for the life of me can't figure out why this has happened. I do know that the ram has a safety feature in case of a hydraulic line rupture so the cab doesn't come crashing down. What could I have done to of caused this problem again. I am thinking that for some reason the safety feature has locked it up for what ever reason. Any pointers as to what I might be able to do to correct the problem. If I cant figure it out then I guess I need to take back to dealer and see what they will/can do. Ram is only 1 week since purchase and only worked for one cycle. Even took it to my hydraulic guy to put on his test bench to eliminate a possible bad pump on my end. We are both at a loss as to why a new ram would act up unless I just happened to get a bad ram to start.

The 3/4 nut is easily accessible without pulling the drum. Once wheels are off the nut is just behind the flange on the drive hub. Only one needs replaced. not sure why Mack says the right hand is available but not the left hand. They also state that the 3/4 nut is no longer available, but that I am sure I can get at my local nut and bolt supplier

yes I do. The studs have nuts on the back side of the drive hub (are not the press thru type) that don't require the removal of the drum etc to replace

I admit I haven't done any "Googling" on this yet. It is a pain in the butt on a cell phone, so I thought I would ask the amazing people (who have helped me multiple times over the past 8 months) on this site for a recommendation on a source for these. The dealer says the left hand thread is no longer available, just the right hand thread. Anybody have a referral to a supplier that might have aftermarket studs? TIA Rob

the factory thermostat does have a bleed hole that does state either forward or up depending on orientation. the hole is now where near 1/8 th. Should I enlarge this?

Are these engines difficult to get all the air out of the cooling system? I know my daughter's jeep is a major pain in the butt to get the air purged out

Changed out the water filter (definitely was totally plugged up) and even though it only takes a sampling of the coolant, being plugged it impeded the flow of the water to a certain extent. The truck now runs about 15-20 degrees cooler in town than before. Still gets hot climbing the canyon though, but it cools down in about half the time.

I want to again thank you for all your insight and help over my journey with the breakdown I had last year. Being a newbie when it came to heavy trk diesel engines, I did learn alot in helping me understand this engine being my goal is to keep the truck in service for a while still.

The fan clutch was one thing that is on the list of replacing. Not sure about a fixed fan though being a cab over and the fan just right there next to the seats. Kinda noisy now when the clutch fan does kick in sounding like a jet engine. It's just not kicking in when I would think it should. Thew truck has been a real good worker even though it is an older truck, 1979. Only has about 145,000 road miles on it, most of which are city miles. But engine miles are more from running the pto for the compactor

I believe the model is MR685. Dealer lists it as a box truck, but it has a garbage compacter body on it

I will definitely look at that when I change out the water pump. Pretty sure the radiator needs rodding out. I'm just trying to understand this engine as I'm sure you are aware of from my "Needing Mack Head" thread

I do have the heat activated clutch fan. I can hear it roar to life at times but not really when I would think it should be. I have a cab over so I'm right there by the fan. That was one thing on my list of replacing as I troubleshoot the problem. Pretty sure my radiator needs to be rodded, but right now my truck can't be down for that length of time so I just watch my temp really close. Its fine all day long in the valley