RS Disposal

When I have adjusted the valves it was definitely one cylinder at a time in the firing order. I would double check the marks on the vibration dampener to make sure I was at TDC. Once I found TDC on #1, I would rotate the engine one tooth at a time via the ring gear. It has 119 teeth so that divided by 3 is just under 40 teeth. I would count 39 1/2 teeth and then check my marks in the front of the engine and adjust it accordingly. kinda a pain in the rear to crawl under 6 times, but I wanted to make sure I as at the TDC. Bumping the engine with the starter I could never even get close.

I do have some "high performance assembly lube" (not sure of brand name, but I like Lucas stuff so I ordered a bottle anyway. I did see that that lifter was also compatible, but was told by two suppliers that those were also unavailable new

I got the cam shaft off of ebay from a truck parts surplus place. He stated it was for the 673, 675 & 676

I picked up a new cam that was listed as being for my engine last January just on a gut feeling I might need it. Hopefully the description was correct. It didn't state whether it was an engine brake or non engine brake cam. From what I read somewhere during my learning journey with this engine is that the 675 cams were the same either way.

I can get the rear side cover off, but the front one would require the injection pump be removed

Apparently my camshaft was also damaged in the major engine breakdown I had last fall. I did inspect the best I could the cam lobes in # 4 where a valve spring keeper broke and dropped the exhaust valve.. The lobes appeared and felt ok, but a real good visual inspection of lobes or lifter I wasn't able to do, but the engine was only run for a matter of seconds after the incident occurred. Over the course of the last several months I was beginning to notice a tappet noise and wasn't able to keep the valve lash in spec on #4. Half way thru my day last week the noise got real bad and the suddenly the engine had what felt like a serious miss. Took the inspection cover off the side for the rear head and noticed that the intake push rod had broken and I virtually all but had no valve lift on the exhaust. Currently in the process of tearing the engine down to pull camshaft. Had to replace radiator anyway and fabricate mounting being direct replacement no longer available, so that part of the job wasn't actually extra work LOL. My questions are, is there anything I really need to pay attention to when tearing down outside of the timing marks on the gears for when I reassemble? What in particular should I be paying close attention to when it comes to putting back together other than the timing marks? I know they (whoever they is) say that a new cam needs new lifters also. The new lifters for this engine are no longer available and when they were, were incredibly expensive. Actually going to relace all intake push rods being the dealer says they cant' order just one, but have to all six. I plan on using a high quality engine assembly lube at the time of reassembly. Again, I appreciate this forum immensely and everyone's help and insight over the last 10 months of me being thrust into being a heavy truck engine mechanic.

Thanks, It was worth a try. Maybe I can locate a blown donor engine. Really weird being the rocker arm itself is readily available. Not sure if they can be rebuiilt/repaired. I believe I have one that is damaged when a valve spring keeper broke and the exhaust valve stuck a piston. This one just wont stay in adjustment

I know this is a really old thread, but did you have any luck in finding a lash adjuster. My dealer says both Mack and PAI show no longer available.

I do agree it seems that the newer manuals are more one topic rather than multiple topics. I would of thought the factory manual purchased at the same time as the truck, 1979, would of been more inclusive. Thankfully I found this web forum. It has been a very valuable resource. Sometimes real world experience, particularly on older vehicles, is better and more helpful than the manual. I feel alot of manuals are not written by real world experience mechanics

That is what I was thinking on the steel washer and "O" ring. Really disappointed in the "factory" service manual as to alot of things dealing with my truck and engine

WOW thanks I will definitely be going thru that. My search on the site for dynatard engine brake kept coming back "error" try again later. LOL

Question #1 Last year when I had to rebuild a head on my 1979 Mack 675 ENTDB engine I notice that the dynatard solenoid wire was all but broken. Ordered a new solenoid. When I removed the old solenoid from the rocker arm I don't remember seeing the steel collar or the "O" ring pictured. Not saying the weren't there, just don't remember The small steel collar I believe is a no brainer as to where it goes on the new solenoid. Question is does the "O" ring just go onto the bottom of the solenoid or the grove that the pencil is pointing to. My thinking is the bottom of the solenoid. Question #2 I am thinking the hydraulic valve lash adjuster on the #4 exhaust valve was damaged, #4 exhaust valve hit the piston. Valve spec won't stay in adjustment. In getting with the dealer, Mack is saying the las adjuster is no longer available even though the rocker arm itself is. Anybody have a suggestion as to where I might be able to get one either new or somewhere somebody might have a blown engine for a used one. Googling hasn't given me any hope. I do have a machine shop. Is this something that can be repaired? Question #3 Being I am really new to heavy truck engines, how does this dynatard actually work? What happens when the solenoid is energized?

Yea, thats the way mine works. Not sure which of the two things (tilt cab specific pump & Mil H-5606 hydraulic fluid) I did at the same time was the actual problem. Ordinarily I would of only done one at a time, but I was getting frustrated, so I did both. The way my brain works I like to know for sure what works and what doesn't when doing repairs that required trouble shooting. But, it's working now. So onto my next item on my list Just want to thank everybody, again, for all the help and insight. This site and everybody has been invaluable.

My lines actually go up the side of the ram and over the frame rail and along side the inner frame rail where they come out behind the front quarter fender to the pump

the truck is parked outside. The problem first appeared before it got cold enough for water to freeze. The plumbing was reinstalled the same way the original cylinder was plumbed.

Im the type of personality that I prefer to do one repair at a time when trouble shooting a problem.. I like to know what works and what didn't. This problem was starting to get me really frustrated so I actually did two things at once. Not sure what the end problem was, but I got the tilt cab system working. I put on a new "tilt cab " specific pump (rather than the generic 2 way pump I had on it) and I flushed and filled the system with the Mil H-5606 aviation fluid. This fluid is definitely much thinner viscosity that regular jack fluid. Pretty expensive also. $55 a gallon of Amazon. nobody here in my town had a clue what I was talking about. LOL. Maybe the newer check valves in the ram are really picky.

In the process of doing rear brakes and this truck the drive hub has to come off so it is a little more time intensive. Hopefully will get back to my cab tilt problem. I do have the 5606 spec hydraulic fluid and a new specific cab tilt pump, also power packer. I normally like to do just one thing at a time until I actually determine what worked, but I think I am just going to put the new pump on and use the fluid. Just getting frustrated.

The cylinders would lock up even during the first half of travel raising the cab. If I remember right my problems started about the time is started getting cold over nite. I agree that I didn't think viscosity was the problem. I also didn't think that a generic 2 way pump might be the problem. The fluid and the generic pump are the only 2 wild cards in the system right now. The hydraulic cab locks function flawlessly. The ram is new from the dealer (power packer- brand). The new "tilt cab" specific pump (also power packer brand) I will be installing hopefully this week. As far as oil, all I can think of is that the safety check valves are really picky about viscosity. Starting to get really frustrated as to what I thought was a simple system repair.

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.