RS Disposal

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

My truck doesn't have a CAC and have washed off the radiator fins. Was the first thing I thought of. Pretty sure I am going to have to eventually take radiator into the shop. But was just wondering about how much of the coolant actually flowed thu the water filter. I do understand the problems a bad thermostat can cause. Right now just trrying the simple things first one at a time. I'm one that likes to know what fix works and what doesn't work.

From what I understand these brass radiators do need to be rodded out occasionally, Which is something I am planning on. But I thought I would tackle the simple things first. In going thru the maintenance history, I don't see where the water filter was last changed. My question is does all the water flow thru the filter or only a portion of it as the systems circulates the coolant? Could a plugged filter be a problem? Going to change that today anyway just so I can log when it was changed. Also bought a thermostat kit That I will hopefully change out later this week, weather cooperating being I work outdoors, just in case I do have a problematic thermostat. The truck runs about 190 all day long in the city. Only gets hot when I climb the canyon, where I do stop and let it cool.

compressor intake is before turbo

I have thought of that but haven't done it. I wouldn't think that would cause the boost gauge to flutter

If I had a loose valve seat wouldn't I get a mechanical sound rather that what sounds like a muffled pop pop? The sound only changes frequency with engine rpm, doesn't really get any louder or softer whether under load or coasting. Truck doesn't appear to have an engine miss and it pulls smooth. Going to, as I stated in my first post, get a clip of the noise and post. Going to do some trouble shooting, check exhaust temps with an infrared heat gun and also use a stethoscope and see what I can hear and find. Will pull rocker covers and double check valve lash and see if something there has changed. Just frustrated I can't seem to locate.

I just recently had to do a major repair on my engine, a 1979 Mack ENDTB 675 which required replacing the turbo (previous topic was "Looking for 1979 Mack head"). Wasn't able to find a direct replacement but this rebuilder stated this one was speced out to be a replacement. The rebuilt turbo has a larger diameter compressor housing (cold side). I have noise in the intake. The truck seems to be running ok, doesn't appear to be missing, idles smooth. This truck never had a boost gauge before for a reference comparison, but the boost gauge will flutter depending how far I'm into the throttle. A quick question, pretty sure this turbo is producing more boost than the original. From what I have been able to find out, the original was around 15 - 17 lbs boost. This turbo looks like it will boost upwards of around 20 lbs boost. I don't let it run that high before I back out of it. Is there a possibility that this much boost for THIS engine might be cause some mechanical issues? I know my Cummins N14 runs around 20 lbs when going up the canyon where my trucks work, but that that is a totally different and much larger engine. I will try and upload a video/audio file in the morning with the noise. If this is the new normal after this engine repair, I'm good with that, because it was a major repair. Rear head rebuilt and #4 piston replaced. I just don't like noises that I don't remember from before the breakdown.

I am still having this noise in the intake. The truck seems to be running ok. A quick question, pretty sure this turbo is producing more boost than the original. From what I have been able to find out, the original was around 15 - 17 lbs boost. This turbo looks like it will boost upwards of around 20 lbs boost. I don't let it run that high before I back out of it. Is there a possibility that this much boost for THIS engine might be cause some mechanical issues? I know my Cummins N14 runs around 20 lbs when going up the canyon, that that is a totally different and much larger engine. I also think I might start a new topic with this issue where as I am no longer looking for a head.

I definitely marked the TDC marks and now that I know they are there, when I need them again I will know

Yea, I do understand the concept of the timing of only one cylinder at a time. Before I realized there were marks on the vibration dampener I was bumping the engine over, but it was hard to know for sure if I was on true TDC because alot of the time the engine would spin backwards a bit due to compression. There is only only one pointer on the front of my engine. The marks were extremely hard to see, but I was able to actually locate them after cleaning off the vibration dampener. I was able to get to the approximate location of the marks by counting the number of teeth on the flywheel for a full revolution from the #1 TDC mark and dividing by 3 to give me an idea of where to look. I was then able to get right on by slowly rotating the engine a tooth at a time untill the TDC marks were right on

I think when it comes time to do the radiator I will take it into a local shop that does heavy truck radiators. I don't have the expertise or tools to do the soldering of this brass radiator

another quick question. The truck was running good up until this point. I was double checking my valve lash and did find some that were out of spec. I may of not actually had the Piston at true TDC. After some clean u9p I was able to find the marks on the vibration dampener at the 120 degree spacing. Readjusted everything using these marks and the truck seems to be back to normal. Question is, "why the hiccup"?

cam was never removed. just the rear head. And the stinking truck was running so good too. Was gonna kinda pat myself on the back for a job well done. Guess I spoke too soon

started the engine with the tube from the turbo removed. Sounded like a popping noise coming out of the intake manifold. was thinking thaty for some reason maybe an intake valve wasn't closing all the way. Took rocker cover off and double check my valve lash. Some of the exhaust were a little loose.. Now when I start it it smokes (white smoke) really bad and idle rough. What the crap did I do? If I tightened the exhaust too tight would that cause the smoking? So dang hard to gauge TDC and rotating engine 1/4 turn.

Well I forgot my heat gun this morning so that will have to wait But I had another issue arise just after I came down the canyon with a load on. I am getting what I can best describe is a pulsating noise coming from the air filter intake. The boost gauge flutters. As to how much depends on throttle position. Haven't had the chance to tilt cab yet and look around. What might I be looking for? Could a rubber hose come loose or cracked? There are several between the turbo and intake manifold. The engine seems to still be running smooth. Seems I just can't catch a break and have just entered into my busy season