alabamaslammer

just got home without the truck. she drove much better today than yesterday evening or last week, and i was unable to get her to bog and die on moderately flat ground (no big hills/pulls) before parking to work on the brakes. i was able to get the truck - and rear passenger side front axle brake - to smoke heavily. after noticing the brake smoking, i saw the truck was leaking air out of the bottom of a bendix valve body after the parking brake was released. i am not sure how long this was going on for. the engine power was incredible today at one point, and that was with one set of shoes grabbing/smoking. the additives are clearly helping de-gunk the fuel system. the electronic malfunction light did not flip on today or yesterday, so no fault codes on engine. or trans. anyhow i pulled the bendix valve body and it looks like they sell rebuild kits for $30-40 so i will order tonight or tomorrow. i agree the tow quote is attractive.

got back to the truck late this afternoon. first thing i did was take a look at the fuel tank vent. it is covered in junk but it should still work- it's crazy to me there is enough pressure in the tanks to push the springs on these things open. next i reconnected the batteries and plugged in my nexiq scanner. nothing. nexiq device tester worked and read all modules but vmac wouldn't connect. found a helpful post on bigmacktrucks.com noting the rocker switch next to the port - flipped the switch and voila - i was in. no active faults but there were 3 historical faults in july 2018 - are the vmac date/times usually correct or no? the blink codes were 6-4, 6-8 and 4-1. 6-4 is a j1939 issue - if the vecu or eecu loses connection to j1939 for more than one half second the code will set and electronic malfunction light will turn on. the fault will become inactive if communication resumes for at least one half second. when code is active, engine speed will default to 900 rpm (LIMP MODE). If communication is lost on both j1587 and j1939 the engine will not run. code 6-8 will set if vecu loses connection with allison hd transmission on 1939 line. code 6-8 can only be logged if the 'use j1939 tailshaft speed sensor' option is enabled in the vecu data file. code 6-8 will always be accompanied by a code 4-1 (loss of road speed signal). test 1. checking for code 6-8. verify code 6-8 is set. if code 6-8 is set, go to test 2. if 6-8 is not set, wiggle the harness and connectors to try to set the code. test 2. check for code 6-4. if fault code 6-4 is set (IT WAS), locate and repair the open circuit in the j1939 serial data line between the vecu and j1939 transmission connector. after checking the codes i ran some laps in the truck and it did much better than before. the electronic malfunction light did not turn on (it did come on intermittently when i drove truck a few weeks ago, tho not sure why those instances did not show in the fault logs unless the truck date/time is wrong?) i suspect the power service additive helped prevent filter clogging, which it says it does. i did many more laps with more power before finally losing power and truck dying a couple times and i called it a night after realizing my primer pump is seized and not wanting to use ether. at one point during one lap the truck was putting out a ton of gray smoke. seems like it burned up some junk or something. i got back to motel, showered and wrote up this post along with the vmac stuff detailed here. need to think about next steps. i have two 55 gallon oil drums (one is clean; one was clean but had dirty diesel in it from a different truck) and a transfer pump with brand new filter, 3 primary filters, 3 secondary filters, a fuel pump and my tools. not sure my path on the fuel stuff yet. radiator shop said they would pressure wash and dry tank for $130. they are 30 min drive away. friend quoted me 1500 to tow it home. lots of options. not sure what path we will take

I will look into getting the tech service bulletins. Ive got all 16 wiring schematic pdfs for it, engine service manual and vmac diag manual. Would like to find MR series operators handbook if anyone has pdf copy (on ebay for 96 bucks...). Will be studying it all to get familiar.

Thanks. Truck had engine and harness replaced by mack dealership after top end let go. I called and got the detailed shop notes prior to buying it. Motor was replaced w/ reman at 92k miles. Odometer shows 108k miles. Kept eating through shift pads (known allison/wtec3 issue), packer floor replaced, fenders rusted out and she got parked. Yea I'm kind of in love with these ai's from what i've been reading. Slow and reliable. Like my 7.3s. Lots of potential mods for improvement.

I watched video when i unscrewed primary filter and you can hear a distinct vacuum release/air rush. Either vent cap is clogged and creating fuel lock/ vacuum, or pump sucking against clogged filter created a vacuum. Here's a photo of the scan with allison doc. I spoke with an allison tech who noted the check trans light should come on with key on engine off and then go out within 10 sec of cranking, so all good there. I will scan truck with usblink and vmac when i am there next.

Thanks. During bidding the fleet manager said it didn't run and had a bad shift pad. After arriving to pick up the truck, getting it running, and bringing a replacement shift pad, he said they parked it because it stopped taking gear up hill. I honestly don't know what that means. I told him the shift pad in it worked - or so it seemed - and he said maybe the batteries being dead reset it... Getting any information from him is like pulling teeth. I've pressed him a couple times firmly to just spill the beans to no avail. The last buyer backed out after arriving to pick up as it didn't fit on a low boy as it was too tall. The mechanic who used to work on it is out on sick leave with cancer, the guy who used to drive it died while I was there (they were loading bush hog onto a trailer one day to prepare grave site for his wife).. The route sheet in the truck was dated 2010, batteries were dated 2020. I appreciate all the insights and suggestions. I've ordered two honeywell 0-100psi pressure sensors (one for pre-pump and one post-pump), two 12v to 5v voltage regulators, sensor connector ends, two lcd digital voltage displays to mount in cab (5v =100psi, 4v=80psi, etc), 3 primary filters, 3 secondary filters, a replacement fuel pump (hopefully don't need) and a replacement fuel cap. My cap was covered in white chalky material - I believe aluminum corrosion - and I think it might have been clogged. I banged it on side of tank a few times after I noticed it but didn't think much of it, and didn't know fuel vent clogs can restrict fuel flow. The fuel cap might qualify as a crime scene and potential cause for lack of fuel flow from what I've read over past couple days. I wasn't able to find a 12v fuel supply pump that had a 1/2" line input/output and decided not to fool with it as I am concerned I'll just be installing a fuel flow restrictor. I tried calling around a ton of places in TN for a fuel polish but frankly I am a cheap bastrd and even if a company offered the service - which nobody does unless you own a million gallon tank farm- I probably wouldn't be interested in paying. My current plan is to remove the tank and pressure wash the inside along with all the lines and then blow them all out with air and let them sit in the sun. I'll save the diesel for fire starter for my wood stove this winter. Will scan the truck with vmac, clean tank/lines and blow them out, install pressure sensors, refill fuel, replace filters, bleed, crank and observe pressure gauges/computer. will also buy a crimper and bring some spare battery cables to replace the ends at the corroded post near the ecm. will check ecm connectors. need to check fuel return restrictor valve- need to get instructions to locate. observe lines for air leaks/collapsed sections/internal separation/flapping. will check turbo (it does not have vanes which I thought previously) find fuse box/check fuses. will also check air filter for blockages. The air filter housing was dented(/cracked?) and had trash jammed up all around it. I am trying to determine what size fittings I need for pre/post pump. Here are links to pump and fittings if anybody can eyeball or check theirs. The honeywell sensors have 1/8 npt male ends. Thanks guys.

Hey Everyone, I run a small garbage business. I recently purchased a nonrunning 2004 Mack MR688S and am working to put it back into service. The first thing I did when getting to the truck was swap out the batteries. The battery disconnect switch was completely corroded so i removed the cable connectors and after cleaning them with my die grinder so they showed clean copper on both sides I vice gripped them together. I connected 4 950 CCA batteries and then tried to crank the truck. Nothing. No crank. Dang it! After an hour or two crawling all over and under the truck I found an 8 gauge red broken wire running to the batteries. I stripped it and twisted it together and voila, the truck cranked up and ran. She ran beautifully. I did not move the truck. I found a motel for $60 and got some burger king. The next day I cranked up the truck and drove her across the yard to put air in the tires. After airing up the tires I realized I needed to lower the arms/forks to be under 13'6", so I flipped on the pump. I had already checked the hydraulic fluid level, and despite it missing its cap and sporting a red rag as its cap instead, the fluid looked clean. After lowering the arms fluid started leaking heavily out of both arms on the front load truck. It was white and milky showing water intrusion. I shut off the pump and ratchet strapped the bar connecting the front forks to my front bumper. I then disconnected the front driveshaft to the pump. The leaking stopped, the truck was now safely under max height requirements and the pump was no longer at risk. I then decided to take it for a few laps around the yard and see how she did. The first lap was incredible. The truck drove great on the first lap, upshifting smoothly into 3rd gear on a 200 ft stretch. Halfway through the second lap the truck started to bog on a very slight incline, making jake brake type noises out of the stack before dying. Cranked it and wouldn't start. Cranked it with ether and then it died. When pouring out the old primary filter I noticed green slime in the drain pan. Bought two new fuel filters, drained the tank and poured in 50 gallons of fresh diesel along with some diesel klean. In hindsight I should have poured in biocide or killem. After the filters and fresh fuel the truck fired back up. I parked it thinking I had fixed the problem. I got some burger king and checked into my motel. The next day I went about some maintenance. I greased the u-joints and front end, I put gear dope in the rears, added another 40 gallons of fresh fuel, hub oil in the front axle, zip tied loose wires and changed the oil and filters (not realizing there was a third filter, the centri-max). I hooked up the truck to my laptop and fired up allison doc. It had a number of inactive codes but nothing active, and transmission fluid was at the right level. I forgot I had vmac-3 installed and did not scan the eecu or vecu. Then the truck died on a very slight incline. I got a can of starting fluid, and she fired up. I crawled around on the truck looking for something I might have missed - the manual indicated there was a third pre-pump filter but on my truck there did not seem to be one. I took the bosch primer pump off and flushed it out. I bled the injector feed lines from the wrong side. I added 4 bottles of injector cleaner and a quart of ATF. After adding the additives the truck started running much worse. ATF and microbes were likely clogging the filters. Any insights appreciated. I am new to Mack trucks but trying to learn everything I can.

It was a dump truck. Will put dump bed on it or 5th wheel. All the separation is in the rear. Thought about replacing outer frame rail sections from cab back but looked better than expected after removing rust and guessing there is a way to correct gap. Here's a few photos

Hey guys. I had some rust jacking in between inner and outer frame rails. I've removed most all of it with a sledge. Now trying to figure out how to get the frame back together - there is an inch gap at it's worst where outer frame rail separated from inner on the top of frame.. Tried map gas and sledge hammering a piece of wood and it had no effect. The c clamps with impact wrench adapter end cost 400 bucks and those for 10 inch.. I need bigger and would need a few.. Does anyone have experience doing this? Was thinking maybe acetylene torch and a loader pressing/hammering a long piece of iron laying across top of the frame rail where it is bowed up. Or a big hydraulic press and big piece of iron to make sure it lays back flat. Don't have any of those things.