Mackpro

I don’t believe there is a reverse switch on a Mdrive like on the traditional manual transmissions. Being the truck is a 2020 it has a light control module (LCM) that gets a signal from the either the gear selector or transmission ECM to send voltage from the LCM to the reverse lights. Check all the LCM fuses in the fuse box on top of the dash , I believe there are at least 5 and possibly as many as 7 LCM fuses.

They had a service bulletin on it . SB 261-008. https://www.yumpu.com/en/document/view/31273801/service-bulletin

We rarely ever cut counterbore on the E-7 or the ETECHs till after they made the coolant filter/conditioner optional in around 2002. Of course fleets and cheapskates ordered trucks without the coolant filter stand to save $50-$75 per truck . 8 to 10 years later coolant in the oil and damaged engine blocks with pitted counterbore ledges everywhere. 2002 was also the year we started seeing the casting core sand not flushed out of the engine blocks during assembly. This clogged the air compressor coolant line causing the air compressor to overheat , blow the air compressor head gasket and pump/force coolant up the air intake pipe and dump coolant into the back of the intake manifold where #6 piston then sucked in the coolant and hydro locking the engine, bending #6 connecting rod. Sometimes so bad we had to cut the rod with a torch to get it out . And this wasn’t rare , one time we had 2 trucks do it on the same day . However, 2002 was my favorite year , a axle forward CH with a CCRS 427 and a Fuller Super 10 trans was my dream truck and still is.

I was think the book says no more than .030” in shims but I remember cutting the counterbore way more. I wish Mack or aftermarket would make some thicker shims than .010” or at least that was the thickest we ever got to use back then. I know the Reman center cuts the counterbore 3/4” and drives a stainless ring into the block to get the counterbore to the 4.00” to top of block measurement.

As Joey Mack said there is another identical pipe plug about 1.5 inches below the one you removed but it’s behind the front timing cover. These usually leak towards the inside into the oil pan and cause low oil pressure due to thinning the oil with fuel and also your oil level will rise. But I have seen one leak to the outside. The plug that is visible is a good place to check fuel pressure. It’s standard pipe threads so it’s easy to adapt fittings and hoses to run to a 1-100 psi guage to monitor fuel pressure during test drives . The original Etech engine was made with two separate fuel galleys , one for pressure and one for return fuel. This is the reason for the 2 pipe plugs. The engine blocks were drilled front to back so there are two pipe plugs in the front and two in the back of the block . They were separated by the middle o-rings on the 6 EUP electronic unit pumps. Later Mack decided that the middle o-ring wasn’t needed so a lot the the rebuilt EUP’s don’t have a place for the middle o-ring. I always thought the middle o-ring was a good idea. That way you could run the higher fuel supply pressure (100 psi vs 60 psi ) which is between the upper and middle o-ring and low pressure fuel return was between the middle and lower o-ring. It would be less chance of fuel getting in the oil past the bottom o-ring into the oil pan . Before Volvo took over the dealerships could actually call and talk to the engineers that built and designed the engines. I talked to one who said that the bottom o-rings would seep fuel regardless but not enough to matter between oil changes. He was right as many times I dropped the oil pan on a hot engine and capped off the fuel system and pressurized to 60 psi with due in the fuel. You could slowly see with a black light the fuel seep past the o-rings but not enough to make a drip. The real leaks were easy to find as they would show up fast with a black light. Fuel supply pump gear bushing , a bad lower EUP o-ring or loose fuel galley plug on the block as talked about above we’re the usual problems of fuel in the oil . Sorry for the long post , I miss working on the old stuff.

There are 2 fuse boxes , One under the triangle shaped cover on top of the dash in the center. The second one is behind the panel by the clutch pedal,

As one of the other posters said earlier in this thread , the engine ECM grounds the starter relay that’s bolted to the starter. The vehicle control unit (VECU ) / key switch might send power to the starter relay but the final decision is made by the engine ECM to ground and engage the starter

With any MP engine that won’t crank , check and see if you can view the engine hours in the dash cluster . If you have the high end dash cluster with the stalk switch , you can view it under Trip Info. If all you see for engine hours is dashes then the engine ECM is bad or not powering up .

The cracks were not gapped open or leaking that we could tell . I believe it was from the weight of the 2 coolant lines and DEF line hanging unsupported off the end of the DEF doser that caused the cracks. We saw it in both Macks and Volvos.

There is a round metal washer type mounting bracket welded onto the lower pan for the DEF doser. They usually crack horizontally about an inch above this mounting bracket. Usually only 2 inches long . I only found the cracks when replacing DEF doser or changing out DPF filters. Didn’t seem to cause any issues. I’d unhook the batteries and weld it while stil on the truck .

If it’s cracked right above the DEF doser I’ve had good luck welding a bead over the crack with a wire feed Mig with standard steel wire. Done it 8-10 times with no issues

The AMI370 uses bigger injectors and turbo than the AMI300. And due the the EPA I don’t think Mack will do a HP bump to the AMI 370. However they will possibly do the HP upgrade to AI 427 or 460. Regardless you will need the bigger injectors and turbo. Your dealership can submit a HP change request to Mack and see what they say .

You are correct the common rail engines use a higher flowing 7th injector. They look almost exactly the same as the earlier version . I have see the incorrect one installed before ,

Are you using Tech Tool? If so , when you go to choose the type of regen ( on some emission years there are 3-4 types of regens) choose the one with the blue circle by it . If you choose the wrong one the soot level won’t drop. What are your T1 , T2 and T3 temps 3/4ways through the regen? Is the T2 temp getting to hot and cutting fuel on and off ? Being a common rail engine, the AHI is in the fuel filter housing. Did you check the air pressure to the AHI? I’m not sure what it should be on a common rail engine but the older AHI style needed 32 psi. , the air pressure regulator seemed to go bad a lot , we used to change the AHI , 7th injector, air pressure regulator and air drier cartridge and drain all the air tanks . The regulator is usually mounted by the air drier

I remember the parts guys had a hard time finding the harness in the parts break down but lucky for us the tag was still on it and the part number was readable.

Here is a link to the Mack Reman center catalog and it can be used it see what’s compatible, https://www.bergeystruckcenters.com/efs/wp/domains/www.bergeystruckcenters.com/wp-content/uploads/2021/09/REMACK-Product-Technical-Brochure_compressed.pdf

There is coolant around the cup so if you don’t drain the coolant before you remove the cup then it will fill up with coolant.

https://static.nhtsa.gov/odi/tsbs/2017/SB-10090649-6903.pdf

I have seen the engine brake plunger/pistons unscrew themselves causing this issue. Also with that high of miles I’d really look for broken valve springs and for the intake and exhaust valves to start wearing up into the valve seats. Especially check this if the engine has been deleted.

I bought lots and lots of the Factory manuals over the years when I was at the dealership. Most were $8-$15 a piece. I have this one in print so I knew what it looked like and just did a quick search and it turned up. The Mack E-Media site is free but I think it’s mostly Service Bulletins now, it used to be full of manuals. Also the Mack Body Builder website has lots of free maintenance info that’s way easier to navigate than the dealership website. In related info RH Sheppard and TRW both have all their steering gear manuals free online. Eaton Fuller has all their transmission manuals online as well . Bendix also has lots of free manuals on ABS/brakes.

Here is a link to the factory manual for several different HVAC models, make sure you use the correct model . https://s6dc2dc82dd3d959c.jimcontent.com/download/version/1549531542/module/8252074015/name/Air Conditioning System Service Manual. Includes US 07 Mack Chassis%2C GU (Granite Series)%2C CHU AND CXU (Pinnacle Series)%2C MRU AND LEU (Terra Pro Series).pdf

The 460 XT was only for the original ETECH series. The CCRS series was like the ASET AC series with a 460P with 487 HP and a 460E with 460 HP, both were same torque at 1660 . The XT files are still showing up in the Mainframe as unchanged from 1999 on the dealership side. We saw very very few of the CCRS 460p trucks as they only made the CCRS for a couple of years before the ASET came out

If it’s locked solid it’s for sure bad . But as the bulletin said , if you put 12 volt and ground the appropriate pins then the fan should slowly disengage after 10 minutes of engine run time at around 1000 rpm. The colder outside the longer it takes to disengage.

https://pdf4pro.com/cdn/service-bulletin-mckenzie-tank-lines-a3dd0.pdf

That style fan never totally freewheels like a air fan. It should always have some resistance. However if it is locked solid and if the only way to spin the fan is by slipping the pulley on the belt , then the fan clutch is definitely bad. If you can still turn the fan without slipping the fan belt then it’s possible other issues causing the fan to stay engaged. I’ll see if I can attach a bulletin later on troubleshooting. There are two part numbers one for the ASET AI engine and one for the AC engine. They both look the exact same and will bolt up but won’t work correctly if the right part number is used. Also a bad engine harness, coolant in engine ECM , bad AC high pressure switch and over charged AC system can cause fan to never disengage .