JoeH

RD688S. Mines a concrete truck. Used to be a dump truck though. Yours it'll be hard to predict how much use the engine has unless it has a ReMack tag on the engine indicating when it was rebuilt. It could have been bought used to replace a blown motor. No telling how much use it had before it was dropped into your truck.

Nice interior; looks like you need a tachometer sensor. And you have a 8LL transmission. Nice trans, mine has one too, but mines a POS in my opinion. Mine shifts nice most of the time, but once in a while it hangs up in gear and ruins my upshift. Mine hasnt had AC since we bought it 12 years ago. I'm guessing its a completely mechanical engine because it's a 91 truck with a 96 engine. Hard to retrofit an ecu.

Nice looking truck. How many hours on the clock? My 95 e7-350 has over 19,100 hours. Hasn't needed much. Watch your pyrometer when pulling hills, my e7-350 doesn't want to be taken over 1025 degrees, but it'll easily do 1150. Gotta be careful to not over heat the heads. You'll wish for more hp sometimes, but that motor will keep you on the road, not in the shop. And at the end of the day that's good on your bottom line.

It'll pull fine til it hits a point where the engine is consuming more fuel than can pass through the filters.

Not a very clear description of the boost drop. You probably have clogged fuel filters. They typically act like a governor slowly lowering the RPM that the boost cuts out at.

Same block as the older endt676 engines and the E6 motors. (Might b minor block changes over the years)

Was in my local paint store interested in a certain color; he looked it up and was shocked it had only 1 "variant". A single color can have 20+ "variants", which are basically batches. You can put 2 "identical" colored cars next to each other and they'll look completely different. Important to be aware of when you're trying to color match and only paint a couple repairs instead of the whole rig.

Usually editors have a rotation option.

Lots of runs on the back of the cab, and the roof didn't get sanded down well enough so I expect to see some paint flaking on the roof at some point, but it is a work truck so it just needs to look nice driving by and run like a Mack.

Just took a peak at the visor in my 1988, visor says "operating range is 1020 to 1750 rpms, don't exceed 2300 rpms." The E6 motor uses the same block as the older endt676 series, which wound out to 2100 rpms, and cautioned at 2300. 2300 is likely when valves start floating, i.e. they don't have time to fully close between cycles. Pushrods get dislodged and bent... I would guess you could be safe setting the governor closer to 2100, but I would probably leave it. Mack Factory settings yielded impressive durability. You can't beat the up time on these older Mack's. They never quit. You ruin one of these and you'll have to buy a new truck that may spend 25% of its life at the dealer, plus cost you every dime the truck earns and then some.

I think flywheel housings and bellhousings tend to be fairly standardized. I.e. if you can put an 8ll on a Mack and a Cat, there's probably a bellhousing/flywheel housing combination that'll match a Mack 10 speed to the Cat.

Primer on the cab, paint going on in an hour. Hood still needs some crack repairs, it'll get done later.

A dipped tank yielding red I've heard is about $6-7k fine.

That's a gorgeous rig.

New frame rails are 25k+ or so unless you're mechanically inclined and can do it yourself.

It'll probably have a right side computer, which people say you have to be very careful with. Its close to the frame and if the engine torques too much from worn out engine mount bushings all it takes is a tiny dent in the housing and the ECU is shot. Personally I like the 2001 etech engines, but I only had limited experience owning one for a year or so.

We just bought a 1988 RD690S with an EM6-300L. The M stands for maxidyne, which has a massive powerband, and the L stands for Low RPM. Governor kicks in at 1750 rpms. Is the low rpm scenario a new phenomenon or have the trucks always been this way? It would help us to know what the engine model is. Like my EM6-300L I referenced. Maxidynes make 90%+ torque through the whole powerband, while the older ones used to wind out to 2100 rpms they started dialing the gov back in the 80's, but the powerband kicks in at a lower rpm too.

By allergy do you mean algae? There's a fungicide fuel treatment you can use. Kills it, but nothing's going to dissolve it. Pretreat fuel with it when you fill a truck up.

Great find. I assume you had it towed out? I assume it's not running yet.

Reminds me of this. I think this has gotta be "fly over" country?... I wish I had this kind of time on my hands....

Nah once the driver gets sea sick he just cuts the wheel, flips the truck over and climbs out the up door!

Heads up algae grows in diesel, or at least in the new diesel, so you may want to make liberal use of the fuel tank drain and flush the tank out real well. They make a fungicide additive that kills the algae but it doesn't dissolve it. It'll clog things up pretty good. Flush tank, change fuel filters, put some fresh fuel in it and pump new fuel through the system via the (hopefully equipped, but if not it's easy to install) fuel hand primer pump. You'll want to prefill the new fuel filters, and make sure you lubricate the fuel filter orings. And make sure old oring comes off. Never know with a 30 year old sitter.... (2 fuel filters)

There's enough mud on that steering tire for 30 years sitting, but that cab looks rust free. Dirt floor barn find? There is no visible rust, must have come from a no humidity state...

I would guess just the fuel pump. Maybe the turbo. Maybe the camshaft too if the maxidynes use different valve durations. Personally I would want higher oil pressure. My 79 maxidyne makes 60 psi at idle, 90+ for the powerband. Higher oil pressure helps ensure the crank bearings have a good film they're floating in so the bearing surfaces can't contact. You really need it IMHO when you're pulling with 90%+ of your peak torque at 1000 rpms. Look through used truck ads for a truck with an em7 and run the VIN through your dealer to see what camshaft/turbo part numbers are used. See if it compares to yours.