JoeH

I will add that our DM was overheating running the blower motor for unloading cement. Swapping over to the fixed fan made a world of difference. Old fan clutch was probably worn out. This truck is a good worker for you, I'd swap the fan clutch and see if that helps.

Which cabover model do you have? Just curious what radiator it has. Our MR688 has a monster radiator. Tons of cooling. Probably half again the size of a typical R model, and the same engine.

Also what kind of fan clutch do you have? The heat activated type or a fixed fan? If fixed then you're getting all the air flow possible out of the fan, and if heat activated then it is possible the clutch is worn out and not pulling enough air. You should hear the fan roar to life when it kicks on. My 1980 DM686 has no thermostat installed and has a fixed fan. It's just a yard truck now for unloading our cement trailer. Runs at 1700 rpms for about an hour to unload, and the engine temp stays between 150 and 180. Side note on thermostats, I always make sure they have pin hole drilled in them to facilitate purging air out of the system. Hate imagining an air pocket trapped against the thermostat and not getting hot enough to open.

I think the brass fitting cracked that threaded into the intake manifold, and it has some sort of a filter screen in it and it was seized into the manifold, so we just deleted it. This truck doesn't have the transmission torque switch, but we had an identical truck one year newer that did. My dad says you'd hear a click when you shifted into 5th and the truck would kick you in the butt. The transmission switch is unnecessary. The whole system is unnecessary at this point.

You get black smoke til the turbo hits 10-15 psi. Then it clears up. No big deal. I have one truck that's still roadworthy with this same engine, the puff limiter just stopped working a couple years ago so we just capped it off, which I believe just involves pulling the aneroid valve (reversing relay) off the rear intake manifold and putting a plug in instead.

My CAC testing kit. Two 3 inch PVC pipe caps from Home Depot, one with a wheel valve stem for pressurizing. Third fitting is a 2 inch cap wrapped in electrical tape to make the difference to the 3" required by my MR688S. Uses a different size CAC outlet than my RD688S. Just tossing this out there into the Abyss of BigMackTrucks info.

Just had my plugs out the other day, I forget if it's 3 or 4 inch, schedule 40 PVC pipe caps from home Depot. Plugs right into the rubber boots on the CAC. Drill one and put a wheel valve stem in it. Should be good for 35 psi, if it leaks you'll know quick.

What cab is this truck, RD690? You could have a fatigue crack on the charge air cooler, my 95 e7-350 had one running most of the way down the passenger side. My truck made 25 psi ever since we bought it in 2009, ran hot on the pyro too. Last year it started dipping closer to 22 psi max. Found the cracked CAC, put a new one on and now I get 34 psi on a good pull, and cooler pyro temps. Rarely over 900 degrees now.

If you're doing the heads yourself, DONT SWT THEM DOWN "RIGHT SIDE UP"! The injector nozzles stick down into the combustion chamber, you'll crush the tips! Either set them down on cribbing or set them down on their side.

Never heard of the 901 part of it.

He is working on an E7 mechanical, not sure if the heads are the same as the E7 ETECH engines. Do the older E7's have this exhaust stud issue too?

Not sure what the E6901 is. Is this an E6 engine? Or an endt675/6 engine? The ENDT engines use plastic fuel return leak off lines that jump from injector to injector and then run back down to the injection pump/fuel return I believe. These lines get brittle and crack eventually, and 99 times out of 100 I'd bet this is the cause for draining off fuel when sitting. Easy enough to buy a coil of this stuff from your Mack dealer and replace any that are damp.

Not level to the ground or not level to the hood assembly? Ground would be frame twist/uneven spring packs I'd expect, and to the hood assembly I'd be out of my league.

On the ETECH motors I think I've heard that the lower exhaust manifold bolts are open to the pushrod passageways, so you can get oil coming through the stud threads. Probably not part of the issue, but maybe?

Up the idle speed to 650 rpms where it belongs. Should just be a screw stopper on the fuel pump that the throttle lever stops against. Micro switch for the engine brake may block your view of it.

How's the frame on the truck? If the frame is rust jacking bad and doesn't have much life then is it worth the fuss other than dumping oil in? I have a 1995 e7-350, 24k hours. I have noticed on my truck that if I shut it off and give it 5 minutes it'll be a gallon low. If I come back in the AM it'll be at full. Sometimes the truck will "load up" on oil while idling and blow a smelly blue haze, but most of the time it runs clean. Mine also developed some fatigue cracks in the oil pan at the corners. New pan was $2,000, came with pin holes for gasket tabs to push through. Of course the dealer gave me the old style cork gasket, and i didnt know about the rubber gasket so I welded the holes shut... What's your engine idle rpm? Over time the setting can dip, and then you aren't idling fast enough to keep the rings sealed well enough on combustion.

So far since the last update we've replaced the steering gearbox, pitman arm and drag link because the insurance company recommended we replace them Incase there's any cracks from collision. We've replaced a few brackets on the passenger side that got damaged: rear cab mount frame bracket, and the V bracket that holds the cab tilt piston. Also replaced the driver side hinge bracket as it got bent in the accident. Need to drop off the cutoff's radiator somewhere in Ambler, PA that can pressure check it. I know my old radiator had a weep from before the accident, so now is as good a time as any to replace it. Both cabs are in the garage so I can swap guts and weld up the floor that salt rotted out on the new cab.

And the dump body looks nice, you might be able to find a buyer for it for a few thousand. Help offset the purchase price.

I will say you'll love working on this truck. I love working on our MR688. You tilt the cab forward and EVERYTHING is right there! Front of engine, back of engine, sides of engine.... Transmission? Once again, everything is right there. You can put an A Frame over it to lower trans out.

With 38k springs I'll guess it's a single frame, former tractor.

Just double check if it's a single frame or double,and see how bad the rust jacking is if it's a double. Always the possibility that the frame is cracked and failing.

Is this a short term get you back to the shop or can the truck be left like this and run indefinitely? I don't have one of these engines, I'm just curious.

What was CCRS?

Good luck! Any clue who he sold it to? Any local old timers maybe recall the truck/buyer?