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1978 R686 Coolant & Oil Dip Stick


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I am looking for medium size Dump Truck to move soil around for some planned property improvements this spring. If I get a truck I'd prefer it to be A MACK. Turned up a 6 wheel 1978 R686.  

Looking over the truck it has 377000 plus mile. Started the engine and if fired right off stone cold. Checked the coolant after the engine ran for 5 to 10 minutes. When I removed the cap the radiator was pressurized, the level was low and I couldn't see coolant. I asked the owner if there was any problem with the cooling system. He said they just replaced the water pump? He assured me there wasn't any known problems or issues with the truck. A little concerning. The seller has contacted me asking if I am interested in the truck. I told him I might be if he tops off the coolant, if I can further inspect the truck and take it for a test drive. 

One thing I found strange, odd or unusual. When I pulled the dip stick the side closest to the frame (facing me) was clean with no oil. I asked about the oil and I was told the oil was just changed. I re-dipped the stick and it came out clean again. Wiped the stick with my finger and the dip stick on the engine side had oil. Dipped the stick again and the same results. The frame side was clean. With the stick pulled I turned it over and it showed full. What the heck is up with that? Anyone ever had that experience? Goofy question - Is it something to be concerned about? 

Mack Dump 2.jpg

Mack Dump 1.jpg

Edited by tenfive0

Mack 11E.jpg

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Great trucks; you're going to want to fix this intake tube though, keep rain from getting in and ruining a nice truck. Also its letting unfiltered air in.  This radiator has the reservoir in the top, you should just barely be able to touch it with your fingers.  You can spot coolant leaks by looking for salt trails, common leak spots are the freeze plugs on the driver side, as well as the crossover hose (very short) between the front and rear head water manifolds, also on the driver side.

Does seem strange that the oil is only on one side of the dipstick. Next time check the oil before starting the engine.  I have an E7 that if I check it 5 minutes after shutting off it'll be a gallon low on oil, but if I check it first thing in the AM it's full.

Screenshot_20240314-212303.png

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  • 2 weeks later...
Posted (edited)

First, (1st) of all thanks to everyone for their input, help and guidance.

Second, (2nd) I wound up passing on the Mack. My little voice inside just said NO. They say first impressions are everything. There was just something about the truck and the hard sell tactic the seller was pushing. One of the first flaws I noticed on the truck was the hole in the intake tube. That would have been the first thing I would have fixed. How obvious of an easy fix would it have been for the seller to just temporarily fix the problem with duct tape. I have no idea how long the truck was run that way. It is an issue I didn't ignore while looking at the truck. I don't want to talk bad about the seller but there were a lot other issues that turned me away from buying it. 

Third, (3rd) perhaps the worse part is I bought a GMC - Combination with an Equipment Trailer. I was looking for a (not for hire) truck and trailer to haul around my Skid Steer and Mini Excavator. Found the GMC for sale with a trailer for slightly more then the Mack alone. Sorry, to the faithful. Maybe I shouldn't even mention GMC? Well at least It isn't a FORD! When I started out looking for a dump truck I would have preferred a Mack but I was willing to settle on a JIMMY. Definitely wasn't interested in a FORD of any kind. 

If there is any consolation? I had he Jimmy Hauled home on a lowboy trailer drawn by a Mack Tractor.    

Edited by tenfive0
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Mack 11E.jpg

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There is room for the GMC here in there other truck brand section.  All our trucks are Mack's, except for a 1995 Ford L8000 single axle cab chassis we picked up for $2500 from a local oil delivery company I drove for briefly.  We slapped a dump on it and a salt spreader a year or two later.  The right truck is the right truck to come along at the right time.

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Posted (edited)

It is what it is. I am trying to take command of our properties with a Bobcat E35 Mini Excavator and Bobcat S205 Skid Steer.

GMC - 1990 C7000, 366 Big Block/Allison AT545 with a Chevy (tilt) plastic nose and trail combination. With slightly less the 50,000 original miles. No complaints so far.

It is the right truck for us right now.GMCDump4.thumb.jpg.bec0e33b7fb6ee39c67a2a3fdbc2c9e2.jpg

Like anything used it needs some massaging and love. The first thing is to add a Tru-Cool  40k Transmission Cooler before we put it to ant serious work.

Edited by tenfive0
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Mack 11E.jpg

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