Mcrafty1

The Rise........and Fall of the Third Reich.

May we NEVER forget.

This was the unit we installed, it came with everything for the R model ( unit, compressor , brackets , condensor, drier , switches and hoses)But as Kscarbel2 said, get a factory AC compressor mount , as the ones that camee in the kit never stayed tight.

Thanks, I see now that the compressor, lines and condensor isn't included with this one. I'll have to check and see if they have those to sell or if I'd have to find those things elsewhere

Thanks Paul for getting the picture up for me, it is a nice truck and well suited for the earthwork business I have. A little slow in the highway (65 maxed out) but I don't even push it up to that most times, I'm a lot more relaxed than I was forty years ago and have learned a few things over the years....lol

Thanks all for the warm welcome, I'll be lurking and asking/answering any questions I think I can help with or need help with.

Mcrafty

As long as you have your pictures in your computer, go to the bottom right of the reply box and click on "More Reply Options" and then follow the instructions.

Ok, I'll give it a shot when I have time to sit and play with it for a minute.

I installed lots and lots of the Red Dot "between the seats" units back in the R model days. Had the be the coldest A/C ever, never saw one that would get above 39 degrees output temp. Had to run them on low. Downfall was your elbow would smack it sometimes while shifting if u had long arms.

Do you recall the name of the manufacturer of the units you installed? I have yet to find one of the between the seat units to compare to the other types. I'm also wondering what peoples experiences are with the roof mount models..ie: do they cool enough to make the entire cab comfortable or just blast your head and shouklders with cool air but not do much else? The price seems comprable to most other styles that I have found, I am still most interested in the between the seat models and would like to find more criteria and some pictures of those.

Red Dot offers a factory style dash unit, for around $1200. I believe it includes the compressor, lines, expansion valve, dryer, and condensor. You could go with a universal between the seats style unit, which in my opinion does a better job for less money, but I'm a stickler for keeping it factory looking.

After looking at the red dot under dash unit the between the seat option sounds a lot less complex and therefore easier to install/maintain but I didn't find those on the red dot website, do you have a link for the between the seat universial models?

Red Dot offers a factory style dash unit, for around $1200. I believe it includes the compressor, lines, expansion valve, dryer, and condensor. You could go with a universal between the seats style unit, which in my opinion does a better job for less money, but I'm a stickler for keeping it factory looking.

Thanks, I haven't taken the time to look yet but I like the idea of the factory look too, I also don't mind the roof mount units but it seems like the air flow coming from above and so near your head my not be such a great Idea...IDK

check with RED DOT corp as i understand they have a nice aftermarket unit for this application, then you can compair it to mack part prices or wrecking yard parts.

Will do, Thanks

Administrators...If this is the wrong place for this please move it to where it belongs.

I have an RD685S 1986MY I would like some input as to what it intales to install an AC unit into this truck and what is the best option.....Factory package vs. Cab mount and which is the most cost effective in terms of actually doing what it's suppose to do. Thanks in advance for any useful info on this subject.

has anyone looked at that( piston cooler) spray nozzle

Yes the spray nozzles where ruled out earlier, Thanks for the reply

Yeah I can see I didnt explain my self very well

if all six exhausts are going into the one manifold then exhaust gases all get mixed together and turn into one gas the result of the six different gases mixed and the pyro temp would be the average of the six

so it is quit possible that one cylinder could be 200 degrees C and the other and another 300 and two at 400 and one at 1000 and I dont know the last one at say 550 degrees C

so if we add them all together we get 2850 divide that by six = 475 degrees which on the pyro gauge would look all ok but as you can see the temps are all over the place and one of them to stage it's gunna melt a piston

Dunno if I have helped to explain or made me look more of a fool

Paul

You done great explaining what you meant to, but that doesn't explain how that could happen, if all injectors are being feed from the same pump...and the pump has been calibrated and known to be accurate, the air is being driven into the engine with the same turbo and the cooling system is working as designed and the water temp never exceeds 200 (very rarely that high) then what could cause the same piston (hole) to burn two pistons to the point of breaking the ring ledges and the other five out live that one by now 2 x's (the original piston after the rebuild....another after that and another season on all five of the others on top of that. That is why I'm scratching my head, I appreceate your input too, thanks

Im no hot rodding type of person but trying to think of how it could happen leads me to think of it like this

If only one cylinder is running hot the pyrometer wont pick that maybe because the overall heat spread across six pots will still measure ok so although you may be watching the pyrometer like a hawk the one cylinder getting hot might not show up due to the rest of the cylinders running cool if that makes any sense

Im just thinking out aloud as stated above the most likely cause is a fuel problem and that can only be two things to much fuel or the timing at least that is my understanding

good luck

Paul

I agree with everything you say, The pump WAS calibrated when it was rebuilt......the only thing I changed the last time around was the piston, rings and sleave AND a new injector, I did the injector change because I suspected the spray pattern was bad, That being said I have run the truck one season since I made this change and so far so good. The only way to know for sure is to pull the head and have a look. I'm not going to do that...oh, and the timing was checked too so too much fuel COULD be a problem but that really don't explain why it's the number 6 hole both times and the EGs staying within spec. It is beginning to be a head scratcher at the moment.

I agree with Glen. Have pump calibrated.

I'm in touch with the rebuilder and hope to findout something soon, if I cant I'll have it done before I start using it this spring. Thanks for the reply.

I agree with Glenn. Perhaps when the pump was rebuilt the #6 plunger was set incorrectly. Did the shop flow test the pump after rebuid? If so, look at the individual flow results.

I don't know that they did any flow testing, I'll have to check and see, thanks for the help....both you and Glenn, I hope to get to the bottom of this before anything happens to this engine. This should help me do that.

Wonder what it would cost to get a pump gone through and setup?

Last time I had mine gone over it was around $1600.00 The pump was worn pretty bad though and in need of an overhaul....This is on a 250 econodyne.

Timing will do this and also setting the fuel up will do this as well as the fuel pump calibration should be pulled and sent to fuel shop.One pump may be fueling more than the other five.The piston oil cooler will in most cases score the shirt of the piston if its bent.

No scoring, just melted down over the edge of the piston to the point of breaking the ring and then the ring ledge......the pump was completely gone through when the engine was rebuilt two pistons ago.....and the timing was checked when the engine was rebuilt and possibly when the first piston was replaced....the second time the piston was replaced and the injector in the same hole was replaced but nothing else was done. The fuel is maxed out but as I said in my OP I am very careful of heat, My concern is the fact that its the same hole each time so the over fueling in that one hole is deafinatly a possibility I'd not considered......However I take your an anyone elses info and advise to heart and appreceate any and all input.

Hello all, As stated I'm the new kid on the block. I own a small earth work business in the great state of Maine and own an 1986 Mack RD685S that I use as my primary truck (its my only truck at the moment) and at my age(59yo) I hope to 'finish out" with it. Its a great piece of equipment which I've owned for a dozen years or so and built up to what I have now. Looking forward to reading about and hearing from thuroughbred Mack owners and all others about thier experiences over the years with these truck and will throw in my 2cts when I feel it will contribute to the mix.

Hello, I'm new to the forum.....I have an 1986 maxidyne 250 four valve engine and have (twice now) melted the rear most piston at the ring ledge Same hole both times? the second time I changed the injector although all tested out ok, this was the beginning of last construction season and thus far the problem has not risen its ugly head,,,,, I have a pyrometer and have always been very careful not to exceed the 1050* heat max. and would like some input into this...also like to know if anyone else has experienced this problem....oh, it was an econodyne engine and I did open the fuel up on it a while ago (before the first meltdown) which I don't believe is related...I've been wrong before.