Stingray698

I recently purchased a 85 mack r from kentucky i drove it back to iowa no problem , lately ive been driving it and the throttle is all or nothing anything in between sounds like im hitting the pedal 30 times a minute , as much as i try to hold it still i cant , its to the point people look at me like im doing it on purpose , ive tried a tighter return spring and looser spring , no difference , also not sure exactly what engine is i know its 2 valve but the tag says meets emisions of 1990 , and i cleaned off front cover below a/c comp where numbers are and theres nothing there and data tag has half of the numbers and setting gone like they were never even stamed , i wanted to figure out low idle , and not sure where to go with this its very annoying to drive it has american bosh pump . any help would be appriciated

by alignment has truck had a tandem alignment or just toe set? also steer shaft u joints , have you checked for equal brake stroke with a tape measurement on steers , also what about on the hubs where the drum rides is there a bunch of alumin oxidation on hubs , what about anchor pins/ roller bushings/scam bushings in brakes , those three things get overlooked quite often people just keep replacing just the shoes and drums ,

As for the compressor i agree sounds like the internal valves in the head , and for the king pins you can do the bushings yourself they are brass and very thick and a needle bearing they do not need to be reamed i just take a small brake hone and pb blaster clean the spindles , then press new ones in also another trick i figured out is take one of the old grease seals and emry down the outer lip so it will fall into spindle by hand then you can determine depth of bushing and needle bearing so when you put the seals in they dont protrude out past the spindle and rub on the axle ,also make sure the grease seals are put in with the lip facing out so it actually looks like the seal is in backwards , it will lock the spindle up when you grease it , if the lip faces the bushings, one other thing when i remove the top grease caps i weld a 1/2 fine nut on the cap and put a small style slide hammer and they usually come right out

They are designed to have up and down as in lateral but if you push in or out on top or bottom of wheel there should be none , if they get too tight they can press themselves out of the axle , how do the tires look are they choppy or cupping on outer side , also on top cap i always peen them in 10 or 15 spots , after setting them i run nut up till its tight then back off until next slot lines up ,then check for up and down ,then after another lesson learned i always grease them right after final adjustment is made -there again if there too tight and you grease them they will lock up then your taking the spider back off and re adjust , they are designed to have some play to tight will wear axle beam , Also i tried a stemco no reem kit in the tapered style and will never use one again , I ended up removing it and returning it , goes to show you aftermarket is crap every time you would grease it it would push the spiral bushings and move them and make adjustment super tight after adjusting, just my 2 cents Ive done probably 10 sets and every one sets up a little different, also i checked a garbage truck for referance once and i bet it had 3/8 up and down , customer didnt want to fix i looked at it 6 month later and it was same way and tires wernt even wearing bad , strange but no lie

Thanks for the info everyone I had a nice superliner hood lined up for next to nothing ,maybe ill get it anyways just to have

Blue one is mine yellow one is a customers

Just wondering if anyone knows if a r model hood and superliner hood are interchangable, onto a r model been looking at them and both cabs look the same but different hoods , kinda looks like the superliners may have a set foward axle ? not sure

I have a 1988 R model R688ST with a 350 4 valve with jakes , complaint low power , and hard starting , i replaced fuel filters still wouldnt start , then ran hose to bucket right from fuel filter got it to start ran ok, then ran new suction line to tank and started truck - ran ok , checked fuel pressure it is 45 at idle and after shutting it off it maintains between 10-15 i looked through a mack tune up book it is from 1985 and every engine and configuration has a different fuel psi it seems like the happy median is 17-31 i also pulled overflow flow valve off pump everthing seems ok , i think im going to check overhead tommorow in the meantime , i know it doesnt effect fuel situation but probably should be checked/set , any ideas or comments would be appreciated , also does anyone know what the fuel pressure should be ?? Thanks

Ive been working a a mack granite the ac will work when the blend is on the defrost position only , the local mack dealer said there is another micro switch on the fan switch behind the hvac controls i couldnt find it am i missing something , truck does not have the diagnostic ac function either , i understand the blower needs to move air through evaporator so it doesnt freeze up but i just cant figure out why the ac wont work on vent or floor or any of the other posistions , any guidance would be appreciated , thanks

well i got it apart not bad at all 2 good hits and the pins fell right on through and hit the floor , i read through the bulletin posted above and im a little confused on the step that says upper clearance should be between .005 and .027 with loaded upward , but then it says lower clearance should be a minimum of .020 , I take it that means unload spindle and let it hang then check clearance , or should I do it by feel like mentioned above I just dont want to tighten that lower nut to the point where I crush or damage anything I guess I'll go in gradual increments and keep rotating spindle to the point to where it starts to get tight then check clearance?

So the truck I was suppose to be getting was not the truck that needed king pins anyways I have the truck now and the post I did the other day is greatly appreciated but not needed at the moment , anyways here is a picture of the king pin kit and axle just wondering what the spec is for final end play and the torque spec on the bottom nut, Thanks

Thanks for that, is there any special tooling needed to drive bushings and king pin out and also are the wheel bearings set like typical wheel bearings or do they have a sleeve and torqued?

Hi just wondering if anyone has torque specs or procedure for king pin replacement on a fxl-12 , any help would be appreciated , I believe they are tapered king pins, I've been a peterbilt mechanic for the last 10 yrs now I opened my own shop and you'd swear the only trucks out there are Macks lol! Thanks

I dont have any manuals more or less just need to know best way to bar it over and whee the timing marks are ?

i Have a 2002 or 3 mack vision with a AC engine in it, could anyone tell me the procedure fr setting /checking valve lash,Thanks