Just spent about 10 hours in this new to me mack. Left Illinois with it yesterday, seemed okay for the first while, further I drove the worse it got, now its almost all the time. Engine seems to surge/ hunts. Started in the middle areas of the throttle, seemed to go away when wide open, or totally out of the throttle. Got worse and worse I first thought it was tires or driveline, but tires wouldn't make any difference in and out of the throttle (it stops doing it as soon as you let off). It's possible that its driveline/ ujoint/ hangar bearing, but I crawled under and gave them all a good twisting, and I really don't think its that. I'm thinking governor springs/shaft, anyone ever been into one of these before on a old manual mack? It's a 1990 old RD series- I think its a EM-6 350,
Change all the fuel filters first..... old scummy fuel starting off and partially clogged filters can do funny things.....
And any rubber hoses too...
Crane was in active use, they had it set up in someone's yard taking down a tree when I showed up to get it. Still possible that its fuel filters, but I would suspect more loss of power, and it really pulls wide open. A full change of fluids and filters is in the list for first things to do though, we'll see if that clears it up. I was a little worried, also- the owner said "I don't think it uses any oil- at least we never put any in it." I'm not sure its had the best filter change schedule. You know when the filters are all pretty faded or covered with old dirt and grime, that its been a while. I will say it didn't use any oil on the way home, a 400 mile run is quite a ways without burning any. It does have a leaking freeze plug on the drivers side, it looks like a cave formation, from old antifreeze seeping ever so slowly out. I'm sure there will be other things too, I'm not real familiar with Mack engines.
For Mack info-Big Mack Truck Forums.com Truck Shop
Turbo? Boost leak???
Yes has turbo- can hear it spooling up, don't hear any big hissing like a boost leak, no boost gauge, something to check though. Don't notice a big drop in power, just really seems to be mostly a mid range throttle hunting/chugging. I would think it would fall pretty flat under hard throttle with a boost leak wouldn't it, and usually you can hear it. Seems to have real good power and the hunting goes away under full throttle.
I had an RL700 with a V-8 Mack that had the most sensitive throttle linkage I have ever seen. A few bumps and you were doing crazy things off road. Mid range was the worst. My old '91 F-800 is the same way.
Is it an air-ride cab and a rod throttle linkage? I have a Volvo like that and I think of the pedal as an on-off switch in all but the top two gears. Is this just in the lower gears, or cruising on the highway?
There was a "campaign" on 2 particular RobertBosch Mack injection pumps for a mid range surge.. There is a 10 digit # on the pump name plate, if it ends w/ 203 or 211 you got one.. It requires a gov. spring change & calibration to fix.. Try ALL the other stuff first, before pulling the pump. Filters, Loose linkage, ect..
It is in all gears, high way or just coming out of a gas station. Is not a air ride cab- I don't think the old macks have such a thing? I'm going to see if it will do it in the yard with just the crane running, to try to eliminate foot vibration, but it did get worse as I traveled home, its not real drivable as it is now. I did try to wiggle the linkage on the pump when stopped yesterday morning, and didn't notice any real loose stuff. I was reading there last night - good site. These threads seems to indicate governor also/ or linkage: https://www.bigmacktrucks.com/topic/28638-e6-350-idle-surging-problems/ https://www.bigmacktrucks.com/topic/18255-engine-surges/ This next one always comes up as printing it? I just hit cancel on the print and then read the article: http://forum.aths.org/PrintTopic67990.aspx
According to that- it is possible to remove the governor without pulling the pump?
Do you have an American Bosch [ambac] or a Robert Bosch pump?? The AB name plate will say PLM****** & will have a large side cover on the pump & the RB will say PES6P******** w/ no side cover & a 22mm allen plug.. An AB pump, the gov will come off on the truck.. A RB, NO..
Looks like I'm ambac on the pump
Check that "break-back" throttle lever REAL GOOD.. The spring gets weak or breaks & will give ALL SORTS of surge problems.. Remove the "helper spring" you have on there & hold the bottom of the lever & try to move the top portion back & forth, without breaking over the spring.. Some play is ok.. ALOT is not.. MORE THAN LIKELY the bushings are worn out in the flyweights.. OR the rear endplate is cracked & the camshaft is floating back & forth.. I've been rebuilding those pumps for 30 years AND worked at the Ambac factory for 3..
Just so we're on the same page- this rig is totally new to me. The air cylinder control (just below the blue circle) is from the upper throttle for the crane. The electric solenoid (above the blue circle, to the right of the yellow circle) activates the yellow arm, shutting off the fuel.? The spring up on the top in red is what you're calling my helper spring, returning the lower throttle pedal. The spring in blue is the "factory return spring" for the throttle return. The white circled lever should be where I'm checking for play,from forward to rear, or just as the shaft goes into the housing, toward and away from the engine? The manual override shut down is a cable to the cab, it looks like its long gone. The upper air throttle control cylinder on this one is not set up on a slider, instead its just heim joints. All my other engine's with dual control (that have this same cylinder), have a slider on the air cylinder, so it doesn't affect the lower throttle, this one is direct heim, I'm wondering if that could be part of my problem also, that cylinder has its own internal return spring. Thanks
Just looking this over, its also possible my blue spring is not factory either, and the return spring is actually internal, and I need to remove the blue spring also?
Remove the BLUE & check it for play at the WHITE.. left to right.. Red is ok, leave it alone.. YOU HAVE TO HAVE a throttle return spring attached to the throttle for normal cab/driver operation..[blue}
Would be a interesting ride though!! I hated running the old bulldogs up on the dyno at Mack St. Louis, would go to surging when got them too far down in torque curve then all sort of crazy crap happened. Came off the dyno backward one night scared the crap out of me!! I also had set the exhaust hood on fire with a set up old B series a man wanted checked, straight pipe and two feet of fire out the stack!! WOOHOO! fire department did not like that one!
Appears I have quite a bit of forward and back play on the throttle shaft. Local injector shop says it's probably not the governor, he wants a intake fuel pressure reading, says I need over 20 psi, which he says is just for checking's sake, but he thinks its a plunger/ worn barrel. Wants to just go through the whole pump. I'm thinking if the governor can be repaired without pulling pump, what am I out for just doing that first? Then if that doesn't fix it, then rebuild injector pump? I wouldn't be out any extra work, and if i do need to fix pump, then I would already have the governor done.
a worn p&b will not give a surge.. a worn rack bushing will, a worn gov. will, a worn throttle lever will.. but a worn p&b?? NO..
Thanks pumpguys, it seemed like he was just interested in having the whole pump. I'm not sure how far we are going into the surging issue right now. When I bought it, the seller told me there was a frost plug leaking. I got it home and it turns out the frost plug leaks a little, but the real big issue is the crack in the block that goes from frost plug to frost plug, front left corner of the motor, behind the oil cooler, straight up and down. They had covered the crack with jb weld, and some oil and dirt, so it just looked like the frost plug. It's just in the water jacket, and it barely drips. i'm not sure if we are just going to try to clean it up and try to seal it somehow, or just replace the motor/ block. I know its not going to heal itself. I don't know why you wouldn't just tell someone the real problem, you really can't see it because the oil cooler hides it, and once the block is warm, it doesn't really leak. I guess he really wanted to sell it. There's all sorts of people I guess....
Belzona works much better than jb weld. If you want to try and fix it. Not cheap last time I bought some it was $200 for about a tennis ball size kit. I used it on a old cat engine 10-12 years ago with a similar leak. still holding.
Second the Belzona, they make lots of different compounds, for a coolant leak like that it's probably a somewhat flexible compound. Also, you can use a rubber core plug (yeah they exist, ask at your local parts store) probably better than driving in the steel ones in this case.
How about some "FLEX SEAL"?? Lol.. it works on TV.. Hell, you could cut that engine in HALF & put it back together w/ that tape.. Its GOTTA BE TRUE.. its on TV.. Sorry fellas, its FRIDAY & it was a LOOOONG week..
The old guys in the pump room at Mack when I worked there showed me the wear spots on a governor flyweight base, showed the least little ring of wear. The Oldest man(I think at the time he was 59!!) said would cause it to hunt at idle as so little pressure where would step in and out of that ring, don't know if could be a issue here.