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Need Mack 5-Ton Power Steering Help!

SixSpeed

SixSpeed

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Hey Guys,

Let me pick your brain for a few minutes. I am trying to sort out the power steering system on a Mack powered 5-Ton.

The steering is VERY difficult in the truck, wasn't working much at all. During diagnosis one of the hoses from the pump to the gearbox blew, so I had a new one made, and refilled the system. After doing so, the steering seemed to be much easier when turning to the right, turning to the left there is no assistance. I figured there might be air in the lines, so I jacked the front end of the truck up, and the steering was nearly just as difficult with the front wheels off the ground, when turning to the left anyways. The previous owner had put a new steering gearbox in the truck, but that was years ago. I think they might have done this in an effort to fix the steering problem. Might be defective...who knows, just thought I would include all information I knew.

Anyone have any idea where I might start for diagnosis? Not sure what TM would cover this? A collapsed line? Bad pump? Bad gearbox? Incorrectly routed lines?

Any help would be much appreciated! Thanks!
 
Goose2448

Goose2448

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Maybe there is a blockage. Like a rock in the line, how it got there I do not know. If It were me, I would drain the whole thing out, and rebuild the pump. If that dose not work, maybe someone else can help. Also make sure the lines go to the right places. Here is an idea, switch lines from pump to gear box, and see if that makes a difference. Just a thought.
 
AMGeneral

AMGeneral

Well-known member
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I'm guessing it has the old style Ross power steering box( mounted on the drivers side frame rail just ahead of the cab).

If so,here are a few things to check,

There should be only 1 hose going from the pump to the steering box,and it should be connected to the fitting closest to the drivers side wheel/tire and just below where the steering colum connects.

The fitting just ahead of the one previously mentioned should return to the P/S resevior.

The 2 hoses on the opposite side of the P/S box closest to the engine should be connected to the fittings directly above each other,the lines should not be crossed end to end,I have seen several like this that have the same problem you describe.

The 2 hoses left that come from the P/S pump should lead back to the resevior.

If this seems all in order,I would disconnect the drag link from the axle and make sure the problem isn't in the axle or knuckle itself.

If all above is OK,then it may be a bit of dirt or grit in the spool valve just below the steering colum not allowing it to send oil to the assist cyl when turned left.
 
SixSpeed

SixSpeed

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Alright, got some nice weather today, so here is what I know:

All of the lines are in good shape, no leaks or collapsed hoses are or anything. Everything is plumbed in the right location as well.

All of the lines are plumbed in the right location.

The little external..fitting? Sliding thing on the steering column coming out of the spool valve appears to be free and clear of debris. I don't know how this piece works or what its function is, any clarification would be much appreciated.

The linkage (draglink/tirerod/knuckles etc) are in good condition, with smooth movement and no binding.

With the above figured out, I disconnected the two lines on the top of the power steering gearbox, jacked up the front end and (with the motor off of course) turned the wheel left & right. The steering was easy both left and right, as it should be. Fluid flowed copiously out of both fittings.

With my new found knowledge I reconnected the two lines on top of the power steering gearbox, except in reverse order. Once again with the motor off, I tried to turn the steering wheel, with the lines reverse, my "can't turn left" turned into "can't turn right".

I reconnected the lines in the proper order and put the truck back on the ground.

With the above said, I am assuming I am dealing with a problem relating to the valve on the top of the steering column (spool valve?)

So are there any TMs out there that cover a rebuild/diagnosis of this part? Are there parts available for it or am I better off souring a new one.

Any info is MUCH appreciated.

Thanks!:driver:
 
highfavor1004

highfavor1004

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I brought the truck from sixspeed and i am doing a fallow up

The truck is a 1960s M246 with a Mack motor.

Do they even make a rebuild kit for the pump, and no one answered if there was a TM for this problem. In addition, another problem with the truck has occurred with a loud clanky noise coming from the trans, however it shifts in all gears and does not slip. the front wrench does not work and i think that the sound is coming from where the PTO out-put comes out of the trans. Any Ideas?
 
5ton beachbuggy

5ton beachbuggy

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Capecod MA
I had a 246 that I put the Mack motor in and change the cab that had the same problem.I had to adjust that link to the valve to get the steering even both ways. I donot remenber how i did it [15 years ago ] but it did fix the trouble. Good luck Mike
 
area52

area52

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Dang, thats a rare bird - a M246A1. Make sure your PTO is disengaged and check all of the linkages also.

Also read through the TM's for the truck and try to troubleshoot your problem.
 
highfavor1004

highfavor1004

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Thank you, yea i was just searching them i am also trying to run down a problem with no power to the lights of gauges. but i wish 5ton beachbuggy could remember how to re-adjust that valve lol. yea its pretty rare even with the Mack motor, and everything with the crane works i just got to work out all the other kinks with the truck. I have a 5 ton dump that i can pull parts from but it has a cumming motor. also anyone know where to get the 1 in high pressure hydraulic hose i blew one out today.
 
area52

area52

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I would drain the oil out of the transmission and see if there are any chunks/pieces in the oil.

You can take the top off the trans also and check inside it.

Ask any auto parts place where to get a hose made.
 
5ton beachbuggy

5ton beachbuggy

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Capecod MA
If you have the old type fittings they are very hard to get. I ended up cutting off the crimp and hose to reuse the fitting. Most truck or heavy equipment shop can make the hose up. I think the pto on the transfer case is always engauged and is lubed by a metal line to the bottom of the case that can be blocked up an not let the oil pump up to the pto
 
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