M51 Power Steering Issue

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M51clueless

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Have what I think is a 1968 M51 dump truck,

The power steering is not working

what I can tell you is the reservoir is full

I disconnected the supply line that goes from the pump to the steering gearbox, turned the engine over and had fluid come out ( pump is doing something)

Sometimes when I crank the truck I feel like I get a hint of it working but then back to it being locked up. It can idle all you want, can rev up the motor, no luck.

checked the steering gearbox was low on gear oil added 80w90 oil to it. No help.

So what do you recommend???

Thanks for the help
 

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eric67camino

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When the power steering on mine went out, it was because the pump shaft sheared, causing no output.

If available, I would try to hook up a pressure guage to verify it has the right amount coming out.

My next step was looking into the steering box. As I understand, there is a diverter valve on the shaft end that directs flow. If it is inoperative, the lines won't get any pressure.

Full disclosure: I've not been that far in on one, so this is hypothetical.
 

M51clueless

New member
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Location
Tennessee
When the power steering on mine went out, it was because the pump shaft sheared, causing no output.

If available, I would try to hook up a pressure guage to verify it has the right amount coming out.

My next step was looking into the steering box. As I understand, there is a diverter valve on the shaft end that directs flow. If it is inoperative, the lines won't get any pressure.

Full disclosure: I've not been that far in on one, so this is hypothetical.
I should be able to pull off a pressure test will have to ask a buddy if he has one that will hook up..

that diverted valve is interesting. I’ll try the old Korean War trick and hit the gearbox with a hammer “ gently “
if the valve is sticking that might do the trick.

Thanks, I’ll try tomorrow
 

eric67camino

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I’ll try the old Korean War trick and hit the gearbox with a hammer “ gently “
if the valve is sticking that might do the trick.
That's called "percussive maintenance". Also known as "hit it till it works".

I don't know what effect, if any, it will have, but never hurts to try.
 

Tracer

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M51clueless, use the search engine and run up M51 power steering, member Robo McDuff. Robo has an M51A2 and has some good posts on power steering issues.
 

M51clueless

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Location
Tennessee
Thanks l’ll have a look
Read the other thread, it was helpful,
Hit the gearbox a few times, no luck
Had some type of red hydraulic oil in the reservoir, drained it and the gearbox oil, replaced both with 10w hydraulic oil from NAPA, no luck

next I guess is a pressure test of the pump.

Any idea on the pressure value I am looking for??
Thanks for any ideas
 
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