Hi folks -

1991 Mack CS300 Midliner ( 6 cyl. turbo )
Over the past year the power steering has gotten progressively worse especially when its cold outside.After she warms up , its a little better but not easy as it should be to steer. As you turn the wheel , theres a easy turn spot then goes to hard turning and so on.

The 10-40 steering oil is full .

Any diagnosis help greatly appreciated.




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Forgot to mention :

The replaceable filter that sits inside the fluid reservoir hasnt been changed in a few years - yet I only put approx. 500 miles a year on the truck. Could this unchanged filter be the problem ??

 

Sounds like your pump might be shot, anyone else?

 

The filter is on the return side of the system, and most of the ones I have seen have a spring that allows it to bypass when clogged.

Pump could be getting tired, possibly as a result of a clogged filter bypassing constantly and allowing dirt to circulate thru the system.

The power steering gear box could be going bad.

What about the kingpins, drag link ends and tie rod ends? Are they greased regularly with the wheels off the ground when greasing the kingpins? (Jacking up the front axle takes the weight off the kingpins and allows the grease to reach the critical areas)

Binding kingpins and drag link/tie rod ends can increase steering effort.

What about the u joints or bearings in the steering column and steering shaft? Are all greasable parts lubricated regularly?

Some support bearings on a steering shaft may be "lube for life", but if they are failing it can cause binding in the steering.

There are bearings in the steering column, just under the steering wheel and there could be binding there also. Does it feel like the steering wheel turns roughly, like something is jamming up in the column?

Just a few possibilities that I can think of.

I suggest you do whatever it takes to get it working correctly, ASAP.

Someone could get injured or killed due to defective steering.

 

Meritors manual specifically says NOT to do this for kingpins. You must do it for spring bushings however.

 

Well, if they say so.

Personally, I can't see why they would say not to.

Grease can flow between the kingpins and bushings a lot easier in an unloaded condition.

When I had my dump trucks they got jacked up to grease kingpins, and at the shop I'm working at now we do it that way too.

The midliner Mack in the original post would not have a Meritor steer axle anyhow.

 

Might want to also check your steering knuckle for slop

 

Thanks for the input guys -

I will replace that filter then its going in for annual inspection sticker .


I found a recall for these Midliners about the steering - although the recall was for 1998 models - its worth checking out.

http://www.tc.gc.ca/roadsafety/recal...sp?recno=2931&


I agree - whatever the cause , its something that needs immediate attention , for safety sake.

PLUS - the days of driving a truck without power steering ended for me decades ago with my old 1968 V8 mack , screaming Detroit w/ twin stacks that smoked like a factory chimney.

Thanks again - will let ya know how this turns out for me in case other Midliner owners have these symptoms.

 

[quote="Splitshifter"]The filter is on the return side of the system, and most of the ones I have seen have a spring that allows it to bypass when clogged.

Pump could be getting tired, possibly as a result of a clogged filter bypassing constantly and allowing dirt to circulate thru the system.

The power steering gear box could be going bad.

What about the kingpins, drag link ends and tie rod ends? Are they greased regularly with the wheels off the ground when greasing the kingpins? (Jacking up the front axle takes the weight off the kingpins and allows the grease to reach the critical areas)

or, in some instances the loaded kingpin forces grease into the thrust bearing rollers instead of purging out around it .....

matter-of-factly, i have uncovered far more service info that tells me to leave axle loaded

Binding kingpins and drag link/tie rod ends can increase steering effort.

What about the u joints or bearings in the steering column and steering shaft? Are all greasable parts lubricated regularly?

Some support bearings on a steering shaft may be "lube for life", but if they are failing it can cause binding in the steering.

There are bearings in the steering column, just under the steering wheel and there could be binding there also. Does it feel like the steering wheel turns roughly, like something is jamming up in the column?

Just a few possibilities that I can think of.

I suggest you do whatever it takes to get it working correctly, ASAP.

Someone could get injured or killed due to defective steering.[/quote

agreed

 

it sounds like mechanical binding;

does the steering always bind or harden up in the same point of steering wheel rotation?

first, check if the u-joints are in phase (they line up together when you look down the shaft)

if they're good, then try removing the steering shaft at the gear, and check all the u-joints.... 1 side of a u-joint cross could be binding, it would be difficult to move that joint in one of its 2 directions