P/S steering groan only when hot

[jimhuiz]

Any help here appreciated...

Low mileage 1989 944 2.7l, no P/S leaks, I get a groan when I turn the steering wheel back and forth (pretty loud) AFTER driving it for about 15-20 minutes.

It's quiet for the first 15 minutes when cold, then starts making noise after...

Sound familiar to anyone?

Thanks,

Jim H

[Jfrahm]

Not particularly, but the Rennbay pump reseal kit is easy and cheap.
You can also find the same kit for a Benz or the like for a similar price.

Check your fluid when it's noisy and if you see foam the reseal might sort it out. Worked on my 928.
-Joel.

[wwdwgs]

Check the belt tension.

[TibetanT]

Take a good look at the steering rack, you may have some issues there.


You might put the front of the car up on jack stands, then start the engine and see if you still have the sounds when turning all the way left and then right.

Report back

[jimhuiz]

Thanks for the inputs...Milton prep pulled me away but will look at the things suggested.

[Monkey Wrench]

what causes the noise? its common for a PS pumo to make that noise when its turned right to the lock so I think it means the hydraulic circuit is bypassing the pressure relief valve.

hydraulic packs often will make a sort of similar sound once the demand is over the pressure that the pressure relief valve is set for. as an example if it[s powering a hydraulic cylinder , when the cylinder reaches the end of it's stroke no more fluid can flow so its designed with a pressure relief valve..
The hydraulic pressure can only increase to the set limit of the relief valve.. that is basically the spring tension on a ball bearing and seat.
this PRV allows it to bypass when there is no flow, that means the pump is still moving fluid but it normally just bypass back to the tank. many machines run in this state 24x 7, they are maintaining the pressure of the relief valve and waiting for he hydraulic pressure to be needed basically.

a lot of machinery has a hydraulic pack and it'll sit there running and the machine is not in use, the tank may be 100 gallons and it does warm up that fluid in about an hour to a point of hot to the touch, that's wasted power.


so maybe if the cylinder is not at it's hard limit but is bound mechanically for some reason it could make the noise when it is at mid stroke?

any chance it has tranny fluid instead of power steering fluid in it? dirt in the ball and seat of the pressure relief valve?

I understand hydraulic systems but I don't normally work on Power steering. I just assume there are similarities.

if its low on fluid that can make it squeal, it may run out of fluid before the cylinder is filled.

two problems are common, one is that it leaks fluid externally, the other is that the seals in the cylinder allow fluid to bypass its internal seals. external leaks are obvious.
tests can be done to see if there is leakage, for example if a cylinder is at the end of its stroke and fluid is still passing from one end to the other , that means it's leaking internally. (bypassing the seals)

usually in a hydraulic system for a machine, the line back to the tank is not pressurized, so it is often possible to open that line and look to see if there is fluid flow. if the fluid is flowing past the cylinders seals then that's bypassing.
in most hydraulic systems, the pump is normally designed to move fluid continuously, that prevents the pump from overheating.

if bits of rubber start floating around, like debris from the seals or from O rings, that stuff can get into the pressure relief valve and block it from seating. normally in a commercial system there is an oil filter but I don't think a car even uses a filter. likely a screen somewhere?

how a car's power steering system differentiates, I could learn more about that and would like to. I'm definitely not a Power steering pump expert.