Power steering fluid

[ElliotCC]

I have a 78 2 door, resto project, recently during a typical evening of tinkering I noticed the power steering fluid was way to low, before I just go out and buy any old stuff any suggestions from the experts?? The current fluid is blood red....

[Toxic_Avenger]

At a guess, Dexron ATF?

Somebody will be able to confirm

[ElliotCC]

II OR III??

[justinc]

2 is now 3...☺

[PhilipA]

I use the Yank power steering fluid Prestone brand available from Supercheap.
It has seal swelling stuff in it, and anything you can do to swell dem seals is good.

Regards Philip A

[ElliotCC]

It's ok to mix brands? I've no idea what's in it, but it does look fresh and bright...

[justinc]

Not ok if mineral vs synthetic otherwise should be fine.

Jc

[ElliotCC]

How do I tell the difference?

[Mercguy]

You can sometimes tell by smell, but most times you cannot.

I would not use ATF in a power steering system.

flush the steering box, lines, cooler and pump, replace the filter and refill with hydraulic / power steering fluid.

Reason being is the friction modifiers in the ATF, which actually help the clutches to 'grip' also reduce the 'slip' and this leads to an increase in wear on metal-metal contact surfaces. in a steering box, there are a lot of metal-metal contact surfaces.

Where ATF was once commonplace and recommended, a lot of owners of classic vehicles are finding that even rebuilt steering units are leaking unusually rapidly.

I've rebuilt my steering boxes on my MB's more often than required and when I say rebuilt I mean properly, to factory tolerances.
The ATF absolutely f*(*&s the seals. excessive wear on metal-metal. so I stopped using it.
I use the same synthetic hydraulic fluid ZH-M (ZF fluid) for the SLS/ASD system. I have not had a leak in 4 years using this.

I'm not suggesting you need to use this stuff (because it is expensive) but you can find specific power steering fluid from penrite etc...

Here's an interesting video. His anecdotal evidence is not hearsay. I've noticed exactly the same issues on vehicles on systems where I have rebuilt pumps and boxes and replaced hoses to ensure a 100% new system, and in under 5 years leaks - where previously it took over 10 for a minor leak to present itself. Fluids change. specification changes can not always be beneficial. Stick to dedicated power steering fluid and don't use ATF.

While this video might be mercedes related, it's no different practice on a LR.

https://www.youtube.com/watch?v=TLR_kdnsJ_0&ab_channel=Mercedessource

[DoubleChevron]

That's quite interesting. I wonder if you can just use a standard mineral oil hydraulic fluid. I have LHM here .... My cars leak it all of the place by the gallon. I could probably use that if it's thick enough (or I could just go buy some power steering fluid :wasntme: ).

seeya,
Shane L.

[Mercguy]

Absolutely no reason why you couldn't, so long as the viscosity matches and the heat rating was equivalent.

LHM should be OK, even though it's mineral based. all you would have to be aware of is a potential for buildup in the box if it got really hot.

The way I see it, the ZH-M in the SLS, is constantly circulating throughout the system, returning to the reservoir before being pumped back to the levelling valve then to the accumulators and up into the struts and back to the accumulators.
I've not ever noticed any 'fade' in those hydraulic dampers, and I'd wager they work a lot harder than a steering box. So perhaps it would be fine. I don't know what the operating temp range of LHM is, so not qualified to make a statement on it, nor am I familiar with the viscosity, but the ZH-M is Low-vis. It's also a little bit on the expensive side to be using in an already-leaky system.

If your PS system isn't leaking 'badly' then it's probably worth a go. But not before the ATF is completely flushed out with the proper flushing fluid. In my experience, it's easier to pull the steering box, strip and clean with B1, replace all the seals, reassemble and refit. Using evaporative solvents on aged seals doesn't seem to do them any favours. they're either too brittle from the hardening reaction with the fluid or solvent, or they swell and then soften, then deform when reassembled. Seen it done too many times now, and a seal kit is dirt cheap, rebuilding a box takes less than an hour, so it's not like it's overly-complicated.

well, it's not complicated if you can pull it apart. You know what I mean. ;)

[DoubleChevron]

Absolutely no reason why you couldn't, so long as the viscosity matches and the heat rating was equivalent.

LHM should be OK, even though it's mineral based. all you would have to be aware of is a potential for buildup in the box if it got really hot.

The way I see it, the ZH-M in the SLS, is constantly circulating throughout the system, returning to the reservoir before being pumped back to the levelling valve then to the accumulators and up into the struts and back to the accumulators.
I've not ever noticed any 'fade' in those hydraulic dampers, and I'd wager they work a lot harder than a steering box. So perhaps it would be fine. I don't know what the operating temp range of LHM is, so not qualified to make a statement on it, nor am I familiar with the viscosity, but the ZH-M is Low-vis. It's also a little bit on the expensive side to be using in an already-leaky system.

If your PS system isn't leaking 'badly' then it's probably worth a go. But not before the ATF is completely flushed out with the proper flushing fluid. In my experience, it's easier to pull the steering box, strip and clean with B1, replace all the seals, reassemble and refit. Using evaporative solvents on aged seals doesn't seem to do them any favours. they're either too brittle from the hardening reaction with the fluid or solvent, or they swell and then soften, then deform when reassembled. Seen it done too many times now, and a seal kit is dirt cheap, rebuilding a box takes less than an hour, so it's not like it's overly-complicated.

well, it's not complicated if you can pull it apart. You know what I mean. ;)

Interesting .... LHM would be fine temperature wise. It's used in braking systems too so is designed for extreme temperatures. I can't help thinking a nice thick power steering fluid with seal softening additives would be better for an aged steering box (if it was brand new I'd throw in LHM in a heartbeat).

seeya,
Shane L.

[ElliotCC]

Ok. So can anyone point me to some good step by step instructions to flush my power steering system? ����

[Blknight.aus]

drain all the fluid out you can, start a syphon out of the reservoir start a gravity feed into the reservoir. start the engine and start turning the steering.

keep going till the fluid going in is the same colour as the stuff coming out.

every year as part of every service syphon out everything from the reservoir and top it up.