Steering box tedium ; radial lower seals

[mpwdhc]

Hi guys, from South Australia.

To the chase - why won’t a radial seal work in place of the quad seal?

I’ve owned a lovely original 3L Mk2c Coupe for nearly 20 years. Upon purchase the box haemorrhaged, which was for years managed with Lucas stop leak.. It’s been inactive the past few years following an attempt to repair the steering box in preparation for suspension bushes and as part of brake servo repair.

The fellow who did the job made a mess of it - it literally never worked. I bought a spare box, which also leaked, so decided to strip both to see why the original didn’t work. The shim and seal on the lower section of the spool valve were missing. Anyway, part of my request to the pro was to permanently address the lower seal problem. He poorly cut the hole to take a modern radial seal. This popped out during testing on account of the poor nature of the cut, which I’ve since addressed.

The seal now stays seated, and doesn’t leak when the wheels are in the air, but the lip curls out and leaks under load. I always presumed the quad seal was there because radial seals weren’t on the radar at the time - but was it actually a deliberate choice, to have the seal sandwiched in there?

The original box is generally better than the spare, and is original to the car, so I don’t really want to build up the spare box with a stock seal. I did consider whether lowering the excessive working pressure might be sufficient? How would this be done?

Any insight would be much appreciated. I’m desperate to drive it.

[3litrekiwi]

I have had a similar journey with a trio of steering boxes. Current situation is an original 1964 box fitted that I carefully picked the quad seal out of and persuaded a replacement into without disassembling the box. For now, no leakage and nice positive power steering that I find to be in the "Goldilocks" zone of not too heavy and not too light which I have not had before, so I'm reluctant to mess with this one.

As far as replacing the problematic lower seal, a radial oil seal is not designed for this sort of pressure, you need an apropriate sized hydraulic cylinder shaft seal. These are double lipped and up to the job of sealing however you may need to get the housing repaired to a suitable diameter by reboring it and maybe fitting a sleeve. I found that increasing the original diameter in depth resulted in a bore that suited a standard seal but you may be able to go up to the next standard diameter. Any sleeve will need to be an oil tight fit so a precision bit of machining and assembly. 

Good luck, I have left my second and third boxes for a future project, the main issue being the operation of the spool. All the parts in the better one look good, no distortion or significant wear however both suffer from some sort of hydraulic jamming. The one that I presume was original had a feeling of a mechanical notchiness when I bought the car and I have also experienced a lock up with no amount of effort able to steer past straight ahead to the right. This seemed ok until the lock up so be really careful! My moment was at walking speed, any faster or in traffic could have been a disaster.

Enigmas (Vince) will be able to supply the details of a shop in Victoria who are experienced in rebuilding these boxes. I like to take on most of these challenges as part of the fun of owning a classic however I think in this case it is probably best to defer to an expert as there is a genuine one available reasonably local to you.

cheers

Martin

[enigmas]

These links should assist you with your hydrosteer box. Eddie is an interesting, quirky character and one hell of a competent engineer. He's not cheap as it is his primary livelihood but he has the knowledge, setup and tooling to modify these PS boxes to work faultlessly.

roverp5.proboards.com/thread/12161/eddies-hydrosteer-rebuild

roverp5.proboards.com/thread/12153/hydrosteer-steering-box-leak

[mpwdhc]

Hi Martin and Vince,

Apologies for my late reply - life, and all that.

That notchiness sounds concerning. Mine had a similar feeling (easily steerable through it, but uncomfortable on a sweeping bend at speed), intermittently, though I think it might’ve been after feeding it one too many bottles of stop leak. The used box I fitted felt quite sloppy compared to the low mileage original.

I was determined to find a solution without further machining. I found a suitably sized Transit rack seal rated well above the requirement. I fitted it today and was able to load it up without a haemorrhage. So far so good - if the floor is dry tomorrow, I’ll bleed the brakes. Why route the pipe in that way ?? If the box has to come out again, I’ll make up another pipe.

[johnwp5bcoupe]

Radial seals are not designed for high-pressure 10psi is about their limit, the shaft seal has to work at both high and low pressure, the quad is, in theory, two O rings working on their borderline pressure! to that add dirt to the oil under the washer ruins both the surfaces of the recess and the shaft.

[mpwdhc]

Feb 9, 2023 18:08:31 GMT johnwp5bcoupe said:

Radial seals are not designed for high-pressure 10psi is about their limit, the shaft seal has to work at both high and low pressure, the quad is, in theory, two O rings working on their borderline pressure! to that a dirt to the oil under the washer ruins both the surfaces of the recess and the shaft.

The vendor and manufacturer claim the Transit ones are good for 60-80 bar, which should be ample - it’s the only high pressure seal in that size I was able to find. The normal one worked other than the lip curling out under pressure - these have a nice stiff shoulder which should prevent it. I suppose we will soon find out!

[enigmas]

Why try and reinvent the wheel. It's all been done for you. Here's the link again...to what you need to do if you want your hydrosteer oil tight.

roverp5.proboards.com/thread/12153/hydrosteer-steering-box-leak

[mpwdhc]

There’s got to be more than one way to skin a cat. I was determined to not pull it apart again, and as the box has been modified, that solution may not be viable. Anyway, it’s dry today. Tomorrow I’ll bleed the brakes and there might well be another suitable solution for others