XJ40 ( XJ81 ) 1986 - 1994

Can Castrol HSMO be replaced?

Old 10-23-2018, 04:37 AM
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Default Can Castrol HSMO be replaced?

I have a 90 XJ6 in which self-leveling suspension has been replaced with conventional shocks. Rack and pinion keeps leaking and needs to be replaced. Can I flush HSMO and replace with cheaper, more readily available fluid? If so, what is recommended?

I replaced rack and pinion unit once without flushing old HSMO. New unit promptly blew HSMO past seals in new unit, filling both boots. Before I replace unit again, I'll definitely flush system, but would prefer using something cheaper than HSMO.

I also wonder if remanufactured rack and pinion units have seals that are somehow incompatible with HSMO? Or was grit in old HSMO the culprit in leaking?

Old 10-23-2018, 08:56 AM
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The steering used DEXRON from 1988-1989 and then again 1993-1994.
The 1990-1992 shared the HMSO with the suspension so if the SLS is deleted and the pump removed from the front of the engine, you can use DEXRON like all the rest of the cars.

Old 10-23-2018, 01:07 PM
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Default Thanks, with the inevitable follow-up questions

Thanks, Bob - greatly appreciated. After posting my original question I came across an answer you posted in 2015:

Remove all the self leveling parts (valve block and pump) and block the return port on the reservoir. (small cap with hose clamps)

Use a hydraulic hose for the NON leveling reservoir-to-pump and throw the 'Y' hose in the trash.

Drain out the HSMO and pour in ATF.


There is a blanking plate for the front of the engine to cover the pump mount area but I have seen the bottom of a coffee can (sheet metal) with 3 holes drilled to cover the old pump drive. There is no fluid in the cavity so you are just covering the driving mechanism.

bob gauff
This leads to a few follow-up questions: (1) By valve blocks, I assume you're referring to the valve blocks near the SLS shocks? (2) Does anyone have part number, specs, or other sourcing info for the appropriate hydraulic hose to replace the y-hose and/or info on the blanking plate. I've got a coffee can ready, but I thought I'd ask.

Thanks again!
Old 10-23-2018, 06:12 PM
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Default I think I'm good to go

Worked on the car today based on your sage tips (thanks again, Motorcarman) ... one thing led to another ... and the pump, plumbing, and obviously now useless valve block are all gone. Just need a length of hydraulic hose, a couple clamps, and a coffee can. Then I can replace the steering gear box while (whilst) kissing the HSMO goodbye forever.

I'm assuming the wire harness that fed the valve block just needs to be short-proofed (unless someone tells me otherwise).

I'm really digging this forum. Thanks to any who offer advice and thanks to the moderators, administrators, etc... who keep it running. Hope I can pay it forward soon.
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