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Stange master cylinder

Keith90

NAXJA Forum User
Location
Arizona
Hi everyone. I'm new here, again. Well got another XJ finally. But it has a master cylinder setup I have never seen before. Been around XJ's awhile but this one has me stumped. Anyway, here are a couple bad pics so maybe someone can enlighten me.
Thanks

Well can't figure out the attachment thing so no pics. But this doesn't have the regular booster, infact it doesn't have a booster at all that I can see.
 
OK, I figured out it is a 1990 ABS master cylinder. I have a very hard brake pedal. It feels like the booster is not working. On a normal system I would know what to do but never even seen one of these. Any ideas on what I should check?
Thanks
Keith
 
Rip out the failure prone ABS crap and install a normal master/booster from a 1995. You'll have far better braking power and it won't fail and leave you with no brakes like the old ABS setup.
 
It's possibly hydro boost, powered by the power steering pump. I've seen it a few times in the boneyards. I don't know if it was a factory option, or even why, but the ones I saw all looked the same. Does it have an odd looking chamber, about the size of an oddly shaped softball on the passenger side, above the heater blower? Is it labeled something like 'Contents under pressure' or something like that? A rare duck, indeed.
 
Last edited:
It is NOT a power steering pump assist.
The booster motor and one accumulator are under the coolant bottle.
Turn the key on-you should hear the motor running until it comes up to pressure.
If you do not hear the motor, the relay is mounted under the coolant bottle plate. There is a 4 wire connector-verify 12 volts to the red wire-if not, check wiring back to 12 volt junction by battery. If yes, check continuity across 2 center pins on motor side-if open, pressure switch is bad-if continuity, motor may be bad-verify relay operation first.

Nick
 
So what I saw was not hydro-assist power brakes? I recently looked at a website (from a link on Modified Tech thread) of a company offering hydro-assist systems, and for safety, in the event the engine stalls, the ball shaped cylinder, near the blower motor is actually compressed nitrogen, to give a few braking cycles. I drove trucks for twenty years equipped with hydro boost, and with no engine (power steering pump), you have NO brakes, just a pedal you connot push. There's one in Harry's U Pull It right now, IIRC it does not appear to have ABS, as there is no motorized ditribution block, like on others. I'll go in and try to get some pics. I'm curious too.....
 
So what I saw was not hydro-assist power brakes? I recently looked at a website (from a link on Modified Tech thread) of a company offering hydro-assist systems, and for safety, in the event the engine stalls, the ball shaped cylinder, near the blower motor is actually compressed nitrogen, to give a few braking cycles. I drove trucks for twenty years equipped with hydro boost, and with no engine (power steering pump), you have NO brakes, just a pedal you connot push. There's one in Harry's U Pull It right now, IIRC it does not appear to have ABS, as there is no motorized ditribution block, like on others. I'll go in and try to get some pics. I'm curious too.....


It is a hydro boost system, just not driven by the PS pump. This system (like most these days) uses an electric motor, and has two accumulators. The big ball mounted next to the master cylinder is for reserve in the event of sytem failure and in good shape provides at least 15 applications of ther brakes.
They do wear out however, and can have that reserve significantly reduced.

Nicik
 
That would explain the sound of the electric motor at startup. On the one I saw recently, I tried to trace the P/S lines, but none seemed to go to the ball. I'd like to see an article on this setup. I'd LOVE to do hydraulic boost, but the cost is prohibitive. Having driven with it for so long, I'd say they are superior to vacuum assist. Just out of curiosity, what would it take to get your system functioning?
 
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