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'90 4-Runner 4X4
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74 Posts
Discussion Starter #1 (Edited)
Does anyone know if the load sensing proportional valve can be rebuilt or fixed on a 1990 4runner 4wd ? It's been leaking for a year now and it's only getting worse.

The valve I'm referring to here is mounted on the rear end of the chassis and has the arm that's attached to the left-side of the axle housing (diff.).

Thanks for any help here.

yeah.....the junkyard :search:

EDIT: nevermind the subject title, the load sensing proportional valve is what I was referring to ;)
 

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Soylent Green sales
rock crawler
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12,801 Posts
That is the load sensing proportional valve.
You can replace it with a manual one or eliminate it.
 

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Soylent Green sales
rock crawler
Joined
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12,801 Posts
That is the load sensing proportional valve.
You can replace it with a manual one or eliminate it.
 

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Registered
'90 4-Runner 4X4
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74 Posts
Discussion Starter #4
Thanks!

Thank you very much....looks like I'll be eliminating it first thing after work tomorrow!
 

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'90 4-Runner 4X4
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74 Posts
Discussion Starter #5
load sensing proportional valve modified...

Started by pulling the actuating arm off and found the leak. The leak was where the valve plunger goes through the rubber seal at the bottom and makes contact with the actuating arm caused mainly by corrosion near the plunger tip.

Brake fluid was dripping from a small crack in the bottom of the rubber boot that covers the bottom of the valve block. I unscrewed the copper cap off the bottom of the valve body. Once it was off I removed the cir clip, plastic guide and the rubber seal. Then I cut about 3/4" off the bad end of the plunger, replaced the seal with a urethane disc and the plastic with a slightly ground down quarter and replaced the cir clip. Installed the spring and shortened plunger, followed by the new cap.

Next I bled the brake system and checked for leaks. All is well now and the brakes work better than ever so far. Needless too say I left the actuating arm off.
 

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'90 4-Runner 4X4
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74 Posts
Discussion Starter #7
update....more leaks

Well the capped-off LSPV started to leak eventually, the quarter used as a plug got domed and the urethane gasket material I used got soft and swollen from brake fluid.

Another leak developed up front which turned out being the master cylinder between the booster.

The fix was to completely remove the LSPV and replace the master cylinder. I've been driving it for over a month now and NO leaks whatsoever...finally.

Total cost was less than $70 for a new master cylinder, 2 brake line couplers and brake fluid.
 
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