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Does the 280ZX have a proportioning valve?


PhilbertZ

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Hi guys,

 

been away for a while - so long that I remember the old forum and cannot for the life of me figure out how to SEARCH on this one...so I apologize for starting a new thread on this (I tried Google for about 30 minutes before posting this).

 

My 1980 280ZX has been pulling to the right under braking at any speed. I took off the front pass wheel and checked out the caliper on that side, and the pads seemed fine (I installed new pads/rotors all around less than 3,000 miles ago). I bled the brakes - stopped well but still pulled to the right under braking.

 

So, took it into Big O tires this weekend to take advantage of the $125 rebate deal and get new tires all around (mine were 9+ years old). I also told them about the braking/pulling issue and asked them to look into it. They called me yesterday, telling me that the brake lines in the front are cracked (this I knew) and they thought that ballooning brake lines on one side were leading to one pad engaging sooner than the other. They also recommended new front calipers, since it could be a sticking piston, and, since they had the wheels off already.....so I bit and had them do new front calipers and brake hoses.

 

Talked to them today and it's STILL pulling (!). The guy is telling me that they need to replace the proportioning valve and are having a hard time finding one. He tells me that the ZX proportioning valve acutally splits left/right and not front/rear - is that true?

 

So, I'm getting up there in repair costs and want to keep it as sane as possible - and I don't like the idea of throwing parts at a problem - I really don't like that.

 

 

Does this sound like a reasonable explanation (the proportioning valve controlling SIDES of the braking system, and thus being the likely culprit)?

 

Is there a good source for these or should I ask them to get a manual one (they seem to run around $50-70)?

 

 

Please help - I don't want to keep throwing money at this.....

 

Thanks

 

Phil

 

PS - if someone could tell me how to search on this forum I'd really appreciate it :)

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There is a proportioning valve,but it's for the front to rear bias- not for left and right. The sides have parallel hydraulic paths. If you have a left to right issue then you need to look at the lines or calipers. Download the FSM and look in the brake section. It shows the entire brake system on a single page. xenons130 has it free to download.

 

http://xenons130.com/reference.html

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Thanks Macambra for the reply - much appreciated.

 

I have the FSM (got it from the same site) but didn't find much in there.

 

But that's moot now, as it seems Big O found the issue - and it's NOT the proportioning valve. My passenger side tension rod is missing it's front washer, nut and bushing, which they think is causing the control arm to pull back when braking, and steer the car to the right. This makes complete sense to me. It also makes sense since I heard/felt something metal and hard bounce off my floorboards on the right side when I braked on the freeway a few weeks back.

 

Little bummed that I didn't figure this out myself (I took the wheel and caliper off to inspect), and that Big O didn't spot it first (I told them about the freeway incident when I brought it in) - they told me it needed brake lines (I agree) and sold me on replacing calipers since they were in there already (to "save on labor")....arg.

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"My passenger side tension rod is missing it's front washer, nut and bushing, which they think is causing the control arm to pull back when braking, and steer the car to the right."

 

Same as my 73! P.O. assembled it without the T/C rod spacer in the bushings---L/F tire would move back in the wheel well about 2" before braking. Couldn't SEE it happening while driving the car, but there was a "CLUNK" and then the wheel wanted to rip out of my hand!

 

I was about to point out that a 'pull' you feel in the WHEEL distinctly is usually on the side of the car you are feeling the wheel pull. But if the car moves to the right and you really don't feel the steering wheel physically trying to turn in that direction---then likely it's the opposite-side REAR brake causing it.

 

Glad you found your missing washer!

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"My passenger side tension rod is missing it's front washer, nut and bushing, which they think is causing the control arm to pull back when braking, and steer the car to the right."

 

Same as my 73! P.O. assembled it without the T/C rod spacer in the bushings---L/F tire would move back in the wheel well about 2" before braking. Couldn't SEE it happening while driving the car, but there was a "CLUNK" and then the wheel wanted to rip out of my hand!

 

I was about to point out that a 'pull' you feel in the WHEEL distinctly is usually on the side of the car you are feeling the wheel pull. But if the car moves to the right and you really don't feel the steering wheel physically trying to turn in that direction---then likely it's the opposite-side REAR brake causing it.

 

Glad you found your missing washer!

 

 

Thanks Tony - sounds like this was it. I replaced the whole suspension bushing set with Poly a couple years back...torqued it all to spec back then, but I guess I should have checked in on the settings more often after that...just wiggled its way loose until it ate it on the freeway!

 

Haven't found the washer yet though...Big O is trying to find replacement parts. I looked online but it appears prothane only sells sets and not these washers/bushings by themselves :/

 

 

Phil

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Big Washer at the end of the T/C setup?

If you can PM me your address, I've scrapped dozens of S30's I'm SURE I have one or two of those washers laying around.

You can have it if I know where to ship it to!

 

A photo would be good, or a circled call out from a parts diagram to MAKE SURE I sent the right bit.

Edited by Tony D
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Pulling from left to right cannot be caused by brake lines as the pressure will be equal between the left and right sides. If it was the brakes causing the issue it would have to be calipers, pads or rotors.

 

Glad you found the problem.

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