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zigenfiver

92 Ls400 Rear Brakes Not Working

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I have an 92 LS400 and the rear brakes are not working. I was told it could be the proportioning valve for the braking system, and that it could only be bought at the dealer. Has anyone encountered this problem before? Thanks.

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I did have a problem with my rear brakes, but it was due to the caliper sticking. As these calipers get old, the tend to hang up. In your case with them not working, it probably is either the proposioning valve or somehow you have air trapped in your lines.

My first step would be to bleed the rear brakes to see if any fluid is being pushed. If it is, it is probably weak calipers. If not, then it is something with the valve. I have never seen many proportioning valves go bad as they are fairly simple.

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I did have a problem with my rear brakes, but it was due to the caliper sticking. As these calipers get old, the tend to hang up. In your case with them not working, it probably is either the proposioning valve or somehow you have air trapped in your lines.

My first step would be to bleed the rear brakes to see if any fluid is being pushed. If it is, it is probably weak calipers. If not, then it is something with the valve. I have never seen many proportioning valves go bad as they are fairly simple.

Thanks for the advice! I had a feeling it may be the calipers.

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I would still bleed them first as it is NOT that common for calipers to stick open, they usually stick closed against the rotor.

If you determine it is the calipers, I can tell you where to get them and send you a pictorial (PDF) on how to change them. It is really easy. email me if you want the information.

Before you assume it is anything else, and above all, check to make sure the pads are not excessively worn. It might be that youyr brake pads are glazed over and just not working well. I have also seen cases (though not on Lexus) where the front calipers leak small amounts of brake fluid and when that happens, whoa watch out, they really grab.

Diagnose carefully, fix once.

Denny

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I would still bleed them first as it is NOT that common for calipers to stick open, they usually stick closed against the rotor.

If you determine it is the calipers, I can tell you where to get them and send you a pictorial (PDF) on how to change them. It is really easy. email me if you want the information.

Before you assume it is anything else, and above all, check to make sure the pads are not excessively worn. It might be that youyr brake pads are glazed over and just not working well. I have also seen cases (though not on Lexus) where the front calipers leak small amounts of brake fluid and when that happens, whoa watch out, they really grab.

Diagnose carefully, fix once.

Denny

Denny, could you let me know where to find calipers and also send me the PDF file on how to install them. Thanks. My E-mail is zigenfiver@aol.com.

Tommy

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how do you know your rears arent working?

Allied Tires told me my rear calipers aren't working plus I looked at the rotor and it has rust on it, like the pads have not been touching the rotor. Could it be the brake lines, proportioning valve, or Master cylinder?????

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i would say it is the proporting valve

but there isn't anything magical in there

i would take it out and clean t up before buying a new one.

Or atleast try and push the pistons back in the calipers to help remove the blockage. Hopefully it isnlt in the abs system.

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i would say it is the proporting valve

but there isn't anything magical in there

i would take it out and clean t up before buying a new one.

Or atleast try and push the pistons back in the calipers to help remove the blockage. Hopefully it isnlt in the abs system.

Fluid is getting blocked at the Proportioning valve. How hard are they to take out and re-install? Does anyone have any tips? I found a used one for $50. Dealer wants $350. Should I give it a shot doing it myself? Thanks.

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If both rotors are rusted then it is the proportioning valve, but if only one, then that caliper is seized.

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Could that be the problem on my car? Most recently, when the roads are wet, the ABS activates very often. Much more than it used to. Also too, when I slow down from highway speeds, the front brakes will make a "growling" sound, but the pads are virtually new. Perhaps too much work going to the fronts?

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If you have traction control...

There is a single electrically operated valve in the trunk that releases and applies brake pressure to prevent wheelspin. If that valve is stuck in the open position.......

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