86 Odd Brake issue

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Apr 14, 2016 | 06:36 PM

86Pacecar

Thread Starter

Burning Brakes

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From: NW MN

86 Odd Brake issue

My 86 had an odd brake issue this afternoon in traffic. I was in stop in go traffic and noticed that the brakes seemed to "hang up" a bit when I released the pedal. The car took a blip of throttle to get moving and I could feel a slight "clunck" as the brakes released and all was fine until the next time to brake than it would repeat. After a few cycles of this traffic started to move again before the next slow down and then the pedal went to the floor! A couple of quick pumps and I had brakes again but the next slow down it was the same thing. Now I'm a bit concerned as there was no good exit for a few miles. Once traffic started rolling again I left plenty of space just in case and a few miles down the freeway before the next exit the brakes worked fine, with a solid pedal. Since traffic was loosening up and I had 4 miles to go I stay on the freeway and had perfect brakes the rest of the way home.

I'm leaning towards a failing master cylinder that starts to act up when it gets hot under the hood. I figured I'd check in here to see if anyone has experienced anything like this on their car and what their remedy was.

So this weekend it's a new master cylinder, brakes hoses, fluid and a bleed of the system.

Apr 14, 2016 | 06:42 PM

antfarmer2

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Check your fluid leval if full might be fluid getting by the seals in the master. I would look at your rubber lines might be swelling shut holding the brakes on.

Last edited by antfarmer2; Apr 14, 2016 at 06:46 PM.

Apr 15, 2016 | 08:18 AM

RWDsmoke

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How long since you had brake the fluid flushed? Moisture in brake fluid will boil when hot and cause weird problems. Mine did that same thing once, hot brakes in heavy traffic then no brakes until it cooled off. Flush and new fluid and it never happened again.

Apr 15, 2016 | 08:24 AM

WVZR-1

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Quote:

Originally Posted by 86Pacecar

So this weekend it's a new master cylinder, brakes hoses, fluid and a bleed of the system.

I don't know that I'd be so quick to condemn the master, I'd do the hoses, crush washers, bleeders (probably) and flush/bleed the system avoiding all of the "newer technology" brake fluids. I'd think the master, ABS and caliper seals would rather see OE spec fluids.

Last edited by WVZR-1; Apr 15, 2016 at 08:26 AM.

Apr 15, 2016 | 10:12 AM

86Pacecar

Thread Starter

Burning Brakes

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From: NW MN

Quote:

Originally Posted by RWDsmoke

Good thought. It has been a while since I've flushed the fluid and even though it looks clean in the reservoir, looks can be deceiving. It does make sense that once I got moving again and the brake and under hood temps went down things stated to work fine again.
Strange condition was the initial brake "grabbing/sticking" that occurred before the no pedal. I can see how stuck brakes would cause high heat in the fluid to the point of boiling but what would cause the sticking to be intermittent at the beginning? Plus they did not stick again when the system worked normally. I know most of the brake components are at least 13 years old (when I got the car) and possibly OE so for an extra $150 for a master I might just do it.

Last edited by 86Pacecar; Apr 15, 2016 at 10:20 AM.

Apr 15, 2016 | 10:56 AM

92ragtop

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The "hanging up" comment sounds to me like one or more of the caliper pistons is stuck and is keeping the pads on that wheel(s) pressing on the rotor. Before doing a MC, you should jack up each wheel and make sure that they are not binding.

Apr 15, 2016 | 11:53 AM

86Pacecar

Thread Starter

Burning Brakes

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From: NW MN

Quote:

Originally Posted by 92ragtop

No they are not binding at all. If I have a bad MC or brake hose causing the brakes to hang up then it would make sense that they may have overheated causing the fluid to boil. The problem did start once I had to use the brakes more in slower, stop and go traffic.
I've had a bad caliper hang up on me before but it was never intermittent. Plus it seems that it is both fronts hanging up as the car does not pull from to one side or the other.

Apr 15, 2016 | 12:35 PM

WVZR-1

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Quote:

Originally Posted by 86Pacecar

I'd say you do nothing but hoses and everything I mentioned a few posts ago FIRST - nothing. I've a friend who might even go so far as to hang each hose in it's own container and pressure flush (sorta) until he was sure everything before the hoses was clear, then do the hoses and proceed with bleed etc. Uses a good bit more fluid but makes sure nothing from the hose collapse is hangin' around. What's busted loose and in the caliper now? Well .. if the bleeders "stream" a person could assume the caliper is free of trash....maybe

Excuse me - you need to confirm maybe that the bleeders will stream fluid first...

Last edited by WVZR-1; Apr 15, 2016 at 12:38 PM.