Weird brake fluid problem
Thread Starter
Race Director
Joined: Mar 2003
Posts: 11,608
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From: Eustis ( Area 51 Bat Cave ) Fl
Weird brake fluid problem
Greetings,
I have a weird problem with my 86, it does have the antilock brakes,
However,
I dont really believe that is related to this problem,
It was about a year ago my brake peddle started going to the floor pumping would help me stop,
After looking things over I replaced the master cylinder and bled all the fluid so I would have good clean fluid,
The car stopped like an 86 vette should for a long time then I noticed the fluid level
Getting lower and I would just top it off,
I don't drive this car all the time but noticed the fluid loss was pretty bad if I drove the car daily,
I figured I had a leak somewhere and started looking,
All the calipers were bone dry, never so much as a drop of fluid on the car port floor,
Nothing wet around the master cylinder either,
I don't think fluid gremlins are stealing it and since I have no brakes due to low fluid and air in the system I need to fix it.
My 78 year old dad says he has heard of a master cylinder leaking back into the power booster and then the fluid gets drawn into the engine so you never see a leak,
Anyone ever heard of such a thing?
I really don't wanna buy parts and do work I dont need,
Thanks for all opinions,
Cheers,
P.
I have a weird problem with my 86, it does have the antilock brakes,
However,
I dont really believe that is related to this problem,
It was about a year ago my brake peddle started going to the floor pumping would help me stop,
After looking things over I replaced the master cylinder and bled all the fluid so I would have good clean fluid,
The car stopped like an 86 vette should for a long time then I noticed the fluid level
Getting lower and I would just top it off,
I don't drive this car all the time but noticed the fluid loss was pretty bad if I drove the car daily,
I figured I had a leak somewhere and started looking,
All the calipers were bone dry, never so much as a drop of fluid on the car port floor,
Nothing wet around the master cylinder either,
I don't think fluid gremlins are stealing it and since I have no brakes due to low fluid and air in the system I need to fix it.
My 78 year old dad says he has heard of a master cylinder leaking back into the power booster and then the fluid gets drawn into the engine so you never see a leak,
Anyone ever heard of such a thing?
I really don't wanna buy parts and do work I dont need,
Thanks for all opinions,
Cheers,
P.
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
I have heard of brake fluid going into the booster. It is not uncommon...
rare, but not uncommon.
I would also check the ABS module and see if any fluid is in there. It's behind the drivers seat under the lid - you may have to remove a bolt to gain access.
rare, but not uncommon.
I would also check the ABS module and see if any fluid is in there. It's behind the drivers seat under the lid - you may have to remove a bolt to gain access.
Race Director
Joined: Dec 2002
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From: SCMR Rat Pack'r Charter Member..Great Bend KS
Originally Posted by The13Bats
My 78 year old dad says he has heard of a master cylinder leaking back into the power booster and then the fluid gets drawn into the engine so you never see a leak,
Anyone ever heard of such a thing?
Anyone ever heard of such a thing?
Larry
code5coupe
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
i've heard of the ''thru the booster thing'' but never seen one....your dad is a year or so older than me, could be he's seen it.
i have seen a number of master cylinder failures that were very hard to find the fluid escape route.
my 86 is on its third m/c..both times only a slight damp area on the booster just below the m/c
i have seen a number of master cylinder failures that were very hard to find the fluid escape route.
my 86 is on its third m/c..both times only a slight damp area on the booster just below the m/c
Thread Starter
Race Director
Joined: Mar 2003
Posts: 11,608
Likes: 780
From: Eustis ( Area 51 Bat Cave ) Fl
I checked out the antilock thing behind the drivers seat, no leaks there thank God, that thing looks hard to work with and expensive,
So I am now assuming it is leaking into the booster,
I've changed the master cylinder once, was it bad or did the booster ruin it some way?
Should I replace the booster and is it bolted on from the outside with the master cylinder bolts or does it bolt from into up over the brake peddle?
I am trying to get an understanding that if it's leaking into the booster how and why does it do this and which part is bad?
Thanks all,
Cheers,
P.
So I am now assuming it is leaking into the booster,
I've changed the master cylinder once, was it bad or did the booster ruin it some way?
Should I replace the booster and is it bolted on from the outside with the master cylinder bolts or does it bolt from into up over the brake peddle?
I am trying to get an understanding that if it's leaking into the booster how and why does it do this and which part is bad?
Thanks all,
Cheers,
P.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Originally Posted by bogus
remove the master and see if fluid is in the booster. if it is in the booster, replace it, cause the fluid will eat the hell outta the diaphram.
if not, gee... then I am really confused.
if not, gee... then I am really confused.
Thread Starter
Race Director
Joined: Mar 2003
Posts: 11,608
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From: Eustis ( Area 51 Bat Cave ) Fl
Well, weirdness gets deeper,
I pulled the master cylinder back from the booster and its dry as a bone,
Where the hell is this thing leaking?
Thanks all,
P.
I pulled the master cylinder back from the booster and its dry as a bone,
Where the hell is this thing leaking?
Thanks all,
P.
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Team Owner
Joined: May 2002
Posts: 24,337
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
There are several junctions at the hard line branches and fittings to the flex lines where it could leak, but I'd be surprised if it did. You can get a closer look at the calipers by removing them and the pads.
Thread Starter
Race Director
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From: Eustis ( Area 51 Bat Cave ) Fl
I decided to bleed the system again,
I was watching the master cylinder and while pumping the peddle to bleed I see a little seep coming from that plastic sensor fitting,
not sure what it senses but it is leaking from where the contacts are,
After a most annoying trip to auto zone where over the phone the fellow said he had it in stock only to learn he didn't really have it I will assume it's a dealer part,
Thanks,
P.
I was watching the master cylinder and while pumping the peddle to bleed I see a little seep coming from that plastic sensor fitting,
not sure what it senses but it is leaking from where the contacts are,
After a most annoying trip to auto zone where over the phone the fellow said he had it in stock only to learn he didn't really have it I will assume it's a dealer part,
Thanks,
P.
Team Owner
Joined: Sep 2003
Posts: 20,179
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Originally Posted by The13Bats
I decided to bleed the system again, I was watching the master cylinder and while pumping the peddle to bleed I see a little seep coming from that plastic sensor fitting, not sure what it senses but it is leaking from where the contacts are. Thanks, P.
I'd loosen the two nuts on the MC and check for fluid leaking into teh booster. ANy sign of moisture is reason for concern.
Yep! The sensor is a dealer part. Runs about 13 bucks.
Thread Starter
Race Director
Joined: Mar 2003
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From: Eustis ( Area 51 Bat Cave ) Fl
I did pull the master C forward and it's dry as a bone between it and the booster,
So that sensor had O rings, hum...mine doesn't...gee that might just be a problem, lol
Which idiot light did it light the only brake related warning light I get is the antilock one,
Thanks
P.
So that sensor had O rings, hum...mine doesn't...gee that might just be a problem, lol
Which idiot light did it light the only brake related warning light I get is the antilock one,
Thanks
P.
Thread Starter
Race Director
Joined: Mar 2003
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From: Eustis ( Area 51 Bat Cave ) Fl
Still leaking...HELP!!!
I bought a new sensor, installed it and it still leaks,
If you are familiar with this connector it is oval with two pin terminals,
In between the two pins on the sensor part that is screwed into the brake master cylinder is a small factory placed hole,
When I push on the brake peddle that is where the fluid leaks from,
Whether the connector is plugged on or not,
I see no where that there could be a missing "O" ring in fact this is an oval shape,
I assume the factory placed that hole there as some sort of vent so what's wrong with my system that is causing it to leak?
Many thanks,
P.
If you are familiar with this connector it is oval with two pin terminals,
In between the two pins on the sensor part that is screwed into the brake master cylinder is a small factory placed hole,
When I push on the brake peddle that is where the fluid leaks from,
Whether the connector is plugged on or not,
I see no where that there could be a missing "O" ring in fact this is an oval shape,
I assume the factory placed that hole there as some sort of vent so what's wrong with my system that is causing it to leak?
Many thanks,
P.
Burning Brakes
Joined: Nov 2005
Posts: 848
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From: 1992 LT1 6 speed Cayman Islands
That hole is probably a weep hole placed by the factory to show if the internal seals on the piston that turns the warning licht on and off are leaking pass under preassure.
I do not know if you put on new brake shoes the first time but it is normal for disc brake equipped cars to have the brake fluid level in the reservoir drop as the brake pads wear. The "lost" fluid is going to fill the extra space behind the pistons as the pad wears and the piston moves closer to the disc.
You have obviously found one source of a leak, but if the reservoir did not go dry, just down a little it could be due to wear on trhe pads.
I do not know if you put on new brake shoes the first time but it is normal for disc brake equipped cars to have the brake fluid level in the reservoir drop as the brake pads wear. The "lost" fluid is going to fill the extra space behind the pistons as the pad wears and the piston moves closer to the disc.
You have obviously found one source of a leak, but if the reservoir did not go dry, just down a little it could be due to wear on trhe pads.
Thread Starter
Race Director
Joined: Mar 2003
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From: Eustis ( Area 51 Bat Cave ) Fl
That weep hole is crying a river, far more than you can live with,
So would that be a problem with the master cylinder?
The sensor is new
My pads are ok, it was running the reservoir dry which is how I knew I had a problem when air got in the system and I lost brakes, not good,
I just need to get this problem wrapped up as I can't drive the car it's unsafe.
Thanks,
P.
So would that be a problem with the master cylinder?
The sensor is new
My pads are ok, it was running the reservoir dry which is how I knew I had a problem when air got in the system and I lost brakes, not good,
I just need to get this problem wrapped up as I can't drive the car it's unsafe.
Thanks,
P.
Team Owner
Joined: May 2002
Posts: 24,337
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
I assume by the flimsyness of that sensor that the area behind it is not supposed to be pressurized.
It sounds like the orings on your combination valve are leaking past. Do you have a brake warning light coming on in the car?
I've never heard of these failing, because the combination valve doesn't really move. (It's located in the secondary cylinder to the passengerside of the main cylinder). I'm not sure if they can be purchased seperately (or if the orings can) from the whole master cylinder assembly.
With that said, I have an extra combination valve out of a used 91ish Corvette, I can even put a bias spring in there that'll work well with your 86, a little step up from stock bias.
It sounds like the orings on your combination valve are leaking past. Do you have a brake warning light coming on in the car?
I've never heard of these failing, because the combination valve doesn't really move. (It's located in the secondary cylinder to the passengerside of the main cylinder). I'm not sure if they can be purchased seperately (or if the orings can) from the whole master cylinder assembly.
With that said, I have an extra combination valve out of a used 91ish Corvette, I can even put a bias spring in there that'll work well with your 86, a little step up from stock bias.
Thread Starter
Race Director
Joined: Mar 2003
Posts: 11,608
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From: Eustis ( Area 51 Bat Cave ) Fl
So the master cylinder is bad,
I do believe it has a lifetime replacment,
let me check that out,
I agree with you that there shoudlnt be pressure on that sensor at all.
The only light to come on was "antilock"
Many thanks
P,
PS,
is it possible to bleed the rears without taking the wheels off?
I do believe it has a lifetime replacment,
let me check that out,
I agree with you that there shoudlnt be pressure on that sensor at all.
The only light to come on was "antilock"
Many thanks
P,
PS,
is it possible to bleed the rears without taking the wheels off?
Last edited by The13Bats; Apr 24, 2006 at 09:50 PM.
Team Owner
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Posts: 24,337
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
The antilock light may double as your brake warning light, dunno.
The rears on 88+ are tough to bleed with tires on without having done it before.
84-87 can be done pretty easily with wheels on if you've got a-molds or c5 wheels on there.
The rears on 88+ are tough to bleed with tires on without having done it before.
84-87 can be done pretty easily with wheels on if you've got a-molds or c5 wheels on there.