Loosing brake fluid.....
Thread Starter
Intermediate
Joined: Feb 2010
Posts: 34
Likes: 0
From: Silver Spring MD
Loosing brake fluid.....
Losing brake fluid*****
I just put a brand new brake booster and master cylinder in my 86 vette along with the new little white sensor that goes on the master cylinder. MY problem is that the little whit sensor is spitting out fluid, therefore i am loosing fluid regularly. At first i thought it was the sensor itself because between the two prongs on it it has a hole, but when i purchased a brand new one the same hole was there? i know that that is where the fluid is coming out of, any ideas how to make it stop!?!?! Thanks
I just put a brand new brake booster and master cylinder in my 86 vette along with the new little white sensor that goes on the master cylinder. MY problem is that the little whit sensor is spitting out fluid, therefore i am loosing fluid regularly. At first i thought it was the sensor itself because between the two prongs on it it has a hole, but when i purchased a brand new one the same hole was there? i know that that is where the fluid is coming out of, any ideas how to make it stop!?!?! Thanks
Melting Slicks
Joined: Apr 2003
Posts: 3,110
Likes: 6
From: Red Sox Nation! RI
It sounds like the seals on the proportioning valve in your new master are bad. I would return the new master cylinder for another one. Before you install the next one, bench bleed the MC with the brake sensor installed and make sure it's not leaking too.
Pro
Joined: Sep 2003
Posts: 588
Likes: 8
From: Tampa Fl
Sorry for digging up the graves, I think I have the same issue. Did replacing the master cyl fix the issue? I just got the remanufactured master cyl installed and it turns the brake sensor into a fountain if I don't have the plug connected. Is this a symptom of a messed up reman master cyl?
Burning Brakes
Joined: Nov 2004
Posts: 897
Likes: 12
From: Land of Whiskey Rebels, PA
WOW!! 
One out of three?? A 67% chance of a failure? I don't like those odds. I'll spend the extra money on a new one--along with peace of mind and less aggravation and clean-up.
Thanks for the information, 94vettelover2.
One out of three?? A 67% chance of a failure? I don't like those odds. I'll spend the extra money on a new one--along with peace of mind and less aggravation and clean-up.Thanks for the information, 94vettelover2.
Navigator
Joined: Dec 2010
Posts: 9
Likes: 0
Master Cylinder Help
I inherrited mydads 94 LT1 but the brakes don't work. It spews the fluid through the hole in the sensor. He had replaced the master & booster but it still had the same problem. I want to test the master cylinder before I replace it. I already have to replace the booster, as I found a crack in the canister.
Thanks for any assistance.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Melting Slicks
Joined: Apr 2003
Posts: 3,110
Likes: 6
From: Red Sox Nation! RI
You can probably find more illustrations if you google "master cylinder bench bleeding" or maybe there's a write up on the forum somewhere. Here's a quick couple links. One for a kit and here's one with pics.
Bench bleeding removes the air from the master cylinder as opposed to bleeding it all the way through the brake system and out at each caliper.
Bench bleeding removes the air from the master cylinder as opposed to bleeding it all the way through the brake system and out at each caliper.
Navigator
Joined: Dec 2010
Posts: 9
Likes: 0
Thanks for the reply C4boy. Ok so if I bench bleed it is there anything special I should be looking for besides the air bubbles and how do I know if the seals inside are good? I'm guessing that if the seals are bad inside then it wont pump the fluid back up into the canister?
If the seals are bad that will cause the sensor to push fluid out? I found out today that the master may not have been brand new
the original could have been rebuilt or a re-manufactured one may have been put on. he had it done by a so called "Friend / Mechanic" that over charged him and probably did the job as cheap as he could.
If the seals are bad that will cause the sensor to push fluid out? I found out today that the master may not have been brand new
the original could have been rebuilt or a re-manufactured one may have been put on. he had it done by a so called "Friend / Mechanic" that over charged him and probably did the job as cheap as he could.
Melting Slicks
Joined: Apr 2003
Posts: 3,110
Likes: 6
From: Red Sox Nation! RI
The 2nd link I posted is as good an explanation of how to bench bleed as any. Once the bubbles stop, the air is out of the MC. I doubt someone would have put a new master on your car, a remanufactured one is pretty standard and what most shops would use. To me it wouldn't really make a difference.
If the seals on the proportioning valve are bad or possibly even the spring in front of it, then it can leak at the brake sensor switch. You could fix it by removing the proportioning valve from the MC if you're handy.
If the seals on the proportioning valve are bad or possibly even the spring in front of it, then it can leak at the brake sensor switch. You could fix it by removing the proportioning valve from the MC if you're handy.
Burning Brakes
Joined: Oct 2009
Posts: 773
Likes: 2
From: Minneapolis MN
Navigator
Joined: Dec 2010
Posts: 9
Likes: 0
The 2nd link I posted is as good an explanation of how to bench bleed as any. Once the bubbles stop, the air is out of the MC. I doubt someone would have put a new master on your car, a remanufactured one is pretty standard and what most shops would use. To me it wouldn't really make a difference.
If the seals on the proportioning valve are bad or possibly even the spring in front of it, then it can leak at the brake sensor switch. You could fix it by removing the proportioning valve from the MC if you're handy.
If the seals on the proportioning valve are bad or possibly even the spring in front of it, then it can leak at the brake sensor switch. You could fix it by removing the proportioning valve from the MC if you're handy.
Melting Slicks
Joined: Apr 2003
Posts: 3,110
Likes: 6
From: Red Sox Nation! RI
Sorry, my post was kind of incomplete. What I meant was, the proportioning valve can be removed from the MC, then cleaned, checked for bad o-rings (& replace if necessary) . But I'd hate to lead you down that path if you are new to brakes and don't have a shop manual. Sometimes the valve can be hard to remove from the MC.
Team Owner
Joined: Sep 2003
Posts: 20,170
Likes: 672
From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
When this happened after installing the DRM spring, I had to manually locate the shuttle valve to center and pin it down with a modified bolt. Did this by removing the white switch and replacing it with the bolt. Then the brakes were bled and the white switch was reinstalled. It worked for me and 20K miles later all is well.
Navigator
Joined: Dec 2010
Posts: 9
Likes: 0
ok, thanks for the replies and information. It's a starting point. I will pick up a manual and give it a shot.
One more question - Does anyone know if the brake booster can have anything to do with the fluid leaking out of the sensor. My booster is cracked, im just wondering if the pressure loss could cause this leak? I placed some duct tape over the crack just playing around (I will never drive the car this way, lol) and the brakes work much better then when I got the car.
Good thing the crack didn't get worse when I drove the car from Washington state to Socal. That could have been very bad flying down the grapevine with no breaks...
One more question - Does anyone know if the brake booster can have anything to do with the fluid leaking out of the sensor. My booster is cracked, im just wondering if the pressure loss could cause this leak? I placed some duct tape over the crack just playing around (I will never drive the car this way, lol) and the brakes work much better then when I got the car.
Good thing the crack didn't get worse when I drove the car from Washington state to Socal. That could have been very bad flying down the grapevine with no breaks...
Team Owner
Joined: Sep 2003
Posts: 20,170
Likes: 672
From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Navigator
Joined: Dec 2010
Posts: 9
Likes: 0
Thanks for all the info guys. I was just told that the booster and M/C are like 4 months old and the receipts are being sent to me. I'm gonna take them back to Napa and get some exchanges as both should be under warranty. Hopefully after changing them out I will be back on the road!
Melting Slicks
Joined: Apr 2003
Posts: 3,110
Likes: 6
From: Red Sox Nation! RI