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IndyBob
Novice
Apr 23, 2014, 7:18 AM
Post #1 of 14
(2028 views)
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Brake Light On
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I have a 91 Chevy truck. The brake light came on and the stopping power is greatly reduced.
I checked the wheels, don't see any visible fluid leaking. The master cylinder seems to be low on fluid.
Should I add fluid and see if that works or do something else before adding fluid?
I am going to pull the wheels and check closely for leaks right now.
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Hammer Time
Ultimate Carjunky
/ Moderator
Apr 23, 2014, 7:29 AM
Post #2 of 14
(2023 views)
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Re: Brake Light On
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The master being low on fluid is enough to put the light on but you need to find out where that fluid went. You could have worn out pads or a leak somewhere.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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IndyBob
Novice
Apr 23, 2014, 10:28 AM
Post #3 of 14
(2008 views)
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Re: Brake Light On
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I pulled all the wheels, no noticeable leakage. Brake pads and linings all appear to have plenty of material left.
Added brake fluid, the small front part of the reservoir was nearly empty. Pumped the brakes with engine off, pedal got stiff. Started the engine, light is still on and the brake pedal went down to the previous level. Still low on braking power. I think the rear brakes are not functioning. I held the brake pedal down and hit the gas, the rear wheels broke loose with ease, the fronts held tight.
Any ideas on what to do next??
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Hammer Time
Ultimate Carjunky
/ Moderator
Apr 23, 2014, 10:33 AM
Post #4 of 14
(2006 views)
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Re: Brake Light On
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You need to have a professional look at this to isolate the problem.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Discretesignals
Ultimate Carjunky
/ Moderator
Apr 23, 2014, 12:28 PM
Post #5 of 14
(2002 views)
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Re: Brake Light On
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The portion of the reservoir closest to the front of the truck serves the rear brakes. You really need to inspect the lines and the wheel cylinders. Fluid has to be leaking from something.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Apr 24, 2014, 1:36 AM
Post #6 of 14
(1985 views)
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Re: Brake Light On
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It's plenty old enough for any OE brake lines to rust out. It is frequently a total surprise.
Smaller reservoir is for rear brakes if found empty that's where this leak is anywhere along the way. Brake lines run along the frame then split at the axle to serve rear wheels.
Brake line is dirt cheap so run new line and check all front and rear as of course it's wildly dangerous. It has to be routed as intended. To a pro this is routine but takes time to make lines to fit and work properly. Not a game - get help with this,
T
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IndyBob
Novice
May 4, 2014, 5:46 AM
Post #7 of 14
(1924 views)
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Re: Brake Light On
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I finally got some time to spend chasing this brake problem. I am bewildered as I found no leaks in the brake lines or the wheel cylinders.
I have confirmed I have no rear brakes, while I had the truck jacked up I had my wife start the truck and apply the brakes. I could easily rotate the rear wheel with the brakes applied.
To go over what I have done: 1) checked master cylinder for fluid and leaks; THE FRONT/SMALL RESERVOIR WAS LOW, NEARLY OUT OF FLUID. 2) I pulled all four wheels and checked for fluid leaks in the hoses, tubing, calipers and wheel cylinders. NO FLUID LEAKS WERE FOUND. 3) I added brake fluid and drove the truck a half mile or so frequently applying the brakes. Returned home and checked brake lines and truck frame, no noticeable brake fluid leakage. 4) Removed rear wheels, looked and felt for fluid leakage, especially around the tubing connection and wheel cylinder NO BRAKE FLUID FOUND 5) Followed the brake lines from each wheel to connection above differential, then back to the engine compartment, eyeballed the tubing the entire distance. NO BRAKE FLUID LEAKAGE FOUND. TUBING INSIDE TRUCK FRAME HAD LITTLE TO NO RUST, OUTSIDE FRAME HAD CONSIDERABLE RUST, BUT NO LEAKAGE. 6) Master cylinder is again very low or out of fluid in the front/small reservoir.
Is there any way the master cylinder can leak into the power booster it is attached to?
Any other ideas of what to check? This one has me baffled.
Btw, I am not an auto mechanic, but I am an engineer that ran a 30 man maintenance department for 20 years, I have seen and fixed all sorts of mechanical, hydraulic and electrical problems. My point is, I am not a rookie regarding mechanics, although I am somewhat 'inexperienced' as an auto mechanic.
(This post was edited by IndyBob on May 4, 2014, 5:48 AM)
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Hammer Time
Ultimate Carjunky
/ Moderator
May 4, 2014, 6:16 AM
Post #8 of 14
(1920 views)
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Re: Brake Light On
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Sure, it can leak into the booster. You can also have wheel cylinders leaking that you won't see unless you pull back the dust caps.
Your fluid ls leaking, there really isn't any question about that. You just haven't found it.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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IndyBob
Novice
May 4, 2014, 8:16 AM
Post #9 of 14
(1915 views)
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Re: Brake Light On
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I did not pull the wheel cylinder dust caps, but I can not believe as much fluid as I have leaked it would not be all over the brake back plate and the brake drum too. They are all dry.
How much trouble is it to pull the power booster?
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Hammer Time
Ultimate Carjunky
/ Moderator
May 4, 2014, 8:20 AM
Post #10 of 14
(1913 views)
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Re: Brake Light On
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You don't have to pull the booster. Just pull the master away from so you can see the back of the master.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on May 4, 2014, 8:21 AM)
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Hammer Time
Ultimate Carjunky
/ Moderator
May 5, 2014, 9:06 AM
Post #12 of 14
(1895 views)
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Re: Brake Light On
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You can leave the lines connected. Just don't bend them too severely.
Yes, you can see if it's leaking that way. Yes, it will harm the booster over time.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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IndyBob
Novice
May 5, 2014, 1:38 PM
Post #13 of 14
(1889 views)
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Re: Brake Light On
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Thanks for all the help in diagnosing my problem. I pulled the master cylinder, tubing left in place - plenty of room to drop it out of way with no kinking, and found no leakage from the master cylinder.
I decided it must be a brake line, so I put paper under the truck from the master to the rear wheels, refilled the master and pumped the brakes. I found the leak in the tubing, just as it moved from the engine compartment to the frame.
I have decided to take it to my local repair guy in the morning so he can replace it for me.
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Hammer Time
Ultimate Carjunky
/ Moderator
May 5, 2014, 1:40 PM
Post #14 of 14
(1888 views)
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Re: Brake Light On
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Glad you finally found it.
Closing this now as solved.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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