Hi all, new here. About five months ago I had the front brakes done at a good repair shop (pads replaced) and then a month ago had the rear brake pads replaced by my boyfriend (he's an offshore mechanical engineer). Both times there were no problems, no air in the lines as far as I could tell, stopping was smooth and the pedal pressure seemed appropriate. Today while slowing at a red light I tapped the brakes and the pedal went very soft and to the floor, and the brake warning light came on (not the ABS light though). I tapped several times and got the truck to stop; after I started moving again the light went off. I then finished the drive home. Every time I came to a stop this repeated itself, with the only difference being that the soft pressure wasn't as soft as the first terrifying time. I checked the fluid level and it's at the max line. I tried resetting the rear brakes by backing up and braking within my parking spot and seemed to firm up the pressure some. Any idea what this is, especially considering the fluid level being fine?

 

Most likely one of the steel brake lines rusted through. Probably somewhere along the frame going to the rear brakes. Both front brakes are on one hydraulic circuit, and both rears on another circuit. When a line sprouts a leak, the combination valve, (sometimes called proportioning valve, or centering valve) shuts off the circuit that failed, (that's why the fluid level is good) your pedal goes down, the red brake warning light comes on telling you there's a problem, (which you already know ). The combination valve will keep the failed circuit shut off until the leak is repaired, and the brakes are bled. Until it's fixed, you only have the use of one hydraulic circuit, (front or rear) if it fails, you will have no brakes.

 

Thanks for the information, Captain! I have a couple of questions though. First, would the light stay on continually until the problem is fixed? The light went off after I "reset" the rear brakes and it seems to be stopping as usual now.

Second, there's not much rust on this truck. It has never lived north of Tennessee and has been in Louisiana with me for the past four years. Not to say some other catastrophe couldn't have knocked a brake line loose, just wondering about the rust.

Once it's light tomorrow I'll crawl under and see if I can see anything obviously wrong. Thanks again, and any response is definitely appreciated. Now at least I have something to start with in trying to solve this mystery.

 

On vehicles with drum brakes, applying them in reverse adjusts them. Your 2000 has 4 wheel disc brakes and they self adjust each time you apply the brakes, no matter which direction you're going.

Applying the pedal lightly might cause the combination valve to center itself, and turn the light off. If that's the case, it will leak fluid when you apply the brakes. It's possible that the master cylinder is failing, which can "fool" the combination valve and turn the light on, without any external leaks. Best to get under and look around for a leak. Look closely, the leak may be very small.

 

I checked for leaks as best as I could without jack stands or tools. Basically crawled around the edges with a flash light and so far couldn't see anything. However I found this recall for the 1997 model and this describes exactly what happened the other day. If this were to happen, wouldn't there be a drop in brake fluid level too? Fluid is still at the max level. I'll call the dealership today and see if this would apply to my truck regardless. If anyone else has had similar issues or dealt with this recall I'd appreciate hearing about it. Thanks again Captain for the response.


NHTSA Campaign ID number : 97V218000

Vehicle Make / Model: Model Year(s): CHEVROLET / BLAZER 1998
CHEVROLET / S10 1998
GMC / JIMMY 1998
GMC / SONOMA 1998
OLDSMOBILE / BRAVADA 1998
Manufacturer: GENERAL MOTORS CORP. Report Receipt Date: NOV 24, 1997 NHTSA CAMPAIGN ID Number: 97V218000 NHTSA Action Number: N/A Component: SERVICE BRAKES, HYDRAULIC:FOUNDATION COMPONENTS:HOSES, LINES/PIPING, AND FITTINGS Potential Number of Units Affected: 19,716 Summary:
VEHICLE DESCRIPTION: LIGHT DUTY PICKUP TRUCKS AND MULTI-PURPOSE PASSENGER VEHICLES. A FATIGUE FRACTURE OF THE REAR AXLE RIGHT-HAND BRAKE PIPE CAN OCCUR CAUSING A SLOW BRAKE FLUID LEAK RESULTING IN A SOFT BRAKE PEDAL. IF THE BRAKE PIPE BREAKS, THE DRIVER WOULD EXPERIENCE A SUDDEN DROP IN THE BRAKE PEDAL, THE INSTRUMENT PANEL BRAKE LIGHT WOULD ILLUMINATE, AND THERE WOULD BE A LOSS OF REAR BRAKE PERFORMANCE. Consequence:
PARTIAL LOSS OF BRAKING AT A TIME WHEN MINIMUM STOPPING DISTANCE WAS REQUIRED COULD RESULT IN A VEHICLE CRASH. Remedy:
DEALERS WILL INSPECT AND REPLACE THE BRAKE PIPE. Notes:
OWNER NOTIFICATION IS EXPECTED TO BEGIN DURING DECEMBER 1997. OWNERS WHO TAKE THEIR VEHICLES TO AN AUTHORIZED DEALER ON AN AGREED UPON SERVICE DATE AND DO NOT RECEIVE THE FREE REMEDY WITHIN A REASONABLE TIME SHOULD CONTACT CHEVROLET AT 1-800-222-1020, OLDSMOBILE AT 1-800-442-6537, OR GMC AT 1-800-462-8782. ALSO CONTACT THE NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION'S AUTO SAFETY HOTLINE AT 1-800-424-9393.

 

It depends how well the combination valve can seal. If it seals as it was designed, you might not see a fluid leak, but the brake pedal would still go almost to the floor.

 

I am "the boyfriend".

The blazer has been fixed. It ended up being the passenger rear caliper locked up after changing the pads and pushing the piston back in to make room for the new pads.

It would get hot enough to boil the brake fluid and make the pedal spongy and also make the proportioning valve shift over since the front was building pressure faster than the rear.

New calipers, pads and master cylinder (changed first due to me thinking it was leaking by when it got hot enough in the engine bay) and a 4 wheel gravity and vacuum bleed to get new fluid through the whole system and now the truck stops like a champ and once again has a firm pedal.

On the bright side, I used a marine grease on the sliding pins the caliper bolts to called "Aqua Shield" and it was still in place like nothing had happened. I recommend it to anyone who deals with road salt. We use it offshore in open bearings running in salt water and its the only thing that works. Good to 400 degrees F. But be warned, if you get it on your hands, a mix of fast orange, dawn soap and hot water may get it off.

Aqua Shield Grease