2000 Chevy Blazer 4-dr 4X4 automatic w/ 158K miles. The pads/rotors were replaced at 115K, so they are coming due, esp. for the front.
Problem:
When engine is cold it feels like there is no power assist with the brakes, it is “normal” (see below) after warm up or hard application of brakes. Problem is much worse when the weather is very cold (under 20*F).
Even when “normal” the brakes are very weak. Pedal travels 2"+ before any braking action happens, and I can not perform a “panic stop”, meaning I can’t get the ABS trigger or even really dip the nose by hitting the brakes very hard. When applying the brakes for normal driving they feel acceptable.
I’m concerned that I may have multiple problems at once, so I’d like to be prepared when I visit the mechanic. He’s great at performing repairs, but I’m not confident in his diagnostics, so I’m afraid he’ll approach this as a “you need new pads” type of problem and it will end up being multiple visits and doubled up labor charges for having to re-do things.
1) With ~40K on the front pads, they are likely due. Rears may be acceptable, or not, I’d let him decide
2) Could I have a failing power booster? Or possible a vacuum leak to the power booster? Is there a straight forward test for power booster operation?
3) Could I have swelling rubber brake lines? With nearly 160K miles and over 10 years on the lines, they may be worn out, but not failed… should I proactively have them replaced, or is that a waste of money? I believe this car has 5 rubber lines… one for each wheel and a “center” line for the the rear brakes?
Thanks
“Pedal travels 2”+ before any braking action happens"
I should have looked at a ruler first because that doesn’t sound right :^) … what I am meaning to say is that I have quite a bit of pedal travel before I get braking, it may be more like 4-5"… I am referencing my “quite a bit of travel” comment based on driving 3-4 other vehicles of various ages and mileages including my SO’s Subaru w/ 90K (which has 40K+ on it’s current pads).
Could be all of the above, and it may also be time to drain all brake fluid and refill with new fluid. See what your manual says about that.
I’d start with the less-expensive stuff first (new fluid/bleed, new pads/shoes where needed). If still not braking right, then I’d start looking at the vacuum booster and master cylinder.
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they may or may not be due, but it’s easy to check.
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There is a simple test. With the engine off, pump the pedal until it hardens. By doing this you’ll relieve any vacuum in the booster. Then, while pressing the pedal, start the engine. The pedal should sink a bit and soften. If it stays hard, your booster is not working.
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anything’s possible, but I’ve never seen a line expand enough to affect braking without blowing a leak. The fiberous sheath molded into the lines has pretty good tensile strength, and that’s what keeps the line from expanding rather than the ruber itself.
NOTE: if you have good tires, it may be difficult on dry pavement to trigger the ABS. The vehicle is heavy enough to really dig in…weight equals traction.
Thanks everyone for the advice. I will ask to check the pads, replace if he feels it’s needed and also flush the fluid–whether there is a recommended interval in the manual or not is some what irrelevant as I know my last car called for it every 24 months, and another car I had 8 years ago had no mention of it… both used DOT 3/4 fluid, and brakes/lines on one car are basically the same as another when you consider the possibility of fluid contamination
BTW, mountainbike, I knew that referencing ABS activating would lead to confusion–I understand what you’re saying and you are correct… I guess my point was that the car takes a much greater distance to stop than other cars I’ve driven–including a 98 GMC Jimmy which is basically the same vehicle–and that a panic stop does not slow the car quickly at all… really every stop beyond a leisurely slow down is a “panic” stop, and then the others are “need new pants” stops… I shouldn’t have bothered to mention ABS…
Rear drum brakes and has anyone checked those?
Worn or out of adjustment rear drum type brakes will cause a low brake pedal and the symptom may be similar to a failing master cylinder.
This vehicle has rear disc brakes
The pads & rotors have been replaced, but the braking feels the same.
I think the best way to describe my concern is this: If I’m driving 5-10MPH and a “stab” the brakes I do not come to a quick & abrupt stop, which what I expect… instead it just sort of slows down and stops… it’s hard to explain… but it’s the same feeling you get when you are trying to stop a car with the engine off and the power booster drained–except that the pedal does not feel like that, the pedal feels what I’d consider to be normal.
Oh well 
Your new brakes will probably start to feel better and stop better once they start to get broken in. With all new friction surfaces, sometimes the brakes will not feel as strong as they should.
Were your old rotors rust pitted or have rings of rust on them? Sometimes that will cause a low brake pedal and a feeling of weak brakes. Also, did you check your caliper slides? If they are frozen, your brakes will not feel very powerful. Frozen slides are very common on this vehicle, particularly in the rear.
Old rotors looked OK.
A professional mechanic did the repairs, so I would hope he cleaned and freed up the slides, though my parking brake is now hardly functional, so it will ave to go back for that.
Did you have him do a fluid flush?
Yes, I had asked him to fluid the brake fluid, and it’s one of the items he listed as being done when he picked up the car… so hopefully he did it
After having gone through a commute I can say that the brakes do feel better, and there is no more groan when creeping at low speed, so things are better and at higher speed I am able to slow down more quickly than before. But, my initial complaint of lack of responsiveness–“stabbing” the pedal at low speed does not result in a quick, jerking, stop–is still true.
I went through the diagnostic flow chart on All Data for lack of responsiveness and it seems to point to an issue with the power booster.
The proportioning valve and master cylinder both have other more obvious symptoms if they fail. I don’t really know if it could be the ABS modulator or not, but I’d guess not?
The test of pumping the brakes while the car is off to relieve the reserve, then holding the pedal while starting the engine, seems to be normal… pedal is high & hard with the car off (after pumping 4-6 times), and when the engine starts the pedal drops and becomes somewhat softer.
I should also mention that the vehicle has always braked evenly–doesn’t pull to any one side when slowing/stopping.
Thanks everyone for your help and replies on this.
I think your master cylinder is showing its age, but not yet failing like the literature you’ve read describes.
It’s a good practice to get the brake fluid replaced every 3 years
For the no brake assist in cold weather, check the brake booster vacuum hose for water. If there’s water in the hose it can freeze and expand into ice blocking the vacuum to the booster for brake assist. Then when the engine gets hot enough it melts the ice inside the hose and the brake assist returns.
Tester
The brake booster can be checked by you. The instructions are in a Haynes manual and you don’t have to be a mechanic to do it. Check the brake fluid level. If it is way down, you might want to have the brakes done now. As the brakes wear, the fluid level gets lower. 43,000 miles is a long way to go on front disc brakes.
Did you have the rear pads done as well? There is an adjustment for the rear discs for the parking brake that also affects the overall breaking in the same manner that you are describing. I would have that looked into.
Keith, I believe you are thinking of spin-back calipers. The Blazer did not have spin-back calipers, it had a separate set of shoes behind the rotor hat for the parking brake mechanism. The calipers in the Blazer are strictly hydraulic with no additional parts or mechanisms. Spin-back calipers do need to be adjusted after pad replacement to prevent a low or spongy brake pedal, though.
I don’t know if what I was thinking about are spin back, I have only worked on one GM car with rear discs and getting the adjustment right for the parking brake was not easy, at least on one side of the car I was working on.
Many midsize GM cars of the late '80s through mid to late '90s had spin-back calipers, which required a special tool to retract the piston. Cars with these calipers included the Lumina, Grand Prix, Cutlass Supreme, and possibly others I can’t think of right now. On those vehicles, after pad replacement, you had to actuate the parking brake repeatedly, normally at the caliper using a pry bar or pair of vise grips, to get the piston to fit close enough to the inboard pad to make the parking brake work and to prevent a spongy brake pedal. The Blazer’s parking brake system is behind the hat of the rotor and looks like a simplified drum brake system without a wheel cylinder or retract springs.
Hi Guys–Front & Rear pads and rotors were replaced…