Soft Brake Pedal

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JHZR2

JHZR2

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Hi,

Are GM brake pedals 'soft' compared to euro vehicles, and even Japanese vehicles?

My 98 S10 ZR2 brake pedal is soft. Before about 3/4-1 inch of travel, there is no real 'feel' to the pedal. Beyond that, the brakes work good, but the pedal still squashes more.

As another example, if Im stationary, and press the pedal, itll press down, then give a lot of resistance, but if I push harder, itll keep going further and further... On my euro cars, if I press, itll get to the point where its rock solid and wont go any further, no matter how hard Ive pressed.

The brakes work perfectly, they stop well, no real issues... Ijust dont like the travel/softness of the pedal, and I dont think its supposed to be there. If I pump the pedal, its as soft every pump, it does not 'harden' up with repeated pumping.

Ive bled the brakes the old fashioned way, Ive bled them with a pressure bleeder, and Ive bled them with a suction bleeder. Ive bled them with the truck at different angles, and Ive tried tapping the calipers while bleeding to dislodge any bubbles that may be there. THe brake lines all seem fine, the fluid stays nice and clean, and the original pads are still in great shape after 50k miles.

Is it my master cylinder thats bad? Are the brakes simply 'overboosted'? SHouldnt the pedal be relatively hard from the first milimeter that the pedal goes down? Or, maybe, because this truck could theoretically be used to tow and have its brake system tapped (there is a note about being able to do this in the owners manual), is there some overcapacity as a result, and when its not used, the pedal seems softer (just throwing out wild ideas).

Any advice or info would be appreciated. Thanks!

JMH
 
The brake pedal in my mom's 2004 Malibu Classic "feels" pretty much like the one in her (now sold and gone) 1997 Ford Escort. Both cars have front disks/rear drums. I'm pretty sure that the Escort's brake components (including the master cylinder) are a Mazda design.

Does the S10 have rear drums or rear discs? It's been my observation that rear discs provide a better feel than rear drums, but even then you shouldn't be able to push the pedal to the floor with increasing pressure. If it's got rear drums maybe the self-adjusters aren't working right?
 
It is possible you have air in the Master cylinder. Disconnect the brake lines and rig something to run lines from both ports to the reservoir. Gently pump it a few times until no air comes out, then reconnect the lines. They sell little plastic kits for it, but they are not the best.

I guess you could also have air in the ABS. About all I know about that is that the shop manual for my last Pontiac said be very careful not to do it.
 
Different vehicles do have different pedal pressures by design, just as with steering effort. German cars tend to be more responsive, mainly because if you are Autobahn burning and need to stop right NOW, there simply isn't time to modulate and getting past that first quarter inch could mean disaster. However, the same touch at 55 mph can throw you towards the windshield, so the American cars tend to dial in more progressiveness and allow more initial "dead space" before really engaging. Both vehicles may stop in the same distance, they just go about it with a different touch. I am used to it, but sometimes folks have a difficult time with the transition if they have a VW during the week then occasionally drive their Grand Caravan on weekends.

Brakes should never go to the floor, however.
 
My mom's 04 Camry's brakes have that mushy feeling too, but since the car is still able to stop when we needed it to we never thought much about it.
 
Soft or soft and spongey? Both my GM cars had comparatively soft pedal feel when compared to my other cars. Soft's probably normal, but spongey never is and is a clear indication of air in the system. If the spongey feel occurs only when the brakes are hot (racing, driving mountain roads, towing and going downhill), then the brake fluid may be boiling due to water content. A pedal that sinks slowly to the floor indicates a master cylinder that can't hold pressure. You must fix that.
 
check your rear brakes... GM's use a "quick takeup" valve in the MC which holds off the fronts until the drums begin to apply. If your brakes aren't adjusted properly it can lead to that mushy initial feel. I re-adjusted the rears on my K2500 and it made a world of difference.. still not like stepping on a rock like my old MR2, but much much better than before.
 
Thanks everyone!

The fluid definitely is clean and clear... I was using ATE super blue racing fluid, now I have valvoline synpower fluid in there... Perhaps my problem is the MC (or air in it), or perhaps it is the adjustment of the brakes...

I guess the feel is just spongey... And in trying to figure it all out, Ive gotten them good and hot, and/or applied many, many times one after another... I could feel the heat from the wheel... Braking performance stays more or less the same, nothing as far as feel or stopping power changes, regardless of use, its just always soft...

Thanks!

JMH
 
i have noticed that domestic vehicles have a softer brake pedal feeling, they seems to be more position sensitive than pressure sensitive. they still have plenty of power, just not much feedback when you step on the pedal.
the same thing goes for the feeling of the steering. domestics usually have more boost on the steering making them easier to turn but giving less feedback.
 
Brake modulation in my Buick and Chevy was comparatively poor. Still, while a soft pedal may be normal, a spongey feel does indicate air in the system. If the brake pedal sinks to the floor, then somewhere the brake system doesn't hold pressure and I'd definitely suspect the master cylinder. If the vehicle has ABS, then you may have to cycle the ABS control unit in order to bleed the brakes properly.
 
A 'trick' used by autocrossers and HPDE'ers on Hondas with rear drums to engage the parking brake a couple clicks to get the shoes closer to the drum to take up any slack that adjustment may not be able to take care of. People have said that it greatly increases pedal feel. My 94 civic has rear discs, so I get a pretty good pedal feel.

However, I wish it was a lot firmer, I do not really like the feel of power boosted brakes when autocrossing or HPDE'ing. I am thinking of fabbing a spacer plate so i can run no booster.
 
have u ever tried driving someone else vehicle that is exactly like yours. FOr example, if i drive a 01 base prelude, and i want to see if my pedals are suppose to feel this way, I would go test out other cars that are similar to mind. More than one would be preferable. ???//
 
Actually I've not ever witnessed the self-adjusters on duty. Cleaned them, tried to lubricate them but simply they are not adjusting the way the shop manual suggest. Per the manual, one should back-up the star wheel so much that actually leaving the drum loose and later drive and brake back and forth to have them precisely adjusted. Just does not work for me. The idea ChrisW says seems very appealing to me, novodays my rears seems a little loose, I will try it at the first opportunity.

If the caliper sliders aren't working right there may also develop a slack that the cylinder can't take up as the pads worn. This, with rear play may be the part of the problem.

Other part of the problem may simply be that the brakes are overboosted. My Chevy has -visually- the largest booster compared to the weight. It is tandem type with dual diaphragms, and yes you can tap up to 1 cu.in. displacement (or so) for trailers. No ABS, I can just lock the wheels at any speed. Naturally progressiveness is uncompromisable, so one can pinpoint the moment that the wheels start just about screaming. Actually it is the most progressive brake that I've ever driven at speed.

I need to note that it does firm up noticably as the speed increse. Past 60mph it is most noticable, yet still more boosted than every other un-American car I've driven. At park wheels may be locked at the steepest hill and I can still push the pedal way further, while I never understood this I think this is the "spare prgressiveness" left for the speed. That position at speed is not going to lock the wheels promptly.

I remember reading something about a system, a valve that is the bleeding the booster vacuum as the speed increase to prevent a deadly lock-up but couldn't find any reference in the shop manual for this.
 
ikeepmychevytoo makes a couple of good points. Self adjusters never worked for me either. And yes, if the caliper hardware isn't working right, it can cause low and even spongy pedal.

By the way, how long have you had it? My one goes back to 1977.
 
quote:
Originally posted by labman:
By the way, how long have you had it? My one goes back to 1977.
Click to expand...
If this is me, I own it since I got my driving licence on 1998. On my college years I've got a cheap '84 just for pracitising and basic transportation, but I liked it so much it is still my last car. I wish I could own it brand new as an '84 model. So, not too long indeed.
 
quote:
Originally posted by tom slick:

quote:
Originally posted by JHZR2:
My 98 chevy has 4-wheel discs... not drums in the rear...

JMH
Click to expand...
you just made me realize i no longer own any vehicles with drum brakes!
Click to expand...
LOL, me too... All the better, I guess?!?

JMH
 
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