Soft brake pedal

Leaks Fluid Level Fluid Condition Rotor Thickness/drum diameter

Steve

I would be curious as to what Rotor thickness,drum diameter would have to do with a soft brake pedal?

Ian

I would make sure your rear brake shoes are adjusted properly. You could try changing the brake fluid, but if neither of the above help....yes, a master cylinder change may be in order. This year of GM truck was notorious for lousy feeling brakes. GM even came up with a brake pedal rubber pad that was quite a bit thicker then the original as part of their "solution" to the soft brake pedal and "low" brake pedal problem. In most cases, adjusting the rear brakes properly, and making sure that the front rotors have an excellent surface finish (if the brakes have been done recently, a poor machining job on the front rotors can cause problems) will make the brakes perform as good as they can. In some cases, I've found that replacing the master cylinder has done wonders. But again, this year of GM truck (and many other years) simply sucked when it came to brake performance.

Ian

Tell me about it. I just did brake repairs on 2 C-2500 6 lug (7200 GRVW) pick ups. Both are Ex-Fleet vehicles with over 200,000 on them. Both have Extreamly soft brake pedels. They get hard when bleeding the system with the engine off. Turn the engine on and pump the brakes they feel like mush. One of the trucks has new rear shoes and wheel cylinder. The other has no front pads and calipers. Both have all new lines running to the rear end flex hose.

The one with new front brakes will hold the truck still untill the rear tires overcome the brakes and spin/burn rubber on concreate. Yet take the truck down the driveway, and you don't want to even go 20 MPH.

Other then master cylinders on these, and rear brake adjustments, any other suggestions? Charles

Not so much the soft brake pedal, the OP stated "brake pedal is soft and able to go all the way to floor." Just one of those things that takes 2 seconds to check, so why not.

I would agree that it doesn't take long to check those items, but there is no relationship between those measurements and the problems that the OP is experiencing.

Ian

Something to ponder... Since I've owned my truck (1999) it's had less than ideal pedal feel. Replaced 1 wheel cylinder, several sets of pads over the 135,000+ miles I've owned it, master cylinder, had it professionally bled, still had crappy pedal feel. I had to replace my brake booster on this 95 K1500 5.7L about 3 months ago due to it pissing air in the cab. This helped the power assist but I still had a weak pedal.

7 days ago this rebuilt booster started pissing air so I had to replace it also. Nice Murray's products! This time however, I left the master cylinder attached to the brake lines & let it just stay in this suspended position while changing out the booster (I did support it somewhat). As it normally sits in the truck, the master cylinder tilts back towards the driver. The suspended way it sat while I did the swap job caused the master to tilt quite a bit forward. I did no bleeding after this fix. The brakes have been in operation a week now & the pedal travels much less and is unbelievably quick to get VERY hard. Operation is FAR better than ever. I'm thinking that maybe some air sat in the end of the master cylinder & would not bleed out no matter how many times it was bled. Tilting the master forwards for awhile might have moved some air enough so that normal operation self bled the master. No matter what, I'm extremely happy now. Similar thing happened to an Austin Marina I once had. The brake lines came off the master in an upward spiral & then down to the proportional valve. Stupid design to in my eyes. I could not get those things bled until I cut the lines at their highest point & installed some petcock bleeders - instant fix. Sometimes on a motorcycle you have to crack open the top banjo bolt in the brake & clutch systems to make them bleed all air too.

INLINE

Correct

Brake fluid is

Wrong

Fluid in a hydraulic brake system that is water

Wrong again. Water is no more compressible than most brake fluids. Water has a low boiling point and in a panic stop can boil and become a gas, which is compressible.

Also water and steel brake lines don't mix. You

Correct

Also it will cost you some

Wrong... Dot 5 is silicone based and it's molecules are farther apart than Dot3-4 which makes it somewhat more compressible.

and

Correct, but that isn't necessarily a good thing. Moisture gets into all brake systems, no way to stop it. Since Dot 5 won't absorb it, the water will pool in the bottom of the lines and other low points and corrosion becomes more of a problem than with the glycol based fluids. Also, pooled water becomes a serious problem in freezing weather.

But there is a pretty good price diffrence and you must

Correct

You will probaly have to have a shop clean your system

Dot 5 can damage seals and other soft parts if put into a system not designed for it. Unless he is planning to run his truck at the local circle track, he should stick with Dot 3( if he is, he could go to Dot 4 which has a higher boiling point and IS compatible with his system).

Dave

On cars and trucks that have sat with broken brake lines. First step in bleeding is Gravity Bleeding. This means you take the cap off the master cylinder. Open the bleeder screws to the point that fluid starts to flow freely. Sometimes you have to remove the bleeder screw for a few minutes. I use a catch pan and let each wheel gravity bleed for 5 to 10 mimutes. Keeping the master cylinder from going dry by topping off, this get the old brake fluid out of the lines, removes air from new wheel cylinders, calipers and the master cylinder. Then I bleed them from there.

You can bleed lines by first cracking them lose. Then having some one pump up the brakes and slowly opening them and closing them. Charles