The brakes in my stretched 93 have never been good. In the summer I have to double pump them and now that its cold not even that will work. What's happening when I step on the brake is I feel resistance but the pedal then slowly sinks to the floor. Then the brake and ABS light come one. I've adjusted the rears a while ago and it made no differance. Could it be a vacuum leak or is it time for a new master?

 

I just went through the same problem! I'd check for leaks first and foremost, if there are none by pass the abs modulator on the rear drivers side frame rail, just to see if that is the problem. If the pedal is the same, reconnect the modulator and replace your master. I would recommend doing the master and booster as a unit ( wish I had!!!)

 

Mine were mushy. I bled them all with a few quarts of new fluid last week and now they're great! Might be worth a shot for you.

 

Search this problem, you are not alone. If it has been a while, correctly adjust the rears (very important).
is there a distinct whoosh when you apply the brakes? Dead giveaway for bad booster. You can remove the brake lines at the MC and plug the holes, if it still bleeds down when applied, bad mc.If they don't bleed down, possibly bad rwal modulator valve. If the mc or booster are bad, replace them as a mated pair,as stated earlier it solves the push rod length issue...Mark

 

Good advice guys. I forgot that I had checked the vacuum this summer and it was good. Anyone know what size bolt will plug the holes from the brake lines?

 

air in the brake lines can cause it to be mushy too. you will need 2 people, try to open the valves and pump the pedal getting all the air out, some fluid will come out too then close the valves and try the pedal do each caliper separately then repeat. just a suggestion i have seen this be the reason for a mushy pedal

 

I'll get the size in the am, I always save those plastic plugs that come with new mcs...Mark

 

Dont think its air in the lines. I had to replace some lines and bleed the brakes then.

P.S. if you have a MityVac you only need one person. Well worth the $20.

 

most likely master cylinder.

 

I had a similar problem in my truck where I would have to depress the pedal twice to get the pedal to stay firm. I replaced the master cyl and that fixed my problem. I would put my money on the master.

 

It is probably your master cylinder, if you apply the brakes, the pedal is hard at first then sinks to the floor under your foot there is an internal leak and needs to be replaced.

When you get a replacement, try and get a new one and not a re-manufactured but if you must then when they bring it out to you, first pop the cap and make sure the sealing surface to the reservoir is sharp and flat, if it is dull and looks banged up then tell them to bring you another one.

If this surface is not sharp and flat, the fluid will leak out from under the cap and eventually cause rust to eat everything it touches.

I just went through this problem with a master cylinder and booster I got from NAPA.

As good as everyone think NAPA is, these parts are from A1-Cardone the same vendor used by Auto Zone and most small Auto Parts stores.

Oh BTW the first NEW master Cylinder I got from them was also defective, probably nicked the seal on the piston when it was assembled, pedal went right to the floor.

Jim

 

I just went through this.
Long and short of it, make sure the rear adjusters are adjusted and installed correctly.
This means adjusted with the e-brake cables disconnected, or the cable adjustment for them backed clear off.

I had literally zero brakes, got the truck up on a lift, yanked the driver's side drum and the adjuster cable was just laying there, looked closer and the adjuster itself was in BACKWARDS!
It would just back off after being adjusted up.
Pulled the other side, same deal, adjuster in backwards.

It had good brakes after that, but I put a reman master on the truck anyway, because the old one had been leaking.

I usually start looking at adjusting the the brakes when I have to pump the pedal to get full brakes.
Even if it seems good on the first stroke, if pedal travel improves on the second one, it needs adjusted, or there is air in the line.
They should be consistantly firm, hot or cold ambient temp, next day, or 30 days from now.

Mark.

 

After the second or third Napa MC can't remember now, I got one from Car Quest. That one worked.
On your stretched 93, a hydroboost setup may be something to consider.

 

My old Carhauler has an 18 foot wheelbase, brake lines that are zig-zagged (VVVVVV) down the framerail (increased volume) and a vacuum booster set-up.
It has BRAKES that WORK GREAT.

If you have doubts about your rear apply pressure, use smaller rear wheel cylinders to compensate for any extra line volume.
A larger bore on the master cylinder will accomplish the same thing.

Mark.

 

Any recommendations for a larger MC Mark?