I have an 86 Olds 98 with front disc and rear drum brakes. I used to have the 32mm bore master cylinder. The brakes felt mushy and were not strong at all, so i bled the system. This did nothing. I replaced the pads (front and rear), which did not help. I then replaced the master cylinder with a 36mm bore and replaced the rear wheel cylinders. The braking is the same as before at best now. I continue to bleed them and out of one brake (rear driver) i get alot of very small bubbles no matter how much i bleed them. Any ideas what this could be and how to get a better feel back int he pedal? I cant even lock up my wheels on wet pavement. If your braking system is similiar to mine, what kind of performance do you get out of it?

Thanks,
Alex

Sounds to me like your left/rear wheel cylinder is going bad, drawing in small amounts of air, as the brakes retract, hence, the tiny bubbles on that one side.

BTW, if you replace it, do both sides.

i did replace both already

i went to a napa and asked them about it, apparently some brakes just need to be power bled, so i have an apponitment for tomorrow to do so. We'll see how it goes

So'd that fix it?

the power bleeding didnt help at all. I tool the master cylinder off, rebled it and pupt it back in and then rebled all the wheels. The brakes are better but still not great. I really dont know what to do. What kind of braking performance does everyone else get from their sedans? can you lock up the wheels? how stiff is the pedal?

Have you set the tension on your drums in the rear? (backing up and stopping a whole lot, to work the auto tensioners?)

yes, i actually just pop the drums off and set them by hand with pliers. i dont think the auto clearancers were properly engineered and allow for too much clearance.

They will adjust to the point of just enough clearance to not drag. So long as they are clean and free, they work great. Sounds like you have problems that go deeper than air in the lines. Is it a spongy pedal, or a hard pedal? If you slam on the brakes, do they lock? I would make sure your fluid is clean, and that your booster is in good shape. You could have a vac leak there, or just a bad booster.

Let us know what you find...

Andrew

i dont think i have a booster problem, the pedal is not hard to push down, and the booster stays functional long after the car has been shut off. Does this rule out a problem with the booster?
When i first start driving the car, the brakes suck, but after i drive for a little, they become better, but not great. I can still floor out the pedal then. Any ideas? My rear passenger brake, no matter how much i bleed it, has very very small airbubbles that come out of it, but no other brakes do that, they are all clear. could there be air in that line that floats back up after a bleed and requires a power bleeder?

How does your fluid level stay in the reservoir? Have you inspected under the car for line damage? You are introducing air into the system somewhere. If there was line damage, or a loose connection somewhere, you'll likely be losing fluid aswell.

Did you bleed the master cylinder before replacing it? You either have air stuck in the master cylinder, or have a leak, like a pin hole in a hose or line. If the booster is functioning, it is fine, and it is ruled out. Are you getting the bleeder screw tight? Is it possible that there is something in the bottom preventing a good seal, sucking air back in? Just more questions... Let us know how your fluid level is...

Andrew

the fluid level stays the same, and there is no leaks anywhere. I checked them all under the car, dry as a bone. I bench bled the master cylinder before putting it on.

I have a theory, tell me if it is crazy:
When i replaced the front calipers, both the piston and the sliders were frozen. The sliders allow the caliper to adjust for pad wear, but with frozen sliders, the caliper cannot adjust for these changes. thus, instead of the caliper sliding on the sliders after pad wear, it would tweak itself sideways, so that the bottom of one pad would hit before the top, and vise versa on the other pad. The old pads i removed were worn in the pattern as if this was happening. Because they were tweaking and not sliding for so many years, it may have bent the mounting hardware and/or the mounting plate so that my new calipers are not on just straight. this would cause the pistons to have to go out more to straighten out the caliper before alot of pressure would be applied. does this make any sense? I think i am going to get new mounting bolts in the morning.

-Alex

Hio abbike18, hello everyone,


That would cause a mushy pedal. However, it should have been visually obvious during reassembly. They would have been extremely difficult, if not impossible, to install. If everything is right, they fall into place.

Once installed, normal use would tend to return them to the original configuration as long as the calipers are allowed to self center.

Recheck your slider pins, just in case. You might also check the fit of the old pads vs the new.

If you find the bracketry to be bent, you might consider giving them a little help with the BFH.


Not much help unless the old ones are bent.

Regards, Norm