I've searched for like 2 hours now, and I still haven't found a case that is similar to mine.

My brake pedal feels soft, as if the system had air in it. But when the engine is above ~1300rpm the pedal is firm, as if no air in the system.

Sometimes I can double pump when the engine is at idle, and I get a firm pedal.

I haven't bled the brakes yet, its on the to-do list.


I was thinking a bad brake Master, maybe leaking past the piston, but there is no clear fluid leak from the MS. weird.


thanks.
tyler

 

Check the shoes on the rear, you get pedal pressure from the rear.

 

When you're at a dead stop with the engine idling. hold the brake pedal down. If the pedal bleeds down....continues to sink to the floor....then there's a problem with the master cylinder.

Otherwise....
When's the last time you've flushed the brake lines? If the fluid is dark like coffee, it is spent. Brake fluid is hydrostatic....meaning, is absorbs moisture/condensation from the brake system heating and cooling. The brakes and lines get quite hot from use. Spent fluid (moisture in the lines) can cause those symptoms.

 

Definitely do that first. Then, if you're still having problems, try to address the other usual suspects. What you're describing (especially double pumping to get pressure back in the pedal), is a dead giveaway of a system that needs to be bled.

 

It might be a bad brake booster. Push the pedal with the engine running and it should be easy to push, then turn off the motor while keeping your foot on the brake. If the pedal starts to get firmer after the engine is off, then the brake booster is not holding vacuum.

Air in the lines is definitiley a possibility. There does not need to be a visible fluid leak to mean that something is bad. There is usually another seal or dust boot that will keep the brake fluid from actually leaking. Do you have a lot of brake pedal travel?

 

whoops double post.

 

bled my brakes and lspv, seemed to do the trick.

I'm still not satisfied, though I will probably leave it alone. Something still feels wrong. Too much travel to get the firm response IMO. W/e its an 88.

I've got bigger fish to fry right now, SAS.

maybe i'll try a 1" T100 MS when i get done the SAS.

 

Brakes that are out of adjustment can cause excessive travel. I usually slightly pull on the parking brake while driving and see if the pedal travel significantly decreases. If it does, then the brakes need to be adjusted.

I would think that if bleeding the brakes helped, then there was air in the lines that had to come from somewhere, so there is most likely a problem. The first thing I would check are the rear wheel cylinders. Pull back the dust boot on them and check for brake fluid as they can be bad without leaking outside of the boot.