Hey,

My 1985 Suburban has the break warning light coming on. The break pedal seems to get firm when pumping it as long as the ignition is off. When it's on, the pedal goes all the way to the floor. The pads had needed to be replaced soon anyway, but while replacing those, one of the calipers seemed problematic (the piston was extremely difficult to push back into it). I've replaced that caliper, but not the one on the other side yet. I had hoped to find out if that was the problem first. The break line to that caliper has been bled also.

OK, that's what I know. I'm not a mechanic, but am trying to play the part (and consulting the shop manual and Haynes). It doesn't look like there are any leaks in the break line system from what I have seen so far, though it's possible that it has just been missed.

What should I most likely look at? I found a post on Yahoo! Answers that mentioned checking the power steering fluid levels. The poster said it had been the cause for his 1984 Suburban brake problems, so I'll check that in the morning. Haven't seen anything about it assisting the brakes in the books so far though...

Thanks in advance!

 

You caneasily tell if you have the vacuum booster ( large black cylinder that the master cylinder is attached to ) or the Hydro - boost system ( no large black cylinder ).

The vacuum assist receives vacuum from the engine manifold for the power assist where as the Hydro-boost receives hydraulic assist from the power steering pump for power assistto the brakes.

In my Haynes manual there is a ( brief ) section pertaining to the Hydro-boost procedures.

You may also check the rear brakes for leakage and not just the fronts.

A tip : when installing the new calipers load them with brake fluid ... this will help with the bleeding process and help with not introducing much air in the system. Another thing that's over looked is when the calipers are still plumbed and you push the piston back ... you should open the bleed screw while doing this.

Just make sure that you perform a complete bleed process : start with the right rear then the front left then repeat the process for the other side starting at the rear.

 

Thanks, golfer. I'll try bleeding the entire system. I guess if the old caliper did have a leak, forcing the piston back into it would have forced air into the rest of the system (ouch). I'm pretty sure Haynes said to remove brake fluid from the reservoir before pushing the piston back into the caliper, so I don't think that it needed to be bled (ie: no one-way valves in the line). The other caliper piston wasn't nearly as hard to adjust either. It also looks like my Suburban has the vacuum booster, but the power steering fluid levels looked fine too.

Thanks, I'll report back.

 

Bled the entire brake system, and while working on the last one (front, driver-side) I heard air being sucked in around the reservoir area. This is the first time I've heard this, and I am guessing that the vacuum has sprung a leak because I don't see fluid anywhere. Anyway, I'll be taking it to the shop tomorrow. Wish I had a little more time to fix this myself... replacing the reservoir/booster(?) would take a little more time than I have at the moment.

Thanks for the pointers!

EDIT: The mechanic said that a leaking vacuum would make the pedal harder to push, not easier. Guess it's the master cylinder.