problem with brakes

[tokki g]

My brakes have way too much play and almost no stopping power. I have a '94 SL. At higher speeds, I have to push the brakes almost all the way in. At lower speeds (1st, bottom end 2nd gear) I get some more feedback from the brakes but they still don't brake as much as they should.
My brake light came on (not the anti lock light) when I first noticed this problem. It only came on during 1st and 2nd gear, even though braking power was noticeably less at all speeds/gears. Fluid level looked a little low, so I went out and bought some DOT3 brake fluid and put some in there. I only had to put in a tiny amount though, the bladder that is attached to the cap is pretty damn big and made some of the brake fluid I added spill out. Also, I noticed that whereas the new brake fluid I added was clear, the fluid already in there looked pretty dark.
Afterwards, I drove around the block to test the brakes. The brake light did not turn on during 1st or 2nd gear, but braking power was still about as weak as before, maybe a little better.
I looked at my brake pads (front and rear), they look OK I think. I don't know what brand they are, the previous owner installed them. No squeaking when braking. Oh, and like a few days before the light came on, I went out and drove around some back roads pretty hard. I don't drive too hard on a daily basis (usually shift at 3-3.5k), but I do brake late/hard.
Anyone have an idea what the problem might be? I'm guessing (from my nonexistent knowledge base) that I need to flush the old fluid.

[Struggly]

Change your brake fluid and bleed your brakes, then see how they feel. If they still give you trouble, get back to us.

Sounds to me like you've just got a bunch of air in the system, and old nasty fluid.

Clint

[bluemax_1]

Yes, the first thing to try would be to do a proper full flush of the brake fluid. Seems like it hasn't been changed in quite a while and for all you know, you might have entrained air bubbles in the system. That's the most liely reason for the pedal going practically to the floor.


Max

[netmechanic]

Originally Posted by tokki g

I only had to put in a tiny amount though, the bladder that is attached to the cap is pretty damn big and made some of the brake fluid I added spill out.

That "Bladder" shouldnt make any spill out as it should be colapsed up into the cap. You need to push it back up in the cap then refill you fluid. You probably have sucked a big gulp of air into the system so fully bleed everyting and see if that makes a difference.

[tokki g]

So I bled the brakes, got rid of the air bubbles and the brake warning light. Brakes work a lot better now. Unfortunately, since it was my first time jacking up my car on all fours, it took a while and I didn't get to do a full brake fluid flush before it got dark. That's next on my list though, as soon as my test pipe comes in I'll install that and flush. Thanks for the help guys.

[Alt0id]

Not to sound like a moron, though I know thats coming..


How do you go about doing a full flush? just open the bleeder thingy and let it all come out?

[Struggly]

Originally Posted by Alt0id

Not to sound like a moron, though I know thats coming..


How do you go about doing a full flush? just open the bleeder thingy and let it all come out?

Instead of just bleeding until the air comes out, you bleed, corner to corner, until you've completely changed the fluid.

If you use a colored brake fluid like ATE, it's fairly easy to tell when you've forced all the old fluid out. But if you're just usuing regular fluid, you have to just go overboard with it.

Clint

[tokki g]

Here's a good thread, details a full brake fluid flush and bleed:
http://www.3si.org/forum/f13/how-bleed-brakes-153864/

[bluemax_1]

Originally Posted by tokki g

Here's a good thread, details a full brake fluid flush and bleed:
http://www.3si.org/forum/f13/how-bleed-brakes-153864/

Try not to use the procedure in the first post above as you could entrain air bubbles in the brake system.

Here's a simple and fairly cheap way to do it on your own:

Originally Posted by bluemax_1

To me, the simplest and cheapest way to flush my brakes properly was simply to replace all the bleeders with speedbleeders. No need to backflush etc.

If you're not familiar with speedbleeders, they're simply bleeder valves that have a ball-spring valve built into them. Makes it very easy to bleed the brakes solo and even easier if there's 2 people. All you have to do is put a piece of clear tubing over the valve (with the other end in a container), loosen the speedbleeder about 1/4 to 1/2 turn, then pump the brake pedal until the new fluid comes out.

I usually give a few extra pumps to make sure all the old fluid is out of that line. Then tighten the speedbleeder and move on to the next caliper. No need to tighten the bleeder between every pump. That's what the built in valve is for. Only other thing to make sure is that you top up the fluid in the reservoir after several pumps, because it will go down. I've found that if I fill the reservoir to the top line (which is about 1/2" - 1" from the top of the reservoir), it'll take about 8 - 10 full pedal pumps before the level of fluid reaches the filter/strainer, where I usually top up the fluid.

Proper order to bleed the fluid is:
passenger rear, driver front, driver rear, passenger front.

Contrary to what some folks think about why the procedure is like this, the simple answer is that the brake system is built on two lines that cross diagonally. The driver front and passenger rear are on one line and the passenger front and driver rear are on the other. It's always good practice to bleed the caliper furthest away from the brake cylinder first, and to finish bleeding both calipers on one line before doing the other line.

Here's a link to speedbleeders:
Supercar Engineering

You can also find generic brand speedbleeders at your local Autozone, Pep Boys etc. They'll be in red packaging with the name HELP! (for some reason). The size of the SB's required vary between the gens. You either need the ones that are M10x1 thread or M7x1 for rears(1st gen). All fronts are M10x1 approx. 34.5mm length (varies between brand). Don't get the short ones which are about 31mm unless you have Stoptech brakes.


Max

You shouldn't just allow the fluid to 'dribble' out because that could allow air bubbles in.

If you don't have or don't want to get Speedbleeders, then ask someone to give you a hand. Simply follow the procedure above except without the SB's, you have your assistant stand on the brake pedal and then you open the bleeder valve to allow fluid to spurt out (use some tubing over the bleeder nipple to some kind of container. Brake fluid is corrosive and toxic even from skin contact). With them still standing on the brakes, close the bleeder valve. Then tell them to allow the pedal to rise again and stand on the pedal again then repeat.

The advantage to bleeding brakes under pressure like this is that a) it prevents air from getting into the brake system. b) the higher velocity of the brake fluid going through the lines is more effective for removing small air bubbles. It's also a good idea to use a rubber mallet to tap the calipers every once in a while as you bleed the brakes to get any bubbles to move.


Max

[sammage]

Just alternate between amber and blue ATE fluids, so you can tell when the old is bled and the new is in the lines...and I highly recommend speedbleeders, makes flushing brakes by yourself so easy.