I've searched the forum and found quite a lot of info, which helped me narrow possible causes for my problem down...

So, here are the symptoms (the car is a 1986 Sport Coupe, came with a 2.8l LB8 V6 and TH-700R4, drum brakes in the back):

- ever since i bought the car last winter, the brake pedal would go down pretty far (but the brakes seem very good otherwise, impressing a friend who drives an 81 Z28)

- this morning, the red brake light on the left side of the dash came on. It went off when I used the brakes once or twice, but stayed on permanently since.

- the pedal now seems to go even further down, and after a few tests I found I have very little braking power in the back. The front locks up easily enough, the back keeps rolling. Very dangerous on a wet road... I slid into the middle of an intersection today, in heavy rain. Outsch!

- it's also a little bit too easy to get the back wheels to spin (do a "burnout") with brakes on. I remember it was significantly harder before...

I've uploaded a video which demonstrates both problems: http://www.mediafire.com/?v19xmtljge1 - I'm afraid it's not very clear (horrid compression), but it shows how front wheels lock up, and rear wheels keep rolling. It also shows a tiny burnout (past the bend in the street) with very little (too little!) effort...

- master cylinder seems to be good. When I build up some pressure by pumping the pedal with the engine off, it gets nice and stiff after a couple of strokes, and doesn't sink if I put my foot down.

- the brake fluid level in the reservoir was low. Also, opening it revealed that the previous owner did a really bad job installing the lid. The seal is nice and soft, but it was crumpled up inside the container. I refilled it and ver carefully installed the seal for a perfect fit. Alas, the brake warning light is still on, and there is still very little braking power in the back.

- the e-brake barely holds. It was much stronger two months ago, when the car was inspected.

Okay... so it can only be three things now, either:

1: my proportioning valve is broken
2: air got into the system due to the badly installed lid on the reservoir.
3: rear brakes are badly worn (there's plenty of evidence of the previous owner doing a lot of burnouts... there was lots of black rubber residue in the back when I bought the car)

Which problem do you think it is? i'm not sure if worn brakes would trigger the warning light, but the first two possible reasons, I'm guessing, would. What do you guys think? Would bleeding and refilling all braking hydraulics solve the problem? Will my proportioning valve work, or could it be that it was damaged? Would air in the system damage it? Would the front still brake so well with air in the system? Is it possible just for the rear to be affected this bad?

 

Still no reply.. Well, I've used up my whole day off just reading through countless threads, and I've gathered up some more pieces for my puzzle.

Okay, it's probably not the proportioning valve. The rear brakes probably need adjustment, but this is likely not the problem either.

Since brake fluid was so low (I really should have paid more attention - I never even noticed the rubber insert was just crammed inside and not providing an seal) there must be air in the system. Brake lines going to the back for sure, and perhaps the portion of the MC responsible for the back drums... right?

Any thoughts?

 

you need to thoroughly go through your brake system now. You probably have:

leaking wheel cylinders
bad master cylinder

but you could also have:

bad brake line leaking slightly
severlely worn rear shoes and drums

the first problem was more than likely the wheel(s) cylinder leaking, which allowed the master cylinder to overextend(from pressure loss), tripping the brake lamp indicator.

otherwise, fluid is being lost from a brake line somewhere.

you're best bet is to replace the master cylinder, and replace anything bad in the rear brakes (shoes/drums/cylinders).

the emergency brake isn't working becuase either the pads are worn out, or the brake fluid inside from the leaking cylinder is not letting the shoes grip adequately.

 

You can also go to your local Midas & have them inspect it for free. They will tell you whats wrong, but you don't have to do it thier. Im pretty sure they give free inspections. Tell them you want a FREE BRAKE INSPECTION ONLY & your braking symptoms. Im not sure how long it would take, you might wanna ask & stick around so they don't do any work they are not suppose to. They are suppose to show you whats wrong with the system & whats causing it.
As for the light I think theres a lil button on the valve under the MC covered by a rubber boot, see if you can push it in & see if the light goes out.

 

Thanks for the input, guys. I refilled the reservoir yesterday, of course, but the problem persisted during my daily commute today (I didn't expect the refill to miraculously cure the problem, anyway).

But then the brake warning light started flickering under braking, and the pedal gradually became more responsive. Then I heard a muffled "tuk!" sound somewhere in front of me (from the master cylinder, perhaps?), light went off for good, and I have excellent brakes again. It just STOPS.

Now I'm totally confused...

Anyway, there's a big Canadian Tire establishment nearby - they do free brake system inspections, too. I'll have them have a good, hard look at it

 

And they're gone... It's pretty clear what happened now:




To make things worse, there's something oozing out of the drum on the passenger side, too:



Oh please let it be just more brake fluid... I'm afraid it's a differential leak going through the axle. More expenses... and I was hoping I could replace my rocker panels and fix the floor in June. Looks like Canadian Tire will have a lot more work today

 

Bye bye wheel cylinders. If you can fix it yourself please try, you'll save a lot of money in labor alone.

Good luck.

Ed

 

All fixed. It was a broken brake line on the driver side, and a differential leak through the passenger side axle. The whole system was flushed (wow, my brake fluid doesn't look like coffee anymore ) and I'm quite happy with how the pedal works now - noticeably better than when I first got the car.

I'm happy my baby is in good health again :-)

 

i also had a low brake pedal too when i bought my KITT. but it was more sinister than that. it was a bad master cylinder and the rear calipers went. they work great now

 

I just started having a brake problem today. You literally have to put your foot through the floorboard to stop the car.

It's pretty scary. If you are going fast or have to suddenly stop it stops without much effort but if you are easily slowing down like at a light, you better start slowing down half a football field away. I'm gonna check the lines and fluid tomorrow. The last time I took a look at the rear shoes they looked pretty good. I know I need to change the front pads. We'll see!!!

 

Well, I finally changed out the master cylinder today. Just the MC.

Tomorrow I will changed out the pads in the front. The rear shoes are good. Anyhow, I changed out the master cylinder and attached the two bleeder plugs with hoses they came with. I filled it with fluid to the minimum line and bled it into a cut-off bottom half of a 2 liter bottle. Did as the instructions said and put the lines back on one at a time between bleeds. For each time I would step on the pedal, I would keep it propped down with a stick, then attach the line, and repeat.

Then I filled the reservoir and stepped on the brake pedal a few times. The first time was spongy still, but the latter times it would get harder and harder. Rather then the traditional brake bleeding method of bleeding the calipers (get ready bomb throwers) I used the tried and true Jamaican last resort brake bleeding method (I will explain). I've done this in the past and it has worked fine. Take the half-cut 2 liter bottle and place it behind the reservoir to catch the excess fluid. Step on the brake pedal slowly until it's almost all the way (not all the way, almost) and prop it with your stick. Put the gasket and cover back on the reservoir and take your stick off.

Try stepping on the brakes again. They should feel as stiff as before you did this maybe even a tad stiffer. Finally repeat the process this time with the car on and a little warmed up. It should be nice and hard like it used to be. Now I just have to take it for a drive around the neighborhood tomorrow to give it the A-OK and we should be all set.

 

I see Daniel-son!!! you have replaced the master cylinder. What brand master cylinder did buy?

"true Jamaican last resort brake bleeding method" Are you Jamaican brother?

 

Nah! Only by friction if you know what I'm sayin' rude boy!
I just learned from one.

As for the Master Cylinder it was whatever was available at Advance Auto parts so it was definitely reman' and most likely a Cardone one. I can't complain because they screwed up and gave me the entire thing fully assembled. Cap, gasket, reservoir, M/C. All I gave them back was the stripped down M.C.

 

I am half Jamaican and how does that make me rude

 

Apparently not half enough! j/k! Sorry, but "rude boy" is a term of endearment. Ask your Jamaican parent and they will tell you. No different then "yardee."

Also, gave it a drive today. Stops really good....feels really good. I gotta say the problem is solved!

 

shaba rastaman

 

Irie!!!!