85 ss monte carlo brake problem

[the nitro man]

a few years back the rear brakes on my wife's 85 ss monte carlo started locking up. so i bought new brake drums, & new brake shoes & did a brake job on the rear of the car. it did help, but not much. the only time they lock up now is when the car has sit overnight , then when we go down the driveway the rear will lock up in the gravel. after you drive it, it's good for the rest of the day. what the hell? the brakes aren't real good on the car & haven't been for a few years. i replaced the brake booster, & the proportioning valve & neither did any good. i've adjusted the rear brakes normal & loose & neither helped. there are no leaks or anything like that getting the shoes wet. i can slam on the brakes & nothing will lock up. it seems like the front brakes are a little weak, & the rear apply early. could the master cylinder be bad some how be causing this? the only two things i've not changes is the master cylinder & the metal lines, & the rubber lines on the front & rear.

[Robert Kane]

Check for an axle seal leaking onto the shoes or a brake fluid leak. Also check the tension on the return and hold down springs as they weaken they can contribute to grabbing when applied. Sounds like a fluid leak on the shoes though which tends to make the shoes grab until they get some heat in them and then it burns off slightly. Alao don't fill they differential until the fluid runs out hte fill hole, that is too much. Fill to 3/8" of the hole. This keeps the level lower than the seal lip and prevents it from dripping as the car sits.

Robert

[MagnumTPI]

Had the same situation with my 94 Dodge Dakota. It's about a half mile to the blacktop from my driveway. Rears would lock up on the dirt for the first 2 or 3 stops. Never found any leaks or harware issues, tried adjusting. This was 5 yrs ago and the stock springs and hardware are still in place. The problem mysteriously dissappeared. I did notice it once or twice on my Camaro also, both kept in the same garage. I did change brakes also due to wear when I first bought the truck but before the lock up issue. I'm thinking brake lining material? Stock drum shoes are usually a light tan or charcoal color. Not sure of the materials that make either of these up but it might be a starting point. Match replacements to original equipment material.

My 86 Camaro had crappy brakes also, wouldn't lock up no matter what. I changed the front rubber lines and this nearly doubled in stopping power. The insides of the hose can break down and block fluid flow. After this the LH front would lock but not the right. Changed the RH caliper and that also made a huge difference in stopping power. Wasn't frozen but seemed tighter than the left side. After this, both would lock but not as hard as just the LH side before the repair. I then got into the proportioning valve and wanted to mod this as sugested on various internet sites. Took mine apart to investigate and found the proportioniong section was full of debris. Cleaned it out and reassembled it, unmodified, and the brakes were better than just about any car I ever drove with front disc, RR drum brakes. (Note if you dissasmble this note the position of internal parts carefully, there is a rubber cup shaped piece that if installed backwards will prevent all oil flow to the rear brakes, ask me how I know!) I cleaned mine out on the car by removing the end cap on the front of the prop. valve. Remove the cap, spring, spool, and rubber cup, allow fluid to gravity flow out the opening, rinsing out the debris. Reinstall the parts and slowly tighten, mine seemed to self bleed as I installed the cap slowly and let the fluid leak around the threads before tightening with a wrench. You can also get air out of the valve by bleeding the entire system as usual.
Disclaimer: Mess with this valve at your own risk!

I'm thinking weak front brakes on your car are causing the rears to do more work and locking up on gravel is a symptom of this.



All good sugestions by Robert Kane, I would investigate those as well.
Hope my rambling reply helps.

[the nitro man]

well i canged all three rubber lines & put on a new master cylinder all at the same time, bled the brakes to hell & back, & now the car has a great pedal, & good stopping power. i'm not sure what fixed it, but it's all better now.

[Dodge Freak]

Have an Olds 1992 Ciera that the left rear driver side locks up first thing in the morning but then after 3 stops or so all is good--or so I thought until last months big snow storm and I was out driving. Was going to a store and there was a few places you can turn in to. I notice the light ahead just turn green and a long line of cars was slowly taking off. So at the last second I decided to slow down and turn in to the parking lot a bit early so I did not have to wait until all the cars drove on past.

The darn left wheel locked up and the car goes doing a 180 and next thing I know I am going backwards heading towards oncoming traffic, lol. wasn't going more than say 35 MPH so it quickly stop and I just drove ahead then in to the entrance but I then afterward notice that the brake was gaping more often than I thought but not so bad it lock up on dry roads. Even during lite snow I notice the wheel locking up but the other wheels were able to hold on. When it did the 180 there was deep snow on the roads an the other wheels just slid. Was like somebody shoved the side of the back end and sent the car in to a skid.

Oh I never looked at the wheel yet, snows gone but I will remember for sure to be extra careful on wet roads. The rest of the winter when the roads were the bit icy I was like avoiding using the brake if traffic was coming. I just downshifted the trans to slow down

[the nitro man]

i noticed after it stopped locking up on my gravel drive way that it still felt funny. that one wheel would grab before the rest. i don't know if it was the rubber lines or the master cylinder, but after replacing them the car has perfect brakes.

[Dodge Freak]

Yeah these pre anti lock brakes are fairly simple. Besides it was always good I thought to hear brakes locking up during a panic stop to warn the other drivers but for some reason we now have one thousand dollar brake systems that in some places--like gravel roads don't even stop as good as the non lock up brakes.

The car was worn out years ago. Its a rust bucket and I am more worry about the frame cracking leaving the driveway, ha ha. But it runs good and is just used for short distances. I don't like driving it on the freeways. Heck it likely could go 90 but best to stay under 50 with it. A very unsafe car for teenagers but sadly its all some can afford to buy.