Soft Brakes

[deejay1272]

Hey gang,

Long time, no post. I've been happily humming along for several months without any major projects for the Terjunken, but the rain is back and I'm starting to think of new ways to keep myself occupied on my weekends with projects. The next item on my maintenance agenda is to address my brakes.

Background:
Every couple of months my red dash brake warning light appears to let me know that my brake fluid is low. I have refilled it a few times, but I'm beginning to think that my master cylinder has a leak in it.

Also, after a recent camping trip at high elevation, I drove downhill for several miles - all the while riding on my brakes to keep from speeding out of control. At a certain point I noticed dramatically decreased braking abilities due to very hot brakes. Ever since this trip, I've noticed that my brakes are markedly softer. I did a bit of reading on this topic and I learned that if you use a DOT 2 or lower brake fluid, one can actually boil the brake fluid in the lines, thereby introducing air bubbles that can cause your brakes to be soft/ineffective.

What I've done so far:
After noticing that my brakes were way softer than normal (after my camping trip), I decided to check the thickness of my pads and rotors to see if they're within spec. I found that my pads were well within spec (~11 mm) and my rotors were close to being out of spec so I replaced them with brand new parts. I haven't checked my rear brakes yet (mostly out of laziness and mild fear of dealing with stupid drum brakes).

Solution?
I'm thinking that my best course of action to address my brake concerns is to get a new master cylinder and bleed out all of my lines (starting with the line that is furthest from the fluid reservoir). Does this sound reasonable to you guys? Also, while replacing the master cylinder is there anything odd or particularly challenging to deal with?

Thanks....

[splatterdog]

It's quite possible you need wheel cylinders instead of a master. A leaky master will usually have a wet streak beneath it on the booster. Unbolt it from the booster(not the lines though) and you will know for sure if it's leaking.

Drum brakes make a huge difference in brake pedal height. Check for sticking adjuster screws, adjust them up to a light drag. Check for deteriorated hoses. They can expand slightly under pressure, causing pedal concerns and eventually failure. Make sure caliper slider pins are free and the pads aren't stuck in the caliper brackets.

Bleed it out thoroughly.

[Highlander]

Also check your flexible lines to the front discs, they age and start to bulge at cracks, and that will take some of your pedal feel away, plus if you REALLY need to hit your brakes hard, they can rupture at the most inopportune time

[dlb]

what they said--don't assume it's your master cylinder. if you are having to top up your brake fluid that means you're losing it somewhere and you will be able to see it once you find it. check the wheel cylinders, the rubber flex lines, the master cylinder, all of the steel brake lines...if you go through it methodically you will see the leak.

petros really likes his brake upgrade but since your pads are in good shape and you have new rotors, i would hold off on upgrading until they wear out. i personally have had no issues with the stock brakes being insufficient but if i did i would give the upgrade a shot.

[ARCHINSTL]

What they all said about everything - and I would reinforce splatterdog's remarks about the effect drum brakes can have on pedal height.
This happened to me on doing all new rear drum parts (incl. cylinders) on the '88 Dodge/Mitsu p'up. I also did well over a quart in bleeding all four wheels. I adjusted the shoes per its FSM and kept getting a soft pedal. I then kept bleeding (too many times to confess to) and was cursing the shop that turned the drums, thinking it shaved way too much. Finally, I adjusted the shoes "too close" to the drum and Voila! - a firm pedal. This was only 1 or 2 clicks on each rear wheel.
Maybe your self-adjusters are corroded?
I was surprised, as this hadn't happened when I did Goldie five years ago, nor on any of the Morris Minors so many years ago.
Tom M.

[Petros]

The test for the master is to pump the pedal several times and hold it down hard, if it slowly bleeds down you need to replace it. The rear wheel cylinders are more common to go leaky, pull the drums off and inspect them for any wetness, pull back the boots if necessary to make sure. If you are adding fluid it most likely is leaking from the rears.

Replace the shoes and wheel cylinders, and rear flex hose if necessary. It takes quite a bit of pumping the pedal and bleeding to get all the old fluid out of the lines. Old fluid can also make for mushy brakes, it absorbs moisture (looks cloudy) and will cause rust inside the brake parts. The brake fluid should be replaced about every two years to keep it fresh and make the brake parts last a long time. Put in fresh fluid and bleed it from the rear until you see clean fluid coming out.

If you replace the master you usually can get by with just bleeding the brake lines where they attach to the master. If done properly you will get all the air out and will not have to push the air bubbles all the way back to the rear wheels (that takes a lot of pedal pumping).

I would not replace the stock master or front brakes with similar parts, they are too small and pron to overheating and heat damage even in regular driving (especially in mountainous areas). IT is just a wast of money for new parts that are inadequate. I highly recommend replacing the front brakes with '92 and later Tercel rotors and front calipers. If if you really want to go first class, replace the master and booster with those from an MR2. You can get these parts when you order them new or reman from a parts store, or go to a wrecking yard and save some money.

See my thread on the topic in the repair guilds section of the forum. See here: https://tercel4wd.com/forums/viewtopic.php?f=7&t=4998

[takza]

Back before they had disc brakes you would NOT have made it down that hill. It's always a good idea to use engine braking when descending mountains. Cause once you reach the point where they won't stop the car...you'd better HOPE you are at the bottom.

[Petros]

The problem with that is a 1453 cc low compression engine does not provide for a lot of engine braking.

[takza]

Worked for me in Wyoming...except that by the time I was down the mountain the temp gauge was close to cold. Just keep it in 3rd and CYCLE the speed keeping it under 35.

I probably overdid it due to having driven a full sized bus around the west...one with drum brakes all around....drive one of these in the mountains and you either learn or you're dead. Came down a hill into Jerome, Arizona and came close to losing them....and on a few others. My first experience was the Grapevine grade (?) north of LA...fortunately a lot of lanes and a straight run....learned the easy way and lived to tell about it.

[danzo]

All great advice, I'll smurf in with my $.02 since brakes are one of my fave subjects. You're definitely not boiling your fluid. If you have ever done it you will never forget it - the pedal will go to the floor with zero braking action. At that point all you can do is pump the pedal, maybe update your will, and wait for pressure to return. I did it once at an autocross with what was prolly 15+ year old fluid, and I learned my lesson to say the least. This is why track day organizers want their participants to prove in writing exactly when fluid was last renewed.

The main cause of boiled fluid is age, not necessarily the DOT rating. As fluid ages it absorbs more and more moisture from the air (e.g. every time you open the fill cap or bleed valves), water has a much lower boiling point than straight brake fluid. This is why every bottle of brake fluid I believe is DOT required to state the wet and dry boiling points. Buy the best synthetic fluid you can find that has the highest BPs. Cheap insurance since econo fluid is $6/quart and the good stuff is like $9. Also a good idea to replace the soft brake lines since they have prolly never been replaced and they cost all of $5 each through the interweb.

I just did my front brakes yesterday since inspection day is tomorrow. BTW if you do the rear drums you might invest 5 bucks in drum brake pliers, they really make it easier. Good luck and let us know what happens.

[ARCHINSTL]

Came down a hill into Jerome, Arizona and came close to losing them...

Boy, mentioning Jerome... On Tom's Excellent (and only) Trip Out West in '85, my GF and I were driving her clapped-out '7_ Malibu wagon. We took a side trip to Jerome and stayed until dusk. Then drove down to the flatlands at night, down those curvy roads. Swear to Goodness, my throat was dry the whole way down - Flatland Tom had a string of impatient locals behind me as we descended at 30 mph (or less, in some places). I thought the road would never end. Our MO Ozarks were like bumps on a blanket. Never forget it - I just knew we'd wind up down in some dark canyon (like the OF did in CA just recently).

I heartily endorse danzo's recommendation on the brake pliers!
Tom M.