Drum brake writeup?

[jhumphrey]

Hey all,

I've noticed that my brake pedal is soft. I've posted about it before, but its a very old thread.

Anyway, I've put new calipers/pads on the front, bled the system, and it doesn't seem any different to me. If I pump the brake up until its stiff and hold down while counting to 30, the pedal slightly drops but doesnt go to the floor. As far as driving, it doesn't seem different than when I had the original calipers/pads on it. If I slam on the brakes, the pedal goes almost to the floor, and the vehicle stops...but not as "quick" as I feel it should (no ABS activation).

I'm thinking it could be a bad master cylinder, though it looks brand new (dont know when/if its been replaced). I also have had the suggestion that the rear drums need to be adjusted (could be frozen). Does anyone know where there is a detailed write up on how to adjust them? I don't know much about drum brakes, so I need a clear, step by step, write up.

Thanks!

 

[nevada]

Hey all,

I've noticed that my brake pedal is soft. I've posted about it before, but its a very old thread.

Anyway, I've put new calipers/pads on the front, bled the system, and it doesn't seem any different to me. If I pump the brake up until its stiff and hold down while counting to 30, the pedal slightly drops but doesnt go to the floor. As far as driving, it doesn't seem different than when I had the original calipers/pads on it. If I slam on the brakes, the pedal goes almost to the floor, and the vehicle stops...but not as "quick" as I feel it should (no ABS activation).

I'm thinking it could be a bad master cylinder, though it looks brand new (dont know when/if its been replaced). I also have had the suggestion that the rear drums need to be adjusted (could be frozen). Does anyone know where there is a detailed write up on how to adjust them? I don't know much about drum brakes, so I need a clear, step by step, write up.

Thanks!

the MC is bad. its bypassing internally.

 

[Mynameistommy510]

I learned a lot about drum brakes just by pulling my drums off and taking a look inside. They slide off the lugs just like your wheel. If they're seized on, get a bolt the size of the holes on the front of your drums. Tighten the bolt into the hole or holes and the bolt will press the drum off. Just don't hit the brake pedal with the drums off, it will ruin your wheel cylinder. I learned this the hard way.

Once your drum is off, the wheel cylinder is literally the cylinder on top of your brake shoes. You'll know what the brake shoes are as soon as you see them. Pull back the rubber boots on either side of the cylinder and if there is brake fluid inside the rubber boot, that indicates a wheel cylinder failure. A possible culprit of your soft pedal.

This check is as easy as removing your rear wheels. Plus wheel cylinders are no more than $20 a piece. Sorry for assuming that you don't know any of this, no insult intended.

Testing your master cylinder is possible by removing the two brake lines from the master, plugging the two holes, and seeing if your pedal still sinks under foot pressure. You better be pretty sure it's the master cylinder before testing it because you will be bleeding brakes for what feels like a life time.

 

[jhumphrey]

the MC is bad. its bypassing internally.

Thanks. I have a feeling its the MC, but Im trying to eliminate the easier fixes first. Sounds like I'll be replacing a MC in my future.

I learned a lot about drum brakes just by pulling my drums off and taking a look inside. They slide off the lugs just like your wheel. If they're seized on, get a bolt the size of the holes on the front of your drums. Tighten the bolt into the hole or holes and the bolt will press the drum off. Just don't hit the brake pedal with the drums off, it will ruin your wheel cylinder. I learned this the hard way.

Once your drum is off, the wheel cylinder is literally the cylinder on top of your brake shoes. You'll know what the brake shoes are as soon as you see them. Pull back the rubber boots on either side of the cylinder and if there is brake fluid inside the rubber boot, that indicates a wheel cylinder failure. A possible culprit of your soft pedal.

This check is as easy as removing your rear wheels. Plus wheel cylinders are no more than $20 a piece. Sorry for assuming that you don't know any of this, no insult intended.

Testing your master cylinder is possible by removing the two brake lines from the master, plugging the two holes, and seeing if your pedal still sinks under foot pressure. You better be pretty sure it's the master cylinder before testing it because you will be bleeding brakes for what feels like a life time.

Thanks for the detail response. While I'm fairly mechanically inclined, drum brakes are a bit of a mystery to me. I think I'll replace the MC, since testing it seems like a wash (if I'm going to have to bleed the brakes anyway, might as well put a known good MC on while I'm there).

 

[TheDurk]

When in doubt, RTFM--it was all I really needed. The 4Runner was the first drum brake I had seen in 30 years. Do one at a time, so you can go look at the other to see how the first one goes back together. One of those brake spring tools and one of those retainer thing tools are useful, but not absolutely essential.

 

[jhumphrey]

When in doubt, RTFM--it was all I really needed. The 4Runner was the first drum brake I had seen in 30 years. Do one at a time, so you can go look at the other to see how the first one goes back together. One of those brake spring tools and one of those retainer thing tools are useful, but not absolutely essential.

Thanks!

I really need to get a manual. I've downloaded one, but its not very user friendly. I can never find what Im looking for.

 

[TheDurk]

Thanks!

I really need to get a manual. I've downloaded one, but its not very user friendly. I can never find what Im looking for.

This on-line version I use is pretty friendly. The main defect is that it is from 2002, so a few things are different. The Table of Contents works well, once you get a little used to it.

1996 to 2002 Toyota 4Runner OEM Repair and Wiring Manuals

 

[LittleCaesar]

A little more pic friendly. Once you get them well adjusted, three to four clicks tops with the E-brake. I use a stubby flat head instead of a brake spoon for adjusting....

View attachment Rear Brake Shoe Replacement Tundra.pdf

 

[jhumphrey]

This on-line version I use is pretty friendly. The main defect is that it is from 2002, so a few things are different. The Table of Contents works well, once you get a little used to it.

1996 to 2002 Toyota 4Runner OEM Repair and Wiring Manuals

Thanks, I like that lay out better than the PDF I have.

A little more pic friendly. Once you get them well adjusted, three to four clicks tops with the E-brake. I use a stubby flat head instead of a brake spoon for adjusting....

View attachment 132008

I like the photos, that helps. Do I need to remove everything off the drum like the photos are just remove/replace the shoes and adjust?

 

[TheDurk]

A little more pic friendly. Once you get them well adjusted, three to four clicks tops with the E-brake. I use a stubby flat head instead of a brake spoon for adjusting....

View attachment 132008

Spec is 7 to 9 clicks, per the attached. That's where I keep mine. That said, I suspect either will work fine. Risk is, the smaller number is closer to dragging if linkage tightens up due to temperature or whatever. Why 3 to 4 tops?

 

[LittleCaesar]

I'd say Durk the reason was when I was using the 4runner to trailer a boat, launching the boat off the trailer and putting it back on solo I wanted to make sure my 4runner didn't end up in the water. Plus it helps take stress off the tranny (I have the 340). I have had zero problems with it being that tight and it never rubs.

I have to replace the right wheel bearing five years later thanks to the axle seals going back in the day so I plan to revisit the drum brakes sometime soon.

To the OP: remove everything off the drum IMHO. It allows you to clean the backing plate and check to make sure the shoes aren't rusted onto the plate, the wheel cylinder is OK, etc.
The 3m copper brake paste is great stuff but use latex gloves when handling it:
http://www.amazon.com/3M-08945-Copp...0-8024749?ie=UTF8&refRID=1N64S7XJZTTDW0DA5VRQ

 

[TheDurk]

I'd say Durk the reason was when I was using the 4runner to trailer a boat, launching the boat off the trailer and putting it back on solo I wanted to make sure my 4runner didn't end up in the water. Plus it helps take stress off the tranny (I have the 340). I have had zero problems with it being that tight and it never rubs.

I have to replace the right wheel bearing five years later thanks to the axle seals going back in the day so I plan to revisit the drum brakes sometime soon.

To the OP: remove everything off the drum IMHO. It allows you to clean the backing plate and check to make sure the shoes aren't rusted onto the plate, the wheel cylinder is OK, etc.
The 3m copper brake paste is great stuff but use latex gloves when handling it:
http://www.amazon.com/3M-08945-Copp...0-8024749?ie=UTF8&refRID=1N64S7XJZTTDW0DA5VRQ

LC: Yeah, the boat ramp could certainly change your priorities. The other concern is the adjusting mechanism needs the e-brake action to work and I'd worry there might not be enough play for that to work right. But I guess your experience says otherwise. I still think 7-9 is good for normal use.

OP: I agree, take it all off. There really is not much left once you get the shoes off. I throw it all on a cardboard beer flat and spray clean the heck out of everything, as well as the backing plate. Then re-lube as appropriate.

 

[jhumphrey]

Thanks, guys. I ordered a new MC today and will report back on whether or not that did the trick. I plan to change the rear shoes soon (they probably need it...). Hopefully the MC will do the trick (hopefully its not the brake booster, since they are crazy expensive).

 

[Mynameistommy510]

Thanks, guys. I ordered a new MC today and will report back on whether or not that did the trick. I plan to change the rear shoes soon (they probably need it...). Hopefully the MC will do the trick (hopefully its not the brake booster, since they are crazy expensive).

My booster failed in the past. The brake was only good for one depression to a stop. Pumping the brakes multiple times then trying the stop was nearly impossible. I could hear air surging out of the booster when pushing down the brake pedal.

 

[jhumphrey]

My booster failed in the past. The brake was only good for one depression to a stop. Pumping the brakes multiple times then trying the stop was nearly impossible. I could hear air surging out of the booster when pushing down the brake pedal.

I'm not hearing anything like that. Guess I'll know by next weekend when I put the new MC on...

 

[jhumphrey]

My MC came today. I was looking it over, seems pretty straight forward. It came with some hose/nipples and instructions on bleeding it. The instructions show it being bled prior to "normal" bleeding. Is that right or do you fill it up and start the standard bleeding procedure?

 

[nevada]

My MC came today. I was looking it over, seems pretty straight forward. It came with some hose/nipples and instructions on bleeding it. The instructions show it being bled prior to "normal" bleeding. Is that right or do you fill it up and start the standard bleeding procedure?

yes, bleed it prior. its called bench bleeding.

you will hate life if you put it on without bleeding it.

 

[jhumphrey]

yes, bleed it prior. its called bench bleeding.

you will hate life if you put it on without bleeding it.

Thanks. I was looking up how to bench bleed and have a question: how can you do it without a vice? I simply dont have one in my garage. I do have the MC bleeding tool (looks like a big syringe made by cardone).

 

[Mynameistommy510]

Thanks. I was looking up how to bench bleed and have a question: how can you do it without a vice? I simply dont have one in my garage. I do have the MC bleeding tool (looks like a big syringe made by cardone).

Put a good amount of brake fluid in the master cylinder not to make a mess. Run a clear line from the feed fluid hole on the side of the cylinder into the top and into the fluid. I was able to hold the master cylinder in one hand and use the butt of a screw driver to actuate the piston. It's recommended not to actuate the piston much further than an inch.

 

[nevada]

Thanks. I was looking up how to bench bleed and have a question: how can you do it without a vice? I simply dont have one in my garage. I do have the MC bleeding tool (looks like a big syringe made by cardone).

I suppose you CAN bolt it in place, just don't hook up the lines. then with a helper to push the pedal, you can bleed it.

just route the bleeder lines from the ports, back into the reservoir, and pump until there is no more air. don't pump fast, go nice and slow, you don't want to aerate the fluid. it will take MUCH longer to get the air out if that happens.

Put a good amount of brake fluid in the master cylinder not to make a mess. Run a clear line from the feed fluid hole on the side of the cylinder into the top and into the fluid. I was able to hold the master cylinder in one hand and use the butt of a screw driver to actuate the piston. It's recommended not to actuate the piston much further than an inch.

this is possible, but probably somewhat messy.