BMW caliper frustration, They're not squeezing Options

[Carlitos Way]

So, I installed a "rebuilt" set of 320i calipers that bought on evilbay. They had already been machined to take care of the clearance. Bolted them right up, went to bleed the system... and all of a sudden I find out that the pads are not squeezing together. There's fluid coming into the caliper, since I can bleed them... but the brake pedal is not getting any harder... and I'm not seeing that the pads are getting anywhere.

I'm guessing the calipers might have one of two problems. Either lack of lubrication from sitting around for a few weeks, or paint has dried on them (they were painted when I bought them).

Anybody got a suggestion to make 'em squeeze? Am I SOL with these?

Thanks,

Carlos

[MartyYeoman]

Take'em off.
Pop them open.
See what's wrong.

They are very straight forward to work on.
Don't take chances with an "on car" fiix.

[Aaron Cox]

you have a new MC right? new calipers and a new MC take forever to bleed!

i replaced to calipers and it took me 6gts of brake fluid to chase all the bubbles out. try tapping on the MC and the calipers with a rubber mallet. chase some airbubbles out...

pedal will NOT get hard until all bubbles are gone....

Keep bleeding...youll get it! (IMG:style_emoticons/default/beerchug.gif)

[Carlitos Way]

I didn't install a new MC (I decided to let a shop do this). So, I was hopnig to get enough fluid pressure to get the car to the shop, but I haven't been able to get them to move.

Would air in the line prevent the pads from moving AT ALL?

I mean, they are not moving... as if the caliper was frozen.

[Aaron Cox]

hmmm.... depends on how much air you got going on......

keep bleeding and report back (IMG:style_emoticons/default/flag.gif)

how long have you been bleeding? lots of bubbles come out?

[Eric_Shea]

A little air in the line shouldn't prevent them from moving. The difference is air compresses, fluid does not. Sounds like you have a "lot" of air somewhere compressing hence, making your pedal "not get any harder" and your pistons not move.

Also, no amount of paint should stop a piston from moving if it wants to. Rust or corrosion inside the cylinder is another story. They may have rusted while sitting.

If'n it was me? I'd bleed and bleed again. Go with A-a-ron's advice. (cause your pedal isn't getting any harder.) Have a partner and have them "SLAM" the brakes. Now... if after you beeld them again and you get a firm pedal and you still can't get those pistons to move then yank them like Marty recommends.

Soft pedal = air, not frozen pistons, especially if you're getting clean fluid up there.

[lapuwali]

Do gravity bleed: take a section of clear tubing, attach it to the bleeder screw, dangle it over the fender and into the open trunk. Put the end in a bottle if you're paranoid. Remove the cap from the reservior. Fill the reservoir completely. Open the bleeder. Put a board or brick or something on the brake pedal to hold it to the floor. Wait for awhile. If you watch, you'll see fluid rise slowly in the tube. After a bit, you should see some bubbles in the tube. You may also see bubbles in the MC reservoir. The fluid in the tube will stop rising once it reaches the level in the reservoir. Add fluid as necessary. Close the bleeder and repeat on the other caliper.

It would be best to do this AFTER you replace the MC. Replacing this really isn't that hard, it's just a knuckle buster.

If the gravity bleed method doesn't get you some brakes, with at least a medium pedal (not firm, not squishy), then there's something wrong with the calipers or the MC. The calipers may be frozen.

[Carlitos Way]

I'd say I've bled through about 1/4 of the "large" bottle... roughly 2-3 refills of the reservoir so far. but I should have had SOME pressure already building up, don't you think?

[Aaron Cox]

I'd say I've bled through about 1/4 of the "large" bottle... roughly 2-3 refills of the reservoir so far. but I should have had SOME pressure already building up, don't you think?

NOPE!

like i said... took me more than 4 qts to get all the air out of 2 M calipers!

[joea9146]

Are the Bleeders oriented to the top of the Caliper ???

[Eric_Shea]

but I should have had SOME pressure already building up, don't you think?

(IMG:style_emoticons/default/agree.gif) with A-a-a-a-a-ron.

NOPE. You'z got some bleed'n to do.

[Aaron Cox]

(IMG:style_emoticons/default/agree.gif) with A-a-a-a-a-ron.

who???? (IMG:style_emoticons/default/biggrin.gif)

[Type 4 Unleashed]

Start at the passenger rear tire, the farest point from the master cylinder, have some body pump the pedal 6,7,8 times hold it, open the bleeder then close the bleeder, repeat this procedure untill you start getting some fluid, move to driver side rear tire, repeat prcedure, move to passenger front tire, repeat procedure, next driver side. Repeat intire procedure, the pasenger side rear, driver side rear, passenger side front, drivers side front, untill no more air bubbles. Some brake systems decide they don't want to be bled. are you going to let this brake system win?

And if that doesn't work, you could allways beat it till it bleeds (IMG:style_emoticons/default/headbang.gif)

Richard

[Dr Evil]

Do you still have the proportioning valve installed in the engine bay? If it is, there is your problem. You need to scrap it and get a "T" fitting.

[Ctrout]

Had a similar problem with mine when I first got it and was trying to get it road-worthy. I bled the system like 4 times and it never got any better. Finally found that one of the main seals inside of the MC had let go. This was in a NOS ATE MC that I had just installed. So my question is, did you ever have good brakes after your MC was replaced? Or did the problem just start when you swapped calipers?

[Eric_Shea]

(Eric answering for Carlos) He hasn't replaced the MC yet.

What's the weather like up there? We had nearly 60 down here yesterday. December 10th driving day! (IMG:style_emoticons/default/driving.gif)

[Carlitos Way]

(Eric answering for Carlos) He hasn't replaced the MC yet.

What's the weather like up there? We had nearly 60 down here yesterday. December 10th driving day! (IMG:style_emoticons/default/driving.gif)

Eric is right. I dediced to save the knuckles and spend the bucks to have a shop replace them. I also decided to let them replace the rear brake hoses, as I couldn't figure out a way to take them out without twisting the original steel line.

So... as the score goes...

Tried all the bleeding procedures... Even went out and bought a vacuum pump. It seemed to work at first... until I accidentally over purged.. and had to start all over again...

Now, after doing it two more times, 2 more quarts, thinking air in the rears was part of the problem, I found out All I'm getting out of the right rear caliper is AIR... maybe 5% fluid..

This is also the hose that I had a hard time replacing.. so I don't know if I left something lose, or if it's just leaking THAT BAD.

I guess I'll spend my morning at AAA getting a membership and have the car towed to the shop first thing Monday morning...

I really wanted to make the fun run today... but... it's kinda hard to do that without brakes.

As far as the weather, it's beautiful.. about 75 or so out here... sunny and warm...

I guess I better get back to the other projects I CAN do in the car.

Thanks for your help!

C.

[Ctrout]

Weather here was great the other day. Went pheasant hunting in a tee shirt. Looking forward to driving the teener all winter although it has been a bit ranier than usual for the past couple weeks. BTW, where is Sandy?

[Aaron Cox]

carlos,

try bleeding right rear first, the left rear, then right front, then left front. Bleed each caliper until thry have no bubbles... you will go through MORE than 2 qts....


to bad you didnt make the fun run today, next time (IMG:style_emoticons/default/wink.gif)

[Tim in MD]

You can also potentially blow out the seals in your MC if it's tired and if you really vent some anger on it while attempting to bleed. I did this to my '78 F-150 (rusty parts hauler) recently and wound up messing up the MC to the point that no fluid was getting to the rear circuit, thus making it seem like I wasn't making any progress on the bleeding process. I used full but gentle compression of the brake pedal to bleed after installing the new MC and that worked fine.

Just another thought for consideration. I do agree with previous posts that air can be maddening to get out of the system after replacing calipers. I'm currently battling that on my '76 BMW 2002.

Tim