Changing Brake Calipers

[RichardLSU]

I just replaced the brake calipers and pads on my 85' 300SD yesterday. I went to bleed the brake system by loosening the bleeder nozzle/nipple on my caliper and when i was satisfied that it was only spirting fluid out I went to re-tighten it back up the damn thing snapped off.

I took my caliper to a local machine shop to have them drill the bleeder valve, and back it out of the caliper for me and I replaced it with one from one of my old calipers. Fits just fine.

So, here is the problem; when I first removed the caliper my hose was dripping brake fluid like crazy, and the bleeding process worked fine (until I broke the nozzle). When I removed the caliper the second time the line was still leaking fluid but when I came back from the machine shop it wasn't dripping any fluid at all. I put everything back together and tried to bleed the brakes again but this time absolutely no fluid is coming out. Whenever someone presses the brake pedal I can hear a small rush of air coming out but no matter how long we repeat the process (loosen nozzle, press pedal, tighten nozzle, release pedal, loosen nozzle, etc...) no fluid would come out. I tried it with the reservoir cap off and on and still can't get anything to come out of there.

I noticed that the little black rubber caps (if thats what they are) on top of my reservoir are cracked, would that have anything to do with it? Everything was fine until I got back from the machine shop so I'd imagine they've been cracked for some time now.

Also, I had to make a run to the store before I bled my brakes and after I replaced the calipers and added some more fluid to get me there and back, did I bust my brake booster?

I'm completely at a loss of where to go from here. Right now I've removed the reservoir cap and loosened the bleeder valve to see if after a while the fluid will start to come out on its own.

Please help!!!

Thanks.

[lutzTD]

Originally Posted by RichardLSU

I just replaced the brake calipers and pads on my 85' 300SD yesterday. I went to bleed the brake system by loosening the bleeder nozzle/nipple on my caliper and when i was satisfied that it was only spirting fluid out I went to re-tighten it back up the damn thing snapped off.

I took my caliper to a local machine shop to have them drill the bleeder valve, and back it out of the caliper for me and I replaced it with one from one of my old calipers. Fits just fine.

So, here is the problem; when I first removed the caliper my hose was dripping brake fluid like crazy, and the bleeding process worked fine (until I broke the nozzle). When I removed the caliper the second time the line was still leaking fluid but when I came back from the machine shop it wasn't dripping any fluid at all. I put everything back together and tried to bleed the brakes again but this time absolutely no fluid is coming out. Whenever someone presses the brake pedal I can hear a small rush of air coming out but no matter how long we repeat the process (loosen nozzle, press pedal, tighten nozzle, release pedal, loosen nozzle, etc...) no fluid would come out. I tried it with the reservoir cap off and on and still can't get anything to come out of there.

I noticed that the little black rubber caps (if thats what they are) on top of my reservoir are cracked, would that have anything to do with it? Everything was fine until I got back from the machine shop so I'd imagine they've been cracked for some time now.

Also, I had to make a run to the store before I bled my brakes and after I replaced the calipers and added some more fluid to get me there and back, did I bust my brake booster?

I'm completely at a loss of where to go from here. Right now I've removed the reservoir cap and loosened the bleeder valve to see if after a while the fluid will start to come out on its own.

Please help!!!

Thanks.

sounds like you ran your master cylinder reservior dry. you might need to bleed the master cylinder. You can get a master cylinder bleed kit from NAPA for around $5. all it is is a couple of plastic fittings that fit in the brake line ports and some clear line. you put the clear line from the fitting into the reservoir and pump the brakes until you get no bubbles, then re-attach your brake line and bleed the caliper agian. while you are at NAPA they also have one man bleeders. its a little plastc cup with a lid and some clear line again about $5. all you do is attach it to the bleed screw and leave the bleed screw just cracked. then you pump the brake for a while until the fluid is clean and no bubbles in the clear line.

[RichardLSU]

Thanks for the tip.

Yeah, when I pump my brakes (with everything fastened securely) I don't feel any resistance from my pedal. It just keeps dropping strait to the floor.

The reservoir is still full though. Over-full actually.

I'll get a ride over to NAPA right now and see what they have to say about a Brake Booster bleed kit.

Do I need a line-wrench to take that off with or can I just use a regular wrench?

[vstech]

you might also want to build yourself a powerbleeder.
basically it's a garden sprayer full of brake fluid screwed into a spare reservoir cap. open up a bleed screw, and pump up the sprayer. bleeds the MC and all lines perfectly.

[Cr from Texas]

[quote=RichardLSU;1776253]

(loosen nozzle, press pedal, tighten nozzle, release pedal, loosen nozzle, etc...)

I was taught the sequence was (press pedal, loosen nozzle, tighten nozzle, release pedal).

Make a difference?

[rrgrassi]

CR, you are correct, however, the older system will actually gravity bleed itself. You can also use the miti vac brake bleeder attachment as well. It also helps to raise the rear end of the car so that the front calipers are at the lowest point.

The power bleeder that Toomany MB is refering to works like a champ, or so I have read.

[tangofox007]

Originally Posted by lutzTD

sounds like you ran your master cylinder reservior dry.

An easy way to prevent that from happening is to place a piece of Saran Wrap over the reservoir opening, then reinstall the cap. That prevents the vent in the cap from allowing air into the reservoir, so you won't loose much brake fluid while the caliper hose is detached.

[lutzTD]

Originally Posted by tangofox007

An easy way to prevent that from happening is to place a piece of Saran Wrap over the reservoir opening, then reinstall the cap. That prevents the vent in the cap from allowing air into the reservoir, so you won't loose much brake fluid while the caliper hose is detached.

great tip.... I lost the fluid in mine waiting for calipers from Advance to show up.

[RichardLSU]

[quote=Cr from Texas;1776454]

Originally Posted by RichardLSU

(loosen nozzle, press pedal, tighten nozzle, release pedal, loosen nozzle, etc...)

I was taught the sequence was (press pedal, loosen nozzle, tighten nozzle, release pedal).

Make a difference?

I see how your method would work, using the built up pressure to release the brake fluid upon loosening the bleeder valve. However, I was using my method and it was working just fine. Just make sure you tighten the bleeder valve before your helper lets off the brake pedal, otherwise your just sucking air back into the system.

I tracked down those two kits from NAPA today and bought a set of line-wrenches to tackle the brake booster tomorrow. Thanks for the tip, I love those little things I can throw in my toolbox to make life easier.

[RichardLSU]

Originally Posted by vstech

you might also want to build yourself a powerbleeder.
basically it's a garden sprayer full of brake fluid screwed into a spare reservoir cap. open up a bleed screw, and pump up the sprayer. bleeds the MC and all lines perfectly.

Could you elaborate on what kind of garden sprayer? I'd LOVE to make one of those.

[RichardLSU]

Originally Posted by rrgrassi

CR, you are correct, however, the older system will actually gravity bleed itself. You can also use the miti vac brake bleeder attachment as well. It also helps to raise the rear end of the car so that the front calipers are at the lowest point.

The power bleeder that Toomany MB is refering to works like a champ, or so I have read.

I tried that "gravity bleed" method. I removed the reservoir cap (to relieve pressure and loosened the bleeder valve and left it to its own devices for a few hours and when I came back the bleeder valve was dry as when I loosened it.

[mobetta]

heres my homemade power bleeder-
do a search, there are more...

the only way to bleed a mercedes.

[barry123400]

Your tightning the bleeder screw and then pressing the pedal is not much better than a gravilty bleed.. Not very productive in many cases in my opinion. You only temporaily compress the air in the system. Then when you loosen the bleeder screw with the pedal up gravity feed is restored.
You want the pressure built up in the master cylinder to flush the brake fluid down the line to drive the air ahead of it. In your case to fill the new calipers internal space as well.
You are not alone as we all manage to do something odd at one time or another. This is just one of them I had not heard of before. Allow I have led a sheltered life though.
A good additional hint is to always make sure the bleeder is at the top of the caliper piston area. In theory and actual practice you can put the opposite side caliper on a car. This can result in a lower position of the bleed screw. Then you will always be compressiong air in that pocket. It has no way out other than absorption into the fluid over time. That may or may not ever happen.

[mobetta]

I did gravity bleed my 85 chevy school bus once, after replacing 25 feet of brake line to the rear axle- just cracked the bleeders and made sure the MC was full for about 7 hours. worked pretty darn good.

[tjohn]

There's also a nice power bleeder called the Motive power bleeder (no affiliation). I got mine for $40 delivered, YMMV. Had it for about 4 years, and I'd never bleed brakes any other way. The homemade version is the same concept, but this was cheap enough that I was lazy.