Caliper Replacement-Bleeding help! - PeachParts Mercedes-Benz Forum

356nen · #1 01-28-2007, 01:22 AM

Hey Guys,
last week I posted a question about replacing or rebuilding my calipers on my 83 300D. From several old post people recommended just buying rebuilt calipers form Autozone. Here what happened to me and some general observations.

1. Bought calipers from Autozone for 72 dollars each. When I went to install the calipers I dicovered that the brake hose would not thread. I even took the hose off to thread it on a bench and it still would not thread. Dicovered that the female thread on both calipers were bad. The hose would not thread, took them back and got money back.

2. I then bought a set of calipers from an independent auto store and these were great. They even came with all the pins, springs, cotter pins, and bleed nipples covers. The Autozone set had none of these things. I paid 75 buck for them each. When I went to bleed the system I discovered that one of the calipers would not bleed. Found out that on bleed nipple was missing the little hole at the bottom. Had to go back and pull the old on my used caliper.

3. I tried to bleed the system doing it the old way by having my wife pump the brakes while I opened the bleed valve. It did not work very well.

4.So, this morning I built one of the pressure bleeder using a ong-gallon pesticide container and pump. I had my dad help me and the bleeder work good, right away I got firmness in the pedal. I go around and do all for wheels.

So, when I backed the car out for a test run, I had no brake force. The brakes barley slowed the car down. It feels like it is not producing any hydraulic force? Did I break the master cylinder by trying to bleed the brakes the first time and pushing the pedal all the way down to the floor? I have bled brakes before and thought I had done everything correct. The only thing I can think of is that when we were using the pressure bleeder, some times there would be gaps of air in the line as the oil from the tank was running to the resevoir. Could that cause this no force problem? Do I still have air in the system? Well thanks for any help or suggestiong. I not sure how to check the brake boost or master cylinder. Do they need to get bled?

Thanks,
rene

Jeremy5848 · #2 01-28-2007, 02:13 AM

Speaking of bleeding...

Did you change the pads? New pads must be bedded in; when they are new, very little surface actually touches the rotors until the pads and the rotors have rubbed against one another for a few miles of gentle braking.

If the pedal is firm, you do not have air in the lines. Do this experiment: With the engine turned off, pump the brakes until the vacuum in the booster is exhausted. Then put pressure on the brake pedal and hold. Does the brake pedal stay in the same place or does the pedal gradually go down?

If the pedal stays in the same place, you have no leaks. If it gradually goes down, you have a leak. If there are no drips onto the floor, then the leak is internal, i.e., within the master cylinder.

Jeremy

DeliveryValve · #3 01-28-2007, 05:49 PM

There is a possibility that your brake lines might have gunk in them and are clogged from being forced bled. Did you try opening the bleeder screw on each wheel and then press the pedal to see how much fluid is coming out?

Prosecutor · #4 01-28-2007, 10:00 PM

what condition of the brakes caused you to replace the calipers. Do you have the same symptoms as now. If not, you probably still have air in the line somewhere. Good luck

Maki · #5 01-28-2007, 10:41 PM

Here's a mistake I've been guilty of when changing calipers: I put the right one on the left wheel and vice versa. The result was that the bleed screws were positioned at an angle that left a small air pocket in the caliper. The pedal felt mushy while stopped, and wouldn't deliver any braking force.

I swapped the calipers to the correct wheels and they bled out fine.

356nen · #6 01-29-2007, 01:13 AM

Guys,

thanks for the help thus far. I tried the suggestion made and pumped the brake with the motor off to remove the vacuum. After several pumps, the pedal still felt firm.

Yesterday when I did this work, I only backed the car in and out of the drive way because I was late and did not want to chance it not having brakes. Today I took her out for a test drive and it seemed like it was semi-braking. At first the brakes seemed like there might have been a glaze or a break in period. At speed, the brakes did slow the car down but not like before. when I would come to a stop and the car slow down to almost a stop, the brakes felt real weak. They would not stop the car by locking up. You know, like if you are moving, bearly crawling and you stomp on your brakes and the car comes to a complete suddent violent stop. My car would not do that. After driving awhile at stop lights the pedal did seem a little soft.

After the test drive and driving back on my drive way I dicovered that if I stomped on the brakes it would slown down hard but then if I imediately pressed on them again it was soft. Almost like it ran out of vacuum boost after the first stomp?? Could that happen?

The reason I was working on the brakes was to do a routine pad replacement (I only get 10k on front pads). One of the caliper pistons was seized so I decided to replace both.

I think I put the correct caliper on the correct side. Both have the bleed valve on top of the caliper when on the wheel. I was going to try to bleed the system again but I was raining pretty good. I will try there this week. Is there a way of testing a vacuum booster or master cylinder?

Thanks again,
rene

Ara T. · #7 01-29-2007, 05:30 AM

Quote:

Originally Posted by 356nen

Guys,

They would not stop the car by locking up. You know, like if you are moving, bearly crawling and you stomp on your brakes and the car comes to a complete suddent violent stop. My car would not do that. After driving awhile at stop lights the pedal did seem a little soft.

Thanks again,
rene

My car only did that after I installed a new master cylinder. I would go and check the metal brake lines that go into the master cylinder. Last time I changed my calipers out sure enough one of them came loose ( could tell because there was a little bit of brake fluid by the connection). Then go ahead and check the connections to the calipers.

If you think you are not generating enough vacuum after a good stomp on the pedal then the pedal would be hard with not much braking affect, not soft.. sounds kind of like a hydraulic issue, be it a leak in your brake lines or a leak in your master cylinder.

csp97 · #8 01-29-2007, 10:27 AM

I don't believe you mentioned it, but did you replace all 4 calipers or just 2? I replaced the rears only last week, and could not get them bled after several tries. I finally bled decided to bleed the front calipers and that was the problem, had some air in the front lines as well.

356nen · #9 01-30-2007, 11:20 AM

I replace both front calipers and brake pads. I bled all four calipers, starting with the rear passenger side, rear driver side, front passenger and finally the front driver side. I also flushed the system out and the oil coming out of the lines looks a lot cleaner than when I first bled it. The oil was black in the begiing! Now its looks like tea.

rene

vstech · #10 01-30-2007, 11:54 AM

it sounds to me like you got air in the master cylinder. this system will gravity bleed without too much problems. other than the mess in the area. it is possible that the booster was weak, and the pedal to the floor caused it to fail. I would refill the pressure bleeder full and start over, to be sure you got the master cylinder bled. for bleeding the master cyl, you can just bleed the drivers front caliper, it will be the shortest line, put a lot of fluid through the caliper.
John

356nen · #11 02-06-2007, 12:22 PM

Hey Guys,

I resolved my funny brake issue this weekend. I took the suggestion of bleeding the brakes again the old fashion way (pumping the brakes) and it seemed to fix the problem. It had been about two months since I drove the car so I cannot remember how the brakes felt before. The brakes seem fine now but they are not great. They are quiet too. It feels great to be back on the road driving my car. Thanks again for all the help, this site is great.

Rene