master cylinder replacement; how much does brand matter? - PeachParts Mercedes-Benz Forum

blueDuchess · #1 07-09-2011, 10:47 PM

'84 300TD turbo, learning how to do the break job today, finished the whole shebang in the rear and then went to bleed front R...endless froth from air.

friend's husband is helping me, he's got quite a lot of experience with mechanics but not tons with Mercedes. he ultimately gave in to being mystified at where all the air could be coming from unless it's a leak in the MC seals following the work on the rear. is that common? we kept the reservoir >50% full at all times during the job.

anyways, they had to get somewhere tonight and he instructed me to pick up a new MC so we could install it tomorrow. have called around and the only one I can get here in town is a Fenco but I see here that the shop only has the ATE and I searched the old threads and saw a posting that stated that a mechanic called Fenco parts "junk" and wouldn't install them.

would like to get this taken care of tomorrow, but it would be possible to sit on it if ordering the ATE is really what we should do. many preemptive thanks for any experience or thoughts y'all might have on this...

timc · #2 07-10-2011, 12:25 AM

Personal opinion, i'd lean towards ATE for this. Some of the others are a gamble. Some things I gamble on, from a bad experience, brakes and cooling system parts I do not.

Stretch · #3 07-10-2011, 01:45 AM

Hi blueDuchess welcome to the forum.

I agree with timc that ATE were good - however, I have recently bought new ATE callipers and found the quality of the castings to be much worse than the old ones. I conclude that quality ain't what it used to be. Click on buy parts above and compare the price of the locally sourced part with the ones for sale here - this will at least give you an idea of value for money.

As for bubbles coming out whilst bleeding:-

BEFORE you change the master cylinder (MC) I'd look at the quality of the flexible hoses - if they look like they've been on there for some time - change them first. Cheaper than a MC.

Secondly get a pressure bleeder - the "end up in the air" configuration of the MC on these cars can sometimes (well often!) cause problems.

So before spending money on a MC I vote for new hoses and a pressure bleeder first.

EDIT:-

I forgot to say - the factory service manual (FSM) says you need to pump the brake pedal during bleeding to help disperse air bubbles

Ferdman · #4 07-10-2011, 06:05 AM

blueDuchess, it's critical to keep both chambers of the master cylinder filled with brake fluid throughout the bleeding process. A pressure bleeder makes it easier to ensure that happens. Regardless, the proper bleeding sequence is RR, LR, RF, LF.

With the 2-person bleed methog the bleeder fitting should be closed on the down stroke of the brake pedal. The clear tubing attached to the bleeder fitting should discharge below the brake fluid level in the bleeder cup to prevent air from being sucked back into the brake system. A pressure bleeder eliminates that possibility.

porkface · #5 07-10-2011, 12:23 PM

afaik fenco is a rebuilder out of canada. didn't know they were doing new and i wouldn't put anything but new ate on the car, anyways. good luck, chuck.

blueDuchess · #6 07-10-2011, 02:13 PM

thanks to each of you. looks like the only thing missing is the pressure bleeder. new hoses were installed & the bleeding system done as directed. so, we'll give it a whirl.

grateful to have found this community...

connerm · #7 07-12-2011, 09:12 PM

search writeups on how to bench bleed your new master cylinder. You really can't skip this step. I did mine with some cheap vinyl tubing.

Stretch · #8 07-13-2011, 01:04 AM

Quote:

Originally Posted by connerm

search writeups on how to bench bleed your new master cylinder. You really can't skip this step. I did mine with some cheap vinyl tubing.

This seems to be purely an American thing. The FSM doesn't say you need to do this. I think it is a throw back to servicing older and different American cars (may be to check the integrity of the seals before you fit it to the car?).

I don't want to start WW3 about this but I don't think it is necessary if you use a power bleeder and follow the procedure in the FSM. I'm sure it won't hurt if you want to do this before hand though. But as you then have to disconnect the MC and reconnect it to the car's system you need to bleed it again anyway as you've introduced air to the internals (again). It seems like a redundant step to me.

rs899 · #9 07-13-2011, 08:28 PM

What they all said.Fenco is a rebuilder, so it's probably a rebuilt old Ate (not bad). Bench bleed- that's your problem with the old one. And get or make a pressure bleeder.

pawoSD · #10 07-13-2011, 09:17 PM

For master cylinder I'd go with a German Made OEM only. No rebuilds or china junk. Then again, I use only the best parts for most everything.

Ferdman · #11 07-14-2011, 05:34 AM

MB dealers sell reconditioned water pumps. You may want to ask if your local MB dealer sells reconditioned master cylinders because that may be more cost effective.