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  #1  
Old 03-19-2000, 08:57 PM
Deezel
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I was changing the brake fluid in my 87 300TDT (for the first time) and ran into trouble. I have bled brakes plenty of times before, but this has me confused. I bled the front calipers with my wife's help, no problem, but when I moved to the back, it seemed to be pumping air. I never got below min on the reservoir either! I applied a little air pressure (regulated at 20 psi) to the resevoir to try a make shift pressure bleeder, but it didn't do any better. I also disconnected the rear brake line right at the master cylinder and blew into the reservoir, and despite being full, it only gurgles, not a stream of fluid, came out the line.

This car has what appears to be an ABS system, not ASR. I also looked in the Mtc CD and I do not have the "y61" switch on the master cylinder and the ABS controller has "ABS" on it ( a Bosch unit I think).

I either tore up the seals in the Master Cylinder during the bleeding or I'm doing something wrong. Even if the seals went bad, I would think blowing into the reservoir would provide a steady stream of fluid at master cylinder exit port.

The CD does not seem to give any special requirements for bleeding the ABS brakes, only ASR.

I'm mad, my wife is mad, the dog is in hiding, any comments?

------------------
Deezel
87 300TDT
150,000 miles

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  #2  
Old 03-20-2000, 12:00 AM
Aaron's Avatar
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Join Date: Aug 1999
Location: Cincinnati, Ohio
Posts: 1,935

Were you drawing the fluid through the system of forcing new fluid in and pushing the old out? With ABS, it's important not to bleed the brakes using conventional methods (i.e. vacuum brake bleeder). The old fluid must be forced out rather than sucked out through the lines. When I worked at the dealer, they told us that the brakes had to be bled that way, and to be honest with you guys, I'm not exactly sure why. Anyhow, just my (and MB's) $0.02


------------------
Rgds,
Aaron Greenberg
MB technician
Precision Motorcars, Cincinnati, Ohio
'67 250SE Cabriolet
'77 450SL
'80 300SD
'85 380SE
'89 420SEL
'93 300E 2.8
'74 Jensen Interceptor Mk.III
'81 DeLorean DMC12
'85 BMW 745i Turbo
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  #3  
Old 03-20-2000, 01:20 AM
Mike Murrell's Avatar
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You might consider something like a "Speedi Bleed"...a $100.00 pressure bleeder. I've used it on my '91 300-SEL with great success.
Also try bleeding the right rear, then left rear, followed by right front; then left front. I've had no success bleeding modern vehicles using the old "2 man" method. The parts connection on this site may sell them.

Regards....Mike Murrell
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  #4  
Old 03-20-2000, 09:49 PM
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Join Date: Jun 1999
Location: Los Angeles, Calif, USA
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Deezel

It is likely that the rear compartment of the reservoir is empty. It is hard to see the fluid level of the rear compartment. There should be a small pin hole on top of the front compartment letting brake fluid to the rear. If what I think is true, you need to fill the reservoir all the way to the top so that the brake fluid can go to the rear compartment. Be sure the pin hole is not clogged. You were pumping the master cylinder dry for a while, I hope it is still okay. You should be able to use 2-man method to bleed the system without problems.

David

[This message has been edited by be459 (edited 03-20-2000).]
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  #5  
Old 03-21-2000, 12:12 AM
Deezel
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David,

You are the man!!! I think you steered me in the right direction. I removed the reservoir and confirmed that the back compartment is nearly impossible to determine the fullness. It does fill very slowly, so I will work on the transfer passage tomorrow in better light and attitude. I also removed the master cylinder as well and put the reservoir back on to cycle it manually. Seems like the first full pumps suck it dry followed by air and the small amount of fluid that back fills the campartment. Exactly what I was mysteriously seeing at the back caliper.

Concerning pressure bleeding, I was going to pick up an extra reservoir cap and mount a tire stem in it and then attach my kids bicycle pump to it. It has a gage and everything! It sure beats a $100 store bought unit that won't even pump up a tire! I'll let you all know how it turns out!

David, thanks for the comments on the trap oxidizer. I agree, but when Benzmac said they always replace the turbo, I had to ask! I guess he was referring to failed units.

Best Regards,

------------------
Deezel
87 300TDT
150,000 miles

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  #6  
Old 03-21-2000, 01:16 AM
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Join Date: Jun 1999
Location: Los Angeles, Calif, USA
Posts: 521
Deeze,

I am glad that helps. One more thing, use Dot 4 fluid. I was told not to use synthetic brake fluid but I do not know the reasons. I found non-synthetic Dot 4 at Pep Boys.

Regarding the trap oxidizer, I looked at about 7 1987 300D's in the past 2 years and they all had the turbo replaced due to the final recall.

David

[This message has been edited by be459 (edited 03-21-2000).]
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  #7  
Old 03-22-2000, 07:03 PM
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Join Date: Mar 1999
Location: Williamsburg,VA, USA
Posts: 106
I also read a BMW page. Brake bleeders come up every couple of months. This is a parts list a DIY model. Gets rave reveiws, haven't built one yet but it's on the short list.

ACE 1/2 gallon pump ump sprayer #74497 $10
> GM Master Cylinder Cap (says you can use HELP! # 42035 w/ RTV in the groove $5
> underneath)
> 1/4" hose fitting with threaded base, associated nut, and a washer for the
> top. $3
> Six feet of 1/4" I.D. poly hose.
>
> Proper pressure=15-20 psi, $3 pressure gauge at ACE
>
> Says to put the hose fitting in the mc cap, whose underside groove you have
> filled with RTV, then connect hose to sprayer bottle, fill w/ 1-2L brake
> fluid, voila.
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  #8  
Old 03-26-2000, 02:36 PM
Deezel
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Well, my wife and I made up and the dog is basking in the sunshine as every #@%*& cat in the neighborhood walks right by him to eat his dogfood!

With David's (be459) pointer about the rear reservoir chamber, I successfully bled the brakes using the old two man mehtod, being very careful to keep both chambers topped. The pressure brake bleeder looked good, but I don't have enough activity to justify it when the old standard works.

Thanx David and I hope my occasional comments pay my debt to this BB.

------------------
Deezel
87 300TDT
150,000 miles

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  #9  
Old 05-12-2000, 10:16 AM
BocaBenzs
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My 1987 16 valve is giving my mechanic the same problem described in first post...with brand new master cylinder...rear resevoir HAS brake fluid...any other sugestions?
Thanks...
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  #10  
Old 05-12-2000, 07:57 PM
BocaBenzs
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Already solved...
Bled the brakes with engine running...worked perfectly...never had to do that with a mercedes before...any explanations?
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  #11  
Old 05-12-2000, 11:09 PM
Deezel
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No explanation from me! After struggling with this for an evening and then putting the post in, I removed the Master cylender for investigation. I did make sure that the reservoir was completly filled by tipping the whole assembly to get the fluid to transfer between chambers prior to installing the unit. After that I bled it with the engine off no problems, but I was extra cautious to monitor the level as I bled it.

------------------
Deezel
87 300TDT
150,000 miles

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  #12  
Old 05-13-2000, 10:30 PM
MikeTangas's Avatar
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Join Date: Apr 2000
Location: So. Cal
Posts: 4,430
Deezel,

I see you've solved your problem, but for future reference you might want to try gravity bleeding (especially good when working alone). Just start at the right rear and crack open the bleeder valve, let the fluid run, be sure to keep topping off the resevoir. Once you are satisfied all air / old fluid has run, close the valve, top off and move to left rear. Repeat. It takes a while, but seems to work OK, I even had to use this method to bleed a clutch once because pumping it produced zero results.

Also, some feller working on his fan clutch is in dire need of a safety speech.

Take care.

------------------
Mike Tangas
73 280 SEL 4.5

[This message has been edited by MikeTangas (edited 05-13-2000).]
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