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-   -   Lost Power brakes! Many other symptoms-HELP! (

Leon Hernandez 05-19-2000 01:19 AM

Hi folks, thanks for all the past help, hope this request is an easy one.
One of many symptoms, xmsn started to shift hard (more than usual), then the Climate control would route all the cold air thru the defrost vents and the defrost mode sent the air thru the center vents. Momentarily, when switching from defrost to normal the air would route thru the center vents(thinking cool!I can live with it) but then it would switch to the defrost vents!
Then on our trip home I stepped on the brakes and the car "felt" like it took off! No power brakes Yikes! We dropped off our grandson and parked the 85 300SD Turbo in the garage and turned the ignition off and yes it just kept chugging! But at least now I know the manual shutoff works!
My MB tech in Houston was chasing the shifting problem but said it would be about 3 hours because they had gotten into rabbit trails with the EGR. So I put it off due to time issues and left with fresh valve adjustments and a peppy car until now. So seasoned doctors of MB woes any clues? I'm thinking the vacuum pump bit the dust and performace Products has a rebuild kit for about 55 bucks or so. If that's it is it a hard task for a avg. shade tree tech? IF that's not it any other ideas? Apologize for the long thread and Thank all of you folks for making this a great source of help for many of us rookie MB owners. God Bless. LH

LarryBible 05-19-2000 08:24 AM


Don't rebuild or replace the pump until you're sure that's your problem. With every thing vacuam operated on the car failing as it is, it may be your problem. To check it, you can disconnect the connector at the pump, connect a vacuam guage and start it up.
If you have vacuam at the pump, then start moving upstream until you find the leak.

Good luck,

Larry Bible
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

stevebfl 05-19-2000 07:14 PM

The way you describe your symtoms, it saounds like the vacuum pump or vacuum pump check valve has failed. The check valve is in the fitting, screwed into the pump. It is what the big vacuum line screws to. If you pull the vacuum supply hose off and can see through the fitting the valve is inside the pump. The valve is MB# 004 997 18 72 and costs MB list $21.50.

If the guts are missing you should also remove the front cover to search for them.

Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Leon Hernandez 05-20-2000 08:59 AM

Thanks for the advice. Removed the pump and found the roller has the mounting pin worn and the boss had rubed into the cam that actuates the pump (still mounted on the enginegear assy.) So-o-o got a new pump on order from the guys a the Benz-Bin on the way. The tip on the check valve is a another 'new' one for me thanks for that one! I just got my MB CD_ROM and did not find the vacuum pump R&R in there so thanks again. Once again this site continues to prove what a great forum it is. Good hobby, great cars and good folks, appreciate all that you all do taking the the time out to help us rookies and all alike! God bless LH

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