Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help

Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Diesel Discussion

LinkBack Thread Tools Display Modes
Old 12-28-2009, 04:19 PM
Registered User
Join Date: Feb 2007
Posts: 181
Brake fluid leaking around bleed screw threads when screw loosened

I was recently using my Power Bleeder to flush the braking system on our '85 300CD-T (123.153) and got to wondering:

Is it typical and the-way-things-are-supposed-to-be that upon loosening a brake bleed screw, that fluid leaks from around the screw threads?

I am loosening the screw just a bit - enough to get a small stream that puts out 8 oz. of fluid in like, say, 2-3 minutes. Hardly loose at all.

This leaking from around the threads happens on the ATE calipers in the rear and the Bendix (ack!) calipers in the front.

Anyone have any insight on whether this leaking is right or not and if not, what to do about it?


Reply With Quote
Old 12-28-2009, 04:37 PM
Registered User
Join Date: Sep 2004
Posts: 8,730
Originally Posted by dogguy View Post
Anyone have any insight on whether this leaking is right or not and if not, what to do about it?
It might not be "right" in theory, but it is quite common in practice.
Reply With Quote
Old 12-28-2009, 04:41 PM
RML RML is offline
Out of Garage Space
Join Date: Jun 2006
Location: Southwest PA
Posts: 1,024
Hmmm. I believe when I was bleeding my brakes I got some fluid coming out through the threads and did not think anything of it. It makes sense to me that some fluid would come through as there is a gap once you loosen the bleeder screw. I wiped everything off as I moved from wheel to wheel.

If you are concerned, take another look after you have bled all four wheels and see if there is any fluid after you press on the brake pedal real hard, and after you have wiped everything down with brake cleaner.
85 300D 72K Anthracite Grey (Rutherford) 0-60 in 13 seconds
84 300D 331K Black (Rufus) 0-60 in 14 seconds (adjusted the ALDA)
00 Toyota Sienna 208K (Sold)
15 Subaru Outback 22K
98 Ford Taurus 62K (Gertie - Was Grandma's - drove it to church and shopping - really) Daughter's car now.
30 Model A Ford 2 Door Sedan (Sold) 0-60 in . . . Never reached 60
Reply With Quote
Old 12-28-2009, 11:18 PM
Registered User
Join Date: Jan 2007
Posts: 21
The threads don't form the seal, even when tight. The seal when you tighten the valve occurs at the conical tip of the screw against the hole in the caliper or cylinder.
I've wrapped Teflon tape around the threads of bleeder screws which helps keep them from leaking, but I've done this mainly to prevent them from seizing up from rust after a few years of sitting around. And no, it doesn't make them come loose on their own.
Reply With Quote
Old 12-30-2009, 12:28 PM
Registered User
Join Date: Feb 2007
Posts: 181
Thanks for the responses to my question. Sounds like some leaking is to be expected given the design of the screw and caliper. I just think that brake fluid is nasty stuff and don't much care for getting it anywhere it doesn't have to be. I appreciate the help.

Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

All times are GMT -4. The time now is 04:06 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page