W123 front caliper bleed screw size - PeachParts Mercedes-Benz Forum

WD8CDH · #1 10-29-2006, 03:32 PM

Hi,

I am going to rebuild the front ATE calipers on my '85 300D. I want to replace the bleed screws with speedbleed screws. Since it is my only drivable vehicle, I would like to get the right size in advance. Anybody know the size?

Thanks

Stevo · #2 10-29-2006, 06:06 PM

I think I would invest my money in a pressure bleeder and use the old bleed screws, as I remember the wrench size for them is 9mm.

WD8CDH · #3 10-30-2006, 02:01 PM

I would still prefer to replace the old bleed screws. They are rounded off by the PO.

riethoven · #4 10-30-2006, 02:22 PM

I recently tried to rebuild my front calipers, but one piston on each caliper was frozen in the bore of the caliper. Compressed air at 80 PSI didn't do it so I thought a grease gun might. I rigged up a setup using a brass 1/8" pipe to a grease nipple, but 1/8 is not the right size. The brass nipple deformed so the calipers were not ruined. But the pistons still would not come out, so I got rebuilts. They are performing well.

If you have a Metric thread pitch gauge, you can determine the size yourself. If you don't have one, any auto parts store should have one.

WD8CDH · #5 10-30-2006, 02:30 PM

Hi Doug,

Once I have them out, I can easily measure them. The problem is once I have them out, I can't drive to the parts store since the 300D is my only drivable car now.

winmutt · #6 10-30-2006, 02:51 PM

Quote:

Originally Posted by WD8CDH

I would still prefer to replace the old bleed screws. They are rounded off by the PO.

This is why you use flare or box end wrenches. I watched a friend bleed his the other day with vise grip and no jack stand.

I corrected him quickly.

Brian Carlton · #7 10-30-2006, 03:12 PM

Quote:

Originally Posted by riethoven

I recently tried to rebuild my front calipers, but one piston on each caliper was frozen in the bore of the caliper. Compressed air at 80 PSI didn't do it so I thought a grease gun might. I rigged up a setup using a brass 1/8" pipe to a grease nipple, but 1/8 is not the right size.

A little trick when you've got a frozen piston:

Get a proper C-clamp and block on the good piston so that it cannot eject itself.

Connect the brake caliper to the brake hose that is hanging and dripping brake fluid all over the pavement.

Get in vehicle.

Step on brake pedal about 15 times.

Return to caliper and pick up piston off the pavement

Clean up brake fluid all over pavement.

Now, get a proper block and gasket on the large open cylinder and eject the good piston with a bit of compressed air.

dieseldiehard · #8 10-30-2006, 04:10 PM

Quote:

Originally Posted by WD8CDH

Hi,

I am going to rebuild the front ATE calipers on my '85 300D. I want to replace the bleed screws with speedbleed screws. Since it is my only drivable vehicle, I would like to get the right size in advance. Anybody know the size?

Thanks

ATE bleed screws: http://catalog.eautopartscatalog.com/smittys/sa/wizard.jsp?partner=smittys&clientid=sasponline.com&baseurl=http://www.sasponline.com/&cookieid=1FR0YX88J1XL0YN8HJ&year=1985&make=MB&model=300-DT-001&category=N&part=Brake+Bleed+Screw

Monomer · #9 10-30-2006, 06:47 PM

it's M8 X 1.25, BTW

mobetta · #10 10-31-2006, 12:22 AM

i just bought one- 8 x 1.25 x 1.4" is what the receipt says. dont know why they gotta add inches in there, but that's how they do it round here, i guess.

Ara T. · #11 10-31-2006, 01:15 AM

http://www.speedbleeder.com/automobile_applications.htm#Mercedes I bought these and they worked great.

WD8CDH · #12 10-31-2006, 07:33 AM

Thanks for the replies. Local store has M8 x 1.25 x 1.5" long in stock.

By the way Doug, I am surprized that you got a 1/8" npt to fit at all. 1/8" npt is about 10mm x .9 pitch.