...if I only opened the rear part of the system?

I replaced rear calipers and am bleeding them now.

Front calipers were not touched and the fluid in the entire system is less than 1 year old. Fluid never ran low on the front fluid reservoir during the rear brake job..

Do I need to bleed the fronts?


I would think no...but I think it's prudent to check :-)

thanks

__________________
-------------------------------
'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

No.

I would say you do not need to bleed them..
but it is so much fun that I can not imagine you not doing it while you have the car there and are giving it the TLC it deserves...
That way all the fluid is NEW.... instead of half one year old and half new.....

__________________
1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

You're most likely to be OK so long as the fluid level in the reservoir didn't get too low. But if you are already working on the rear (for whatever reason) and you haven't touched the front brakes recently I'd advocate giving them a bit of a bleed too if only to make sure that everything is fine and dandy there too.

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

the fluid will eventually mix via the centrally located MC.

remember that the brakes are in a criss-cross circuit (driver front/passenger rear and vice versa).

since you will be all dirty and greasy anyway, just bleed them all and do a complete brake fluid job.

__________________
Ben
1987 190d 2.5Turbo

In fact, you might want to forget that.

Maybe you are confusing brakes and power windows. For a W123, anyway.

Subaru does that criss cross...but I do not think our MB's do...

__________________
1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

The front most section of the reservoir is for the rear brakes, the fronts have two lines.

Attached Thumbnails

 

__________________
83 SD

84 CD

Thanks guys.

I am all for flushing fluids and PM - but I just did it last August and I know I'll have the front end of the car up later this summer for tie rod replacement and a wheel bearing repack, so I'll flush the fronts then.

__________________
-------------------------------
'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

MB maintenance schedule states to flush once a year during the spring. Reason is moisture contamination is higher during winter season.

The system as a whole will still get contaminated if only the rears are flushed.







.

Attached Thumbnails

   

__________________
1983 123.133 California
- GreaseCar Veg System

Since you're in boston, I'd do a check on the front bleed nipples regardless. Make sure the rubber caps are in place, etc.

If the fronts weren't touched and you kept the reservoir at least partially full, then you can't have gotten air in the lines for the front so no need to bleed them for air.

If, while replacing the rear calipers and refilling and bleeding those lines, you let the fluid drop then yes, you do need to bleed the front lines because you may have let air get into them from the top.

You might want to take a closer look at the design features of the brake fluid reservoir.

No, you dont NEED to bleed the fronts, but understand that 99% of brake component failure is due to lack of proper service and maintenance. Brake fluid is hydroscopic, (Absorbs water from air). Many believe it is very important to change your brake fluid annually, biannually at minimum.

So why go through all this effort and not at least "flush" the front half of the system?

__________________
85 300D 3 pedal. Current project.
83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.

And 83% of statistical data cited on the internet is totally fabricated!

So even your statement is only 68.89 percent probability of being correct.... or only partly fabricated !!!
83 multiplied by .83 = 68.89
LOL

__________________
1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html