Brake Fluid or Master Cylinder?

[benzwallah]

Recently, the brakes in my '65 230SL are going closer to the floor.   The car still stops dead when I brake, but there is a squishiness to the pedal.  Start by draining and replacing the brake fluid (which has not been done in years) and see if that's the problem?  Any thoughts or advice very welcome.   Thx!  Benzwallah.   

[kampala]

Benzwallah, 

The techs on this site will know better, but as a start:

If the master cylinder is going bad, one way to tell is when you push down on the pedal it will hold for a second or two and then the pedal may travel a bit further.  This usually means the master is going.   Another way is to pump the pedal a couple times and it should get quite tight, but then it will soften up within a couple seconds.  This would also mean master is probably going bad. 

Of course check for leaks at calipers and flex hoses at each wheel.   May want to change flex hoses at each wheel at this same time as these cause other problems if really old. They are easy and not costly.

A fluid change and good all around bleed will do wonders if the master is okay.

[ja17]

The 230SL has drum brakes in the rear. Occasionally they need adjusted, or the pedal may become lower. As mentioned the usual cause is a leak or master cylinder going bad.

[benzwallah]

Thank you for good advice, Kampala.  I checked my records and see that the fluid and rear brake lines were replaced in 2004.  Since then, the car has been driven less than 12K kilometers, but I will still have the fluid drained to be safe since it has been such a long time.  I doubt it is master cylinder given your advice.  Had to brake hard yesterday (dumb Washington DC  drivers....) twice & all was good.

Pls forgive late response - greatly appreciate your expertise!   Benzwallah

[benzwallah]

Thank you also, ja17!   Excellent advice and greatly appreciated!   Benzwallah

[Pawel66]

I think you should change fluid, as you said, but I also think you should change all of the flexible hoses - they go with age, not necessarily with usage. They get swallen with age, then they may just crack.

[Mike Hughes]

You mention that the rear brake lines (hoses?) were replaced, but what about the fronts?  I'd suggest checking the rear drum brake adjustment first, followed by flushing and replacing the fluid.  If you have a better pedal afterwards, you are probably good for the short term, but I'd still consider replacing at least the front flex hoses soon, if not all of them.

I'm in Alexandria, too, and there are a number of other Pagoda owners in NoVa if advice/support is needed.

[benzwallah]

Thank you Pawel!  I will be sure the flexible hoses are replaced.

[benzwallah]

Thanks Mike - excellent advice!   I will have all of the hoses drained, and as necessary (but probably) replaced.  Might as well have the whole hose system checked and replaced. 

My 230SL is silver w/ navy blue top.  Honk if you see me in Alexandria.   

[Benz Dr.]

The push pin on the master cylinder may need to be adjusted. Most cars will work well with the notch on the eccentric pointed towards the firewall but I've seen some cars where the brakes would lock up if adjusted that tightly.