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1974 SLC450
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7 Posts
Discussion Starter · #1 ·
All,

Apologies, I suspect my questions has been posted before but cannot find a satisfactory answer by using the search tool.

I have an early 450SL. The brake warning light lit up yesterday (hadn't driven the car recently) and the brake pedal offers resistance but if you push harder it seems to give up and you can push it down further, all this with engine running.

Could this indicate low brake pressure due to low brake fluid level (the level in the resevoir seems a tad low)?

My SL handbook tells me never to top up the brake fluid myself - but surely this is something I can do myself?

So I'm curious if my suspiscions are correct and if yes can I top up the brake fluid myself and if again yes how to do this and can I use generic brake fluid or not.

Thanks all for your thoughts.

Marc.
 

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Registered
1987 560SL
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285 Posts
Hi Marc, yes you can top up the brake fluid yourself. However unless the level is really low it shouldn’t affect the operation of the brake pedal.
When was the brake fluid last changed ? As it sounds more likely that you need to flush and bleed all the brakes using fresh fluid.
Brake fluid absorbs moisture from the atmosphere and over time loses its hydraulic efficiency. Brake fluid ideally should be changed every 2-3 years.
 

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1985 380 SL
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511 Posts
Generally, if the pedal slowly goes to the floor under steady pressure, there is an internal leakage in the master cylinder. If the fluid is low, it may have leaked into the booster due to a bad rear seal on the master cylinder. If you dont see any leaks around the calipers or hoses then this is the likely cause.
 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
Joined
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13,872 Posts
All,

Apologies, I suspect my questions has been posted before but cannot find a satisfactory answer by using the search tool.

I have an early 450SL. The brake warning light lit up yesterday (hadn't driven the car recently) and the brake pedal offers resistance but if you push harder it seems to give up and you can push it down further, all this with engine running.

Could this indicate low brake pressure due to low brake fluid level (the level in the resevoir seems a tad low)?

My SL handbook tells me never to top up the brake fluid myself - but surely this is something I can do myself?

So I'm curious if my suspiscions are correct and if yes can I top up the brake fluid myself and if again yes how to do this and can I use generic brake fluid or not.

Thanks all for your thoughts.

Marc.
Brake fluid level will drop as the pads wear. The reservoir should never be topped off to compensate for break pad wear, otherwise subsequent replacement of break pads will cause the reservoir to over flow and spill the paint removing break fluid everywhere. There is a minimum lever on the reservoir. If the fluid falls below the minimum, that is a sign of break leakage somewhere or pads or rotors worn beyond serviceable limits.

Your quick lube places are quick to top off reservoirs all the time and charge you extra for their destructive service.
 

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Registered
1986 560SL
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511 Posts
The reservoir should never be topped off to compensate for break pad wear, otherwise subsequent replacement of break pads will cause the reservoir to over flow and spill the paint removing break fluid everywhere.
...Unless you purge the caliper fluid by retracting the pistons with the bleeder valve open. Besides not overflowing the reservoir, you also prevent forcing contaminated fluid back up the lines and into the ABS unit, if equipped.
 
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