1982 240D living in Mexico. Had the red parking brake light come on while driving, and sure enough, fluid is low. Slight leak out of the drip hole on the bottom side of where the Master Cylinder connects to the vacuum assist thing. Some fluid down on the body, under the Master Cylinder, but not enough to drip to the ground. I just had the system flushed and new fluid added before I left the US, about a month ago.

Here in Mexico, the only brake fluid I can find so far, is labeled “classificacion LF3 (DOT 3)." The manual asks for DOT 4.

Three questions:
Will I cause a problem topping it off with DOT 3?
Is a new Master Cylinder in my future?
How long can I safely get by with this problem, just adding DOT 3 fluid?

Thanks,

Clay

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2002 E320 Sedan 93K Designo Mocha Black Metallic!
1995 E320 Wagon 205K Black Wagon
1982 240D 183K SloPoke

I believe each of these cars are the final production year for that model.

I don't beleive the parking brake light has anything to do with the actual brake system it self. It is simply an indicated activated when the parking break is in use. there is a toggle switch (similar to the ones on the doors that activate the lights in the car whe the door is open) that causes that light to come on when the parking brake is on. Occassionally when one hits the parking brake lever with one's leg it will come on (mine does atleast). I don't believe it actually has anything to do with the car's braking system.

i'm not all that familiar with the brake systems on these cars; however i have experience chaning pads.


Kris

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82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k

The light does indicate the parking brake is in use, but it also indicates when the brake fluid level is too low.

ahh i never knew that.

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Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k

As far as I know you can use Dot3 but it will absorb water and boil easier, just to warn you. I would get that MC fixed asap. If the seal isn't holding that means you are getting air into the system which means your brakes won't be working as well. MCs are cheap and new ones really transform these old cars.

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1985 CA 300D Turbo , 213K mi

Get a rebuilt MC soon - you may be putting fluid into your vacuum booster, I had to suction some fluid out of there when I finally changed mine. The weeping fluid will also eat any paint it contacts. I think my rebult from NAPA was $43 or so.

I flush my system with DOT 3 - I don't drive my 240 like a race car. Anyone can correct me if the DOT 3 will have adverse affects.

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'85 300D - 206K (sold)
'81 240D - 149K (sold)
'03 Jetta TDI - (sold)
'79 300D - (sold)

One frequent symptom of a master cylinder going bad is "pedal fade". That is when you apply the brakes while sitting still, and the pedal slowly fades down with time. If your master cylinder is not leaking, there will be no pedal fade at all.

This is not the only issue that a bad master cylinder can cause, but it is pretty commonplace.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles