Brake Fluid Change?
 

How often should the brake fluid be changed on a 124? I have a '93 300E 2.8 with 159K that I bought a few months ago and I don't know when the brake fluid was last changed. It needs new pads which I'm going to replace myself; I thought it would be a good idea to change the fluid as well.

Also, can the system be completely flushed (along with abs) without any special equipment? All my other cars are non-MBs with Dot-3 fluid and no abs systems; I've done all brake pad and fluid changes myself. I change the brake fluid on my other cars by opening the bleed valve, having an assistant pump the pedal to drive out fluid, and keeping master cylinder topped off. I'm not yet familiar with the MB abs system or Dot-4 fluid used in these cars.

Any help would be greatly appreciated.

P.S.: I couldn't find the answers I'm looking for through the search function. :computer:

Brake fluid should be changed in ANY/ALL cars every 3 years! Dot 4+ is the recommended fluid for all MB's.

You should bleed a liter(qt) of fluid thru the system. NO special tools needed for that car!

Go buy a power bleeder!
 

If you are going to do this yourself, I strongly recommend you spend $40 or so on a power bleeder. Forcing the fluid out with the pedal does a bad thing -it extends the MC piston all the way into the cylinder repeatedly, which is bad for the seals.

And no need for an assistant.

Just opening the bleeders and letting the fluid drain is a better method IMHO.

Also recommend that whatever way you do it, siphon off the old fluid in the resevoir and refill with fresh rather than running the old dirty stuff through the MC and the calipers.

I think that I recently demonstrated this concept. My master cylinder sprung a leak while I was bleeding the brakes, using the "pump & hold" procedure. Lesson learned.

Can anyone recommend a power bleeder? I can imagine some are better than others. I don't know where I would find one of those.

Mike

Here's a nice one A little pricey though. Do a search and you'll come across a guy who made one from a $10 garden sprayer. You can see the resemblance from the picture in the link. All you'd need is a brake m/c cap and a couple pieces of hose. The guage is a nice touch, but probably unnecessary. That's what I'm planning on doing this spring, when I do an "all fluids" change for the first time.

Brake fluid is supposed to be changed in my 240D every year and in my 210 chassis every two years according to the manual. Not sure what it is for your car. The manual will tell you.

I agree - get a pressure bleeder.

Len

Will this one fit on my Mercedes? This looks pretty good. Does anyone know of a cheaper one? I can see how I could make my own but would rather not.

Thanks,

Mike

The pump & hold method mentioned above can cause problems if you bear down too hard on the pedal. Many believe you need to do this to flush/bleed effectively. Not true.

I've used the pump & hold method and have also used a pressure bleeder. The pump & hold worked as well, if not better. The bleeder I bought was one of the typical diyer units that connects to a tire. I doubt that any of these $50-$100 units is as effective as a professional model that can apply more pressure.

My 2 cents.

So if I made my own, does anyone know what PSI is recommended for flushing? Maybe 10 or 20 psi??

MP

Vaccum type bleeder?
 

I found out my local autozone loans out brake bleeders. They said it's the vacuum type that you basically connect at each wheel's bleeder valve and suction the fluid out. Besides the fact that you have to manually keep refilling the master cylinder, are these any better or worse than the types that apply pressure from the top?

A respected tech on another site once said you're wasting your time with pressure bleeders unless you can get at least 30 psi out of them. Professional units can go that high easily. The instructions with my unit said to set it to 15 psi. I never felt that I got as firm a petal with this unit as I did with my foot.

Again, my 2 cents. I suppose not all bleeders are created equal.

Yes if you need to BLEED, then more pressure is better. The thread here, though, is talking about FLUSHING. For flushing, 15 or 20 PSI works great. If you have air in the system, then you need to BLEED and you will need to use the two man method or a higher pressure bleeder.

Merry Christmas,

That's every 2 years on a 124, the coolant is every 3 years.
Gilly

You need to be careful with pressure. Recently I watched a friend hook up a pressure bleeder to his Honda and pump it up to about 30 psi at which point the plastic reservoir blew off the aluminum m/c, and its contents flew far and wide. (What a mess!) I think our Merc's reservoirs are held in place by a couple of thick O-rings that fit in recesses in the m/c and reservoir, and at some pressure differential the plastic reservoir will either blow off or fracture and explode.

If you have an integral master cylinder/reservoir like the old GM cast iron units from the sixties and seventies you can probably use more pressure, but I really don't think it's necessary, and you need to use caution when dealing with a modern m/c that has a plastic resevoir.

I noted on the instructions for my buddy's pressure bleeding kit that is said to use 20 psi, but I would start with 15 psi, which should be plenty to rapidly purge fluid and air.

The recommended fluid change interval appears to be different for some years, but it represents an average for all climates and use. If you live in a very dry climate, like the southwest desert, it's probably okay to extend the change intervals. If you live in a damp climate (most of the rest of the U.S. other than the desert southwest), then it's probably a good idea to follow the recommended change interval if you want to maximize the life of the hydraulic components by preventing internal corrosion due to moisture or reducing the boiling point of the fluid, which can cause lose of pedal due to the water forming vapor at high temperture under severe brake useage.

Duke