I recently (a year ago) replaced my front and rear rotors and pads on my 1986 240, but I never saw much brake performance improvement. Yesterday I took a look at my brake fluid reservior and saw that my fluid was BLACK (most likely the original fluid). I plan to do a complete flush because I know that running this contaminated fluid must be no good for the brake system.

Any chance that the new fluid will improve brake perfomance????

Thanks!!!

I answered your question on Monday but it appears to have been booted by "the kick inside"

Anyhow, if your fluid is black, chances are you have a black slime coating the reservoir walls as well as the Master Cylinder piston. You may also have rust waiting to tear at the MC piston seals if you use the pedal pump method to bleed the brakes.

So as cbremski suggests, use a pressure bleeder.

Also you could remove the MC, disassemble it and clean it. It's easy. I have done this but haven't noticed any posts suggesting this.
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1980 245 Canadian B21A with SU carb and M46 trans

ROB,

I wouldn't recommend ATE 'expensive' fluid unless you are racing. the only advantage of that is a slightly higher boiling point. DOT 4 brake fluid boiling point DRY is about 440 degrees F and since your fluid is black, I would suspect that it has a lot of water and contaminants in it causing the boiling point to go down considerably, which causes a kind of brake fade, though not noticed in the pedal but in performance. I would do the following since your brake lines are probably cruddy as hell.

1. buy a new Master cylinder and resivoir with a new cap. Even if you keep the old one, you run the risk of ruining it during bleeding because the MC seals could be pushed into an area of the MC that is usually doesn't go and the crud in there could rip a seal causing a MC failure. MC's are cheap in comparison to what they provide for safety. Furthermore, the new resivoir makes sure that you have a CLEAN resivoir of fluid to hold clean brake fluid.

2. do a good bleed of your lines, make sure there are absolutely NO bubbles and the fluid is a clear/amber color when coming out of the bleeder screws. Use a small clear hose too, this keeps air from getting sucked back in.

3. Be prepared to deal with stuck bleeder screws, depends on where you live in the country, but here in MN, we do get rust and it sucks...things break.

Good luck
chuck
(4 weeks from becoming ASE certified in automotive Brake systems. YEA!)
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'88 244 174K, '87 BMW 325e 180K (used to feed a '84 245, '84 244, '85 744)

Chuck,

My point on the Ate Super Blue is the color. IMO, it means a lot to see it coming thru, and saves unnecessary bleeding "to be certain". And where Brakes are concerned, I feel that the extra 3 or 4 bucks for a fluid that exceeds DOT 4 specs is trivial. One liter does a 240 with some to spare.

Replacing the MC on an 86 is a good idea, but in that case "Bench Bleeding", as with Aye Roll's setup (photo) is usually recommended. However, I'm not all that sure it's really needed anymore, given the current availability of pressure bleeders for the DIYer.

He should also dump the old fluid behind the pistons (after ensuring all bleeders are free & clear) by depressing them with the bleeder open. The Volvo 700/900 Brakes manual shows clamping the pistons depressed and leaving them depressed while flush-bleeding.

Bruce
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

I agree, i wasn't thinking of it in terms of color. As with the ATE it is easier to tell when the old stuff is out and gone.

good point.
chuck
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'88 244 174K, '87 BMW 325e 180K (used to feed a '84 245, '84 244, '85 744)

need more info...engine type, trim level etc...

does it have leather, does it have aircon, does it have climate control...also does it have the walnut dash etc...

what stereo does it have, wagon or sedan...etc...

I don't know about performance, but would recommend flushing with Ate Super Blue Racing fluid (about $8/liter at FCP and others). When the Blue fluid comes out a bleed valve, you know that line is completely flushed.

In my experience, a liter is plenty, with some left over. But I don't use the current power bleeders. Their large reservoir might require more.

I pressurize the actual MC reservoir to about 15#, using a Mityvac hand pump and a hose connected to an adapted spare MC cap, with an old vac/pressure gauge Tee'd in to the hose. I have to top off and repressurize about 4 times for the total flush. Not a big deal, IMO.
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.