Brakes: Flush before or after?

I bought new pads and rotors for my car. I want to change the brake fluid as well. Should I do it with the old brakes or after I install the new ones? Does it matter? Thanks, Pete

after last thing you do after changing pads and rotors. Get or borrow a Motive power bleeder. It will save yu a tone of time and you can do it by yourself Also don't forget to bleed the clutch slave. Lots of DIYs here and on Pelican Don't use parts store brand brake fluid at very least ATE 200. about $15 a liter and 1 liter will do the whole system

It doesn't matter, I do it after changing the pads on each wheel, so one at a time. If you don't have a bleeder, I do and am in Forest Park.

See if Paul lets you use his microscope as well.

I do After , since you need to push the piston back to accommodate new pads.

I also have a motive bleeder, and I'm in the NW suburbs...

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x2

Thanks everyone for the advice and the offers to borrow a brake bleeder. I bought this unit along with a plastic catch bottle. If anyone is in need of a bleeder on the SW side of the city I would also like to extend the offer to borrow mine. Pete

Do it after, when you have properly bedded in your brakes you will have heated everything up including your fluid, best to flush then so everything will be fresh.

It doesn't really matter... Just make sure its flushed completely... I try to use a different color so I can see that the line is clearly been flushed. I also have a bleeder if anyone needs to use it... I'm in Naperville.

Yes, using a different color would make it easier to see when the old is out. Since Super Blue is no longer made, any ideas on what to use with a different color?

Dot 4.

old fluid will be a bit darker in color. Getting fluid hot is not the issue. Having water in the fluid is the issue. Brake fluid is hydroscopic (absorbs water). this will cause steam when hot which makes brakes fade. water also causes rust.

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+1

When I did my flush, the old fluid was still very clean and almost impossible to tell the difference. I found a thread here or another forum that specified the volume of fluid per caliper to pull out and used that measurement method.

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That means your fluid was still good. Bad fluid has air bubbles, black crud and is dis-colored. The fluid does not circulate through the system....it always stays close to the caliper and that is why you only need to bleed until the fluid is clean. In most cases it's only a few tablespoons worth at each bleeder screw if you stick to a regular regime. When bleeding on a DD very seldom the fluid gets used to its capacity. On a car that is tracked you need to bleed before the DE and sometimes twice on a weekend. Regarding the ATE Blue.....the die in that stains everything it touches like catch bottles and clear silicone tubing.

Per Porsche WSM, you should bleed out about 250mL per wheel. I always use about 1L of fresh fluid to bleed out about 125mL per nipple and that works pretty well. Brake fluid is cheap so I don't mind using what seems a little excessive.

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Brake fluid is hygroscopic meaning over time it absorbs moisture. Under heavy braking the heat buildup can boil water in the brake lines into gas bubbles. As gasses can be further compressed in the line (unlike the brake fluid) the result is loss of effective stopping power when you need it most. In a high performance car that can ruin your day. Just because it looked clean, does not mean it did not need to be replaced. That is why regardless of mileage, brake fluid should be replaced every 2 years As you mentioned, since I am tracking the car a little, I need to bleed/flush more often. At the track, the brakes get exceptionally hot. Yes, the ATE blue is just had blue dye added, but the fricking govt has decided that all brake fluid has to be clear or amber. It does make it a little harder to tell when the old is gone. I marked my collection bottle with ounces and the rear calipers take around 6 oz and the fronts around 5 oz each. The clutch IIRC is around 6 oz as well . 1 liter is good for the whole thing

The shop where i picked up a motive bleeder carries a probe for testing the water content of brake fluid. Looks like a cigar tube with two electrodes on one end, the perfect addition for a gadget collector.

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Did you just copy and paste a portion of Joe's response? In a way I guess we both understand how the fluid works. IF you do a normal regime of bleeding the less fluid you will need to be bled each time. During the DE season I would do this the Friday night before and sometimes the following night....If you do it that often you are basically flushing your system over the course of a few events and after a while you will know boiled up fluid when you see. Like I said bad fluid has air bubbles, black crud and is dis-colored (meaning brown-ish). Personally I don't use ATE fluid at all but let's not turn this into an oil type thread.

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Nope didn't copy Joe's response. If the fluid is reasonable fresh, it does make sence to just bleed them a little before track use, rather than a full flush. As there is not any special formulated brake fluid for a M96 and the rabid opinions that go along with an oil discussion, a discussion of different brake fluids would probably not go off the rails and be useful. If you don't like ATE, what do you like?

For street driving, I love ATE Type 200 (amber). More than good enough and it won't stain the whole brake system with blue/green. If you use a clear tube to bleed and look closely, you will see a slight color change between the old and new fluid. With the measured volume method, color change is irrelevant anyway.

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Motul 600. I have been wanting to try Castrol SRF though.

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At $70 a liter, it's liquid gold Motul is about double ATE cost From what I read, SRF is a great product and if you have a full on race car and are racing all the time, it makes sense. Fir me, mainly spirited street with track a few times a year, either ATE or Motul is fine, especially if bleeding often What about Redline RL-600 its ariound teh same cost at Motul 600

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The Red Line looks like another good option. When looking at the all the numbers look at the wet boiling.

For those that don't know, the more hardcore track oriented brake fluids like the SRF tend to absorb moisture a lot faster than more street friendly fluids like the ATE. There is no free lunch here. It depends on if you're a track junky and need that extra performance at the cost of having to bleed your brakes more often.