DIY: Brake fluid flush

Hi folks,

Someone asked a while back how to do a brake fluid change. After my last track event, I flushed my fluid and took a few pics. Hope this helps!

Warning - All the standard stuff applies. Get that car on jack stands and stable. Don't be an idiot. Be careful with brake fluid, it will eat your paint.

What you'll need:

A couple feet of clear plastic tubing (1/4" I think)
An old soda bottle
9mm wrench (rear)
11mm wrench (front)
brake fluid
A friend or a pressure bleeder
jack and jack stands
17mm socket and a breaker to remove the wheels

1) Put the car up on jack stands
2) Pull the wheels off (wouldn't this be a good time to give them a nice bath?)
3) Assemble your old fluid bottle. I poked a hole in the soda bottle cap and fed the tubing through. Put enough brake fluid at the bottom of the bottle to submerge the end of the tubing.



4) The brake fluid reservoir is under a panel on the driver's side of the engine bay, right under the windshield. Three screws and a button removes the panel, but be careful, there's a couple wires there still attached. I just flipped the panel over. There is a plastic piece surrounding the reservoir and the abs pump (still there in the pic) that just pops out. You don't have to remove it, but I found it easier to see how much fluid was in the reservoir with it gone.



5) Start at the furthest wheel from the master cylinder (passenger rear). With the wheel removed, you'll see a small nipple under a rubber cover on the backside of the caliper. There is a small nut on the bottom of the nipple. Pic of the nipple with the rubber cap removed:



6) Get your wrench around the nut - you only need to turn the nut about a quarter turn (maybe less), so position your wrench accordingly. I use the closed end of the wrench. Put the end of the tube leading to your fluid catch bottle over the nipple. Paper towel optional, but there will probably be a little dripping.



7) Here's the part with no more pictures. Make sure your brake fluid reservoir is full. You can use a turkey baster or something to remove as much old stuff as you can so you don't have to pump it through. If you have a pressure bleeder, attach it to the reservoir, and pressurize. If you're reading this, I'm guessing you don't, so have a friend pump the brakes a couple times and hold the brake pedal down. Once your friend gets to the hold it down stage, open the nut and you'll see fluid coming out the nipple into the bottle. Close the nut, pump and hold brakes, open nut, repeat until fluid runs clean. Once the fluid is clean, move on to the driver's side rear, then passenger side front, and finally, driver's side front.

If your fluid isn't that dirty, it can be hard to tell if you're pumping out new fluid or not. If you're going through a whole reservoir of fresh stuff, you're probably good. If you look at the first pic, that black cloud is dirty fluid .

A few things to watch out for:

Don't let up on the brakes when you open the nipple. This will draw the dirty fluid back into the system and worse, possibly air. This is why you want to stick some *clean* fluid at the bottom of the catch bottle.

Make sure your brake fluid reservoir is always topped up - you don't want to pump air in the system from the other side either. If you do get air in the system, you'll have to keep pumping the pedal and flushing fluid through until you don't see any more air bubbles coming out the tubing.

Great write-up man. I always use a vacuum bleeder, which you didn't mention. Same instructions, sans the friend/pumping .

By the way, clutch uses the same reservoir, and I'd do it after the brakes, especially if car is lifted (I don't need to lift the car for the brakes).

As a final comment, on modern cars, ABS/DSC pump pistons need to be activated by diagnostic equipment to push old fluid out, but with frequent bleedings (I like to do it every year; it's cheap and easy), fluid is fresh enough not to need that IMO. But if you wait until fluid is nasty, I'd get it done at a dealer to avoid a much more expensive repair down the road (more reason to do it yearly). The good news is BMW does it once for free (the second time would be just out of warranty).

Hm, I've never flushed my clutch...can you elaborate a little on how it's done?

Thanks!

CeeP wrote

Hm, I've never flushed my clutch...can you elaborate a little on how it's done?

Same as the brakes buddy. Reaching the valve (nipple) is obviously harder, especially with the tranny cover in the way, but if you have the car lifted, it should be simple enough. Just notice the feeding hose for the clutch sits pretty high, so you need to watch the reservoir's level much more carefully; you DON'T want to suck air. Since I do all those jobs by myself, I use one of those bottles that keep the reservoir full all the time, so I don't have to worry about running out of fluid while under the car. By the way, it's always better to at least depress the pedal (either brake or clutch) by hand once, to push all the old fluid out of the master cylinders, but not essential. When I can summon one of my daughters, I do that. Good luck, and post some pics of the clutch slave cylinder if you decide to do it, and also in what condition the initial fluid comes out. I only have 2K miles on my car now, and the 2-yr service is up in June, so might wait for that, but will do it yearly thereafter. Good luck.

CeeP wrote

Hi folks,

Someone asked a while back how to do a brake fluid change. After my last track event, I flushed my fluid and took a few pics. Hope this helps!

Warning - All the standard stuff applies. Get that car on jack stands and stable. Don't be an idiot. Be careful with brake fluid, it will eat your paint.

What you'll need:

A couple feet of clear plastic tubing (1/4" I think)
An old soda bottle
9mm wrench (rear)
11mm wrench (front)
brake fluid
A friend or a pressure bleeder
jack and jack stands
17mm socket and a breaker to remove the wheels

1) Put the car up on jack stands
2) Pull the wheels off (wouldn't this be a good time to give them a nice bath?)
3) Assemble your old fluid bottle. I poked a hole in the soda bottle cap and fed the tubing through. Put enough brake fluid at the bottom of the bottle to submerge the end of the tubing.


4) The brake fluid reservoir is under a panel on the driver's side of the engine bay, right under the windshield. Three screws and a button removes the panel, but be careful, there's a couple wires there still attached. I just flipped the panel over. There is a plastic piece surrounding the reservoir and the abs pump (still there in the pic) that just pops out. You don't have to remove it, but I found it easier to see how much fluid was in the reservoir with it gone.

5) Start at the furthest wheel from the master cylinder (passenger rear). With the wheel removed, you'll see a small nipple under a rubber cover on the backside of the caliper. There is a small nut on the bottom of the nipple. Pic of the nipple with the rubber cap removed:

6) Get your wrench around the nut - you only need to turn the nut about a quarter turn (maybe less), so position your wrench accordingly. I use the closed end of the wrench. Put the end of the tube leading to your fluid catch bottle over the nipple. Paper towel optional, but there will probably be a little dripping.

7) Here's the part with no more pictures. Make sure your brake fluid reservoir is full. You can use a turkey baster or something to remove as much old stuff as you can so you don't have to pump it through. If you have a pressure bleeder, attach it to the reservoir, and pressurize. If you're reading this, I'm guessing you don't, so have a friend pump the brakes a couple times and hold the brake pedal down. Once your friend gets to the hold it down stage, open the nut and you'll see fluid coming out the nipple into the bottle. Close the nut, pump and hold brakes, open nut, repeat until fluid runs clean. Once the fluid is clean, move on to the driver's side rear, then passenger side front, and finally, driver's side front.

If your fluid isn't that dirty, it can be hard to tell if you're pumping out new fluid or not. If you're going through a whole reservoir of fresh stuff, you're probably good. If you look at the first pic, that black cloud is dirty fluid .

Question - So in step 7 you need to suck out the old fluid first and then fill it up with the new fluid right ?

doba_s wrote

Question - So in step 7 you need to suck out the old fluid first and then fill it up with the new fluid right ?

You don't have to, but it's a lot quicker if you suck it first; there's A LOT of fluid in there. Otherwise you have to vacuum it out thru one of the calipers, and it takes MUCH longer. Besides, you can suck air with vacuum even with a few millimeters of fluid; safer and quicker to suck it out. But yes, you're not done until you're sucking FRESH fluid thru each caliper. Do it in this order: RR, LR, RF and LF.

And after sucking the old fluid and pouring new one for the first time, start sucking thru a caliper quickly so the new fluid doesn't mix with the old (takes a few minutes). It's an easy job, and only takes a $10 (32oz) bottle. I use Castrol GTLMA Dot 3/4 synthetic fluid (made in Germany ), but track junkies usually use racing fluid, which has a higher boiling point. Hope this helps.

As a comment, if BMW had put the valves on the outside (like many Brembo calipers), it could be done thru the stock 19s in minutes, without even getting dirty. Oh well. It still can be done without lifting the car, but you have to be skinny .

doba_s wrote

Question - So in step 7 you need to suck out the old fluid first and then fill it up with the new fluid right ?

Yup. Just keep the reservoir topped up, and you'll be fine. Doba, I lost the original brake fluid flush thread you posted, so I never saw your response to my original offer to help. I can still help you out some weekend if you like. I thought you sold your car though?

I am actually going to change the fluid while swapping the pads. Any importance of the order in which I will do this: swap the pads first before bleeding, or vice versa? I would imagine it does not matter...

How often will this need to be done?
I don't track it.

A few quick questions since I just started this procedure:

* do we need, or is it even possible to remove the little filter that is inside the fluid tank in order to suck out more old fluid?

* what does the warning on the cap mean? Does it simply mean that we have to be careful not to put any dirt in the container?

* I am using a pressure bleeder. I increase the pressure to ~ 20psi and, ok I have a slow little leak that I need to fix, but overall, very few liquid is coming out of my Rear Passenger caliper... and I think there were even some bubbles, so i am not happy with the last job performed by the dealership. Any ideas on what is going on? (Note, I had just replace the pads so should I have pumped back on the break pedal?)

Thanks for your comments.

MTROIS wrote

(Note, I had just replace the pads so should I have pumped back on the break pedal?)

No. It's always better to bleed brakes with pistons fully pushed in, and that's exactly the way yours are now. As a comment, I like to bleed my brakes regularly so I don't have to either push pistons in, or activate ABS pump (another piston). Just remember to pump your brakes when you're done man, and BEFORE driving the car, because your brake pedal will go all the way to the floor a couple of times until pads touch the rotors.

I have everything apart, but will start tomorrow. Haven't looked inside the reservoir, but when I removed the cap (along with level sensor) didn't see any filter on my '08, but will report back tomorrow. And don't forget the clutch if you have a 6MT. Just looked at the tranny without the cover, and was surprised to see a plastic slave cylinder. And the bleeding valve is plastic too. Oh well. The other weird thing is our tranny doesn't look like a typical RWD tranny, which is one piece after the bellhousing. Seems like our bellhousing is an integral part of the tranny, and the tranny is split in the middle. Very weird design if you ask me.

MTROIS wrote

A few quick questions since I just started this procedure:

* do we need, or is it even possible to remove the little filter that is inside the fluid tank in order to suck out more old fluid?

* what does the warning on the cap mean? Does it simply mean that we have to be careful not to put any dirt in the container?

* I am using a pressure bleeder. I increase the pressure to ~ 20psi and, ok I have a slow little leak that I need to fix, but overall, very few liquid is coming out of my Rear Passenger caliper... and I think there were even some bubbles, so i am not happy with the last job performed by the dealership. Any ideas on what is going on? (Note, I had just replace the pads so should I have pumped back on the break pedal?)

Thanks for your comments.

Don't try and pull out the filter! It is a real bastard and I ended up tearing it and having to replace. There must be a special tool for this. It goes to the bottom of the tank and you can get most of the fluid out. When I flushed the system, I used the Ate super blue to calibrate how much fluid one needed to push through each caliper to flush the lines. I'll be using Motul from now one based on a vast number of recommendations. I also lightly thumped the caliper with a rubber hammer to knock air bubbles loose.

MTROIS wrote

do we need, or is it even possible to remove the little filter that is inside the fluid tank in order to suck out more old fluid?

Okay, just started doing the bleed. Filter doesn't reach the bottom, but close enough (to the 'min' level). Filter has 4 'tabs', so removal without damage would require a thin sleeve to push them all in at the same time. FORGET IT!!! The good news is there's no need to remove it at all; there was zero crap floating around inside the reservoir. Only cars I've seen this is Lexus and BMW; all others have always had crap floating around.

A warning: you could suck the rest of the old fluid thru one of the calipers, but I'd resist the urge to go below the 'min' line, especially if you're using vacuum. You'd suck air well before fluid runs out, and once you hear that sickening slurping sound, it'd be too late. Not the end of the world if that happens, but you'd need an extra 32-oz bottle plus another hour of your time. And that's if you don't have to perform a reverse fill first . Just don't suck below the 'min' line and you'd be fine.

And leave the clutch at the end, so you suck clean fluid. Removal of the tranny bellypan is easy; just 9 fasteners and you're done. Looks like there's very little space to turn a wrench on the slave valve (6MT here), but will report on my procedure when I'm done.

Pleasant clutch bleeding surprise folks. After half an hour of turning the bleeding valve a full turn with my vacuum machine attached to it (no freaking s p a c e -why the hell the system censors that word????) and no fluid, I knew I was dealing with a check valve. Got out from under the car, opened door, push clutch pedal with hand and it went in like butter. Did that 10 times more and I was done. Clutch worked perfectly after closing it. Next time it's going to take me 2 minutes after removing shield.

Here's the drill:
- Remove belly pan (3 screws in front, 2 in back, and 2 on each side).
- Remove cap from valve and loosen it one full turn with a 1/4" ratchet and 11mm standard socket.
- Valve will just spew fluid when you push the clutch pedal, so use any method you want to catch it that won't splash. This is a one-person job folks .
- Push clutch pedal slowly (and return slowly as well) about 10 times, and you're done.
- Screw valve clockwise with ratchet until you feel a 'click' and it stops turning. DO NOT apply too much force since it's PLASTIC.
- Reinstall belly pan and you're done. This is the easiest clutch I've ever bled, and the most effective way is by pushing the pedal, but I never do it that way since helper can screw up. No chance for that here; great feature .

By the way, rear brakes require a 9mm closed wrench and front 11mm, and are regular valves (the way I like them on the brakes). Job done in about an hour with a vacuum bleeder (the best way IMO). Fluid was clean (no debris inside the reservoir, like most of my new cars), which was good news, so no need to destroy the filter to clean the reservoir. Just amber in color. From now on will do it yearly, like all my other vehicles. Just $10 and an hour of my time. Well, probably 2 hours since I like to clean the undercarriage . Hope this helps folks.

I just switched my pads out with Pagid RS 19's and also did a flush with a couple bott, les of Motul 600.

But now when I brake I have a soft pedal when I start to brake, but when I lift up and brake again then the car really bites nicely. Did I screw up and let air in the system?

TrackRat wrote

New pads must wear into worn rotors so it may take awhile for the pedal to improve assuming you bled them properly and didn't get air in the system. When you pump twice the first pump moves the pads closer to the rotor and the second applies the stopping pressure. When the pads wear in they will already be close to the rotor on the first pump. With new rotors this isn't usually as much of an issue as the pads and rotor are both flat and the pads will stay closer.

aahhhhh, that makes sense, when I was bleeding the four corners I got very little air out after flushing a liter(2 bottles) of fluid in the system. The rotors were bedded in with the stock pads. How long before the pedal feel returns to normal? The brakes feel really good on that "second pump" after bedding them in last night per instructions felt fine.

The only point air could have gotten in the system was when swapping the pads I lowered the fluid(get old fluid out also) a bit so it wouldn't over flow when compressing the cylinder and such. I filled/pressured/flushed after they were swapped.

edit: Only other thing I can think of, pads are a race material, the first brakes heats them, second immediate brake up to temp needed for the task..

elp_jc wrote

I always use a vacuum bleeder..

What brand of Vacuum Bleeder do you use?

ff1600 wrote

What brand of Vacuum Bleeder do you use?

I have this one buddy: http://www.griotsgarage.com/p2p/searchResults.do?method=view&search=basic&keyword=oil+extractor&sortby=newArrivals&page=1

But you can probably find it cheaper somewhere else by now. It comes with 3 different 'attachments'. It's great to suck oil out of the filter housing too. And I used it to change the oil on my boat as well. Still working perfectly after many years, but need to find new silicon tubing since brake fluid deteriorates plastic, and my original brake fluid hose is already too short after cutting off cracked pieces over the years. The beauty is vacuum makes brake bleeding a one man operation, plus minimizing risk of sucking air. Hope this helps.