Jnosol

Hello 991 folks, this is a community effort to create a fool proof brake bleeding/flushing procedure - Step by step. Jump in and chime in... Thanks.

I plan to flush my brakes soon. I have Motiv pressure bleeder and fluid extractor, but just need to validate my list of steps below before proceeding. Any help or insights is appreciated.

I'm using ATE Gold (ATE TYP 200), Porsche OEM fluid is rip off ($55 vs $18)

Tools Needed: Motiv 0109 BLACK LABEL EUROPEAN BLEEDER, Motiv 1701 POWER EXTRACTOR 1GAL (optional), Motiv 1820 PAIR OF POWER BLEEDER CATCH BOTTLE, wrench for brake bleeder screw, and torque wrench (optional) - Jack/Jack Pad Adapter for Porsche/Jack Stands obviously

Proposed 991 Brake Bleeding Procedure Steps:

1. Remove the master cylinder brake resevoir's cap and remove the filter screen *Note: Screen is tough to come off and can get messy per @Porsche_nuts. Up to you if you want to leave the screen in or remove.
2. Optional Step, skip to #4 if you don't have a fluid extractor: Using the Motiv power fluid extractor, extract the existing fluid out of the reservoir *Important: Do not remove all the fluid, need to leave a little to avoid air in the system)
3. Fill fresh fluid into the master cylinder to the "max" line
4. Dump the rest of the fresh fluid into the Motiv brake pressure bleeder container (wet pressure bleeder method)*Alternative dry pressure bleeder method: Only use the Motiv pressure bleeder as a pressure source. Remove the cap and top the fluid off in the brake reservoir as it hits the minimum line. Less cleaning, but more pumping.
5. Attach the fitment from the Motiv brake bleeder to the master cylinder's
6. Pump to 10-15psi (keep the pressure between 10 and 15 at all time)
7. With the car jacked up, one corner or all, start with the RR > RL > FR > FL (driver front) - Further from the master cylinder to closest
8. Release fluid one bleeder spot at the time, starting from the outide of the caliper then work inside (2 brake bleeder screws per caliper) - 250ml the first caliper, then 200ml, then 150ml, then 150ml (less fluid is needed as you work towards the front) *Important: position the brake flud bleeder catcher above the bleeder screw level to prevent the vacuum effect. Optional: You can use to rubber mallet to tap lightly on the calipers while the brake bleed to remove stubborn bubbles against the caliper walls.
9. Torque the bleeder screws to 8-10lb-ft (8 to be safe)
10. Lower the car
11. Uncrew the bleeder tank to relieve the pressure so excess fluid can go back into the Motiv canister. Then uncrew the adapter Motiv adapter from the master cylider reservoir. *Important: Do not do this in reverse, you'll have a mess on your hand.
12. Top off the fluid on the reservoir to right below the "max" line and put the fluid screen/cap back on
13. Pump the brakes to ensure there's firm pedal feel, then do a quick road test at low speed

Warning: Never let brake fluid get on the paint. Probably good to wash the car afterwards in case it gets on the wheels.

Cleaning: If you use the wet pressure bleed method, clean your Motiv tools/containers with denatured alcohol and allow dry before storing.

Bleed = Just let out enough fluid so the brake lines are free of bubbles (same fluid type replacement)
Flush = Full change of the brake fluid or change fluid type

Porsche Service Instructions (Thanks Plenum): http://plenums.blogspot.com/2016/10/...e-system.html/

bittrl1000

When I bled my brakes a few months ago, I couldn't get the screen out of the reservoir. So I just pour the new fluid into the reservoir with the screen in place.

Jnosol

Interesting, good insight. I added your comment to the instructions above. I just looked at mine, I think you can use a needle nose plier to remove. Using a brake bleeder, it's best not to have the screens as my theory is it creates micro bubbles.

Porsche_nuts

The screen does come off. It really is a pain to remove (you really have to pull, and make sure you have a cloth to cover any splatter from pulling) but it does come off.

Jnosol

Thank you, notes updated. Do you know if there's any overflow hose to be clamped off prior to using the pressure bleeder? (991 specific)

3Series

Bleeding = removing air bubbles that may form at the end of the brake line near the caliper

Flushing = replacing all the fluid in the system

Your steps are for flushing and not bleeding. When you bleed, you don't need to remove fluid from the reservoir. When flushing, it just saves you time to remove the fluid from the reservoir, but you don't really have to do that step.

Lastly, I recommend the "clean" version where you don't dump brake fluid into the Motive Bleeder tool and just use it as a pressure source. It's a little more involved but makes cleanup 10x easier. Plus brake fluid is nasty stuff.

Jnosol

Understood, thanks for the feedback. I added instructions to use a rubber mallet to lightly tap the calipers in order to remove stubborn bubbles.

Brake fluid collect moisture and boiling temp goes down, probably best to extract the old stuff out of the reservoir regardless if the tool is available. Good point on the using the brake bleeder on the pressure source, I actually haven't had too much trouble with the fluid in the containers then pump it in. I clean the bleed tool/container with denatured alcohol after use, good as new. I added your suggestion as an option.

Any feedback on bleed psi and if we need to clamp off any overflow lines on the 991?

MJG911

if you do put fluid in the motive bleeder (that is the way I do it), just be sure to unscrew the cap of the bleeder first, and not the adapter on the master cylinder. It makes it MUCH cleaner. Of course, if you do it backwards, you will only ever do it backwards once!

991carreradriver

I flush my system every two track events or about four times per season. Personally, I am too lazy to clean the Motive bottle, I use it just a power air source and flush using no more than 12 PSI. 20 PSI is a lot of pressure and could cause a problem. I think you missed a couple critical parts to the process:
1.) After flushing is completed and everything is back to gather, depress the brake pedal to make sure no air was introduced and that you have brakes.
2. ) Test drive and check each caliper and master cylinder for leaks.

Good write up and thanks for sharing, wish I had it before I went through the learning curve.

Also as a general comment, I use a brake fluid tester to measures moisture in brake fluid. It cost less than $20 and is used by pro's. This is a good way to keep tabs on your fluid if your are a spirited driver. If there is very little moisture indicated but the brake pedal is a getting a bit mushy, a simple bleed may be all that is necessary.

Churchill

X2 -- much, much easier.

You don't need to clean up with denatured alcohol. Just use warm water and dish soap. Also, don't let brake fluid drip on the calipers, and if it does, wipe it off immediately with water. Brake fluid is kryptonite to paint.

As far as the fluid flush goes, unless you're going to the track I wouldn't get too obsessive about it. Brake fluid is just hydraulic fluid, not motor oil. Doesn't break down or wear out. When the time comes I'll probably bleed the calipers but not flush the entire system. That's where you don't want moisture in the fluid, because when the heat generated by hard braking makes it boil, you get air bubbles, and air is compressible. You don't want anything compressible in a hydraulic system.

BradB

Thanks for working on a write up. My thoughts...

1. Motive bleed PSI: pumping to 12-15lbs is more than adequate.

2. There are no overflows to worry about.

3. There is no need to partially empty the master cylinder prior to bleeding. New fluid pushes out old fluid. Plus, you risk sucking air into the system. That's a mistake you'll never do twice!

4. There really is no need to ever remove the screen in the reservoir. In fact, its safer to leave it in place. The action of removing the screen can, at some point, cause a piece of plastic from the screen retention clip to come off and fall in the reservoir. A piece smaller than you can see has the potential to be deadly. Better to be safe.

5. As 3Series mentioned, I also pressurize the system "dry" using the Motive only as a pressure source. I like the quicker clean up and one less chance of the fluid getting contaminated. Plus it always leaves a little fluid left in the Motive container and hoses. I hate to be wasteful. I use Motul which is $$$. Call me cheap! It's a personal choice. Both methods provide good results.

6. I have never, ever, needed to hit my calipers to dislodge bubbles. There are none. Pressure while flushing takes care of this. And unless you have opened up the system, or sucked air through the master cylinder reservoir then you will likely never see bubbles coming out of the calipers themselves. If you have air in the lines then your brakes weren't working prior to you starting! The only bubbles you will likely see are those from the length of hose you are using and the outside end of the bleed nipple exposed to the elements.

It also should be noted that the evacuation (bleed) hose that covers the bleed nipple doesn't always have a 100% tight seal and on occasion you will see a bubble slide past. Many people panic when seeing this thinking the bubble has come from the calipers. It hasn't. It's just air slipping around the bleed hose. This is harmless since it's 'after' the caliper.

7. I don't position my catch bottle above the bleed nipple. I simply hang it or set it on the ground. I have never heard of or experienced the vacuum effect you mentioned.

8. The wrench you should be using is an 11mm Flare Nut wrench. This wrench wraps around the bleeder on three sides but is has a slit, or opening in it to allow you to take the wrench off and reposition it or remove it without removing the bleeder hose. Trust me you will love it. (Sears, $10)

Again, nice job. My suggestions are just mine.
.

Cbst09

This video I made details the process on my 997, it should be the same for your 991. Tip, I have since made a bleeder bottle using an old rubbing alcohol bottle and some high strength magnets glued to them. The bottle sticks to the brake rotors and is much more efficient than the method I used in the video of using an old brake fluid container balanced on an upside down wastebasket :-)

Dan Darst

I just make or buy a cap that fits the master cylinder with a male air chuck screwed into the center. Then clip on an air line with 5 to 10 psi max at the line. Never over 10. Suspend the air line in such a way that there is no stress on the cap. Cycle the fluid level in the master cylinder between the high and low marks. No air, no mess.

Jnosol

Thanks for the feedback. By the way, here's the source from the 996 forum on pressure and bleeding sequence on cars with PSM. Does this apply to 991? That's where I get 20psi from.

996 - Bleeding Brakes for PSM:
https://rennlist.com/forums/996-foru...-with-psm.html

Need to validate, but it looks 20-24psi is for flushing the brake fluids out of PSM/ABS too. You'll need a Durametric tool to open the valves of the PSM/ABS for full flush. This is only required if a lot of air is in the system or a major brake component is replaced (ABS unit, PSM unit, master cylinder, etc.).

Jnosol

Thanks for the insight. I would likely do a flush as I'm replacing OEM with ATE TYP200.