drcollie

A lot of discussions on this forum have to do with the pretty stuff like deviated stitching, paint colors. loud pipes and the like which is fine, but I like more the meat and potatoes of getting dirty with the car, which I don't see much of. So I'm going to try to post up some more "How To's" because there are also a lot of complaints about dealer charges and the like. Here's something you should do regularly in your Porsche - and all your other vehicles as well. BRAKE FLUID CHANGE. Due to the nature of brake fluid, it deteriorates with time and loses its efficiency, so in two years time its like running water in the system. That means a very low boiling point (heat tolerance) and corrosion of your calipers and lines. Keep the brake fluid fresh and your brake system stays healthy with the performance you need for high speed repeated stops and track days.

Here with the right tools, you can do a brake fluid change in under an hour on your 991, it's easier than changing the oil. You don't need a helper with the right equipment and you don't have to worry about air in the system with this method. You will need:

1) Air Compressor. If you don't have one, buy one. Preferably not a direct drive cheapie so you can hear yourself think. 2-stage belt drive units last much longer and are so much quieter. They don't have to be pricey. https://www.northerntool.com/shop/to...1297_200641297

2) Mity-Vac 7300. This runs off your air compressor and is a suction device. It comes with a special brake fluid hose & attachment (you do not need to purchase the accessory). Great tool, it allows you topside oil changes on any car with a dipstick or orifice that you can snake the tube into (I use it on my Audi SQ5 for oil changes) and is just the ticket for brake fluid service. $ 100 tool and worth every penny.


3) Two bottles of DOT 4 brake fluid.

4) 11mm open end wrench

5) Brake Tester to see how your fluid is doing (optional) - under $ 10:


My brake fluid in my 2014 was last done as part of the dealer service two years ago, so I decided to test it. I remove the cap off the Master Cylinder, turn on the tester and simply put the electrodes in the fluid. As you can see in the photo, it needs changing; The great thing about Porsche is they put the bleed nipples on the outside of the caliper (unlike my Audi SQ5 which is inside) so you don't have to pull the wheels to do this or jack the car up if you can get clearance to swing the wrench. On my HRE P40's there is plenty of room. This will make it quick and easy.

1) Hook up the air hose to the Mity-Vac 7300 and leave the lever CLOSED on the brake fluid adaptor. Let some pressure build and while that is going on go to the closest wheel to the Master Cylinder (driver's side front), remove the rubber cap off the bleed nipple and position my 11mm wrench over it. Set the suction cup over the nipple, OPEN the valve on the brake fluid lever and at the same time crack open the bleed nipple with the wrench. Brake Fluid will be sucked out at once in a fairly steady stream into the Mity Vac. No need to hold onto the tube the suction will keep it on top of the brake nipple.

2) Watch the reservoir level - DO NOT LET IT RUN OUT - if you do, you will introduce air into the system. Keep topping it off with your new DOT 4 from a sealed container until you feel you have all the old fluid out. You can use a colored fluid for the new stuff if you can find it, then when it begins turning the new color you know the old stuff is out. Take your wench, close off the bleed nipple and the remove the suction cup. Replace the rubber top on the nipple and that wheel is done.

3) Go to the other three wheels and do likewise, they don't need to run as long you are just getting the old fluid out ot the line for that particular wheel. Keep topping up the master cylinder as you go. Again, do not let it empty. Once the last wheel is done the car is ready to go. Very fast, and once you have the tools your fluid cost about $ 8.

Ridiculously easy and a hundred times better than having someone mash the brake pedal while you turn the nipple to get a little fluid out. No air can go into the system so you have a firm pedal ready to go as soon as you back the car out of the garage. Your Mity Vac will pay for itself very quickly......

911-TOUR

Very nice write-up...some new tools I didn't know existed :-) Bookmarked. Thank you.

alainpp

Thanks for the instructions and recommendations.

How much brake fluid do you use to flush the whole system?

daberlin

Great write up! A few comments/questions:

1. I thought you should use a Flare Nut Wrench on Brake Bleeder screws? I know VW/Audi makes a big deal of this on brake lines themselves (ie, replacing rubber brake lines with braided lines, etc.).


2. Does it matter which wheel you start and end with? 'Old school method' is to start bleeding with the wheel farthest from the brake fluid reservoir. Thus the order would be: RR, LR, RF, LF.

3. How easy is it to see the color of the brake fluid in the suction device? Using a Motive Bleeder, I use the catch bottles to see when the discolored fluid turns clear (thus confirming the caliper now has clean fluid and it's time to move to the next caliper).

mreloc

wareaglescott

Thanks for posting. Will order up the tools and they will pay for themselves quickly.

Does this same technique and tools work on pretty much every vehicle?
I have heard how nasty brake fluid is. Will it destroy any components on the mityvac?

drcollie

You can do the whole system with one container (12 oz) though I go a couple of ounces into a second one to be sure of my purge. I did three vehicles yesterday in my garage so I had plenty.

Flare nut wrenches are pretty much a requirement when working on brake lines - but not on bleeder nipples, usually they're too thick. I am a huge fan of Snap On wrenches as they are made thinner and stronger that most other brands, so their regular open-end has plenty of throw room on a bleeder nipple.

There are different manuals that tell you which line to start on - quite honestly I don't think it much matters, the whole goal is to get get as close as possible to 100% changeout of the fluid. On my 991 I do the driver's front first and give that a long bleed because I can keep an eye on the master cylinder - because you don't want that to run dry and have to keep it topped off.

3Series

Did you flush the other side of the caliper? There are two valves. You have to take the wheels off to get to the inner along with getting a wrench on the valve. Some might say you can do it without taking the wheels off and it depends on the wheel you have but for most it's nearly impossible.

Also, you want to start from the caliper furthest from the master cylinder. Not a big deal in my opinion if you flush all the time for track purposes. Also a flare nut wrench is not needed, it actually makes it a little harder.

LavaGTS

Good post man!

Need4S

Nice write-up. I use a box end wrench, which I think is a safer choice than the open ended one, but to each his own preference.

Also, are you sure the Mityvac 7300 comes with the brake bleed kit? If not, you will need a Mityvac 7205 brake bleed accessory kit in addition to the Mityvac 7300.

3Series

Also, on a street car, you could probably run the same brake fluid for 10 years with no impact to the driving experience. Is it good for the parts, no, but it's not as critical as what people make it out to be. There's a higher likelihood of your master cylinder going bad before the fluid is useless.

Also, a lot of folks use a Motive Bleeder using the dry method. Less cleanup.

worf928

This-^

I always take the wheels off when I flush. This allows me to
- get easy access to both bleeder valves.
- clean the corrosive brake dust off of the entire caliper and then wax the outside
- clean and re-wax the inside of the wheels

bkrantz

First of all, thanks. And I agree with the need for more "dirty jobs" with some degree of mechanical achievement. My own personal preferences for bleeding brakes:

1. Always take off the wheels. Besides providing access to both bleed nipples (where present) it also allows for inspection of the calipers and pads, as well as suspension, tires, and other critical components.
2. I bleed all access ports. Yes, this might increase the effectiveness of fluid change by less than 1%, but does make air extraction more likely.
3. I have used both vacuum methods and pressure methods. Both can work if done right, and have various more or less convenient aspects.
4. When changing fluid, I try to remove as much old fluid from the master cylinder reserovoir before refilling with new and starting the flush and bleed.
5. Some ABS and other complex systems may need external service computer control to operate valves and other components for a full bleed.

drcollie

LOL, no I did NOT know there was an inside bleed valve on the Porsche calipers! I've never come across a car with dual bleeders - the thought never occured to me. Well, I'll do it again in the Fall or as soon as my tester shows in the red again, and catch the inside ones next time. Appreciate the tip!

Yes, Mity-Vac 7300 has the brake bleeder attachment included in the box.

arter

Do the rear brakes first.

Do both the inside and the outside chamber of each brake
( brake fluid enters the inside chamber and then passes through the little line at the bottom of the brake to the outside chamber.
Therefore if you bleed the outside chamber nipple, you probably will get everything out, but being safe is nice).

Removing as much of the old fluid in the master before starting shortens the bleed needed.