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C4: Brake bleed / hydraulic system bleed procedure

 
Old 12-29-2011, 04:12 AM
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RicardoD
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Default C4: Brake bleed / hydraulic system bleed procedure

Another thread to document some work on my car. Credit has to go to dfinnigan and garrett376. I followed garrett's procedure exactly to start for the brake caliper bleeds. I will post how to do each of these as I complete them.

Here is the summary, partly from dfinnigan, of the thirteen total bleeds required on a C4:

(8) Brakes - 4 brakes x 2 nipples each = 8 bleeds
(1) Clutch - 1 slave cylinder left rear wheel area
--- section below is if you have a C4 ------ can stop here if you have C2
(1) Accumulator - 1 in front trunk; bleed via onboard hydraulic pump
(1) Dual solenoid valve block - 1 in front trunk
(2) AWD/PDAS - 1 transverse lock and 1 longitudinal lock; bleed via Hammer or equivalent (PDT999)
-----------------------------------
(13) total bleeds

Flare nut wrenches needed for bleeder valves: 7mm, 9mm, 11mm

Do yourself a favor and treat your 964 Carrera 4 super car properly. Don't destroy your bleeder valves by using regular wrenches that could slip and damage the nuts. I didn't have a 7mm flare nut wrench but its on my list now. Don't know what a flare nut wrench is? Look at the attached photo. It will securely grip the bleeder valve nut and allow you crack it open if its on super tight with little risk of bleeder valve nut damage

I started with the brake caliper bleeds because I changed out all 4 flexible brake lines on the car. The way to do this is with a positive pressure
Motive brake bleeder Motive brake bleeder
. Essentially you pressure the reservoir with 15 to 20psi of pressure. You MUST pinch off the reservoir overflow to do this. I used some vice grips.

I followed garrett376's procedure.

(8) Caliper bleeds

1)pinch off brake reservoir overflow line with vice grips or equivalent

2)I am doing this dry like garrett376, which means I put no fluid inside the motive bleeder. My car had ATE blue at the last bleed so I am using ATE gold now. I opened the reservoir and overfilled with ATE gold beyond the max line then hooked up the motive bleeder and pumped to 15 psi. Make sure the pressure holds. I had to tighten the motive cap on the reservoir the first time with some channel lock pliers to get decent hold of the pressure.
UPDATE with comment from Darrell below: Its a great idea to use a turkey baster to suction as much fluid out of the reservoir as possible so to not have to flush that out via the system.

3)Start with the caliper furthest from the reservoir which on a USA car is the right rear. There are two bleed points per caliper on a C4.

4)I used a 11mm flare nut wrench on my bleeder screws but others have used the closed end of an 11mm combination wrench. I prepared a water bottle to catch the bleeding fluid.

5)You basically crack open the bleeder valve, after removing the little rubber caps of course, and the positive pressure in the system will force the fluid out. You don't open the bleeder unless you have positive pressure in the system. All this happens slow enough so you can check the PSI gage on the motive bleeder and make sure pressure is being maintained or pump it up some more if it drops a bit. You also keep an eye on the reservoir fluid level to make sure it doesn't drop below min. If you use different color fluid every other bleed you can use the color change in the fluid to make sure the system is totally flushed. Close the bleeder valve after the bleed is complete. Please note ATE blue will stain your reservoir tank. A previous owner had already done this on my car so I am using this two color approach. Garage queen purists may not want to do this to their cars.

Repeat this procedure working your way closer to the reservoir. On a USA car this is right rear, then left rear, then right front, then left front. Since I did this without any fluid in the motive bleeder you have to occasionally refill the reservoir with fluid and re-pump up the bleeder. I used a bit more than a liter of brake fluid to do this.
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Last edited by RicardoD; 10-20-2018 at 04:59 PM. Reason: Added update about flare nut wrenches
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Old 12-29-2011, 04:23 AM
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RicardoD
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Next up is the clutch slave cylinder bleed. The first question is where the hell is it? Its on top of the transmission and accessed from the left rear wheel well.
Thankfully previous rennlisters pointed me in the right direction and I tried to provide better photo documentation below.

(1) Clutch slave cylinder bleed

1) The procedure for this is the same as bleeding the calipers. You pinch off the reservoir overflow line (unless you did the TSB and went to the vented cap, see Laker's post below) and hook up the motive bleeder and pressurize the system to 15 to 20psi.

2)Remove the rubber cap on the bleeder screw, hook up the bleeder bottle and tube, and using a 7mm flare nut wrench (or box end of a 7mm combination wrench which I regrettably had to use) and crack open the bleeder valve. I did about 250ml. Close bleeder valve, put on rubber cap and your done.

Wow, thank goodness I did this one, as first shot of liquid came out black. The rest of my car's fluids look clean but its obvious that either previous techs skipped this step or clutch slave cylinder fluid dirties faster.
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Last edited by RicardoD; 12-30-2011 at 03:57 AM. Reason: updating procedure
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Old 12-29-2011, 05:16 AM
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nice and easy to follow and good photos thanks for that
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Old 12-29-2011, 08:47 AM
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Great write up, on my list to do so will be following this
Thanks
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Old 12-29-2011, 10:31 AM
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If you use the motive dry keep a close eye on the reservoir level.

The last thing you want is to push air in to the system and it is very easy to do!
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Old 12-29-2011, 04:01 PM
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excellent write-up Ricardo! great photos and details-
If you carry out this TSB, you replace the brake fluid reservoir cap with a vented one, and get to remove all the tubing.
Most importantly, you never have to pinch the brake fluid overflow line again!
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Brake_Cap_Hinweis.pdf (32.1 KB, 1074 views)

Last edited by Laker; 12-29-2011 at 08:15 PM.
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Old 12-30-2011, 04:57 AM
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First, thank you Laker for the interesting TSB on the vented reservoir cap. Now on to the Accumulator and Dual Solenoid valve block bleed.

Here is where I put in a plug for
Adrian Streather's Porsche 911 Enthusiast Companion Carrera 2, Carrera 4, 1989-1994 Adrian Streather's Porsche 911 Enthusiast Companion Carrera 2, Carrera 4, 1989-1994
I am listing his procedure below with my comments and photographs. When I first joined Rennlist Adrian actively participated in the 964 section and his book is a valuable reference to understand all the systems in our cars. Buy his book if you haven't and do not mess with your Rennlist Karma.


(1) Accumulator bleed

1)Open the front trunk, lift up the carpeting and remove the spare tire.

2)Remove the black plastic ABS Hydraulic unit cover and the Hydraulic pump cover. There are some screws and nuts holding these items down (see photo below)

3)Study the large hydraulic system map photo below where I point out the locations of all the components. Find these on your car. Work clean. Did you know brake fluid eats paint? So be careful pouring the brake fluid, connecting the bleeder tubes, put some towels down because drops of brake fluid will spill.

Here is Adrian's procedure in italics with my comments added (buy his book!)

Step 1

- Ensure brake system is completely depressurised.

The way to do this is with the ignition off pump the brake pedal about 25 times until the brake pedal feels super stiff.

- Ensure brake fluid is full

- Ensure ignition is OFF

- Disconnect hydraulic pump power connector
(see photo below)
Many of the 964 connectors use the automotive style with a U-shaped spring retention clip. You need to carefully remove this clip first with a small screwdriver to help, and then you can disconnect the power plug.

- Connect brake pressure bleeder equipment
Pinch off the brake fluid reservoir overflow and connect your Motive brake bleeder and pump it up to 15 - 20psi.

CAUTION: the brake pedal must not be operated as long as the brake bleeding equipment is installed

Step 2

- Connect collection of overflow bottle and transparent tube to pressure accumulator bleeder valve and open the valve

- Turn ignition ON

You better have remembered to disconnect the hydraulic pump power connector prior to this step otherwise you will quickly have a brake fluid fountain in the front of you car. The first thing a C4 does when you turn it on is power this pump to pressurize the complete hydraulic system in the car.

- Connect the plug to the hydraulic pump. As soon as no bubbles are visible anymore at the transparent bleeder line of collection bottle, disconnect electrical plug and close bleeder valve on the accumulator
This is a neat step. As soon as you connect the power plug to the pump it runs and you get this quick purge of fluid. Be sure and have your reservoir filled up before this step especially if you are using the dry method like I did. In my case I was watching for the ATE blue to turn into ATE gold brake fluid.

- Reconnect plug to hydraulic pump and allow pump to completely pressurize the system. When the system is fully pressurized the pump will switch off
Its obvious when the pump is running, I actually hear this in the car, so when you are right next to it you will know when it turns off.

- When the pump switches off, turn ignition OFF

- Disconnect hydraulic pump power plug

- Holding the bleeder tube firmly to the accumulator bleeder valve, open valve and completely drain accumulator pressure. When pressure is completely relieved tighten accumulator bleeder valve.

Now you are bleeding the accumulator "bomb" which is fully pressurized at this point so open the bleeder valve carefully the fluid will bleed out quickly. Remember to always be watching the brake fluid reservoir level.

- Repeat this procedure until brake fluid coming out into collector tubing is free of air bubbles.
Make sure your Motive bleeder is maintaining positive pressure, watch your reservoir fluid levels, take your time, do it right. I only went through this cycle once.

- When bleeding is finished, ensure accumulator bleeder valve is correctly tensioned and reconnect hydraulic pump plug.

Don't forget about the connector plug spring clip!
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Last edited by RicardoD; 12-30-2011 at 02:54 PM.
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Old 12-30-2011, 05:06 AM
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Next onto the Dual Solenoid Valve Block bleed. That is in the trunk on the side opposite the brake fluid reservoir. See photo below.

Again, I am following Adrian's procedure. Did I mention you should buy
his book? his book?
.

(1) Dual solenoid valve block bleed

The procedure is identical to the Accumulator bleeding except where it says accumulator bleed valve above just change that to Dual Solenoid Bleed valve. Its a 11mm bleeder nut.




... onto the traction control slave cylinder next...
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Old 12-30-2011, 05:54 AM
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RicardoD, thanks a million for posting this. I'm so glad you have C4 as well! This thread will save me a lot of headaches when I swap out my brake lines after I get her rolling.
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Old 12-31-2011, 04:42 AM
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And now finally, the holy grail for the C4 home mechanic, bleeding the differential locks of the PDAS all-wheel-drive system.

There are a couple of options to do this properly:

Option 1)Find and buy a Bosch "Hammer" 9288 diagnostic tester, plan on spending somewhere between $1200 - $2000 and you need to make sure it is configured properly for a 964. Here is the link to garrett964 using his hammer to bleed the locks

Option 2) Fellow Rennlisters Theo Jenniskins, a 928 Rennlister, and P. Moers used their considerable engineering skills to replicate the Bosch 9288 via software and a PC. But in addition to this they developed a handheld stand alone unit as well!! It's called a PDT999 and it sells for 399 Euro ($517 as of 12/2011). Click here for link to these products. . I bought one of these in October and for the C4 owner this is all you need. Its handheld, no PC required, powered from the 12v of the car, and completely emulates the Bosch Hammer. I want to send Theo a love letter after using this thing. Theo also gives you access to an FTP site filled with additional diagnostic information for our cars and various modules.

[Side note: You may notice in my signature that I also sell an ODB1 tool for our cars. It requires you to use a PC. My device uses the hardware schematic and free software that was made publicly available by other Rennlisters. I basically made a nice hardware package for people to run the free scantool software. If you own a C2, and don't mind using a PC with it, its all you need to diagnose all your modules, and sells for about half of the PDT999. But if you own a C4 the free scantool software will NOT bleed the locks on the PDAS system]


(2) AWD/PDAS - 1 transverse lock bleed and 1 longitudinal lock bleed

1)Remove the engine, transmission and center driveline covers underneath your car. Its a bunch of 10mm bolts. My lift got in the way of removing the cover right underneath the transmission but turns out removing that one is not necessary. You have to remove the center tunnel cover however.

2)Locate the transverse (sometimes called lateral) and longitudinal locks on your car (see photos below). They use the same 7mm bleed screw as the clutch slave cylinder.

3)Top up the brake fluid reservoir over the Max line as you will be pumping about 250ml out of the system per lock (about half a standard 500ml water bottle in my picture below) and put the cap back on reservoir. This bleed doesn't use the Motive pressure bleeder and so no need to pinch off the overflow tube.

4)Hook up the PDT999 to your OBD1 port. Its on the right side footwell in the outer kick panel area. My car's connector is such that the backshell of the PDT999 would prevent it from plugging it in. I seem to be the only 964 owner with this issue as I tried to use this same connector for my OBD1 tool. My ODB1 tool uses a narrow body backshell of my own design to prevent this problem. If you have this problem with your PDT999 just unscrew the backshell and carefully plug in the OBD1 connector in your car. I customized my PDT999 by modifying one of my narrow body backshells (one of perks of being in the OBD1 tool business

5)In preparation for the bleed, remove the rubber cap from the Transverse bleed valve, get your 7mm wrench on the bleeder valve, and hook up your bleeder bottle and tube. Do NOT open the bleeder valve yet.

6)Turn the ignition ON and using the A and C buttons on the PDT999 select 964->PDAS-Drive links->Bleed (see menu sequence photo below). The A and B buttons navigate the menus, the C button selects the menu. It's a simple interface that takes a few minutes to learn. This thing is awesome.

7)Just follow the instructions on the PDT999 screen. Its that simple and works just like the Bosch Hammer. See the menu flow below that tells you exactly when to open and close the bleeder valve. Everything happens slowly enough that you don't have to worry about going back and forth between the wrench on the bleeder screw and the PDT999. I did about 250ml of bleeding and had a nice clear golden fluid at the end.

8)Repeat this procedure when finished to bleed the Longitudinal lock on your vehicle. Make sure to top up your reservoir with fluid if necessary before doing the Longitude lock bleed.
- although I advocated using flare nut wrenches earlier in this post, in the case of the longitudinal lock bleed I think the closed end of a combination wrench is the way to go. It allows you to get the wrench into the tight space and properly align it so you can crack it open. Try with a flare nut wrench first but the combo maybe the way to go for these smaller bleed screws.

My fluid first came out very dark and again makes me think it has not been done in a while. Feels great to have fresh fluids in my entire hydraulic system now. Can't wait to drive the sh*t out of my car now.
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Last edited by RicardoD; 12-31-2011 at 05:18 AM.
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Old 12-31-2011, 12:50 PM
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Thanks for sharing , really interesting
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Old 12-31-2011, 12:53 PM
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Thanks for the great write-ups and photo documentation. Really appreciate the extra effort.
A few comments and suggestions:
- I found it is unnecessary to remove the spring clip on the hydraulic pump electrical connector. Merely squeeze or push in the clip to release the plug, and pull the connector away from the pump. Push the connector back on, and the clip will "click" back in place to lock the connector.
- Use a "turkey baster" to suction out as much of the old fluid from the reservoir as possible prior to starting the flush procedure, and refill with new fluid. I use a battery fluid suction bulb gizmo from the parts store.
- The shop manual specifies the bleed quantities:
- 250 cc at each wheel, bleeding both nipples (thus, 125cc each nipple - I usually find that I need to bleed more than this amount on the first caliper - right rear - until I see a full color change of fresh fluid. And, the other calipers will show fresh fluid with much less fluid purged.)
- 50-100cc at the clutch slave cylinder. (My experience is that the fluid from the clutch slave is usually dark+nasty and requires 100+cc to get a clear fluid. Not sure why the clutch slave fluid gets dark+nasty so quickly)
- 250-300cc at the Lateral PDAS lock (side of differential)
- 200 cc at the Axial (longitudinal) PDAS lock (front of transaxle)
- (my experience has been that I see a fluid color change with much less quantity from the locks)
- I bleed the differential locks the Poor Man's Way, using the manual lock switch on the console. Attach a catch bottle to each lock nipple. 1-Turn the PDAS switch (with key ON) to the right to activate the PDAS and pressurize the locks. 2-Crack open each nipple for a tiny "squirt" of fluid. 3-Close each nipple. 4-Turn the PDAS switch to the left to deactivate. Repeat steps 1 thru 4 about 30-40 times. Obviously this is VERY tiring if you do it yourself, crawling under the car 40 times and up to the console. Get a patient friend to activate the switch for you at your command. BUT, this is a lot cheaper than a Hammer.
- The shop manual recommends doing 2 full purges (pressure relief) from the accumulator and the solenoid valve bleeders. This will use a LOT of fluid, close to a full liter. But it is worth it - I find that this cures the problem of long pump-up time when first starting the car (and getting the ! and warning bell).
- So, from all of this you will see that you need a bare minimum of 2 liters of fluid for a complete flush, so it is best to have 3 cans available.
- I originally used alternating ATE Blue and ATE Gold fluids for my flushes to confirm fresh fluid to all points. However, I found the Blue to stain the reservoir made it difficult to view. Thus, I now use the shop manual recommendations for quantities at each bleed point as my confirmation of fresh exchange of fluid.

Have Fun, Be Safe!
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Old 12-31-2011, 02:29 PM
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great documentation Ricardo!
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Old 12-31-2011, 05:27 PM
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Darrell,

Great comments. I can't believe it didn't occur to me to turkey baster the original fluid out of the reservoir as much as possible. I was thinking it will take a while to dilute the ATE Blue back to gold. Duh. I will update my procedure with your comment. I think this caused me to go over 3 liters of brake fluid in this whole process. I lost a lot of fluid as well from the brake line change that preceded this.

Also your fluid bleeding approximations just about matched what I did. And you are right, the procedure from Adrian Streather on the accumulator and valve block includes a full pressure relief bleed which does go through a lot of fluid.

In general I agree about staying away from ATE blue and just follow the CC recommendations you posted above.
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Old 01-01-2012, 01:12 PM
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Ricardo,

Did you purchase the 9288 emulator from Theo??

If so, did you have to pay any import duties beyond their posted shipping rates???

Happy New Year,

Dan
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