Hi guys,

I've fitted new discs and pads in preparation for a wicked track day (bloody weather allowing) in a few weeks. I have bought some ATE high spec fluid, and am now contemplating bleeding the brakes to flush out the old crap (who knows when it was last changed?!)

Without a power bleeder,(but with the help of a mate) is this a pain in the rear to do or not?

I understand the electric pump will have to runj to pressure the system enough for me to bleed it, but I hear stories of having to bleed the traction control and clutch as it all shares the same pressure accumulator.

Is this right?

I am a 911 virgin, so your comments and views would be greatly appreciated

Cheers

Adrian

 

Hi Indycam,

Cheers for the response. I don't have a bosch hammer, or even know what one is!
I was going to bleed the clutch also, as the pedal doesn't fully return after being depressed.

Without a power bleeder, Is it possible to bleed the whole system?

i'm kind of thinking not.

Obviously, with the pump running, and with pedal pressure, I'm thinking I could bleed the brake system, and bleed the clutch in the same way, but with the T/C, there would not be pressure in that particular part of the system until the ECU detects wheel spin, and therefore pulses fluid pressure to the offending wheel ? Hence the need for a power bleeder?

Would flushing through 2 litres of fluid not fully dilute the remanats anyway?

I've never had a car where I have struggled to be able to do such tasks, are these really that complex?!

My apologies for all the questions!

Regards

Adrian

 

Its not worth the effort and potential problems (ruined master cylinder) screwing around using the brake and clutch pedal to bleed the system. Pressure bleeders (Motive) are available for around $40USD and they are almost fool-proof (just remember to clamp the overflow tube in the front wheel well).

You can flush the whole system with around 1 liter.

A 964 is very easy to work on as long as you have good manuals (Adrian's book and the workshop manuals and this place). I'd even go so far as to say they are easier to work on than the older (carbed) 911s.

 

Amorgan,.

Reading Adrians book( a quick scan anyway) if i recal correctly he says the only way is to use a pressure bleeder. And you have to bleed 2 other things as well. I think the low/high pressure pump? Thats where I stoped because I dont have one and I was a little unsure about the other things to bleed.

I'll dig out the book tomorrow and have a look for you.

 

Cheers fellas,
Much apreciated.

JasonAndreas, I have no idea where to get one of these bleeders, and considering it will only used every other year, it seems easier to take it to a specialist for them to do. I already have 2 litres of ATE blue 'fluid' to offset the bill slightly!!

Pesty, I believe that is because the residual pressure in the system is too low to bleed, and the pressurised equivalent much to high, and that a power bleeder is the safe way to regulate the pressure between the two?
I must admit, I was going to go out with the tools tomorrow and get involved!!

Please tell me changing discs and pads doesn't affect something else 'upstream'!!

Regards

Adrian

 

A Bosch Hammer is the device to read and reset error codes in the car's DME.

Marc

 

Where do you live? I'm sure there is someone local that sells the Motive PowerBleeder and you have to think about it as cheap insurance when you consider a replacement brake master cylinder is $500USD. If you search the archives here you'll find more than one very experienced DIYer that blew out the seal in their master cylinder using the pedal method. The factory workshop manuals warn against using the pedal method for this exact reason.

As long as you don't open the brake lines you can change pads and discs without affecting something upstream. To help retract the brake pads in the caliper remember to open the cap on the brake fluid reservoir in the trunk.

 

Here's what the 964 FAQ says about bleeding brakes in a C4:

"Some people don't care for the 964 C4 all wheel drive system (as compared to the different and improved system of the 993, for example), so be sure you're OK with it before buying one. C4's have a high pressure (up to 180 bar or 2,600 psi) hydraulic-based brake system, as opposed to the more conventional vacuum-based system. This is important if you bleed your own brakes, as it's difficult, if not impossible, to properly bleed the 964 C4 brakes without a Bosch 9288 system tester, aka "the* hammer". This tool runs around $3,000, needs a Porsche-specific software module, and Bosch no longer supports them.* C2's and RS America's use a vacuum-based brake system and can be bled at home (2 bar or 30 psi on your pressure bleeder)."

Notice that it says, "difficult if not impossible" to bleed them yourself. Don't muck around with the brakes if you don't know what you're doing. You can buy Motive brake bleeders from any number of sources (including directly from them). Cost is about $60 including shipping here in the States. From the above, I don't think you can use it to bleed your brakes. Where I live, the local Porsche specialist (using a Hammer) charges $85 for the one hour it takes to bleed the brakes on a C4. Hope this helps.

 

I think that quote is by someone not familiar with the 964 C4 (sounds like they're a fan of the 993!). You don't need the Hammer to bleed the brakes or the clutch, or accumulator or solenoid valve block. You do need a pressure bleeder. The brake system is totally separate of the hydraulic pressure assist that is run by the electric pump. The only thing you need a Hammer for, is the hydraulic locks on the longitudinal and lateral differential. And that can even be done without a Hammer if you're careful.

 

How can you bleed the hydraulic locks without the hammer controlling them???

 

You can activate the traction control program (turn the **** on the dash) and this will pressurize both locks to maximum pressure to completely lock the differentials. Then open the bleeder VERY carefully (meaning slowly) and let out a bit of fluid. By cycling on and off the traction control program you will pressurize, then depressurize the hydraulic lock circuit. Each time it's pressurized (meaning the traction control is on - dash PDAS light is blinking) you can open the bleeder to release fluid. The problem with this technique is that you have a chance of running the reservoir dry if you let out too much fluid and it is slower than the multiple and more rapid pulses provided by the Hammer. Don't get me wrong, the Hammer is the best and only method Porsche describes; but when in a crunch, using the traction control program has worked as well. And who knows, it may just do the job just as well...

 

I've used my Mityvac for several things but it's not the best for bleeding brakes. For what it it is, it's great. A Motive Power bleeder (is that correct name) bleeder runs circles around the Mityvac. About U.S. $65 delivered. I use it on all of my vehicles with no complaints.

 

I'm with Richard regarding the Miti-vac - I got one of these but could never quite get it to work for bleeding brakes. The Motiv Power Bleeder is truly the best - and the simplest. With the miti-vac you have to pump and pump... but the Motiv you pump once, then just bleed all the corners! So simple! Simple if you keep it dry; some people fill it with fluid to bleed which you don't need to do - that's just messier!

 

You forgot to depressurize the canister before you disconnected from the brake reservoir? I wrote "CLAMP OVERFLOW VENT" on a piece of masking tape affixed to the side of my Motive after the first time I forgot.

 

I cannot stress the importance of bleeding the brakes the clutch and the 4X4 system in the C4. I cannot believe the difference it has made in the behavior and noise of the vehicle. If I had not felt and heard the difference in the pump noise I would have not believed it.

Tobago Bob