Jimjacqmx5

I have just fitted a brand new brake master to my 964 C2 after issues with old master. After bleeding master cylinder and pumping bucketloads of SRF through all 8 nipples To bleed air from lines and calipers, we still have no 'pedal'. WTF is going on? Pedal was fine previously but we were getting issues with dropping pedal on the track hence master change.

Rocket Rob

Sounds like you still have air in the system. How are you bleeding? I use a pressure bleeder (Motiv).

jembolt

+1 on air in system. It can take lots of brake fluid to get all the air out of the lines, especially if originating at the master cylinder. Motiv bleeder is a great help.

PNine64

When I changed my lines out it was recommended that I turn the ignition on between bleeding each of the nipples to ensure that fluid was getting into the ABS unit.

Jimjacqmx5

Thanks for your replies,

Can I just confirm the following.

Firstly, why is a power bleeder better than the old foot pumping method?
Obviously with an old master cylinder, the foot pump method runs the risk of stuffing the seals due to a lipped master bore but this isn't an issue with a new master cylinder. Would it not pump any air out just as effectively as a power bleeder? If not, why?.........

Secondly, what is the theory behind having the ignition on for the abs unit?
Is the worry getting air out of the ABS unit, and if so, wouldn't pumping it through achieve this?

We rebled the system yesterday and still have almost no brake pedal. This iw really strange.

I have ordered a power bleeder but it will take a few days from the US.

There is no 'fluid leaks' from master, or calipers.

I am racing this weekend and need brakes so any help will be massively appreciated....

Is there anything else that could cause this?
I figure if the brake booster was stuffed you would still get a decent pedal, it would just be hard to stop and other issues such as a leak would be pretty obvious after pumping several litres of SRF through the system.
This only leaves the lines and ABS unit.


Thanks again.

Bill Verburg

It happens to the best shops at times(was just speaking w/ a 964Cup owner w/ a similar issue this wkend), when a m/c is replaced it's very difficult to remove all the air from the system.

Take it to a shop that can pressure bleed and cycle the abs pump w/ a Hammer or pst

Indycam

Do you have access to speed bleeders ?
http://www.speedbleeder.com/
If you install them at all four corners and them pump like heck , you might just get that bubble to move .
Have some one stand by the reservoir with a filler bottle .

PNine64

I borrowed a pressure bleeder from Simpsoap and he summarized the following exchange when he handed it over.

https://rennlist.com/forums/993-foru...-question.html

Jimjacqmx5

Thanks again. I mentioned to my mechanics the 'hammer and pst' cycling and they knew what you were talking about so that's a good start! I have ordered a Motive Bleeder but it won't arrive until late this week.

ttAmerica RoadsterAWD

Sounds like you still have air. Here's a good tip...... go to NAPA and buy their cheap dot 4 stuff, they have 32 oz plastic containers, you may need to get three of these. Once you get all the air out, then use the good stuff.

Doh! just realize you are in Melbourne. I don't think you have NAPA auto parts. In any case, use cheap fluid to bleed then use the good stuff.

Jaime

Jimjacqmx5

So I gather from all the responses that this must be an air issue and that foot pumping is not as good as a power bleeder. (Still unsure as to why.)
It also appearas that as we don't have fluid pouring out of any calipers etc that there is no other 'hardware' that would result in this problem. I figure the only other hard wear is the brake boster and ABS pump.

The mechanics are back on it today so we'll see how we go.

Running out of time for a race meet this weekend.... Grr

boxsey911

Do your local auto stores not sell the eezibleed kit? They work on the same principle as the Motiv but take the pressure from a tyre. They only cost about $10.

Bill Verburg

foot pumping is bad because the m/c pistons are forced to travel in virgin sections of their bores, w/ time these virgin sections become pitted and rough from moisture absorbed by brake fluid. The rough sections damage the seals- result new m/c is needed.

low pressure bleeding is best, though some will argue for gravity bleed

tbennett017

When/if you get to using a Motiv Power Bleeder, be sure to pinch off the overflow tube at the brake fluid reservoir, otherwise you will just create a neat puddle on the floor of new brake fluid.

Jimjacqmx5

Aha, handy tip. Thank you