Hi,

Just upgraded to GT3 calipers front on a 2006 c2S, also 350mm rotors rear. I have only bleed once so far, still sinking pedal. Before I go around again I am using the Motive pressure bleeder, I noticed a posting in the 993 section with Porsche instructions that if a larger amount of air was introduced into the system to pump the pedal slowly 3-4 times, I could tell if that meant under pressure....so is it ok to pump the pedal with the system under pressure from the Motive bleeder?

Thanks, I am also doing the GT3 mater cylinder, holding off on that until I'm comfortable I've got base system bleed again, I'm losing confidence in doing the master myself...….

 

Yes, I do it every time I bleed. If you just put new calipers, try doing a bleed and push your pads all the way back so the pistons are fully retracted, sometimes air gets in that part and it is really hard to flush out. You can use a spreader type tool, or use pliers with a rag or some sort of pad to protect the calipers, and squeeze the top of the pad and the caliper together, to push the piston back into the caliper. If you do use a spreader that requires you to take the pads out, make sure not to have the system pressurized when there is no brake pads in the caliper, as the pressure can slowly push the pistons out, and if there is no pad there, pop, out comes the piston and all your brake fluid!

 

Thanks for the info, appreciated. Think I probably have a long air bubble in the line and the front calipers were dry to start so assuming a “blob” of a bubble there. I didn’t have an expectation that one bleed was going to get me a full pedal.....but I have say a half of pedal now, less once running......

I installed new pads all the way around and have had to collapse the pistons fully already so think I’m good there.

So another question and this might be more about logical work effort than technical,

Since I have some pedal, would you install the master cylinder now????? Knowing I’m going to have to go all around (most likely twice) either way on another bleed cycle with the Master swapped out???? Thinking work/ effort here.....I’m no spring chicken and busting off 4 wheels x 2 is not easy on the back these days but I do enjoy the work overall. Thanks

 

I found bleeding the mc to be figity. It took a number of bleeds even after I bench filled it.
I think I’d want to get the calipers airfree before installing the mc. Fix one problem before creating another. Just thinking out loud.

 

If you're definitely going to replace the master cylinder, I'd ust do it now and bleed everything afterwards. A sinking pedal is sometimes a bad master cylinder, so if yours is failing you may never get to a firm pedal before the swap. You may need to bleed the abs pump too, which requires a Durametric or a slippery / sandy road. If it's a MT car you should bleed the clutch slave too - above the gearbox.