[mattahmadi62]

Hi all,

I bought the gt500 rotors and brakes and swapped everything from my stock GT brakes. The conversion went smooth and well, but after bleeding the brakes the pedal is still extremely spongy and it definetly feels like there's still air in the system. I tried bleeding each caliper about 5 times and air keeps coming out but there are no fluid leaks anywhere. Also, when the car is off the brakes feel nice And tight after pumping, but when I turn the car on the pedal goes back to being completely spongy. I tried driving around the block, but it didn't help at all. Any suggestions? Do I just keep bleeding the brakes over and over again? I've gone though one bottle of dot 3 brake fluid already... Help!

 

[5.0 Candy REDCS]

Dismantling the entire stock brake system,then bolting the new one on completely filled the lines with air.
One of 2 things is happening,either there is a lot of air in the system (and there is) or it's taking air in from somewhere;
Do a pressure test on the system and look closely for any evidence of fluid leakage... have a buddy sit inside with their foot on the brake pedal(hard) and do a through search at all 4 points.
When bleeding the system, start with the farthest wheel from the master cylinder,second farthest,and so on,running 2/3 bottles of brake fluid through the system should not surprise you either.
Do NOT reuse the new fluid that comes out, it would be full of micro air bubbles.
I'd do it old school; using a clean clear glass bottle and plastic hose and keep your eye on what is coming out into the bottle as you open/close the bleeder valve... if you are still seeing air coming out,no matter how little, you still have air in the system, keep your reservoir filled almost to the brim ( careful with brake fluid and paint).
If after a through proper bleed sequence the pedal remains spongy,you need to start thinking outside the box... check and make sure ALL caliper seals are seated,all connections are tight and secure, that sort of thing.
All the best on this, hope you'll get it resolved soon :bigthumbsup

 

[wproctor411]

Same as above the micro-bubbles may be hard to see but they will cause the spongyness, and Autozone may have a brake fluid pump you could borrow which makes getting the air out much easier.
I have the Dorman version of this:
Product Page

 

[Guest]

OP just wondering how you were bleeding the brakes? I'd suggest using a pressure bleeder as was recommended above, if you haven't already.

 

[mattahmadi62]

Thanks for the suggestions everyone! I'll definetly try that next. We were bleeding the brakes by opening the cap on the master cylinder (while maintaining fluid in there), bleeding the back two tires, then front passenger and lastly the front driver. I sat and pumped the brakes till it was completely stiff and couldn't press it to the floor, then my buddy used a hose attached to the bleeder valve and open it and close it right before the pedal would reach the floor. Repeated this process on each caliper about 5 times but didn't see improvement. We went through about 5 ounces of brake fluid and we never used the old fluid that came out from the calipers. Started to worry about the caliper being a faulty part, but like I said I didn't see any fluid leaks. We're going to try using a bleeder pump and the suggestions above next. Hopefully thatll fix it.

 

[tx50autoX]

Building up pressure like that will cause cavitation as the fluid moves through restrictions. The pedal should be manipulated gently, preferably by hand. You don't need a linebacker doing squats on the pedal. Just press it down gently when the bleeder screw is open. This isn't a brute-force process, you're just pumping out the old fluid.

I would expect to go through a couple of bottles of fluid after a complete component swap like you've done, not five ounces. Just keep going as long as you see any air at all.

 

[Lewis26]

5 open/close cycles is not nearly enough to bleed the brakes properly. Not to mention, the brembo brakes have two bleeders to work with. It will probably take you a few hundred pushes to get all 4 fully bled.

I would recommend picking up some ATE Super Blue brake fluid which will allow you to see when you've bled all the way from the master cylinder. Or pick up a power bleeder.

 

[mattahmadi62]

Not to mention, the brembo brakes have two bleeders to work with.

There was my issue! Thank you!!

Here's the end result. Check it out - Brembo brakes from a used GT500 (with about 500 miles) and it all cost me $600. Not bad (crappy Iphone pics)