Had an install day today, with a good used Stop-Tech BBK. Calipers, rotors, SS brake lines. All components were inspected solid. No warpage on the rotors, no stuck pistons, no bad lines. Machined the rotors just in case. The parts came from a donor G35 and sat in storage for a few months, so I double-checked to ensure all components were operatring correctly before install.

The install went overtime and the co-op shop I use had to close so there was no time to do the rear wheels, just the fronts.

The problem I am having is that I now have massive pedal softness, to the point that the car is unsafe to drive. It takes two pumps just to come close to normal stopping power. Also, hard braking results in a massive shudder. Oh, and the pads are noisy.

I will chalk-up the noisy pads to them being mixed-up and possibly being placed in a different caliper than before. I expect they'll quiet down once they've worn a bit.

The pedal softness baffles me. We bled the lines (on all wheels), then bled them again. There's no evidence of a fluid leak and the reservoir seems to remain ok, so what's the deal? I've done brake jobs dozens of times. If there's air in the system I'll be damned if I know where it is. Are there any tricks to the G35 I should know about? I didn't touch the ABS, Didn't touch any parts of the brake system except calipers, rotors and the soft-lines.

Since I didn't have time to do the rear wheels, is there a chance the imbalance of huge brakes up-front and OEM ones in the rear is too much for the proportioning valve?

The weird thing about all this is there's no warning light indicating brake issues. As far as the car is concerned everything is fine.

Unfortunately I won't have time to address this issue again until next Sunday when I can get back into the shop, so in the meantime if any of you learned G-men have any suggestions, I'm all ears.

 

Is the bleeder valve on TOP?


I made that mistake before on a 240 and put Z32 brakes on upside down, had same problem you just described.

 

The valve is on top, which I thought was weird. But the calipers are stamped R & L so that's why I installed them that way.

So do I have them backwards?

 

I haven't seen that setup, but the valves should be oriented upward so that any air bubbles will rise up and out the bleeder.

What you're describing really sounds like air in the brakes. Do they happen to have two bleed valves per caliper? I found a stoptech install manual here and noticed this bit on how to bleed the brakes:

Bleed the brake system, using an 11mm box wrench to loosen the bleed screws. The sequence for bleeding the brakes should be:
1. Right outboard bleed screw
2. Right inboard bleed screw
3. Left outboard bleed screw
4. Left inboard bleed screw

After initially bleeding the system, gently tap the caliper body with a non-marring mallet to dislodge any small air bubbles, then re-bleed the brakes.

 

I went through almost 2 quarts of brake fluid bleeding my BBK. Take your time and I think you'll be fine. Just like 180 suggested, sounds like air in the brake lines. When you bleed remember to start with the caliper furthest away from the master cylinder....right rear, and work your way in.

 

Hmm, well it's only one bleeder per caliper.

But 2qts sounds like a lot - I didn't have to add nearly that much, so I probably do have air in the lines. Damn, bled them twice and the air is still there.

Also, I noticed I have installed the rotors on the wrong side (vanes sweeping "reward" not "forward"). Probably doesn't make a huge difference in the short-term but will remedy that on Sunday as well.

Unfortunately I have to drive about 300 miles before I can fix this. They will be 300 very careful miles indeed.

 

I'm hoping to do more bleeding (the brakes, not me) and do the rear brakes on Sunday. Hopefully adding the rear half of the BBK will improve matters as well as a good bleeding.

Sheesh, improper bleeding, backwards rotors, and taking way longer than should be necessary - I really f***ed this one up!

 

You really shouldn't drive this car. You could have an accident because of this issue Yuppy!

 

The mis-matched brakes shouldn't be an issue in and of themselves. I'm running Wilwood 6 pot fronts with 14" rotors and have the stock rears on. Brake bias is good, hard braking is balanced and pedal feel is nice and hard.

I also suspect you have air in the lines, good luck and hope all works out well.

 

^^THIS!! It's a safety issue man, grab a friend and bleed these in your driveway. Or rent a car for the week. It will cost a lot more if you injure yourself or others.

 

Okay, third bleed was successful. Pedal is back to normal. However, there's still some bad shuddering at hard braking. I hope once the pads seat a bit this will remedy itself.

 

Okay so after a 60 mile drive at highway speeds I'm pretty sure the only remaining issue is a warped rotor. I machined them on Saturday but maybe it either wasn't enough or one warped due to the backwards install (no cool air getting inside). Taking them to a local shop in the AM. Fortunately I'm staying in tis area for a few days, with no long drives expected before Wednesday night. Lots of time to get it right.

Bothers me to have to take this to a pro. It's not rocket science!

 

Have you followed the bed-in procedure?

 

I did to a degree, but as all the components were used (from a donor car) I wasn't as vigilant as I would have been with a new set. Besides, the shuddering was present right away.