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Well, the disappointment here isn't that GM will not pay (if it's being used for track/comp use) but their lack of response/resolution to the issue.
Their marketing of a car purposed for track use (wtf else would anyone need a Z07 in lieu of a Z06) yet insistence of turning their back on track-related issues is JUST STUPID!
Come on GM! If it's a track car, support it as such. If it's just marketing gimmickry for waxers and buffers, just put some more blinky lights/shiny trinkets on it which a lifetime supply of spray detailer.
2014 Z51 here.... been racing Corvettes over a decade, never had a fluid leak. Prepped my new-to-me car with Carbotechs and SRF for VIR this weekend and doing a spot check I see leaking from both fronts. Haven't pulled the wheels yet.
I'n **** with prep, cleaned each screw before bleeding, bled, then cleaned each and stuck a rolled up paper towel corner in each screw. They were dry the first new drives but drove it to the alignment shop across town Sunday and back Monday and see this... car has not even been tracked yet!
Original owner had never touched the brakes.. some bleeders still had paint overspray.
If it's not leaking from the thread, but just the fluid leftover in the nipple, the only way to avoid that, per my experience, has been flushing them out with air compressor before putting the plastic caps back on.
As a side benefit, it also adds a nice carcinogenic fragrance/mist to the air : P
If it's not leaking from the thread, but just the fluid leftover in the nipple, the only way to avoid that, per my experience, has been flushing them out with air compressor before putting the plastic caps back on.
As a side benefit, it also adds a nice carcinogenic fragrance/mist to the air : P
I got all that out with tightly rolled paper towels.
I think I figured it out... spent four hours going over it all. Cleaned, checked torque, blew out bleeders, re-cleaned.
OEM spec is 9 ft-lbs, Brembo spec for M10 bleeder is 8-12 ft-lbs. I torques all mine to 10. All but one we're already 10 with my Heman version of snug with a light touch on a box wrench.
Here's the kicker... I put my rubber-tip air gun at 90 psi (what I used for my impact to remove the wheels) to the bleed screw and a huge amount of fluid came out all around the threads. I was shocked, but all my C5s had horizontal single bleed screws and my Wilwoods have tiny vertical ones. Using a pressure bleeder (I use a Motiv for pressure only) the thread space fills with fluid. As you drive this fluid seeps out around the threads and and residual out the bleed hole. My guess is people then over-torque the bleed screws distorting the caliper seats chasing what they think is a leak.
I could be all wrong after I drive to VIR Friday, but I've never seen fluid come out around the threads of a sealed bleeder like these did tonight. I repeated air, brake cleane, and rolled up paper towel corners in the bleed hole until everything stayed totallly dry with air in the bleed hole... then I held pressure on the brakes and checked again. Bone dry.
I think I figured it out... spent four hours going over it all. Cleaned, checked torque, blew out bleeders, re-cleaned.
OEM spec is 9 ft-lbs, Brembo spec for M10 bleeder is 8-12 ft-lbs. I torques all mine to 10. All but one we're already 10 with my Heman version of snug with a light touch on a box wrench.
Here's the kicker... I put my rubber-tip air gun at 90 psi (what I used for my impact to remove the wheels) to the bleed screw and a huge amount of fluid came out all around the threads. I was shocked, but all my C5s had horizontal single bleed screws and my Wilwoods have tiny vertical ones. Using a pressure bleeder (I use a Motiv for pressure only) the thread space fills with fluid. As you drive this fluid seeps out around the threads and and residual out the bleed hole. My guess is people then over-torque the bleed screws distorting the caliper seats chasing what they think is a leak.
I could be all wrong after I drive to VIR Friday, but I've never seen fluid come out around the threads of a sealed bleeder like these did tonight. I repeated air, brake cleane, and rolled up paper towel corners in the bleed hole until everything stayed totallly dry with air in the bleed hole... then I held pressure on the brakes and checked again. Bone dry.
Fingers crossed.
Sounds like I was right : ))
Yep, compressed air is our friend, and fingers crossed.
My calipers didn't seep a drop after 3 sessions running the car hard 150+ mph in each straight at VIR. It's 100% residual fluid in the bleeder threads. Some may think it's a leak and over-torque the bleed screws.
Taking my student out...
An interesting comparison looking at a C7Z with a less picky owner... not my car. The residual seeps out but they don't leak after that.
^and those are the iron rotor caliper, not the CCM calipers. My OEM calipers with iron rotors do the same thing. I just ignore it. Never had a braking issue or air when bleeding.
My car didn't seep a drop all weekend after clearing the bleeder column. I think some see the residual as a leak, then over-torque the bleeders and create a leaks by distorting the bleeder seat.
My car didn't seep a drop all weekend after clearing the bleeder column. I think some see the residual as a leak, then over-torque the bleeders and create a leaks by distorting the bleeder seat.
No, but the car I pictured was a CCM car to start and Dave has CCMs and had the same issue as the car pictured. Initial seepage then nothing once the bleeder column is cleared. If you torque them tighter than "snug" or tighten while hit the bleeder seat will distort and they'll never seal. Much like over-tightening a AN fitting. CCM calipers don't have a different bleed screw setup.
No, but the car I pictured was a CCM car to start and Dave has CCMs and had the same issue as the car pictured. Initial seepage then nothing once the bleeder column is cleared. If you torque them tighter than "snug" or tighten while hit the bleeder seat will distort and they'll never seal. Much like over-tightening a AN fitting. CCM calipers don't have a different bleed screw setup.
Yeah, I get that. But the rotors do run hotter; hence the calipers do also. I think that there is a significant difference in heat coefficients between the calipers and bleeders that is exacerbated by the additional heat of the CCMs; hence they are more prone to the leaking brake fluid around the outside of the bleeder. When everything is cool, the bleeder appears to be, and is, tight again.
Yeah, I get that. But the rotors do run hotter; hence the calipers do also. I think that there is a significant difference in heat coefficients between the calipers and bleeders that is exacerbated by the additional heat of the CCMs; hence they are more prone to the leaking brake fluid around the outside of the bleeder. When everything is cool, the bleeder appears to be, and is, tight again.
YMMV.
This is not an issue specific to CCMs. Gen5 Camaros, with their high weight, run even hotter than Corvettes, and they do also have this issue on Brembo brakes of SS and ZL1 cars. The fix is always the same: use compressed air to really flush out all the remaining fluid from the bleeder, and NEVER re-tighten the bleeders when hot. Actually, never re-tighten them: if you need to, unscrew them a bit first : )
09-05-2016, 07:31 AM
