This could be wrong. Depending on how the bleeder enters the cylinder, you could be trapping air by doing this. Edit: I can’t find the diagram I was looking for, and this one isn’t perfect. But if you draw a line along the path of the bleeder you can see that it enters the cylinder below the level of the fluid. This will bleed perfectly, but traps air in the cylinder. You would need to rotate this caliper about 80* clockwise to get the bleeder entrance point to the top of the cylinder.
I haven't been able to pressure bleed yet. I took the lid off the Corvette MC, drilled then soldered a fitting in for pressure inlet, but I can't get it to seal against the MC. Even the original gasket and original lid will not hold pressure. Still working on that. Yes as I said before, if the MC and calipers are working correctly, which I think is the case, that leaves only the PVs and RPV. The lines can't malfunction except for pluggage. There is too much flow from each caliper for that to be the problem. I do have a brand new 2# rpv I could swap in for testing. I have the PV plumbed upside down according to the writing on it. it could be holding air, but I don't think so. I wouldn't think its mounted position should matter. I have to take the left side of my new all welded exhaust system down to get to the PV and rpv. But I think the PV and RPV;s are where I am headed.
Again with my circle track experience. All my race cars had the same calipers all the way around. with two 3/4" MC connected with a balance bar controlled from the driver's seat. I was always able to get the balance correct. I figured the same setup on the hotrod only with a PV ought to work. Wilwood's next size down is a dual piston 1.62 piston. I was afraid that wouldn't be enough. Mine are all 2.5" pistons. I was also trying to factor in the bigs and littles on the car requiring more brake on the rear than if the tire/wheel combo was the same all the way around to compensate for the larger rear tire/wheel.
A friend swears by vacuum bleeding. I’ve never had it work successfully. It seems like it should. Not having SWMBO have to “help” is priceless.
The Wilwood calipers are drilled straight in on a diameter line. So at the top is "at the top". The GM metric calipers that were on the car were drilled on angle. Those had to be rotated so the bleeder is off to the side a little bit.
Man, I have tried pump and release. I have tried release and pump. I have tried open bleeder with hose in bottle then pump a quart's worth of fluid. I have a vacuum bleeder. I tried that. I bought a pressure bleeder. I have tried that. I tried it while pumping the pedal. I tried reverse bleeding by pumping the caliper piston out to where I thought it was going to fall out, then forcing it all the way to the bottom of the bore, pushing all the fluid back to the MC. I clamped it at the bottom of the bore then did the same for all 4 and bled again. I'm out of ways to bleed.
I want to thank you guys for trying to help out. I know remote diagnosis is almost impossible. And it is hard to judge some random guy on the internet for his skill level. I know some of you guys are thinking this guy don't know his ass from a hole in the ground, but I am not a novice by any means. I am almost 72 years old and have been hot rodding and racing since I was 16. Brake systems are nothing new to me, but this one's got me by the short ones. EDIT: So far! I ain't done yet.
There is no pressure being applied to force fluid to run back from the calipers into the master reservoir . If you have too much pressure to the rear brakes , your calipers are not sized correctly .IMO . also , IMO , aftermarket brake manufacturers are a bane to folks setting up break systems , they simply don't have the R&D capability of a major manufacturer . If you lift an entire system off of a similarly sized OEM ,& adapt it to your chassis , the engineering & experimentation is already done & proven , no need to beat yourself up trying to reinvent the wheel , unless you enjoy that sort of thing ?
Hard to describe this, but yes. About a half second on the push stroke, and 3-5 seconds on the lift return stroke. By watching the fluid come out using clear tubing, too soft a push would look good, but then a hard push would still show bubbles coming out.
You mentioned the PV being upside down earlier. That seems like a likely place for air to hide. Without knowing how it’s built internally, can’t say for sure.
Why are you removing the calipers to bleed them. What are you putting between the pads to keep the pistons from blowing out when hand held bleeding? This may be part of your problem. I have always bleed calipers on the car. By moving the pistons around with the calipers off the car you may be introducing air back into the caliper.
Gravity. That's what proportioning valves and balance bars are for, within a range. Even the OEM's have PVs in them. All that notwithstanding, the presence of the RPV's or the PV in the system is not part of my problem here as long as both are functioning properly. Which has yet to be determined.
There has been a long going problem of air getting trapped in through frame brake line fittings. Art Morrison did an article on this subject but all I can find right now is this mention from this sales sheet, about halfway down the page. Air gets trapped in the fitting and won't come out. https://artmorrison.com/products/components/brakes
Exactly the reason my rear calipers are the same size as the front plus the rears are a lot heavier. Bigger flywheel to stop.
Make it easy on yourself, get a jacking beam for your 4 post lift. I'm 63 and feel similar to you, already. I have a garage pit and a jacking beam. But working off the floor is a pain, and going up and down the pit ladder gets old quickly too! A 2 or 4 post lift is in my near future, but I'm headroom compromised! You've probably pissed away enough brake fluid to pay for most of a jacking beam anyway. On the pressure bleeder you only need a few psi, maybe 5? I have a kit that uses the spare tire as an air source (I have a compressor though). 20 psi of brake fluid makes a heck of a mess when it goes wrong. I love my vacuum bleeder though. And no mess whatsoever. And I use it for all kinds of things in addition to brakes. Overfilled the transmission. No problem! Good luck with the elevation! Chris
When I had the 8.8 rear built for my replacement it would have been easy for rear discs since they are so common but I wanted drums and F150’s had great sets. I had read that disc/drum combos were great for our retrofits especially since anti skid/lockups were not used. I know there will be a solution… it just so frustrating to read this post..
Theres some flawed reasoning . Do you really believe that the size / weight( within reason) of the rotating mass affords any measurable input to braking performance ?
Regrading vacuum bleeding, I always used my MightyVac when I replaced a wheel cylinder or caliper. It came apart on me when I was pumping away on a rebuilt dry system. Damn. I had an old electric vacuum pump rigged up with the little MV jar. Worked so well I never replaced the MV. What I noticed with vacuum bleeding, it looks like you always have air bubbles coming through, I learned to disregard them. I assume it’s drawing air in from cracking the bleeder. Anyways, MVs used to be about 30bucks.
OK.. never had a catalog. I looked them up for kits for different cars using stock spindles and only showed individual piston sets in 4 or 6. But since they are in the aftermarket brake business it would only make sense. Brakes are a secondary part of their business.
Absolutely. I can tell you for a fact that when I put larger wheels and tires on my Quad, it took a lot more to accelerate it and a lot more to stop it.
Thank you. That is the style I have, but what is shown is the dual piston caliper. Mine are the single 2-1/2" piston with 4.90 sq. in. The 1.62 duals are 4.12 sq. in. I went with this style because that is the bracket style already on the car.
Yeah. I noticed this. That is one of the reasons I decided to abandon the vacuum bleeding. Too damn confusing. Never could figure out where those bubbles were coming from.
Less to do with mass, more to do with leverage. A larger diameter wheel/tire combination will increase the distance from the axle to the contact patch, which will increase the loads applied. This includes extra loads on axles/spindles, brakes, steering components, etc. It also means extra force is required to accelerate the vehicle, and on the other side of that coin, extra force is needed to decelerate, placing more strain on the brakes.
Actually there is a bushing there that the pin slides on. The bushings all move nicely and they are greased up along with the pins with white lithium and working correctly.
In a PM it was suggested that I check for "knock off". In other words, the piston and pad pulling back from the rotor. I took a .003" feeler gauge around the car and could not get it in anywhere between the pads and rotors. It doesn't appear as though there is any pullback of the pads. That tells me that the calipers are not low drag style and that the RPVs are probably doing their jobs. That just leaves the PV. That is where my next attack will focus.
The Jalopy Journal
