Wilwood Brake Problems!

[Tom 72RS/SS]

Installed Wilwood Big Brake Kit about 6 months ago and have always had a "honing" sound as you come to a stop. Let off or push harder and sound goes away, just drives me nuts and it just shouldn't be there. Over the summer I've only driven the car for 20-30 min. distances to some cruises and noticed that by the time I get there, the brakes are dragging and the noise is more constant.
OK, fast forward to last week coming home from Goodguys and I smelled something and the car was slowing down so I pulled off the highway and saw smoke coming from the right front caliper so it was binding and the pedal was hard as a rock when I stopped.
Called the tow truck and 40 minutes later I was able to drive it up the flatbed and when we arrived at home, pulled it off and drove it into the garage. Jacked it up and it spun like normal.
Contacted Wilwood on Monday morning and they said they thought the adjustment rod from the pedal to the master was adjusted too far out and too much residual pressure was the cause and effect of the caliper siezing although not sure why both sides wouldn't do it.
Today I made several adjustments and still hear the sound. The more you drive it, the worse it gets and I hear it coming from the rears as well.
I have a big cruise to attend about an hour and a half away on Saturday and the street machine nationals in Springfield in two weeks, which is over 2 hours away. There is no way this car can go that far without incident. What the heck is going on with this thing? Any suggestions before I flatbed it to the local speedshop and drop a bunch of $$?

[Jody SS]

Did you call Wilwood technical department yet?

Tobin also has a lot of knowledge about Wilwood brakes.

Jody

[gsxrken]

Clearly your brake system has pressure when it shouldn't. That's not the calipers fault.
You do have to figure out why that is the case. Often the pushrod is too long and is mildly applying the brakes and you don't notice it u til they lock up from heat. Bad boosters can apply the brakes, and old brake lines can block the return of fluid so the brakes stay on.
Next it e it happens, crack a fitting on the master cylinder and see if you have pressure. That should also release the caliper temporarily anyway.
Good luck and let us k ow what is was.

[jpgolf14]

Yup, agree with above. Sounds like an issue between the front tee and that caliper. Check for crushed brake lines. What is the condition of the soft line to that caliper?

[Tom 72RS/SS]

Everything is brand new: Wilwood master, booster, brake lines front to back and SS Braided flex lines. Nothing is binding, pinched, leaking or otherwise. Seems that pressure is building as you drive making for a firm pedal after 20-30 min. of driving. If I push in on the clutch at low speed, the car comes to a stop and holds. It definately has some residual pressure that builds up then goes away after it cools down. Rotors are perfectly centered and nothing is loose or mis-aligned.
Today I checked the rod between the booster and master and it's right. Adjusted the rod from the pedal to the rear of the booster dozens of times to no avail.
The local hot rod shop I trust is so busy they can't get my car in to look at it for 3-4 months. UGH!

[Hydratech®]

This could end up being VERY simple... Make sure that your master cylinder isn't overfilled. We have at least one customer a month that has overfilled their master cylinder, which can cause the brakes to drag when hot. We will instruct the customer to suck out brake fluid out of the wells until they are just a bit over half full, then call us back with their findings. Guess what? All better!

How? Why? Brake fluid is glycol based and will act just like engine coolant when hot. We all know engine coolant expands considerably once hot, but very few know that brake fluid does the same. If the fluid expands with heat, and has literally nowhere to go, it will build pressure inside the MC fluid wells and will cause a rock hard pedal with dragging brakes, with the problem mysteriously clearing up as soon as things cool down even a small amount. Also, the Wilwood MC's have two itty bitty little tiny vent holes in the black oval lid - make sure they aren't plugged up somehow.

If that doesn't do it, go back to reviewing the MC piston preload condition. If your MC pushrod is adjustable, back it off even futher. An air gap of 5 thou can tighten up into zero and even go into MC piston preload when underhood temps are high. You will not be able to feel 25-30 thou air gap in the brake pedal, so err on the loose side. If you do not have an adjustable MC rod, find two washers of equal thickness and temporarily install one under each mounting flange ear of the MC (acting as shims to induce more MC piston to pushrod air gap). If this clears up your problem, then you can sometimes slip the MC pushrod out of the vacuum booster in certain designs and carefully buzz the forward tip a hair to provide more air gap.

We have observed that these new design Wilwood MC's have their comp ports (in the bottoms of the brake fluid wells) set to provide as little travel as possible before piston travel closes them up to start building pressure to the brakes. Most OEM MC's have about a 1/4" of travel before the comp ports get closed, while these Wilwood MC's seem to only have about an 1/8". These means that OEM type MC's can handle MC piston preload much further than these new design Wilwood MC's will tolerate. I'm sure they did this to provide as tight / low travel brake response as possible during initial brake apply, though this means that they are also VERY sensitive to any MC piston preload what so ever. If your brakes are locking up when hot, and you pull over and loosen the MC mounting nuts, then find that the vehicle will roll again = absolutely no doubt about it having an MC preload condition.

[Twentyover]

Doesn't the cap for the master provide a vent above a rubber diaphrgam to accommodate barometric and temperature changes, along with permitting pressure equalization for pad wear? Wouldn't that diaphragm go convex in this case, unable to build significant pressure?

[Hydratech®]

Even though the new design Wilwood MC is essentially the basic C3 Vette MC in overall design parameters (despite its considerably different appearance).... The good ol' C3 Vette MC's had the stamped steel domed lids, while the new design Wilwood lid is dead flat. The rubber bellows doesn't have the ability to do much against that flat lid = why considerably more air gap is needed on these particular MC's. You can see how much engine coolant expands in the later model coolant recovery bottles - the difference between 'COLD' and 'HOT' can be up to 2" or more. The late model MC's with the translucent brake fluid tanks can provide visual evidence of brake fluid expansion. If you have one of these with the plastic tank, mark the fluid level precisely cold, then take it out for a "beat session" to get the brakes and engine compartment good and hot. Check the fluid level again and see what level of expansion you may find. Look at some late model trucks and you see some really big brake fluid reservoirs. Yes, it is to cover dramatic amounts of pad wear between service sessions, but also to help accomodate thermal expansion of the brake fluid during heavy use too.

Got some brake lines anywhere near some header pipes? Underhood temps pushing 220? Brake caliper temps pushing 300? Brake fluid will definitely expand and needs somewhere to do that. That's why an overfilled MC can cause brake drag when hot - especially on a performance car pushing high horses (which translates into heat).

[Tom 72RS/SS]

Wow, learned something new! I have to admit that the mc is as full as I could get it because of the angle. I asked a mechanic at a local dealership if filling it all the way would have any effect and he said: NO! The symptoms you described are the same in my situation. Seems to build pressure and the pedal gets firmer and firmer and the brakes begin to drag. The rod between the booster and master is not adjustable and I actually thought of shimming the mc to see if anything changed.
I will pull out some fluid tomorrow and take it for a spin to see what happens and post my results. If this works you've saved my from buying another mc/booster setup and a whole lot of $$. Wish me luck!

[Tom 72RS/SS]

Well, I don't have good news. I removed the cover from the mc and one hole was plugged. Then pulled out fluid to about half full or less, reassemble and off I went. Within 30 min. I could feel the pedal getting firmer but this time the noise seemed to be mostly coming from the rear brakes and at slow roll, coasting to a stop, it wouldn't roll on it's own. Needless to say, the brakes were heating up again and making that noise again. I tried adjusting the prop. valve but no significant change.
Drove home and jacked up the left front and it was hard to turn. Popped the bleeder valve open for a second and it was better (not free wheeling) but better. Did the same for the left rear with similar results.
I bought the Wilwood mc, chrome 11" booster and prop. valve from CPP as a package. The master is 1 1/8 bore which correct for that size booster so unless something is faulty I'm really at a loss here. The only thing I haven't tried is shimming the master away from the booster to see if there is any change. What do you guys think?

[Hydratech®]

Shimming the MC away from the vacuum booster IS a considerable part of the diagnostics spelled out, so get busy.

Here is some further reading about the Wilwood MC and the spacer bullet / plug:

(4th post down)

http://www.lateral-g.net/forums/showthread.php4?t=17060

Even if you don't know it, you are very likely using the spacer bullet / plug in the backside of the MC (in conjunction with a short MC pushrod sitting BELOW the MC mounting surface in the front of the vacumm booster). If you have a really deep MC pushrod hole that you can stick a pencil into about 1 1/4" AND a long MC pushrod that protrudes well beyond the MC mounting area on the vacuum booster, then you have the other design (highly doubt it though). Assuming you have a CPP short MC pushrod design vacuum booster, you may be able to fish the Wilwood spacer bullet out of there (sometimes hitting it with compressed air will coax it out - other times it is in there to stay no matter what). Buzz the forward end of the aluminum spacer plug / bullet IF you can get out. If not, an air or drill motor with a larger round carbide burr can deepen up the concave MC pushrod pocket in the spacer bullet to provide more air gap to the MC pushrod. If the MC pushrod will slip out of the front of the vacuum booster, chuck it up in a drill motor and buzz a few thou of off the end that actuates the master cylinder.

The bottom of this webpage shows the difference between the long and short GM MC pushrod designs:

http://www.hydratechbraking.com/GM_1stgenF_Body.html

While not Wilwood information, the same spacer bullet / plug info applies:

http://static.summitracing.com/globa...-1-2-3-4-5.pdf

The quick fast easy step one here is to shim the MC away from the vacuum booster first, then road test. IF this takes care of business, then you are performing the mods spelled out above as the permanent adjustment / solution.

[Tom 72RS/SS]

Today I shimmed out the mc with 2 shims per side. Drove around for about 30 min. and although the pedal travel was long because of the spacing, it didn't seem to heat up and create a hard pedal like before. There was only a hint of noise coming from the rear brakes but only faint for a second. I also noticed that the car will easily roll back at a stop light so the binding seems to be gone.
I will try to remove one set of shims tomorrow or the next day to get a better pedal and drive it for at least an hour doing my best to heat up the brakes to see what happens.
I have the Street Machine Nationals on the 29th in Springfield, MO which is a week and a half. More importantly it's over 2 1/2 hours away so I need to get this figured out asap.

[boostin05blacksti]

Tom,
I can’t promise I have the answers but can share my story as it seems a bit familiar. I have manual wilwood brakes with their 7/8 master, 6 piston fronts and 4 piston rears, all new stainless lines w/ stainless flex hoses on the ends. Put it all together and filled with dot 4 fluid that I had laying around that had been opened for about a year but always had been stored with the cap on tight on a shelf in my garage. Brought the car to get tuned and the brakes where sticking when we pulled it off the trailer. Cracked a value and they would free up. One of the guys at the shop told me that he thought my brake fluid had been contaminated. As the car got warmed up the brakes would stick worse. Got the car back and drained all the old fluid out, bench bleed the master, blew out all the lines and the distribution/proportion valve with air...reassembled. Filled with new dot 4 fluid, bleed and no more problems. I don’t know if there was something in the line or if it was the fluid but it seems that my problem has been resolved.

Good luck in finding the problem and getting to the show, Steven

[diesel25lrs]

I had a similiar problem...Check the play in your brake pedal for starters-you should have a little back and forth-about half an inch or so of freeplay. I ended up taking out the rubber bump stop above the pedal which on a first gen is about 1/2" thick. I also ended up putting 1/8 of shims behind my MC and this fixed everything! Next I would look at a new prop valve if I were you- maybe bad?

[Tom 72RS/SS]

All the fluid was new so contamination is not going to be an issue. As for the proportioning valve, it came from CPP but you never know. As I said earlier, shimming the master out seemed to eliminate the brake binding and heat issue but the brakes didn't start to grab until they were 3/4 down. I will have to drive it around for way more than 30 mins. to make sure I have no issues when it's time to hit the road. Now it's going to be about making all the little adjustments to get a full pedal without the brakes draging. At least I'm heading in the right direction.

[ROBS6T8]

A big THANK YOU to Paul for the above information. I have some reading to do!

Tom did you ever get this figured out?

[Tom 72RS/SS]

Sort of Rob. I'm down to one set of shims between the booster and master which allowed for more pedal travel. Minor adjustments to the adj. rod is better but not perfect.
Drove around for 2 hrs. last weekend to see if they built up predal pressure or worse, locked up and they did not. Although there was some noise coming from the (I think) left rear. Going to jack up the car tonight to check the pads and alignment, then re-bleed the brakes before we take the 2 1/2 hr. drive south to Springfield Sat. morning. I feel confident that even though the brakes aren't exactly how I want them to be, they'll get me there and back.

[Tom 72RS/SS]

Turns out the rear calipers were ever so slightly off center so I remedied that and drove the car for about an hour Friday evening and no issues.
So fingers crossed, we drove to Springfield early the next morning after meeting up with friends and topping off with fuel, we hit the road. All the way up and all the way home on Sunday - no problems! I can finally sleep at night, zzzz.