temp replacement for Wilwood 7/8 MC?

[ehummelman]

I need to know what off the shelf MC will swap in for my Wilwood. In short, I think it's leaking internally and they won't send me a replacement until they look at mine. I can't have my car down in the garage all that time so I'm thinking of putting in a NAPA MC in the meantime. Any suggestions of which car/model/year etc. that would have the same specs would be great. Thanks.

[neki67]

May I ask why you think it's leaking internally?

[ehummelman]

I have bled and bled and bled and bled, all 4 calipers and bench bled the MC. I still have to pump once before I get a firm pedal. It is not knockback either, it happens on straights, turns, in the driveway...

Do you think it is something else in my system like a prop valve or something? I just can't think of anything else, and Wilwood told me about the potential for an internal leak between the front/rear pistons when I explained the issue to them.

[neki67]

I'm facing more or less the same problem (also with 7/8 Wilwood MC) although in my case pumping the pedal doesn't really improve the situation. Had a firm pedal at a certain point but it didn't last long and I had to redo the rear brake hard lines . After redoing them I couldn't get the "air" out of the system. I have the prop valve next to the driver's seat and I can imagine it getting and keeping air trapped. I will first replace the entire hard line and go w.o. the prop valve to see if that's going to improve the situation but I was also thinking it might be internal leakage of the MC. I do have a couple of other MC's laying around but all of them are old and used . . . .

[TheJDMan]

Have you tried power bleeding the brakes?

[Skip Fix]

I thought I've seen a GM 15/16" cast iron, not sure the application.

[ehummelman]

Have you tried power bleeding the brakes?

I've been using my Phoenix Bleeder which is a pretty good system. I rebled the MC today and it made absolutely no difference. I'm either a very bad bleeder (100% possible) or the MC is screwed. I didn't take the MC off the car and put it in a vise since Phoenix allows you to bench bleed on the car, but maybe that's worth a try. I'm so frustrated at this point I can't even tell you. Brakes can be a real PITA compared to other things on the car.

[Wilwood Tech]

Hi, I'm sorry to hear that you are having a problem bleeding your system. It sounds like you have done everthing right; however, let me offer the following. It is highly unlikely that the M/C is leaking since we never see that. Almost every time we hear of this problem, it is the result of improper bleeding of either the M/C or calipers (sometimes both). It is essential that the M/C is first bench-bled; then the calipers should next be bled the old fashion way in the following sequence: rigth rear, left rear, right front and left front. By old fashion, I mean have someone pump the brakes while you crack open the bleed screw. When doing it this way, make sure your helper doesn't let the pedal return until you have re-tightened the bleed screw, otherwise you will draw air back into the system. It is also essential to have the caliper as close to vertical as possible. Sometimes it may be necessary to remove a mounting bolt so that it can be rotated to a verticle position so that the bleed screw is at the highest point. Air bubbles will rise to the highest point in the system and if your bleed screw is positioned below the bubble, you will never get air out of the caliper. Also, only bleed the top screws, never never open the bottom bleed screws. One final thought, make sure that you are not drawing air into the sytem from any other source, a loose fitting, etc. I hope this explanation helps and I aplogize if it is too rudimentary; sometimes it just helps to return to the basics. If you continue to have a problem please email me at [email protected] with your contact info and I will call you back.

Thanks and good luck, Ken

[Skip Fix]

Just for some input I usually don't actually "bench" bleed them do it on the car with tubing into the reservoir but I did my Strange Mopar style on the bench and even with a good feel it took forever to get all the bubbles out. So convinced me that it is easier than even pressure bleeding to get all the air out.

[ehummelman]

Hi, I'm sorry to hear that you are having a problem bleeding your system. It sounds like you have done everthing right; however, let me offer the following. It is highly unlikely that the M/C is leaking since we never see that. Almost every time we hear of this problem, it is the result of improper bleeding of either the M/C or calipers (sometimes both). It is essential that the M/C is first bench-bled; then the calipers should next be bled the old fashion way in the following sequence: rigth rear, left rear, right front and left front. By old fashion, I mean have someone pump the brakes while you crack open the bleed screw. When doing it this way, make sure your helper doesn't let the pedal return until you have re-tightened the bleed screw, otherwise you will draw air back into the system. It is also essential to have the caliper as close to vertical as possible. Sometimes it may be necessary to remove a mounting bolt so that it can be rotated to a verticle position so that the bleed screw is at the highest point. Air bubbles will rise to the highest point in the system and if your bleed screw is positioned below the bubble, you will never get air out of the caliper. Also, only bleed the top screws, never never open the bottom bleed screws. One final thought, make sure that you are not drawing air into the sytem from any other source, a loose fitting, etc. I hope this explanation helps and I aplogize if it is too rudimentary; sometimes it just helps to return to the basics. If you continue to have a problem please email me at [email protected] with your contact info and I will call you back.

Thanks and good luck, Ken

Thanks Ken. I gave the MC some more attempts yesterday with the tubes into the MC method. Didn't change a thing. It needs more attention than I have the patience for.

[ehummelman]

Bringing this back to the forefront. I finally had a shop do the bleeding this time, using the old fashioned 2 man method. It worked. I had a great pedal, high and firm, for 2 days. Seriously, after about 200 miles I lost the pedal again. I'm back to the one pump and then brake.

What is the deal? Somehow air is getting in after it's been bled out.

[silver69camaro]

What calipers are you using?

[TheJDMan]

I can tell you that it took me the better part of two weeks to finally get my brakes properly blead working off and on. I had to use virtually every method available.

Just a side note: I'm a little dissapointed with the cover on the Wilwood MC. I was led to understand the cover was black annodize, turns out it's just cheap paint which the brake fluid promply removed.

[neki67]

Don't want to HJ the thread but like I said before, I have more or less the same issue.

I did remove the prop valve from the system just to minimize the number of connections and thus potential problem areas. I now have 1 uninterrupted 3/16" Cunifer line going from the MC to the rear end where it splits to the left and to the right and then SST braided hoses to the LT1 calipers. Up front 1x 3/16" Cunifer line going from the MC to the left/right splitter, 3/16" Cunifer to the left and right,then SST braided hoses to the C5 calipers. Bled the system (including MC) with fresh brake fluid. Had a nice hard pedal but it was difficult to lock the brakes. Still braking was satisfactory.

Took it to the track this Sunday. After just a couple of "harder" brake actions, I was once again faced with a pedal going to the floor . . . Which isn't exactly confidence inspiring while on the track.

[ehummelman]

Matt, I am running Wilwood 6 piston in front and 4 piston in back. The rears are the old style fixed caliper so I thought at one point that it could be knockback, but I'm pretty sure it's not since it happens all the time, not just after cornering. Not sure if that's why you asked about the calipers, but...

I do have all of the unnecessary prop valve/distribution block nonsense still plumbed in there. I guess that could be part of the issue, but I still don't understand why it was bled out well, I had a good pedal for 2 days, then it went soft again. Air must be creeping in from somewhere. I don't see any leaks or drips anywhere, but who knows.

neki67, it sounds like your issue was boiling the fluid or pad fade. Hard track time will do that. My situation is with just normal driving, so something is faulty other than me. ;)

[silver69camaro]

I ask because some calipers are prone to allowing air getting sucked in past the piston seals due to rotor runout. Those calipers shouldn't have that problem, but I'd check rotor runout anyway - it can cause the problems you describe.

One thing I would suggest is to follow Bendix's literature for bench bleeding:
http://www.remanbrakes.com/pdfs/benchbleedinggmquicktakeup.pdf

I use this guide for all master cylinders, QTU or not. Step 4 in the process does a really good job at removing air that normal processes wont do. It's amazing at how many brake problems can be attributed to improper MC bleeding, whether it's a garage guy or a "pro" builder. I know you said you already bled the MC but I'd really give it a try.

[ehummelman]

I see. I just got off the phone with Ken from Wilwood and he alluded to the same issue with some calipers. He also said that the ones I have shouldn't have this problem, but it wouldn't hurt to check runout anyway. His suggestion was to go through the entire brake system plumbing and retighten every single fitting. We agreed that air is getting in somewhere in the system and that it is not likely the MC as I first thought. It could be, and I will be putting in a new seal kit as insurance when I bench bleed again. It can't hurt. I'll repost after I get that stuff done.