WILWOOD TANDUM MASTER BRAKE BLEEDING PROBLEMS

[werner]

JUST BOUGHT A NEW TANDUM MASTER CYLINDER (7/8 BORE) FROM JUST SUSPENSIONS. MOUNTED AND BENCH BLEED MASTER ON CAR. TOOK QUITE A WHILE TO GET OIL UP THE HOSES,CLEAR OF AIR (5-10 MIN) THEN WHEN BLEEDING ON CAR TOOK 30 MIN TO BLEED BRAKE LINES TO GET A DECENT PEDAL.
DROVE CAR FOR 1/2 HR AND PEDAL STARED GOING TO FLOOR. FOUND SMALL LEAK AT FRONT BRAKE LINE. (NOT DRIPPING JUST WET) TIGHTENED BRAKE LINE A TRIED TO BLEED BRAKES ON CAR. sPENT 1/2 HR TRYING TO GET GOOD PEDAL. bRAKES WILL PUMP UP AND HOLD WHEN PRESSURE APPLIED, BUT IF YOU RELEASE PEDAL AND LET SIT FOR 15 SECONDS AND REAPPLY, PEDAL GOES TO FLOOR. IS THERE SOMETHING I AM MISSING HERE. INSTALLED TONS OF STOCK MASTERS BEFORE BUT NONE THAT TOOK AS LONG TO BLEED AS THIS.
PLEASE HELP

[Long Island RT]

I have the same master cyclinder and when I finally filled and bled everything last week - I have the same problem.  I will try re-bleeding again when I get the chance - but I'm curious to see who has some thought.

Power or manual?

[John_Kunkel]

When the pedal finally pumps up is it firm or spongy? If spongy, air is the problem.

If the pedal pumps up firm, your problem is volume, each time you stroke the pedal you move some more fluid until the system is satisfied and the pedal becomes firm...when the pedal is released all of the fluid returns to the MC and you have to start the cycle again.

Either the MC is too small or the system is too loose.

[maxwellwedge]

I agree with John. You said bench bled on car? Try bleeding it on a bench to take any variables out the picture like the pedal rod etc. and see if that makes any difference.

[werner]

Up date. Bench bleed in Vise. There was still air in master. Thought great problem fixed. Installed in car. Hooked up lines at mastercylinder. STarted bleed there.  Cracked lines at mastercylinder first couple of times. Then went to rear apssenger and bledd from there.
No luck. CAn still pump up themn feels good. Did find out though that there are residual check valves in the old master that I took off. Guy I bought master off says I dont need them. Will talk to Wildood today but there is a 3 hr time difference. Will Check all brake shoe clearances tonight. altough they were ok with stock master cylinder. They were vaccum bleed before with no change. There is more travel in pedal when bleedingt he rear brakes than the fronts. Don't know if this is normal or not.

[John_Kunkel]

You need a residual pressure valve in each circuit that has drum brakes, some discs require them and some don't.

[werner]

Well after contacting Wilwood Tech again they said I need residual check valves to keep 10 psi pressure in lines. So ordered them yesterday from Vancouver and received in Toronto today at 9:30 this morning. Last night decided to check brake shoe adjustment to make sure they were adjusted right. Rears got 1 full turn each on adjusters and on front I got almost 2 turns each until slight drag felt on drums. Putting car back in garage and step on brakes.......  Holy crap, problem fixed. Pedal is hard as a rock. Took for drive can lock all 4 wheels up.  I guess with out check valves inline when you step on pedal you loose a lot of fluid in wheel cylinders to take up gap between shoe and drum.
Will install checks this week, should only make them better.
Thanks everone for your help.
Cheers Werner