Brakes

Have front and rear waggy 44's in my '98.

We put disc brakes on the rear and since then I've had odd things happening. I had another '98 with an XJ 44 rear and discs with no issues so this one's puzzling me.

60-70% of the time when I hit the brakes it will go to the floor before the brakes grab. The rest of the time I have good pedal feel. Brakes always work either way. We removed the prop valve spring and it helped some. Brakes have been bled (to death) and if there's air in them I don't know where.

We're thinking the master cylinder is going bad. I just wanted some other opinions and to ask about the E-350 MC. I know I can use an early '90's E-350 MC with minor mods...BUT it seems that is more for the 3/4 and 1 ton brakes...not the half ton and down.

Anyone??

I would go with a wilwood adjustable proportioning valve (you don't ever want the rears to lockup). Place it inline with the rear brake hardline. Also be sure the bleeder screw is as high as possible (i.e. correct caliper on the correct side).

I have Chevy 1/2-ton calipers front and Cadillac metric calipers in the rear. I'm using the '76 Mercury Marque MC that was used in the 4-wheel disc, hydro brake application. It has a 1-1/8 cylinder, and requires NO mods to install on an '88 booster. You do need one brake line fitting adapter, however. I find the pedal feel good with this MC. When I switch to a dual booster, I'll probably try a larger MC, but I think the 1.125 cylinder is probably sufficient. You need to gut the stock proportioning valve, or replace it with a ZJ valve that was used with 4-wheel discs.