1972 FJ40 - Front Disc Conversion, little power to front

[GregoryB]

Hey

I started this conversion during COVID and am finishing it up now, so have forgotten some vital things that I was sure I'd remember or wouldn't need as I'd be done quick. I used the JT Outfitters kit, put a Wildwood Proportioning valve on the rear line. I've never had good stopping power since I've put these in. I'm able to lock up the rear drums easily, but not the front discs. I just bled the lines again, the volume that comes through rear lines is much greater than the front, 2x to 3x more. I have the proportioning valve set to lowest braking power for the rears. I can't find info for the master cylinder I bought, but believe it's for a late 70's FJ40 that has stock discs in the front. I'm thinking I may need a different MC, before I do this, is there something else I should be checking? The brake booster is getting vacuum.

Thanks
Gregory

 

[MDH33]

Pedal height and free play adjusted to spec? How confident are you that the front circuit is fully bled? Could be air.

 

[GregoryB]

Pedal height and free play adjusted to spec? How confident are you that the front circuit is fully bled? Could be air.

Yesterday I bleed from MC to the wheels all around, starting with driver rear. Today I bench bled the MC, didn't notice many bubbles.

Attached is a video, rear reservoir has huge movement, front reservoir doesn't move until pedal is pressed halfway down. First two pumps are only half pressed, third time I go to the floor.

 

[nuclearlemon]

did you pull the residual valve from the master when you converted to disc?

 

[GregoryB]

I adjusted the free play / push rod distance as @MDH33 suggested. It was short about 2.5mm. While doing that I checked about residual valves, I couldn't remember the status. There aren't valves in either circuit. I bench bled again, put it back on the vehicle and bled the brake lines again. It seems to be braking better, but I still can't look up the front.

 

[wesintl]

If you converted the rear to disc is when you pull the rear residual valve. If you still have drums you should have it in since you have springs to pull the drums back. On a 76-77 it shows a check valve in the front and rear for the master. I would try putting them back in, maybe you don't have them anymore?

 

[GregoryB]

I have drums in the rear. The MC was purchased at NAPA for a 76-80 FJ40, I found my receipt and looked it up. There were never residual valves in either circuit. Would adding a 10# inline valve on the rear help?

 

[wesintl]

I don't know. From looking at the parts break down it has them in on a 76 oem master. When i did discs in the rear a long time ago i removed the residual valve on the rear and added in a proportioning valve like you did. It was so long ago but i don't think i removed the front. though. I have an oem master sitting here on my desk and it does have residual valves in it both front and rear.

 

[GregoryB]

Sorry, my sentence was misleading. I meant there were never residual valves in the MC I purchased. Yes, according to your diagram it looks like there should a valve in both.