investinwaffles

I have 2 lingering issues after my ZJ disc conversion. With the ZJ prop valve I got - the rears are locking up before the front?

Anyone have issues with this after their conversion? I only noticed it when I was bedding in the brakes earlier today.

I do still think I have air in the lines. Tried the 1 person Bleed method but I don't think I got it all out. Might have a shop do a legit vacuum Bleed (or just buy the harbor freight vacuum bleeder), but the pedal feels like 80% good so I am wondering why the rears are so easy to lock up


Second issue is that the parking brake cables I bought from Morris 4x4 are not working in my application. The passenger side cable (long one) is the right length, but the drivers side cable is too long and isn't engaging the parking brake properly. Thinking of having an exhaust shop weld a spacer on the cable by the equalizer to essentially "shorten" it, if that makes sense (take up the extra slack in the cable)

investinwaffles

Well, to simplify the question

Does anyone know what "bias" the XJ prop valve is compared to the ZJ?
As in, which valve sends MORE pressure to the rears?

I am assuming the ZJ valve does but haven't been able to confirm. Might swap back to my factory XJ prop valve to test with if nobody knows

XJlimitedx99

I would think that the XJ prop valve would be more biased towards the rear because the drums need more pressure as opposed to the discs. I have no information to back that up, more of a thought.

I used a ZJ prop valve with my rear disc swap and it seems to be very balanced. I cant compare the two though.

CobraMarty

There is alot of debate on just what that valve really does. I don't think that it is a proportioning valve but more a residual valve. Comparing the XJ and ZJ, one has a slight amount of residual pressure to drag the pads and other no residual pressure. It also functions as a system failure check, that is if F or R fails and leaks, the valve shifts position and trips the brake warning light. The F + R circuits are separate.

I vote on air in the lines. Get a set of 'speed bleeders' with the ball and spring inside, available at most parts stores. They greatly simplify the one man bleeding. I thought that they were BS until I got a set. Now I'm sold.

investinwaffles

Well, I guess that might be pointing me to air in the lines. The right rear will lock up just before the left rear in most cases, and I have not gotten the fronts to lock up because I don't want to flat-spot the rear tires, so I don't know where their lockup point is and how much braking I am "missing" out on.

I had a set of speed bleeders on my Mustang and loved them, till it started leaking one day. Didn't notice till I had almost zero brakes so I stayed away from em after that (they were the Russell ones). Probably luck of the draw but I like the regular bleeder valves more
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I do think I'm gonna pick up a vacuum bleeder from Harbor Freight (less than $30 w/ coupon). Makes cycling fluid once a year really easy and I think they would make bleeding easier since the overwhelming vacuum will prevent air from getting in around the bleeder valve

investinwaffles

That is logical to me as well (drums requiring more pressure to operate)

Going to try bleeding it tomorrow once more and see if there's any improvement

Thanks for the sanity check gentlemen

cruiser54

This is a great tool to have:

http://www.harborfreight.com/brake-f...der-92924.html

CobraMarty

I made something like that out of a pressure cooker in the early '70s. Yeah I'm old.

cruiser54

Can't be older than me!!!!!

CobraMarty

Just had a Bday a few days ago. Still a few years away, as in 3 years, from collecting early social security.

cruiser54

I could get the early now, but I'm gonna wait 2 more years to get full.

investinwaffles

I am going to buy one of those as soon as I get my paycheck this month. Would be great for siphoning fluid from pretty much anywhere - even motor oil from the lawn mower, coolant overflow, power steering reservoir, etc.

I think I was -19 years old in 1970, born in 1989


Never bled the brakes - gonna have to wait until after Thursday but I will update this thread to let you all know the outcome. Might swap my XJ prop valve back in to see if there is any change

bad_idea

I'm fairly confident it is air in the front lines.

I swapped an 8.8 from an Explorer into my 90. (The Explorers have discs rear brakes) When I did the swap I didn't swap the prop valve right away, drove it for a few months with the XJ prop valve. Later swapped to the ZJ prop valve internals in the XJ housing. No noticeable difference.

The greatest improvement to the braking was swapping in a WJ booster/master. Night and day difference in stopping distance. I can now lock up 33s at speed where as the stock booster wouldn't lock up 31s.

Turbo X_J

The proportioning (also called bias) valve is designed to do exactly just that, once the front wheels lock up your steering is gone.

cruiser54

http://www.classicperform.com/How/Ho...-Prop-Work.htm