Alright fine, I'll make a new build thread :finger: :sonicjay:
Bought a MandM offroad chassis from PJ, super good dude to deal with and super nice. HIGHLY recommend. http://mandmfab.com/id68.html
This is chassis #20
Stoopid fix but works, put a 10 psi check valve in the lines right off the master Cylinder, so it keeps a low 10 psi to all 4 brakes (hasnt historically been a big deal for the ones ive installed) that way all the lines are pre filled with 10 psi, so ur pedal and booster only have to create a few more pounds of pressure and move lots less volume.
Usually do it to help 1 ton brake conversions on jeeps, when they still dont work 100% after a 1.25" ram master Cylinder.
What's the fluid capacity of your new vs old? Smaller master dia bore= more psi= better brakes provided you can move enough fluid to push the pistons as far as they need to go. How much vacuum do you draw at idle? Not positive how a booster works exactly but you had 4 or 5(ratio) x 60 sq in (minus bore) x your vac psi with the 8.75" booster vs 7(ratio) x 38.5 sq in (minus bore) x your vac psi now if that makes any sense to you.
Anything more than a 2 psi check valve is a bandaid anyway. My Durango mastered TJ has kung foo brakes without them.
Resivors are the same size with the 1.250 and 1.125 masters. Honestly if they didn't say on them the size, you wouldn't be able to tell them apart. Both came on the same application. Difference is 2wd vs 4wd.
I would.imagine vacumn is standard amount as my motor isn't anything crazy.
Bore x stroke = fluid content. Smaller bore with same stroke moves less fluid. Resi doesn't matter as long as the bore doesn't suck air prior to movement.
Vac should be constant since it's the same engine so your looking at 300 to 240(8.75) vs 269.5(7"). Should be about the same provided your 4-5" f250 guess was close.
Block the rears off so your only moving fluid to the front and see if you have enough pressure to hold with just the fronts. Should eliminate the fluid capacity question.
I didn't try and drive it with rear blocked, but with the rear blocked the pedal travel and firmness really didn't change. Same with the front blocked.
Mine will stall out on low lock with just foot pressure( no booster) locked with a ball valve for my e-brake when I forget I set it. To not be able to lock the brakes up baffles me.
I wouldn't waste any time tracking down the vacuum, that's an assisting system. The brakes will will still function the same without a booster but would require more physical input from the driver. You have an issue in the hydraulics, either an air bubble, a line expanding, a seal in the MC leaking, or a leak elsewhere.
How is the pedal? can you hit the floor with it? get better on the second pump? or is it hard and just not enough pressure. With the smaller mc and more pedal ratio you should have more pressure unless you don't have enough stroke (fluid vol.) The only way to fix that is back to a bigger bore or lessen your pedal ratio. A residual press vavle might help if it gets better on the second pump.
Were you running the complete F250 brake system on the last rig? Nothing removed?
Reason I ask is because of the proportioning valve. Its the one item that you haven't stated you are using in the new setup that would have been in the old setup unless you removed it.
Without it the fluid and pressure gets split 50/50 between the front and rear calipers. Which would cause your issue.
NOT sent from an iPhone
If you want to borrow an adjustable prop valve to test this theory mine out of the truggy is just laying on the bench. That way you don't spend the $100 on one and find out you have another issue.
Shoot me a text if you want me to bring it with me tonight.
The master has a Brake Master Cylinder Fluid Control Valve on it. Attaches between the line and the master only for the rear brakes.
The bronco had the stock master from a 96 f250 1.250 bore, 03 ranger booster, and the stock pedal assembly from the 96 f250. And the same calipers in the rear as the buggy. Front calipers were 95 f350. Buggy fronts are 89 f350.
Went and got a f250 pedal assembly (4:1) and installed the booster from the EB. Pedal travel is way better. But it doesn't feel like I have much power assist. So half way there lol. Gonna pick up new hose for booster as I don't like the hose I am using. Grab my timing light and vacumn gauge from work.
03 ranger booster - 92-97 f series pedal assembly - 1 1/8 92-97 master cylinder.
I now have brakes.
Its loaded and headed to Drummond tomorrow....
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