Bad brakes after RDB and 4Runner calipers...

[Tigerstripe40]

So I finally got my FJ40 buttoned up after months of sitting.
Before I tore the rig down to install some 4.88's, Longs, Locker, Monte Carlo RDB's, and v6 4Runner Calipers, I drove the truck with the stock brakes.

The stock brakes were OK. One pump would be ok for regular stopping, but 2 pumps was better (rear drums needed to be adjusted). So I tore the truck down and installed V6 4Runner brake calipers, and monte carlo rear disc brakes.

Now, the truck doesn't stop worth a ****. It takes 3 pumps of the brake pedal to get the truck to stop, and even then it's still scary. The aftermarket prop valve is turned all the way out, (More Brakes) and nothing is leaking.

I removed the stock proportioning valve from below the master cylinder (and kept it in case I need to un do the RDB conversion) and installed a Summit Racing proportioning valve between the rear output of the stock 1976 M/C and the line that goes to the rear.

When I was installing the lines on the rear axle, I turned the 'T' that connects the rubber Frame-To-Axle line to the hard lines, and have it oriented slightly differently.

Any ideas?

[Box Rocket]

air in the system? I'm guessing you bled it out well, just wondering.

[Tigerstripe40]

air in the system? I'm guessing you bled it out well, just wondering.

Yeah, I bench bled the Master Cylinder, then bled the system. I tested the system, and decided to bleed it again after spongy brakes.

[ericjcline]

x2 on air. those 4runner calipers should stop you real quick, no pumping needed.

sounds like too many things done at the same time! did you swap out your master cylinder? it looks cleaner than the brake booster.... if you did, you might need to adjust the actuator rod. if that is out of adjustment, your truck wont stop right at all. ask me how i know.

[Tigerstripe40]

x2 on air. those 4runner calipers should stop you real quick, no pumping needed.

sounds like too many things done at the same time! did you swap out your master cylinder? it looks cleaner than the brake booster.... if you did, you might need to adjust the actuator rod. if that is out of adjustment, your truck wont stop right at all. ask me how i know.

The Master Cylinder was a new OEM MC installed about 3 years ago. Everything was fine with the stock brakes.

I could easily pull the MC and adjust the rod (are you talking about the rod behind the MC or the rod on the pedal?)

[Scott Howe]

I wonder if volume is your issue the V6 callipers up front and the new calipers in the rear may require more fluid volume than the stock master is capable of producing. Something like an FJ80 master is usually recommended for this type of setup since it has a large bore for 4 wheel disc brakes.

Just a thought.

[Tigerstripe40]

I wonder if volume is your issue the V6 callipers up front and the new calipers in the rear may require more fluid volume than the stock master is capable of producing. Something like an FJ80 master is usually recommended for this type of setup since it has a large bore for 4 wheel disc brakes.

Just a thought.

Yeah, that's actually what I have been thinking.

[ericjcline]

i thought the same thing, about the MC volume, at first too, but i thought the giant masters were present up past james' vintage. my master, '72, has the same large bore as the 80 master, 1", so that may be why i had no issues.

just curious, why did you do both the front and the rear at the same time?

[Tigerstripe40]

i thought the same thing, about the MC volume, at first too, but i thought the giant masters were present up past james' vintage. my master, '72, has the same large bore as the 80 master, 1", so that may be why i had no issues.

just curious, why did you do both the front and the rear at the same time?

I regeared my diffs to 4.88's. Since you have to tear the axle completely apart to swap thirds, I figured that would be a good time to install the monte carlo RDB's. I also was planning on replacing the front calipers w/ new callipers. After doing some research and asking a few questions, I decided to go with new 4Runner calipers (I had cores).

I also had the RDB conversion parts sitting in my dads shop for the last few years but never really had the motivation to install them, since you have to remove the rear axles to get teh backing plates off. Again, doing the diffs requires that you pulled the rear axles and installing the rdb's was a non-issue as far as time goes.

I guess I should try an 80 series MC.

Eric you got one?

[dmaddox]

I have battled with similar situations.

Ideas: (some you may have tried - if so, sorry)

1. Yes, as others mentioned; make sure you have adjusted the pedal rod. There should be about an 1/8" between the rod and the m/c.

2. When I did what you did, I had to swap out the master/booster setup to accommodate a larger m/c to push the volume needed to get the front calipers to bite.

3. My normal "bleed" method didn't work. To get all the air out, I had my body builder brother hammer about 10 times to build up huge pressure in the lines and hold it down while I released a bleeder. Yes it makes a huge mess - I just used a small cardboard box filled with used paper towels and some old smith ski goggles - lol. ONLY THEN - was I able to bleed out all the air.

4. Make sure the booster is not leaking at all nor is the check valve.

5. I used the stock proportioning valve out of a 77 fj40, not an aftermarket. My rears didn't bind that much - but the fronts bit really well. Might try that?

6. How are your rotors? If you put new pads on some pretty worn rotors - it will take a while for them to seat.

Likely stupid ideas - I know, but it's what I dealt with when I was there.

Good luck!

[ericjcline]

i have one, but i am going to be using it. besides, mine is ABS. i hear the non-ABS master is the way to go for the conversion. i half expect i will have to swap the ABS unit for the non when i finish my truck in 2045.

just a suggestion... i have done too many things at once and had problems i wasnt able to solve. i would have done the rear brakes and got them working, and then done the front brakes later. then you could have isolated the problem a little better. but, done now, so it doesnt really matter.

4. Make sure the booster is not leaking at all nor is the check valve.

this was a huge problem for me. i went through a couple of used boosters and a rebuild before i ditched the thing. that plastic hose nipple has a rubber grommet that seats it to the metal housing and once that thing dries out, you wont ever get a good seal on the booster. i went to pick and pull and got a booster out of an old mini. they have all metal housings, including that hose nipple. i was amazed by how much better my brakes worked. might be worth considering in the future.

[Box Rocket]

James, I have an 80 series MC that I had planned on using on my old blue minitruck but never did. It's new and I could be talked into selling it if you're so inclined.

[Scott Howe]

If James doesn't want it I would be interested.

[ken]

Did you pull the residual valves from under the reserviors? I put monte carlo calipers on my prior FJ40 (a '76). I pulled both residual valves, the front is a 2#, the rear is an 8#. Also if your pedal is spongy and you are pumping the brakes it's almost always air somewhere. If you read through mud more often than not the final answer to spongy brakes is air in the line. Any decent shop can flow a ton of brake fluid through the lines at pressure to remove air. At home it can be a pain to get enough volume and pressure to move the air from a high spot.

[mistapuggs]

on that note, James, be absolutely sure that you don't have calipers swapped side to side. They look almost identical but if you switch them (and yes, they will fit like that) the bleeders will be on the bottom of the caliper and unless you have secret powers you won't get the air out. So, look for the bleeder on the top part of the caliper.

I think more than likely your problem is specific to the front brakes but affecting the entire system. Like ken said...Squishy pedal= more than likely air in the lines.

[Tigerstripe40]

Did you pull the residual valves from under the reserviors? I put monte carlo calipers on my prior FJ40 (a '76). I pulled both residual valves, the front is a 2#, the rear is an 8#. Also if your pedal is spongy and you are pumping the brakes it's almost always air somewhere. If you read through mud more often than not the final answer to spongy brakes is air in the line. Any decent shop can flow a ton of brake fluid through the lines at pressure to remove air. At home it can be a pain to get enough volume and pressure to move the air from a high spot.

I pulled the residual valve for the rear circuit, but didn't pull the valve for the front circuit as the fronts already have disc brakes.

RyRy:
Yeah, I got the calipers mounted properly. The brake bleed screws are at the tops of the line.

I have some time this afternoon. I suppose rather than shotgun another mastercylinder at the truck, I could take it by a shop and have the system force bled and then see where that goes.

[Tigerstripe40]

So I turned the 'T' around. I didn't have it hooked up correctly.
I rotated it and connected the brake hose from the frame to the slightly wider part, and my brake lines to the original location.

Its much better. now I get a nice firm brake pedal on the second pump. I ran a bottle of brake fluid through the system. I don't think I am moving enough brake fluid.

Also, a few peeps on 'Mud are saying that the braided SS lines will expand a little, and cause mushy brakes. I might end up flaring some hard line and installing the rubber hoses I got with the Monte Carlo calipers. But again I think I am just not moving enough fluid when I hit the brake pedal.

So next step is a larger diameter M/C.
Will keep y'all posted.

[ericjcline]

did you replace hard line with SS braided? if so, then yeah, no bueno. otherwise, if you just replaced the rubber line with stainless, that would give you better braking, not worse.

[Tigerstripe40]

Yeah, braided SS lines from the 'Tee' to the calipers.

[Trent Ashby]

So next step is a larger diameter M/C.
Will keep y'all posted.

I think that Dave Helm had the same issue until he added a FZJ80 master cylinder.

[Tigerstripe40]

I added a 1" bore Master Cylinder last night (thanks Adam!).

WHOA BABY, now THATS What I'm talking about!

Truck stops like it should with a good firm pedal and this was without bleeding the system again (going to do that tonight).

[rdublt1]

Nice James. Did you install an 80 series booster & MC or does the 80 series MC bolt up to the FJ40 booster?

[Tigerstripe40]

I think its an 80 series master (its much cheaper through Marlin Crawler or Trail -gear than it is through the dealer.

I used JUST the master cylinder, and it bolted right up to my Brake Booster. I did have to bend the brake lines a bit but otherwise it was very straight forward.

[Box Rocket]

Nice! Glad it worked out for you.