IH8 my new brakes

[snailwagon]

I asked around and the only most sensible answer I have recieved yet is "get used to it". A while ago I did a front disc conversion on a 69' pig. The brakes stop very quickly, but pedal feel sucks. There is no resistance at all until the pedal can no longer can be pressed down. The pedal hits the stop point about 40% into its travel. It also returns well. If you barely press the pedal, the brakes actually work well. Originally my problem was the push rod adjustment b/w the booster and the MC, but that is now adjusted correctly. Having no pedal resistance is dangerous, in a panic situation you would not be able to modulate the pedal well. Without the booster hooked up and the manifold plugged, the brakes are a little too hard to press, but feel much better than with the booster running vac.

I am running hard parts, booster, and proportioning valve from a 1984 4x4. The 1" master cylinder and 4 piston calipers are from a 1991 4runner 4x4. The rear brakes are the original cylinders, which do not leak at all (one adjuster likes to stick, but that is what the air chisel is for). The hard lines for the front are from the same 1984 truck, the rear hard line is the original single circuit line, with plugs in the T's.

The brakes are currently biased towards rear. Not noticable on the asphalt, but slightly noticable on dirt hills. When bleeding, maybe twice as much fluid comes out per pump from the rear compared to the front. Is just the lack of a proper proportioning valve causing the zero resistance feel? Currently I feel like going back to drums (which I only got rid of when getting rid of the single circuit MC, one thing leads to another, the worked great otherwise when adjusted every month), or slapping on rear discs to see if it helps.

 

[Yoda]

Can you take pix of your setup? Sounds like a bad master cyl. What proportioning valve (is it the level sensing valve in the rear of a toyota truck)? Which line hooks to the front of the MC (front brakes=front port or rear port of the master cyl)

It certainly seems wrong to only get a little fluid from the front.........sounds like the fronts are not functioning either.

I just installed a 79 DB axle on my 71, used the calipers and 1" MC from a 95 4Runner. I have not driven it yet, haven't even bled the brakes yet. But my 71 had a dual system already. For now I have front brakes on the front port.

 

[beanz2]

Sounds like the front circuit still has air in it. When you do a panic stop in the dirt, do only the rears lock? Can you make the fronts lock at all? Have some else watch from outside the vehicle when you do that.

Dave

 

[Dave E]

You said "The brakes are currently biased towards rear." I think your frount should be getting the most fluid. I think thats how its supposed to be set, althought I've never done it. Any chance you got the lines reversed on the proporting valve?

Dave

 

[mancinator]

if you run discs front and rear without a booster....what type of braking characterissitcs are you going to have?
i know its not totally related to the problem here, but ive always wondered.

 

[snailwagon]

It is not the master cylinder, I have two of them, an aluminum and a cast iron one, both do the same thing. The proportioning valve is the old one found on 4wd and 2wd toyota pickups from the mid to early 1980's. The way the proportioning valve is set up, splitting for the front, the lines cannot be reveresed on the proportioning valve. Maybe I am wrong with the MC, I have the front line hooked to the front port, rear line to the rear port.
I guess it could be possible there is air in the front circuit, but I've bled those puppies four or five times now. The fronts do lock up. On the road the bias feels great, the fronts seem to stop the pig more than the rears. It will nose dive a bit when braked hard. Driving around town, the pedal only needs to get pressed about a quarter of the way into its travel to stop, which is even before the point of feeling resistance. I don't know what's the matter here, brake systems aren't exactly complicated.

 

[treerootCO]

Not sure if it is related or if I don't have another problem but...I flipped my springs and in the process replaced both front and rear with new longer brake lines. Brakes were perfect before the change. Original setup was stainless braided lines and teh new longer ones are rubber. We bled the brakes over and over, and the pedal feel stinks. Brakes work perfectly but the pedal acts like you described. We only changed one variable and that was the lines from the frame to the axles.

 

[beanz2]

I guess it could be possible there is air in the front circuit, but I've bled those puppies four or five times now. The fronts do lock up. On the road the bias feels great, the fronts seem to stop the pig more than the rears. It will nose dive a bit when braked hard. Driving around town, the pedal only needs to get pressed about a quarter of the way into its travel to stop, which is even before the point of feeling resistance. I don't know what's the matter here, brake systems aren't exactly complicated.

Any rapid deceleration may cause a sensation that a vehicle's nose diving. Try it in 2WD, put it in low gear and let out the clutch. The brakes are not even applied. The rears may do all of your braking, so check it on a loose surface while a buddy watches you from the outside.

When you pump the brake pedal, do you get higher and higher resistance? If you do, there may still be air in the lines. Also look carefully where all the brake line fittings are. If there is any moisture at all, clean them up with brake cleaner. Let it dry for a few minutes, apply the brakes again several times and see if any moisture comes back.

Another possibility that comes to mind is the pedal ratio (distance of booster rod mount on the pedal to the pedal pivot point compared to length of the pedal itself). If the vehicle came with no power brakes, adding a booster reduces the pedal feel. Then moving the rod mount down, closer to the pad, might help the feel. Never heard of other cruiser owners having this problem when going from non-boosted to boosted brakes though.

Dave

 

[snailwagon]

Treeroot, ya' get those lines from napa? When pumping the brakes, the pedal does not get higher and higher. It stays the same each time. Both the fronts and the rears lock, but the rears are locking first unfortunately. Maybe I'll figure this one out eventually, I'm sure it is just one simple thing somehow overlooked.

 

[IDave]

Try a 4 wheel drum brake conversion. I have drums all around on both of my rigs and they stop great, straight, and no mushy feel!

 

[MarkFJ40]

Just throwing this out there but check the sliders on the calipers.
I worked on a truck with similar symptoms. Turned out to be the slider sticking sometimes on the caliper.

A friend of mine can't fix a problem with his where he bleeds it and the pedal pressure is good but two or three days later after driving it drops to near the floor. He isn't losing any noticeable amount of brake fluid.

 

[theo]

I also think you should check the sliders. If they're sticking, them light pressure will only engage the pads on the piston side.Then, with enough pressure to overcome sticking sliders, the other pads engage and you suddenly have more brakes.

This only applies if you have sliders. Seems like maybe some Toyotas have pistons on both sides of the disks? Can't recall. If so, maybe sticking pistons.

 

[snailwagon]

O.K., some newbie questions here. What are the sliders? Are they the brake pins that the pads are held in place with? I have 4 piston calipers, pistons on each side. To check if they are sticking, do you just have someone press the brakes with the calipers off the truck and observe? They are rebuilt autozone calipers, possibly karma for giving them frozen, 1981 calipers as a core.

 

[patpend2000]

You mentioned that you are using a proportioning valve from a mini truck. Did the mintruck have the same sized caliper pistons front and rear that you have? Since your rears lock up first, and you are getting less fluid from the fonts I would guess that the proportioning valve is wrong for your application. You should plumb in a seperate valve for the rear brake and remove the one that you have in there now.