drpdmazda

i will start with the basics: 1986 toyota x-cab 4x4 22re motor 5speed. I loaned my truck to a friend for two days so he could move. My friend brought the truck back last night and i asked if it gave him any problems, he tells me " the brakes acted up once, the pedal kinda went to the floor but after a few pumps everything was fine".

I needed to get some stuff from lowes today so i decided to take the truck. the first time i hit the brakes the pedal goes about half way down, clicks and then drops pretty much to the floor, then the braking is very irratic. the brake fluid is full and there is no fluid visible on the wheels or in the rear near the lspv? valve.

can anyone give me any suggestions as to where to start to try and figure out what the issue is? i enjoy working on my own truck and try to avoid taking it to mechanics but i have never really dealt with brake issues before so am kinda new to it.

the drivers side caliper was replaced about a year ago by the previous owner right before i bought it, and the pads were changed at the beginning of the summer, other than that the brakes have not been messed with to my knowledge.

any help would be greatly appreciated.

tried4x2signN

Master cylinder...

morena67

-Brake fluid bleed ?.
-Look at your master cylinder, cause it may be worn out...
-If you change it, buy it original...
-Good luck...!

cheesencrackers

May not be a bad idea to try and bleed the brakes. Start from the set that is the furthest from the master cylinder and work your way in. You'll need a helper for that. Have 'em pump the brake pedal a few times, then open the bleeder valve. If it's gray and bubbly, there might be air in the lines. Do the same with the other wheels and finish with the wheel closest to the MC. Hope this helps. Luck!

tried4x2signN

If you wanna do the 1" bore "upgrade" I highly suggest you research this thoroughly b/c I'm having MONDO problems.

I have yet to find where the residual valves are in these brake systems...

I've had to roll all the way back to a 1975 LC to get a 1" bore and residual valves where I know they are.

...And I just so happen to have them in the next window.

75 FJ40... Image is on-end. NOTICE the residual valves.



87 4WD Pickup, 13/16ths bore. NOTICE the residual valves.



92 Landcruiser, According to Napa's site smae P# as 4Runner...
Notice the... WTH!



Both Marlin's and AllPro's site will have the same M/C in their "upgrade" but none seem to know where the residual valves are, or care for those that are retaining the rear drums.

tried4x2signN

noooo ya don't...

Mine is a piece of rubber hose @ 3' long, with a small piece of vac hose inside it (for the fitting) and the other end just stuck in an old see-through juice jug.


http://www.youtube.com/watch?v=UvyztDFHhaY

drpdmazda

I was thinking master cylinder as well but was wondering if there is any way to test it before i replace it? i just had all the windows in my house replaced so money is pretty tight right now and i dont want to start replacing things that dont need to be replaced. i am going to look more into it today as far as leaks near the firewall etc but was just wondering if its possible to test or narrow down to the master? i am also going to bleed the brakes today or tomorrow to see if that fixes the issue


thanks for the advice so far

swampfox

just unbolt the mc and pull it forward to check for leaks. it may not be bad enough to leak in to the cab yet.

tried4x2signN

Yeah, and though I have no experience with it I have heard of an "internal leak".


And if you look at a rebuild kit, there is a central plunger that to me can fail, but the outer rear most may still hold...


http://www.google.com/search?sourcei...+internal+leak

snare

So, for those of us retaining the stock front calipers and rear drums, would you even suggest the 1" bore upgrade at this point? Have you done it yet? How is the pedal feel and travel?

I have an 88 xcab 4x4, 22re, 5spd. MC is letting go when I am at a stop. Needs replacing and just wondering if I should bother with an upgrade or just replace. Also, any suggestions on where to find a good, new stock replacement? I see Marlin has the Aisin clutch master and slave, but only the upgrade brake MC. I can't seem to find an Aisin brake MC anywhere.

tried4x2signN

Factory AISIN would be the way to go... I would only use or adopt the theory of aftermarket parts as a last resort... Or how deep my pockets are at the time.

I don't think 1" will be worth the hassle...

I finally found a 1" M/C... But it had to come from California and I'm still rigging up the reservoir to work.

Then I still have the small single diaphragm booster... So we'll see...

But I went from a factory 7/8ths MC...

Your 88 should have a 13/16ths IIRC. IFS rears have a larger wheel cylinders.

This would be a WHOLE lot easier if I could just find those damn residuals...

PS, I have a IFS rear and 4cyl IFS calipers on my truck...

My turbo's came with a 13/16ths M/C but they were both bad, so 13/16ths should be fine.

myyota

Just get a master cylinder for a 92-95 truck or 4Runner, its a 1'' bore and its a direct swap. I have a duel diaphragm brake booster and master cylinder from a 92 4Runner on my 86 4Runner and it made a noticeable improvement in braking.

xxxtreme22r

tried4x2signN I am still kinda confused with you residual valve thing, can you explain what the issue is with it? I upgraded mine not too long ago with an autozone unit that is the 1" master but was for a t-100. Also got a Junk Yard dual diaphram from a v6. I have yet to see an issue.

tried4x2signN

A residual valve is a check valve. It keeps a certain amount of pressure in each line.

And as you can see, there's two. One is the front circuit and one is the rear...

Rear drum brakes have stronger springs that pull the brake shoes back off the drum when you let off the pedal.

Discs do not require it.

All over the web, 10lbs is used on drum brakes. And 2lb is used on discs.

If you didnt have residual valves on drum brakes the pedal would be vary soft and you'd have to pump the brakes to even get shoes to contact the drum.

W/o a valve, the springs will pull the drum brakes all the way back in. Get it?

xxxtreme22r

yeah, but not sure why I don't see an issue with mine. maybe the one I have has the RV?

http://www.autozone.com/autozone/par...2439_0_0_22296

sebastianholmes

i had the same problem a few months back on my 4runner.
bled the brakes a few times and tried a few other things.
then changed the master cylinder and bam it was all better! i think it was the residual valve thing tried 2x4 is talking about. just change the master its only about 50 bucks at auto zone

tried4x2signN

Maybe they are internal past some point, IDK...

I did get a late M/C for a LC and 4Runner, but didn't want to blow the chances of me returning it to find out...


Another thing is, most if not all the ppl I see doing the "upgrade" are also getting a proportioning valve, and I feel they're dialing in the brakes w/o one...

I couldn't afford one, and didn't want to mess with it at the time so I just played it safe and got one I know has them.

xxxtreme22r

I didn;t go with the proportioning valve, not sure if my LSPV is working correctly or not, but I don't see any issues so far. I guess I will find out once the snow comes. lol.