TurboKH

I have an 88 truck (4x4) with 4 cyl and automatic. Have replaced every brake component except the pedal and the PV. It still will not lock up a wheel or stop well in general in a panic situation. I think will all new (yes, lines, pads, rotors, drums, shoes, springs, master cylinder from a 91 3.0.. all brake parts new. Bled and bled again).. I think I should be able to lock up a wheel or 2 if I press the pedal hard enough, just as a sign that it's capable. I have new Toyo 31x10.50-15 tires.. not huge by any stretch of the imagination. Any ideas where to look next? could it be the PV? I've tried manually moving the valve to extremes and it doesn't seem to have any affect. Hydraulic pressure and 4 piston calipers should make this thing skid.

Any ideas???

-Karl

snobdds

I had a tough time with getting all the air out of the system too. I had to bench bleed the Master Cyl. before I did the normal bleeding process.

The order that worked finally for me was

Driver Rear
Pass. Rear
Pass. Front
Driver Front
LSPV

Also, are your bleeding screws free and clear of any dirt, I had one that had a little piece of gunk in it and would let a little bit of air into the system. I got new ones from the dealer and that seemed to do the trick.

TurboKH

I think that's the standard order for bleeding a system with a left hand MC. All the bleeders are good.. new calipers and wheel cylinders so it's all really clean. I wonder about that PV.... I forgot to mention, pedal height is up there, and pedal pressure is excellent. Both feet n the brake will make the truck stop fastER, but not fast.

toyotacharles

what brand are the calipers? What type are the pads and shoes? How about drumes and rotors? what are there surfaces like? Glazing will cause this, the p/v will only affect the rears since its linked to them only, have you measured the actuall pressures of the 4 hydraulic lines at the calipers and wheel cylinders? if you power brake it does it move or stay still? Also did you have the new rotors and drums machined no grease on friction surfaces? how well are the rears adjusted? can you pull the parking brake handle and skid the rears with it? please dont try that in traffic. What about in the dirt? can you find enough to get some decient speed and try to lock up wheels in dirt? let me know.

Justin McMullan

is your truck lifted much?? On you're rear axel I think there is a load sensor it goes from the brake res. on frame. its just a pice of steel to the axel to sense if you have a load the higher the arm the more pressure. I cut mine and raised it up to the body .... I skid my tires with 35 12.5's

toyotacharles

the p/v is that valve and thats what he meant by addjusted it to extreems and no difference. its call the load sensing proportioning valve and yeah my spelling can suck

TurboKH

I haven't checked the actual hydro pressure at the corners yet,, don't have a gauge.. yet. I bought OE spec pads and shoes at first, switched the pads to cheepies just to see if it made a difference. The ones I pulled out did look a little shiney, but the rotors still look good. Rears are adjusted correctly. There is no grease on any of the contact surfaces, but maybe my next step should be to pull th rotors and have them touched up in case there is glazing.. hard for me to tell. Power braking: you're thinking of a test to see if the fronts or rears work better than the other? I can try that.

corax

Try a good set of brake pads - I recommend Hawk LTS pads (get them over the internet if you can't find them locally). The friction material on cheap pads isn't nearly as good

toyotacharles

want to see brakes will keep it still or if tires will lock in dirt
is the brake pedal hard to push or is it about normal? possible lack of booster help?

wyoming9

iTrader: (1)

You replaced all the steel lines did you make your own?? Or buy The Toyota ones from the dealer??

What brand rear drums since most drums come from china. i have seen new drums with dimensions so far off as to be by law worn out brand new. You are using the ebrake to keep the rear brakes adjusted.

You did give the pads and shoes time to wear in. How many miles have you driven with all the new brake parts ??

You say a Master Cylinder from a 91 3.0 is that a new one or used.

I am not real sure if I could lock the brakes in a panic stop I never tried or had to.

Justin McMullan

Least I know the name now lol I don't care about spelling lol look at me...


I'm going to guess but when you installed new brakes you wanted to see how good they stop.. so you slammed on them...... The propper way is to speed up real fast then slowly give preassure till you stop..... a long stop I call it... It soun ds to me like you glazed them a poor mans way is to use like 80 grit and tuch up the surfaces... the right way is to get new pads lol... or deal with bad brakes till those wear out. then go in reverse and do the same... it will adjust them to I think lol

TurboKH

I bought this truck with all the new parts already installed. Toyota OEM stuff except for the lines. I don't know how he broke in the pads, but I suspect glazing somewhere I tried new cheapie pads just as a test and it made no difference. Ordered rotors and pads yesterday so I'll be replacing the front stuff probably tuesday when the FEDEX guy gets here. I just bought this truck because it's so rust-free and all the new parts.. the price was hard to resist and I thought it would be fun to mess around with. The brake thing has become an obsession! I'll make the things work right if I have to spend $5k doing it.

Oh.. the MC from a 1991 3.0 truck is new. I bought it for the bigger piston/fluid capacity.

TurboKH

The pedal is high and pressure actually feels pretty good. When you start the truck and there's vacuum, the pedal goes down a bit like it should. Based on that I think the booster is okay. No way you can put it to the floor. If I 2-foot the brake, it'll give your face a rush from the negative G, but it's right on the edge of breaking a tire loose... and it shouldn't be necessary to exert that much pedal to create that effect. If i stomped one of my cars (or even the Tundra) that hard they'd stand up on the front bumper.. well.. kinda.

waskillywabbit

iTrader: (-1)

So you have a stock lspv or a manual one?

I had V6 calipers, upgraded MC and manual pv and I could lock up my 39.5s on my 85 easily.

:wabbit2:

toyotacharles

if you really want to spend 5k to fix it for that price you could pay me to travel there and fix it for you.


lol

TurboKH

Waskillywabbit:
So the calipers on V6 trucks are different? What would it take to adapt them to my truck? Maybe that's (another reason) why my other trucks all stopped better.. this is my first 4 cyl... Stock PV.

blake.nemitz

the v6 calipers bolt on and have 4 pistons

waskillywabbit

iTrader: (-1)

The V6 IFS calipers are different in that they have (4) of the LARGE pistons per caliper for more surface area to the pad for braking. With upgraded calipers, MC and the double diaphragm booster your brakes should be primo.

The 4 cyl calipers have 4 pistons too. They just have 2 small and 2 large

:wabbit2:

corax

don't forget you have to swap rotors also, or you'll end up like this:

here's my write-up

RBX

Can't lock mine up either, my rotors are wavy, not grooved but smooth groovy like the pads were replaced without turning the rotor.
I have a t100 MC, and its better. My lspv is also wet, so I suspect this is the reason for some pressure lose.
I'm going to get t100 rotors and calipers the replace the booster with the dual diaphragm when I ad the manual lspv.
If that doesn't work, on mine, then I will suspect the problem is in my lines.

This is a long shot, but brake fluid attracts moisture, and mosture in the fluid is bad. You are suppose to change your brake fluid, but I don't know the interval.
Good luck