offset442

I have been going through my 88 getting it up and desert ready, to go wild goose hunting for gold, so far I have ironed out all of the most annoying issues yet one escapes me, when I hit the breaks the front end pulls hard to the left and makes the wheel turn left at the same time...

heres what i know,

-New Rotors
-New Pads,
-calipers not sticking,pulled and inspected all and cleaned 8 pistions
-did lots and lots of two man bleeding, seems like the flow is not restricted
-new wheel bearings
-New front bushings
-steering linkage in good shape
-tried adjusting the camber

basically the left side is grabbing right but the right side seems like its not getting enough hydraulic pressure, the left side is closest to the first T right under the master, while at the right side there is a second T the Leads to the rear load proportioning valve,

I not sure how exactly this valve works other than it is actuated by a linking rod to the rear end because this valve gets 2 lines to it, one line from the T at the front right caliper and one line from the second chamber of the master cylinder, then it has one line that comes out of it and goes directly to the rear drums

My last 87 4X4 had this exact same problem and i was never able to figure it out on that truck either It really sucks when you ahve to hit the breaks hard at speed on the highway and even is troublesome on the dirt at 30 mph let along 60 on the pavement

Does anyone know what goes wrong in the hydraulic path trouble shooting guide for these trucks, every manual i have looked in just talks about the big parts and mentions nothing about anything that is related to my problem

Ocean

69SSRat

Look at your brake flex hoses they will swell inside and cause this problem. They are supose to be replaced every 7 yrs.

offset442

checked the brake flex hose, and it does not seem restricted I was able to run a 10 or 12 gage steel wire clean though it without any resistance seems ok......

I have been trying to bleed at the LSPV, but seems like its not getting much fluid flow though the valve, is this normal when the truck has no load?

Ocean

69SSRat

what kind of pressure do you have at the wheels ?
what kind of bleeder are you using ?
checking the hose with a wire has never worked for me 23 yr old hoses have passed there life expectancy they may be open but restrict back flow for release also so for what they cost i would replace them.
now are you sure the front or is it the back pulling

angrybob

One easy thing to do is to check the friction. Aftermarket pads (yes?) can have pretty big variation in friction levels. And all green pads have some variation.

Pop both front wheels off and swap the pad pairs left to right & right to left and see if it follows the pads. If you now pull to the right, its your pads. The main fix if this is the case is to mix the pads up - 1 from the original left side and one from the right. Yeah its but it works most of the time if friction is your problem.

Its an easy check since the pads come out the top and its free.

offset442

been messing with it some more, figured out that it was dirt in the lspv bleed valve, bleed the lspv no air,

started bleeding the the rear wheel cylinders, and kept getting air on a 2 man bleed bleed each rear cylinder 5 -6 times collecting 100ml of fluid at each bleed and kept getting noticeable/audible amounts of gas bubbles, in waves about every 6 or 7 full presses of the peddle

now im stupified, I thought it was the second man letting the brake up to early but I ruled that out because i can here the peddle hinge make noise and the man says hes not letting up until i say ok after i have closed the bleed valve every time.

I cant find any signs of brake fluid leaks, around any of the slave cylinders or the master, or any of the lines......So where are the gas bubbles coming from? is it possible for a brake cylinder to suck air but not leak fluid?

seems to me Air in the rear lspv circuit would explain the pressure drop and the right side caliper since its on the second T in the hydraulic chain it could have a pressure drop grater than the first T that feeds the left side caliper, because its closer to the pressure leak, so when I hit brakes the pressure surges into the caliper allowing it to bind then leaks out though the lspv partially open valve (aka an orifice) to gas ballast.

When I hard brake test on the highway both wheels lock up at the same time but then the right side releses I get about 10 feet of skid out of the left side but only about 2 feet out of the right side then it lets go and the left side just keeps skidding

I think im going to try and put tiny steel ball in the right side T fitting that leads to the LSPV to isolate it from the circuit and see what happens.

pinoaktwh

Unless I missed it posted. The reference to the flex hoses being the possible problem is not about restriction, it is about loss of pressure. They can swell when the pressure increases (when the padal is depressed) which gives you less pressure to that particular line. Hence the other side having more pressure (brakes grab harder).

Like squeezing a balloon and it pops out the end of your hand.

If that was already stated my apologies.

offset442

ok added the ball bearing, which was damn hard to find and isolated the lspv, still does it, its int eh front........ went on another road test took a closer look at the skid marks right side is acutely locking up 6 feet after the left side........was looking at the marks reversed in the review mirror, woops..... well that blows away my lspv air theory, which is a good thing. As we can ignore that extra line now

going to try the pad flip next, will have to wait until i have more free time maybe tomarrow or the next day, I use auto-zone semi-metallic pads i don't really care for the ceramic ones as they seem to over heat and warp the rotors more, the sulfide composite based SM's ware faster but they are so easy to change, its never bothered me, I like the fact that they generate less rotor heat and seem have a broader window of pressure response, but as for noticing a friction difference i never have in all of the pads i have changed, but i think im at a try anything point, here.........

then I'm going to look for restrictions,
try swapping the left and right side hoses for the hell of it if they interchange, other wise i will just buy a new one, encase its a pressure activated clog.

oh ya I forgot to mention funny thing is, it didn't do this before i replaced the rotors and pads, as was required by the California salvage title safety inspection, the pads where about half and the rotors where 1mm under minimum so they made me get new ones to pass, ever since then its pulled to the left bad..........might have pulled a little before that but i didn't really notice it until after the swap. that was almost a year and a half ago, didn't have much interest in this old truck other than being a backup until recently, my 00' tacoma has become enslaved as a full time work truck for my contract job as a sat tech, now i need a backup trail rig so to say, I sure miss my 00' for running around in the back country.....

69ssrat:
as for bleeding, Im using a 10mm wrench and a metric graduated collection bottle with a clear hose attached to the bleed screw using the 2 man system calling out up and down to the man in the cab, cracking the the bleed valve just before the down stroke and sealing before calling for the up stroke, watching the bubbles and fluid flow out of the valve, also accompanied by some hissing where air is coming out. i'm just going to ignore the mysterious air in the back system for now

I haven't tried taking actual pressure readings, as i doubt i have enough parts put together a pressure gauge rig, though i doubt reading the pressure would help much anyway, i was making an estimate based on observation that turned out to be backwards

as for the front or back pulling my best indicator is the action of the steering wheel turing in my hands and the skid marks on the pavement, after accellerating to 30mph and braking hard its a bit hard on the tires maybe but gives a good "Graph" of whats going on, the back does not lock up at all unless a get the e-brake involved

ttl

Ocean

69SSRat

Well Pinoaktwh explained it better than me (Thanks Pino) didn't know thought you were using a vac. bleeder. I have had this same thing happen replacing calipers and pads on other cars so I'm still leaning to the hoses.

MrPeepers

man I feel ya on this. I was hunting a similar issue on my 4runner for a long time. Mine was several issues all combining for a perfect storm. Some things that were contributing in my case were calipers (after noticing one was sticking I got new ones, and one of the new ones was still acting up wearing a pad at an angle so had to swap again), the bushings on the anti-sway bar were severely worn, steering dampener worn, the rear brakes needed to be adjusted so the fronts weren't doing too much of the work. It's still not the greatest but decent now, doesn't steer the car when I hard brake anymore.

offset442

didn't have any time today to mess with it, one thing for sure this problem is going to go away no mater what, I want o have a tip top trail rig again.......

Ocean

offset442

Ok changed the hose today, and bleed the system again, still have the ball baring isolating the rear LSPV,

As much as i try i cannot find anything wrong with the old hose, however the ball game has changed somewhat now with the new hose right side hose, when i hit the breaks at 30 mph on the pavement instead of just getting a hard pull on the steering wheel to the left, I now get a somewhat softer pull to the left and the rear end of the truck is now kicking out to the right, so im, effectively and consistently after several tries going into a sideways skid automatically now, even more dangerous.

Back to head scratching i guess

pinoaktwh

Probably need to replace all your soft hoses. If one was bad then others are or will be soon anyway.
You might be suprised of the result.

69SSRat

You will not be able to look at the hose and tell there bad now that you changed one change the others back one also. This will give you a better read on adjusting rear shoes and you shouild see an improvement