Brake Pull

Hi all. I need to little help. My ute failed a wof for pulling to the right when braking. So far I've removed, cleaned, regreased the caliper slider pins. Checked for stuck piston, thats algood. Replaced both pads. gave the system a good bleed. Checked the brake hose for leaks or collapse, seems fine but I might swap the two front hoses around to see if theres any change before I spend money on a new hose. Put on another set of rims and tyres, no change. The left rotor way have a slight warp? I ran a test by jacking up the front, applying a small amount of brake pressure, just enough to be able to still rotate the front wheels with a needle style torque wrench to see how much pressure each brake was producing. Right hand brake was 60 ft-lb, left was 44. Thats a considerable amount, question is, WHY?

does it have ABS? maybe needs a proper flush out using the right equipment (think they have to be hooked up to a machine)? speed sensors not working the same on either side?
just throwing shit out there i dont know

Swap the discs over , the left is probably out of specification ie a bit warped .

check to make sure that there is full articulation of the calipers.

Make sure there isn't a stone in there stopping the caliper from grabbing the disk properly on the weak side. Thats my guess

could also try swapping one pad from side to side. Whats the ute

Swap the disc's over and recheck? If the fault doesn't move you might have a partially blocked something in the system. That can be pesky, but more than even there is a mechanical cause over a blockage.

I know you said you did a brake pressure test and you’re following that line of thought, but out of curiosity you haven’t done a tyre rotation recently ? Even slightly different tyre diameters can play hell with rolling goad brake testers. Have you done a basic test on level tarmac by hitting brakes in straight line without holding/controlling steering wheel or brake test on gravel road. Gravel can show initial uneven braking even with abs/asc.

If it had different sized wheels on the same axle it should of failed wof on it

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Originally Posted by scotty

does it have ABS? maybe needs a proper flush out using the right equipment (think they have to be hooked up to a machine)? speed sensors not working the same on either side?
just throwing shit out there i dont know

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No abs

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Originally Posted by blip

could also try swapping one pad from side to side. Whats the ute

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It has all new pads. rodeo

Ok. I've completely stripped, cleaned, checked and reassembled the left caliper on no difference. also swapped slider pins between the two front calipers, no difference. I'm in the process on swapping around brake hoses to see if that changes anything but Murphy's law, damn hose fitting is seized and I almost completely rounded off the nut. If I'm successful in getting the hoses swapped around and that makes no difference then I'll swap the rotors around.
There's some weird brake pad markings on the rotor though.
Attachment 234061

I almost checked how bad the rotor warp is with a dial, .04mm travel. Also my brake tests are showing the left brake still not quite applying the same amount as the right, only 5-10 ft-lb off.

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Originally Posted by blip

If it had different sized wheels on the same axle it should of failed wof on it

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Diameter from tyre wear, not different size.

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Originally Posted by Three O'Three

Ok. I've completely stripped, cleaned, checked and reassembled the left caliper on no difference. also swapped slider pins between the two front calipers, no difference. I'm in the process on swapping around brake hoses to see if that changes anything but Murphy's law, damn hose fitting is seized and I almost completely rounded off the nut. If I'm successful in getting the hoses swapped around and that makes no difference then I'll swap the rotors around.
There's some weird brake pad markings on the rotor though.
Attachment 234061

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So, after swapping hoses around you will more or less have changed brake fluid in front system. You ma y find that you had an air bubble or moisture in system. Assume brake pads or rotor weren’t contaminated when pads changed?

Does the brake drag on one side after releasing it. Mark on rotor might be from being parked up with wet pads possibly. Also check that the brake pads are moving freely in the caliper brackets.

Something that I almost tore my hair out tracking down was attempting to get my fully rebuilt Land Rover to brake in a straight line. The 350kg donk I had shoehorned in in place of the 350lb Rover V8 needed a tad more stopping power so I fitted discs. Took a week pulling everything to pieces to find out why it braked sort of straight with modest brake pressure, but lurched to the side doing an emergency stop. And bugger me when I was down to grasping at straws I used an air line to blow out all the hydraulic lines. One flexible hose made a screaming sound, so I inspected and blow me down, there's a small piece of rolled up swarf sitting inside the end fitting of a brand new brake hose:wtfsmilie:

I’ve heard of a flaw inside a brake hose that was acting like a non return valve when under extreme pressure - just throwing it out there.

Yeah, partially blocked brake line on the left side creating a restriction. There's not that much force in the setup of a vacuum assisted brake system so any restriction really shows up. If you have a master cylinder in that with individual lines to the front disc's it could be in there even. I've had gunge getting caught up inside the connection to the caliper and making a restriction there, gritty crap. Not easy to find...

I dont see how anything could get inside the system if you havent had it apart.

sounds like caliper pistons aren't moving out evenly when fluid pressure rises.
suggest replacing seals around pistons or just free up/clean manually.

The rubber seals to swell over time, and eventually restrict piston movement.

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Originally Posted by Finnwolf

I’ve heard of a flaw inside a brake hose that was acting like a non return valve when under extreme pressure - just throwing it out there.

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had that problem quite a few times over the years.

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Originally Posted by trapperjohn

sounds like caliper pistons aren't moving out evenly when fluid pressure rises.
suggest replacing seals around pistons or just free up/clean manually.

The rubber seals to swell over time, and eventually restrict piston movement.

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Yeah what he said
And give everything a good dose of red rubber grease don't use any other lubricant.

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Originally Posted by trapperjohn

sounds like caliper pistons aren't moving out evenly when fluid pressure rises.
suggest replacing seals around pistons or just free up/clean manually.

The rubber seals to swell over time, and eventually restrict piston movement.

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What also happens is you can get a band of rust in the caliper between the dust boot and the piston seal. You have to pull the piston out to see it sand it or we give it a fine bead blast. That binds the piston up

Update: I went to swapped around brake hoses to see if its a hose problem but fitting nuts are seized so I swapped around disc rotors. seems to make a difference when driving but the roads around where I live are not nice and flat. sometime it would pull to the right, sometimes to the left, but half the time it would stay straight. I'm gonna take it for another drive tomorrow for another test. If it continues to pull mostly to the right I'll try what @XR500 has done by blowing out the brake line and may buy a piston seal kit. If it starts to pull mostly to the left I'll know its the rotor and pick one up in a few days

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Originally Posted by tac a1

I dont see how anything could get inside the system if you havent had it apart.

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Corrosion from moisture getting absorbed into the fluid, particles break free and collect at restrictions is what it seems like.

I took the ute for another drive, 5km round trip. Under normal mind braking ute stays mostly straight but under heavy baking where the brakes lock up it still pulls to the right. I did another brake pressure test after swap around rotors and the left now has higher brake pressure whereas it was then other way round. I did replace all shocks two months ago so wondering if it needs a wheel alignment, also noticed torsion bars arent set the same height.

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Originally Posted by Three O'Three

I took the ute for another drive, 5km round trip. Under normal mind braking ute stays mostly straight but under heavy baking where the brakes lock up it still pulls to the right. I did another brake pressure test after swap around rotors and the left now has higher brake pressure whereas it was then other way round. I did replace all shocks two months ago so wondering if it needs a wheel alignment, also noticed torsion bars arent set the same height.

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Ah yep, get the suspension leveled, pop the shocks out and check/replace if needed, check the rear leaf springs, check the tyre tread depth pressures and then do the alignment.