truck pulls to right when braking

[Rich Johnson]

My mechanic has again been trying to figure out why my truck pulls hard right when you step on the brakes.

Its been going on since I bought the truck and just seems to get worse.
So far I have replaced all the tie rods, the kingpin cones, the shocks, and the calipers.
The mechanic has had the truck for two days racking his brain and replaced the proportioning valve and one caliper trying to find the problem. He has also bled the system out several times, so he says.

To me it just seems that the right brake is braking before the left one but he cant figure out why. Hes blaming it on being a special military truck.

What the heck to do or look for now?
Should I go to a brakes only shop?

 

[1ton cucv k5 turbo]

given the numerous parts that have already been replaced... I would look for a possible pinched line on left side somewhere..... there is something thats being overlooked... Yes its a Military truck.. but the braking system is exactly the same as a civi 1 ton chevy.. i've had issues in the past with my brakes..changed out hydro boost, calipers, pads, kingpins... my pedal still went to floor with hardly no brakes.. ( it was only after i adjusted the rear correctly and rebled everything, did they started to work correctly again )

i do know that these are a pain in bleeding... and only after several.. and i mean SEVERAL tries in bleeding the system... they started to act right again as they should.

if your mech still gives that its "military" as a excuse... 'I'd look for another..

hope that helps...

 

[wikallen]

I would double check the rotors and calipers, wheel cylinders, drums on the left side. Do not take it back to that "mechanic" (part swapper)

 

[hendersond]

Start with a left brake hose, then left calliper. If it pulls right the right is working and the left is not. I have had on several old chevys the inside if the rubber hose split on the inside and "flap" or "balloon" obstructing the hose under high pressure. They bleed fine as it is generally no/low pressure. Other times I have had it allow the brake to actuate, but not allow pressure to release and lock up a wheel.
If you replaced the calliper once and the piston pushes back, it is good, don't replace it again.
Let us know what you find.

 

[hendersond]

By the way, the proportioning valve "proportions front and back. NOT right to left. Don't replace it. Start by tracing the steel line to the left wheel looking for kinks. Then check the calliper and then buy a hose.

One other thing, look at the spring pack and make certain the axle is mounted solid and not sliding. if the right center spring pack bolt is sheared it could allow the axle to shift under braking and give you that same feel.

One more other thing, Frame is known to crack around the steering gear boxes on chevys.

Keep us posted.

Dan

 

[bguy193]

I agree with everybody. Another place to check for blockage is the "T" that splits the brake line to both front calipers, I have seen blockage in that spot before. You tend to get gunk built up any where that there are two fittings connected. The flare connectors are just slightly smaller ID than the brake lines themselves. Hope you catch the problem, I am sure it is a blockage issue.

 

[4x4 Forever]

Going to a brake shop might help, they have a power bleeder that some of the 'parts swappers' don't have.
I agree with one of the lines ballooning/collapsing on the inside, it has happened to me. It was a bear to find, until I realized that they are hoses and they need to be replaced every once in a while.
Just make sure they are using DOT5 fluid and not DOT3, unless you completely flush the system before going to DOT3. Come to think of it, you might want to pop the cover and take a look at the fluid and make sure it is not all gummed up...your mechanic might have topped off the cylinder with DOT3...

 

[DonK]

I'm with "Hendersond"....replace the Hose.....Been there done that!

 

[Rich Johnson]

Well, my mechanic is pretty good with 4xs, he builds and services the baja racers here in san diego during season on his weekends.

The comment they made about it being military was they were eluding to vehicle abuse more than standard offroad use.

I agree about the proportioning valve, I dont want to pay for it but may have to.

I think that the front hoses is a good place to look and will probably do it if they didnt when they put new calipers on last year.
He said he also blew the lines out with air and bled them with a whole bottle of dot5. So were probably good there.

What about a warped right side rotor?

 

[hendersond]

Does the steering wheel begin to shake when you step on the brake?

What calliper was replaced? R or L?

Did you check your spring pack and frame?

Also, 120 psi air is no where near the 1200-2000 psi the system operates at.

If your frame and spring pack center bolt is good, it comes down to 2 things:


1. Does the right grab too hard?

or

2. Doesn't the left grab hard enough?

There are not many reasons why the right would grab harder than it was designed to.

 

[197thhhc]

Dont overanalyze it. Check the hard lines for kinks or crushed sections then replace the front hoses. Chevy trucks have had hose issues forever.Replace the front hoses and you should be fine

 

[BigRix]

I've run into brake pulling problems before where the issue was not with the brakes on the side where it pulls, but rather the opposite side not working and all the braking was being done with only one side. I always replace calipers in pairs. If it comes down to it, call around and find a shop that has a brake presure guage so you can eliminate a hydraulic problem. Many things can cause a pull and the severity of the pull can give you some indication. A gentle drift could be an alignment problem. If it rips the wheel from your hands I would bet only one caliper is working.

 

[Heath_h49008]

I'm on board with the crushed line theory... but the same issue can be caused by a badly made flare or someone trying to use a ferrule fitting instead of making a proper double flare.

Might sound silly, but open both bleeders/lines and pump. I'm going to wager the slow side has significantly lower flow rates. Either the Hose is "check valving" ... Replace them first... or you will need to check the steel.

You're going to have to track it back from the caliper and inspect the line and flares all the way back to the "T."

But replace the hose first. It's cheap and the most common failure point for this type of issue.

Keep us posted and good hunting!

 

[WillWagner]

Seen where an out of adjustment rear made it pull to the opposite side before, Check the rears too, it's a quick, easy inspection. Also, I fought this on my 85 1 ton 4X4. I ended up taking a file with emery cloth on it and cleaning up the calipers and their mounts, assembled with never sieze and the issue cleared up.

 

[Rich Johnson]

Ok, recap here;
before we started this venture last week I had allready replaced
front springs, hangers, bushings
all tie rods
king pins
both calipers
shocks

the steering wheel is not jerked out of my hand. Simply stop quickly at 35 or higher and hold the steering wheel straight and the truck drifts at least a half lane or further to the right depending on how quickly you come to a stop, IE pressure applied to brakes.

The mechanic changed both calipiers again because they were warrantied any way, the propertioning valve and both front hoses. He also visually inspected the steel lines.
He called me on saturday and said he had it so I went and drove it and it still did it, though slightly not as bad. I got him and took him for a ride and he was shocked that I made it do it, he said he drove it a bunch and it had gone away from changing the hoses.
So he kept the truck and is continuing to try.

What the heck do we do next?

 

[rickf]

Have you tried rotating the tires? Rear spring pins?

Rick

 

[Heath_h49008]

With the wheel held straight, the truck drifts under braking?

Whoa... I'm sorry I misunderstood.

If I'm reading this right, we are talking about fairly significant geometry changes. Front wear components seem to be ruled out.

 

[135gmc]

One spot that can be overlooked is brake fluid - If the truck was converted from DOT 3 to DOT 5 brake fluid, the changeover HAS to include flushing the system with alcohol since DOT 3 & DOT 5 are not compatible. If the two are both in the same system, you can bleed and bleed the brakes and never get them to work right. I used a power bleeder filled with alcohol on my '135 and blew a gallon through the system, followed by blowing the system out with my air compressor. The end result was a brake system with -0- problems.

 

[cpf240]

To rule out suspension geometry questions, mount a camera, like one of those Go-Pro things, under the truck and see what happens under braking.

Oh, and please be sure to post any such videos here!

 

[clandr1]

I had this same problem (civvy '89 Jimmy), and went through everything you have (replacing everything but the hard lines).

In the end, it ended up being mismatched brake pads. I purchased a caliper/pad combo when I redid the brake system after initial purchase of the truck, but it turns out the pads weren't manufactured together, at the same time.

Try buying a new set of brake pads (in the same box) and try replacing them. You might be surprised.

I know I kicked myself for buying a brand new proportioning valve from Year One, although it sure looks purty