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Honcho Emeritus

07/13/2021 5:14 PM

My Chevy Express cargo van recently started pulling to the right when braking, most severely the moment of full brake engagement, then immediately relaxing (not pulling right while still braking), but simultaneous with the relaxation, the steering wheel would pull left abruptly, but not severely, as if there were a left directing pavement rut creating the left steering load to the steering wheel.

Calipers of right front wheel are in good shape (pads, clearance, closure, etc.). (Right rear has not been checked.) Otherwise no braking issues (good general stopping, no dragging sounds, fluid loss, etc.) Same with power steering (no fluid loss, no squeals, no jerkiness, all smooth and normal except for braking weirdness).

Chevy repair says anti-lock braking unit needs replacing. Maybe, but why the weird steering wheel pulling to the left as braking takes place while brakes still engaged? Dunno, but Chevy repair claims replacing the anti-lock braking unit should fix the problem. Maybe, but what does an anti-lock braking hydraulic unit have to do with power steering? There is no hydraulic or mechanical connection.

What must Chevy repair and/or I missing here to explain what is going on?

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#1

Re: Honcho Emeritus

07/13/2021 6:49 PM

When was the last time you changed the brake fluid...bleeding the brakes thoroughly...and replacing the brake hoses .... that would be the first thing I would do....

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#2
In reply to #1

Re: Honcho Emeritus

07/13/2021 7:17 PM

A collapsed inner lining of a brake hose is the most likely culprit.

What happens is that when the brakes are first applied, the side of the vehicle with the restricted brake hose gets less fluid than the other side resulting in unequal braking. Over time while brake pedal is depressed, the pressures eventually equalize, and the pulling to one side ceases to be noticeable.

When the brakes are released, the reduced flow leaving the caliper causes the opposite effect. Don't listen to your "Chevy" repair person. They don't have any idea of what they are talking about.

Buy the new brake hoses and just do it. If one is bad, I would replace them all and be done with it.

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#3

Re: Honcho Emeritus

07/13/2021 11:10 PM

How old is your vehicle?The flexible brake lines will deteriorate on the inside over time.They will begin shedding small particles into the brake fluid.When just one of these particles gets in the return line port of the master cylinder,that caliper will not release properly,sometimes not at all.

The sudden swerve to the left is caused by fighting the right hand pull by applying steering pressure to the left.When the brake releases,this bias toward the left is felt as a swerve to the left because the brake is no longer pulling it to the right.

Replace the flexible brake lines,replace all of the brake fluid,and bleed the brakes thoroughly.There will be a procedure on line on how to prevent your brake warning light or error code from coming on when you bleed the brakes.

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#4

Re: Honcho Emeritus

07/14/2021 9:59 AM

"... what does an anti-lock braking hydraulic unit have to do with power steering? There is no hydraulic or mechanical connection."

The anti-lock braking unit detects when a wheel has locked up and releases the brake momentarily, allowing it to turn and maintain directional control. It sounds like the anti-lock braking unit is releasing the left or right front wheel brake causing the car to pull in the opposite direction.

The power steering has "feedback" from the wheels to the steering wheel giving the driver the feel of the road that he would have with manual steering, but with much less effort. This is how the anti-lock brake unit can affect the steering wheel.

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#5

Re: Honcho Emeritus

07/15/2021 12:28 AM

Not sure I followed the sequence of events but consider a look at the suspension bushings while you are checking the brake hoses. The bushings may be old/worn and deflecting under braking.

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#6

Re: Honcho Emeritus

07/15/2021 5:39 AM

Firstly, check the brake booster where the master cylinder is. If the diaphragm has a pin hole in it, this can be the cause of your troubles as the pressures equalises on both sides of the diaphragm and snatch the closest brake, (shortest route, which is the right hand front brake).

I have had this previously and replaced the booster diaphragm and all was fine again.

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#7

Re: Honcho Emeritus

07/15/2021 6:50 AM

"Calipers of right front wheel are in good shape (pads, clearance, closure, etc.). (Right rear has not been checked.)"

What about 'left front'? It's pulling to the right: so surely it's the left brake which is suspect.

(You almost certainly know a lot more about this than me, so, the question is more for my benefit than yours.)

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#8

Re: Honcho Emeritus

07/15/2021 11:01 AM

Consider the possibility of reduced performance of one or a number of braking components on the left side of the vehicle as the cause of its pulling to the right when they are applied and correcting to the left when released.

In the UK, the performance of individual wheels' brakes and a balance between them when applied is an important part of the MoT Test.

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#9

Re: Honcho Emeritus

07/15/2021 2:24 PM

Replace the cheapest parts first.

I've been down this path and spent a lot of money replacing perfectly functioning calipers.

Brake hoses are about $20 each. One caliper sets you back about $90.

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#10
In reply to #9

Re: Honcho Emeritus

07/15/2021 3:26 PM

No, just sell the Chevy Express and buy a Mahindra Bolero, It will be far cheaper and more longer lasting and less hassle. And they come with great brakes.

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#11

Re: Honcho Emeritus

07/15/2021 5:06 PM

If you have rear drum brakes, check for brake fluid on them. Otherwise I would change what the experts say is wrong.

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#12

Re: Honcho Emeritus

08/09/2021 1:48 AM

You have some great recommendations from the guys here. I agree it's most likely a brake hose/dirty fluid problem. Could also be something in the caliper causing it to drag. Here's why I don't think it's an ABS issue.

The ABS computer has a self check system. If something goes wrong, the ABS light on your dash lights up. The ABS grab/release function isn't working right, due to a collapsed hose or fluid problem - it's a mechanical problem, not a computer problem.

I've had quite a few GM trade ins with a bad ABS computer. The ABS lights up and when we put a scan too to take it off, the light comes back on. The only solution is to replace the computer. It's not as expensive as you would imagine - there are lots of used parts out there. From the large number of GM vehicles in the junk yards.

Let us know how it turns out.

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#13

Re: Honcho Emeritus

08/09/2021 7:27 AM

The cause of the pull is uneven braking.When you apply the brakes,the right front brake engages first,and it pulls to the right.Naturally,you apply a correction and try to correct by steering left.When the right brake releases,and the braking becomes even (left+right), or you release the brakes,there is still the correction (left) that you put in when it started pulling right.The correction is no longer needed,so it pulls to the left temporarily till the computer corrects the error.Even 100 milliseconds in correction time can be significant if you are traveling at 60 MPH(88 Feet per second).

This uneven braking could be caused by air in the system,so the cheapest,easiest thing to do is a complete bleed of the brake fluid,using the approved type of brake fluid.

The easiest DIY, solo method I have found,if you do not have or cannot borrow a pressure or vacuum, bleeder,is to connect a small,snug fitting host to the bleeder port,and put the end of the hose into a container of clean brake fluid.Open the bleeder,and pump the pedal twice.

The fluid in the container at the end of the bleeder hose will act as a check valve to prevent air from getting back into the system when you release the pedal.

Top off the master cylinder after each 2 pumps of the pedal.

4 Pumps should clear any of the lines.

The master cylinder must be kept full during the entire procedure to prevent air from getting into the fluid.

Buy a quart container of brake fluid..you do not want to run out in the middle of bleeding the brakes.

Glycol based brake fluid will absorb moisture from the air and the fluid will boil,causing erratic braking behavior.

Silicon based fluids will not absorb moisture,being heavier than water,so any moisture will go to the lowest point.

This can cause similar problems,including rust inside the caliper.They have not invented a perfect brake fluid yet.

Has your brake fluid been topped off recently?

Has fluid from an opened container been added?

Never use fluid from a previously opened container.

Sometimes the quick lubes will top off your brake fluid and power steering fluid as a courtesy,using fluid from an opened container.

They do not understand the damage they may cause.

Good luck,and avoid the dealer unless ou have no other choice ,unless you more dollars than common cents.

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#14
In reply to #13

Re: Honcho Emeritus

08/09/2021 11:53 PM

I'll add a very important step. When pushing on the brake pedal with the bleeder open, don't push the pedal to the floor. Sometimes, there's some oxidation on the master cylinder piston. It'll be clean in the area of normal brake pedal movement (the constant use keeps it clean). If the brake is pushed to the floor, the oxidation may cut or scrape the seal, causing fluid to leak past the piston when pressurized. You'll know this happened if after bleeding, you push the pedal and it keeps sinking to the floor.

The only solution is to replace or rebuild the master cylinder.

Don't ask how I know this!

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