Lurching violently to right on heavy braking

gbjeppm

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Ideas please:

My 560 SEC is lurching quite violently to the right under braking, the harder i brake the more it lurches. This afternoon on a test run, it even skidded/wheels locked up and ABS did not kick in (this was braking very hard at 60 mph).

It was doing this a little before, and I noticed that the passenger side front caliper was leaking slightly through the pistons. I had both front calipers professionaly refurbed 4 months ago.

Anyway I sent the weeping caliper away again,thinking that this was the problem, and got it back yesterday, all fully working pressure tested etc, and all good.

I fitted it this morning, bled the brakes, all running clear through the front bleed nipples. I did not bleed the back brakes.

Anyway after that, test drive, and symptoms as above.

Is there anything else that can cause this? I took the passenger side tie rod off a few weeks ago, as it was seized. And then have had a full wheel alignment, so I know that my measurements are good.

Could a malfitted tie rod cause this? I dont think so, It still feel its a brake issue.

Anyway, does anybody have any ideas?

Thanks
 
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markjay

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I think that there is almost certainly significantly less braking on one side.

Did you check the caliper guides to ensure that the caliper can move freely all the way in and out? In the olden days we use to coat them thinly with copper grease.

Could the pads or discs on one side be contaminated in any way? Oil, grease, or brake fluid?
 
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gbjeppm

gbjeppm

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Could the pads or discs on one side be contaminated in any way? Oil, grease, or brake fluid?

Mark, I think that may well be it, the pads were covered in brake fluid after leaking through the piston.

Whats the answer, new set of pads? Probably the safest bet.
 

stwat

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Did you replace the flexible brake hoses when the callipers were refurbed?
 
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gbjeppm

gbjeppm

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Whats the best thing to clean the disk with? I don't really want to change the disk as well.
 
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gbjeppm

gbjeppm

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Stu, no I did not, but they look fine. Don't know how old they are though.
 
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gbjeppm

gbjeppm

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They can collapse internally causing the issue you are having.

Thanks, well will see if the pads/rotors covered in brake fluid is the issue first, if that does not fix it, I will replace the hoses.

Aftermarket, they are only about 6 quid each from Febi.
 

bolide

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I'd replace the flexis and bleed the whole system through carefully. I'd also recommend checking the wheel bearings for noise & play and checking the runout on the discs

Does the car have sliding calipers or four-pot brakes? If sliding, the caliper has to be free to move along the pins. If you have two or four-pot calipers the pads have to be free to move in the caliper

Excess runout on the disc or hub can cause pad knock-back but I doubt it'd make the car pull to one side as much as you describe

Corroded discs can cause this kind of effect on hard braking. If they are corroded on one side only it's usually caused by a sticking piston in a 2 or 4-pot caliper. It happens a lot on the rear of W124s

Nick Froome
 
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gbjeppm

gbjeppm

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Thx Nick.

It is a twin opposed piston caliper setup. Front calipers recently fully refurbed by the Brake Caliper Specialist in Nottingham, all pressure tested, new seals etc.

IMG_1671.JPG


Disks look good, I am leaning towards contaminated pads, if not will change flexis.

Will have a look at the bearings, but they seem OK.
 

E55BOF

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Stop looking for complications. Clean the fluid off the discs (any non-oily solvent will do - meths, thinners, whatever you have; even petrol in emergency, but beware of the very high risk of fire...) ) and dry them with cloth or kitchen roll, then change the pads. If you still have a problem, then is the time to start looking for other less likely causes, but do the basics first.
 
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gbjeppm

gbjeppm

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Stop looking for complications. Clean the fluid off the discs (any non-oily solvent will do - meths, thinners, whatever you have; even petrol in emergency, but beware of the very high risk of fire...) ) and dry them with cloth or kitchen roll, then change the pads. If you still have a problem, then is the time to start looking for other less likely causes, but do the basics first.

Agreed, thought that was what i said. First job for tomorrow morning:D
 

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Had this on a 500sec and one side of the anti roll bar had come adrift/snapped causing tension on one side and not the other when braking.
 

bolide

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Had this on a 500sec and one side of the anti roll bar had come adrift/snapped causing tension on one side and not the other when braking.

Have a think about what you are describing

When braking in a straight line there is no tension in the ARB - it pivots at the mounts and the dive is the same each side

When one link has broken there is no tension in the ARB - it pivots at the mounts and one end is disconnected

Nick Froome
 
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gbjeppm

gbjeppm

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Update:

I cleaned the pads and disc.

The pads i used brake cleaner, then heated them up with a propane torch to burn off any residue, and then sanded them to roughen them up.

Much much better, planning on changing the pads though in the next day or so when i can get a set.
 

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I have in the distant (and penniless...) past boiled brake-fluid-contaminated pads on the kitchen stove to rejuvenate them, and it worked after a fashion, but I wouldn't do it now. I'm glad to hear you've found the fault.
 

Auto-mobile

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Have a think about what you are describing

When braking in a straight line there is no tension in the ARB - it pivots at the mounts and the dive is the same each side

When one link has broken there is no tension in the ARB - it pivots at the mounts and one end is disconnected

Nick Froome

Thought about it..... Nope definitely happened.
 

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