Brake Test Failure Advice needed

Ben911

Hi there,

Brought my Volvo S40 for retest after having all the break fluid, lining and a break pad also replaced, which was not even part of the NCT report.
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Car failed again allegedly as there was an imbalance on the rear of 32%, I think about 30% is acceptable. I had the car in the garage 2 days earlier. Rang garage immediately after failing NCT and was advised break pad needs 250 miles to settle in so that there is no imbalance.

So far, I have not found any posts or advice from other garages on this, is this really correct?

Also I am getting NCT to call me back as tester state there was another problem that car failed break test, but he did not tell me what exactly it was and it is not on the report. Do they have to tell me this?

Many thanks for all your hep

visual

While its true it takes a little time for brake shoes and pads surfaces to bed into the surface of the discs and drums to give maxium preformance. It shouldn't cause any noticeable imbalance as both sides are bedding in at the same time.

32% imbalance is a fair amount to be off. I suspect there is something amiss

Dark sun

Could be a sticky caliper causing imbalance ,nct should inform you of the fails, it should be on the bottom of the report sheet, if there's nothing there your in the clear.

christy02

Calipers on s40's can stick. I used to have a 00 s40 1.9d and it failed for the handbrake first. I replaced sticky caliper and then it failed on imbalance. Replaced other one and fine. Pick them up refurbished cheap enough.

However I notice you changed 1 break pad. That could also be problem. Really should change pads in pairs. They wear equally.

Bio Mech

christy02 wrote: »

However I notice you changed 1 break pad. That could also be problem. Really should change pads in pairs. They wear equally.

Definitely. I would say do the other pad and it should be fine. But do it now before the first one beds in and then drive it for a few days before you retest it.

mullingar

Brake pads should ALWAYS be replaced in 4's - thats why they are sold in x4's

christy02

mullingar wrote: »

Brake pads should ALWAYS be replaced in 4's - thats why they are sold in x4's

They are sold in pairs. Some cars still have drums on the back and discs on the front.

No need to change all 4 together. Whoever told you that is misinformed. Obviously front and back could wear differently.

slimjimmc

christy02 wrote: »

They are sold in pairs. Some cars still have drums on the back and discs on the front.

No need to change all 4 together. Whoever told you that is misinformed. Obviously front and back could wear differently.

He said "pads" so he's accurate when he says you should replace all 4 brake pads (ie 4 on the same axle - whether front or rear) at the same time. You can still change the rear pads (if rear disc) or "shoes" (if drum brakes) separately from the front but they too should be changed on both rear hubs at the time.

christy02

slimjimmc wrote: »

You misunderstood. He said "pads" so he's accurate when he says you should replace all 4 brake pads (ie 4 on the same axle - whether front or rear) at the same time. You can still change the rear pads (if rear disc) or "shoes" (if drum brakes) separately from the front but they too should be changed on both rear hubs at the time.

Fair point. I think poster was suggesting replacing front and back.

Ben911

Thanks everybody,

am still waiting for feedback from NCT guy - nothing on the test sheet about cause of imbalance, so I am definitely going to question this with the supervisor there.

Thanks for the tip on calipers will check this out

bucketybuck

Ben911 wrote: »

Thanks everybody,

am still waiting for feedback from NCT guy - nothing on the test sheet about cause of imbalance, so I am definitely going to question this with the supervisor there.

Thanks for the tip on calipers will check this out

Can you clarify how many brake pads you changed, because I don't want to believe that somebody changed just one brake pad.

By the way I don't believe the test centre needs to tell you the cause of the imbalance, thats not their job. They will simply perform the brake test and show you the results, pass or fail.

christy02 wrote: »

Fair point. I think poster was suggesting replacing front and back.

No, he said they are sold in fours and he is right. Four pads in a box, 2 for each side on one axle. You are misinformed.

GTE

Would a single new caliper really cause an imbalance?

I'd have thought they either work or don't. What makes an old caliper work less effectively over time if there are no leaks and the fluid is changed as required?

bbk

bbk wrote: »

What makes an old caliper work less effectively over time if there are no leaks and the fluid is changed as required?

In my experience it is normally the rubber boots on the slider pins failing and damaging the lubrication on the pins = sticking calipers.

slimjimmc

Ben911 wrote: »

Also I am getting NCT to call me back as tester state there was another problem that car failed break test, but he did not tell me what exactly it was and it is not on the report.

Can you clarify what this statement means? Are you saying the NCT tester found another brake fault but did not record it as part of the test? Tbh I don't find that credible. Sometimes they advise you that something passed this time but will need attention in the near future.