@forum mechanics. Anyone good with cars. MOT fail…

Bamberdele2.0

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Hi,

I have just been failed on:

- Parking brake efficiency below requirements

- Service brake efficiency below requirements


Just to point you in a picture the car was bought as a little runaround to the golf club and back. It’s done below around 5k since last years MOT. I have a family car and van for work for all other mileage so this car is used the least.

Now what is frustrating is this failed on the same thing last year. Obviously paid to get it fixed without batting an eyelid. I’ve taken it to the same garage btw.

Is anyone able to tell me what the parking brake and serve brake efficiency is and a common cause for this to fail please.

Much appreciated
 
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jim8flog

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I would ask what the repairers did last year. Did they just bleed the brake system.

One simple question I would ask is when was the brake fluid last changed? It is supposed to be changed every 2 years as it is hygroscopic (absorbs water from the air) and looses efficiency.
 

GreiginFife

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Hi,

I have just been failed on:

- Parking brake efficiency below requirements

- Service brake efficiency below requirements


Just to point you in a picture the car was bought as a little runaround to the golf club and back. It’s done below around 5k since last years MOT. I have a family car and van for work for all other mileage so this car is used the least.

Now what is frustrating is this failed on the same thing last year. Obviously paid to get it fixed without batting an eyelid. I’ve taken it to the same garage btw.

Is anyone able to tell me what the parking brake and serve brake efficiency is and a common cause for this to fail please.

Much appreciated
Are you asking what the definition of brake efficiency is or the values that the pass/fail occurs?

There are a number of causes that can lead to decreased brake efficiency. Jim has pointed one out, brake fluid that has become old and, effectively, stale.

But, there could be a number of others. Brake disk or pad issues (worn or defective), caliper leak, air in system (as Jim says, bleeding will help but bleeding the system doesn't stop air from getting back in if there is a seal issue anywhere), parking brake cable worn or stretched (these auto adjust in most modern cars but once stretched or worn adjustment doesn't help).

As above, what did they do last year? Seems like they dealt with a symptom rather than the cause.

Is it a manual parking brake or electronic?
 

Bamberdele2.0

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I would ask what the repairers did last year. Did they just bleed the brake system.

One simple question I would ask is when was the brake fluid last changed? It is supposed to be changed every 2 years as it is hygroscopic (absorbs water from the air) and looses efficiency.

I have not asked but it’s one I will this morning when I get the full quote for repairs 👍

Are you asking what the definition of brake efficiency is or the values that the pass/fail occurs?

There are a number of causes that can lead to decreased brake efficiency. Jim has pointed one out, brake fluid that has become old and, effectively, stale.

But, there could be a number of others. Brake disk or pad issues (worn or defective), caliper leak, air in system (as Jim says, bleeding will help but bleeding the system doesn't stop air from getting back in if there is a seal issue anywhere), parking brake cable worn or stretched (these auto adjust in most modern cars but once stretched or worn adjustment doesn't help).

As above, what did they do last year? Seems like they dealt with a symptom rather than the cause.

Is it a manual parking brake or electronic?

Just really trying to understand what it is.

The lady at reception has told me that the disc brakes and pads (front and rear) will be the cause but I am a little confused as they never changed these last year. For a car that isn’t driven very much I am a bit perplexed as to the cost of the vehicle repairs especially seen as these are the same problems that were fixed last year without the need to replace F+R DBP’s.

Think repair costs are about a grand as the wheel bearing and coil spring (I was aware of this) needs doing but still seems very steep none the less. Only route that seems cost effective is to take it somewhere else and use after market products to lower the cost.

A new clutch was put in April 2023 so I don’t really want to scrap the car.
 

GreiginFife

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I have not asked but it’s one I will this morning when I get the full quote for repairs 👍



Just really trying to understand what it is.

The lady at reception has told me that the disc brakes and pads (front and rear) will be the cause but I am a little confused as they never changed these last year. For a car that isn’t driven very much I am a bit perplexed as to the cost of the vehicle repairs especially seen as these are the same problems that were fixed last year without the need to replace F+R DBP’s.

Think repair costs are about a grand as the wheel bearing and coil spring (I was aware of this) needs doing but still seems very steep none the less. Only route that seems cost effective is to take it somewhere else and use after market products to lower the cost.

A new clutch was put in April 2023 so I don’t really want to scrap the car.
Ok, so brake efficiency is the amount of force that any given brake can apply relative to the weight of the car. Expressed as a percentage. I think (or at least it used to be for passenger cars) that the pass is >58%. That's a simplified version but you get the gist. Service brake is braking under the pedal, parking brake is under the handbrake (either manual or electronic).

Second paragraph would probably explain why the receptionist isn't out fixing cars. Discs and pads, whilst these will have an effect, are least likely to be the case IMO (unless seriously worn but then you'd probably have a wear sensor fault or it would be noisy). Brakes are hydraulic, the performance of the braking is dependent on the pressure that the closed system can apply to the calipers and in turn the freedom of movement that each caliper has to apply force to the disc via the friction pads.

It's more likely that old fluid, a leak somewhere or even a corroded brake line are the issue way before discs or pads would be suspect, again IMO as a time served mechanic. What they did last year would be of interest as it's rare for a service brake efficiency fault two years running. Parking brake maybe as if it's a cable operated manual brake the cable can stretch or snap.

One thing I will say though is don't disparage aftermarket parts, many are actually of better quality than the originals. And in some cases, exactly the same e.g. I replaced HID's rear caliper on her old X4. BMW wanted £220+VAT for the caliper, I got a TRW kit for £110 inc VAT and £30 rebate for returning the old caliper for refurb. Guess who made the old caliper... yep, TRW. Exact same part number except one had BMW stamped on it.
 

RichA

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A complete overhaul of your brakes by a local indie garage with non-Audi parts shouldn't be too expensive and definitely worthwhile if you're planning to keep the car for a few years.
Underused and old brakes are always going to be inefficient.
My previous old Saab failed it's MOT for the same reason a few years ago. It was a friendly local garage and the guy just took the car out on their property, with my permission, and spent 10 minutes accelerating and braking hard forwards and in reverse before testing again. Don't know about your Audi, but the parking brake for the Saab used a cable compressing the rear pads onto the disc, so the reversing bit was most important. It passed afterwards.
Not so much with modern cars, but with older cars the advice was always to thrash it a bit for a few days before an MOT.
 

Bamberdele2.0

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Ok, so brake efficiency is the amount of force that any given brake can apply relative to the weight of the car. Expressed as a percentage. I think (or at least it used to be for passenger cars) that the pass is >58%. That's a simplified version but you get the gist. Service brake is braking under the pedal, parking brake is under the handbrake (either manual or electronic).

Second paragraph would probably explain why the receptionist isn't out fixing cars. Discs and pads, whilst these will have an effect, are least likely to be the case IMO (unless seriously worn but then you'd probably have a wear sensor fault or it would be noisy). Brakes are hydraulic, the performance of the braking is dependent on the pressure that the closed system can apply to the calipers and in turn the freedom of movement that each caliper has to apply force to the disc via the friction pads.

It's more likely that old fluid, a leak somewhere or even a corroded brake line are the issue way before discs or pads would be suspect, again IMO as a time served mechanic. What they did last year would be of interest as it's rare for a service brake efficiency fault two years running. Parking brake maybe as if it's a cable operated manual brake the cable can stretch or snap.

One thing I will say though is don't disparage aftermarket parts, many are actually of better quality than the originals. And in some cases, exactly the same e.g. I replaced HID's rear caliper on her old X4. BMW wanted £220+VAT for the caliper, I got a TRW kit for £110 inc VAT and £30 rebate for returning the old caliper for refurb. Guess who made the old caliper... yep, TRW. Exact same part number except one had BMW stamped on it.

I forgot to add it’s an electronic brake.

Just read through the cert and the service break didn’t flag up last year, it was the parking break 2 years in a row. My bad as didn’t read properly as just assumed they were the same thing.

i think the next step is to just gather quotes for this work to be done from different places as whenever a garage says ‘worst case scenario cost’ I can’t help but feel that is a cop out by them to charge me top wack without even a consideration into getting this cost down.

In the meantime would you think I would be fair in challenging the garage to attempt to repair the service / parking break efficiency without an overhaul and expense of breaks pads front and rear?

Much appreciated
 

williamalex1

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I forgot to add it’s an electronic brake.

Just read through the cert and the service break didn’t flag up last year, it was the parking break 2 years in a row. My bad as didn’t read properly as just assumed they were the same thing.

i think the next step is to just gather quotes for this work to be done from different places as whenever a garage says ‘worst case scenario cost’ I can’t help but feel that is a cop out by them to charge me top wack without even a consideration into getting this cost down.

In the meantime would you think I would be fair in challenging the garage to attempt to repair the service / parking break efficiency without an overhaul and expense of breaks pads front and rear?

Much appreciated
Years ago I was charged for a full MOT re-test a few days after I got the faults fixed at a different garage.
 

GreiginFife

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I forgot to add it’s an electronic brake.

Just read through the cert and the service break didn’t flag up last year, it was the parking break 2 years in a row. My bad as didn’t read properly as just assumed they were the same thing.

i think the next step is to just gather quotes for this work to be done from different places as whenever a garage says ‘worst case scenario cost’ I can’t help but feel that is a cop out by them to charge me top wack without even a consideration into getting this cost down.

In the meantime would you think I would be fair in challenging the garage to attempt to repair the service / parking break efficiency without an overhaul and expense of breaks pads front and rear?

Much appreciated
There are a few things you can check yourself. If you can see in to the side of the caliper through the alloy, is there less than 5mm of friction material on the pads? Looking at the disc, does it look overly corroded or are there any deep scores or grooves or any large lips around the rim? If yes then these would need replaced. If not, then it's not the problem.

EPB works on a solenoid that opens and closes the rear caliper pot by winding it in and out. If the caliper has a broken or worn seal then this can cause it not to grip properly (reason I had to replace HID's caliper on the X4 was the caliper seal was burst, meaning it lost lubrication and was sticking). But it can also be a fault on the EPB itself causing it not to wind in or out properly.

I think you could challenge them, but as there is no single fault that always causes this, I doubt they would agree to it. Take it to an independent and ask for a brake inspection. They will assess the condition of the discs and pads (caveat, some might use it as an opportunity to generate business, it's just the way of the world) if you are not comfortable looking at them yourself. If you were nearer I would offer to do it myself.

The causes of service brake issues and parking brake issues could even be the same issue (if the caliper, or calipers, has/have an issue then this will affect the overall braking ability. But it could just as equally be two different issues. Brakes are more complex than they need to be these days, but they are also critical so don't leave it to chance.
 

Bamberdele2.0

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There are a few things you can check yourself. If you can see in to the side of the caliper through the alloy, is there less than 5mm of friction material on the pads? Looking at the disc, does it look overly corroded or are there any deep scores or grooves or any large lips around the rim? If yes then these would need replaced. If not, then it's not the problem.

EPB works on a solenoid that opens and closes the rear caliper pot by winding it in and out. If the caliper has a broken or worn seal then this can cause it not to grip properly (reason I had to replace HID's caliper on the X4 was the caliper seal was burst, meaning it lost lubrication and was sticking). But it can also be a fault on the EPB itself causing it not to wind in or out properly.

I think you could challenge them, but as there is no single fault that always causes this, I doubt they would agree to it. Take it to an independent and ask for a brake inspection. They will assess the condition of the discs and pads (caveat, some might use it as an opportunity to generate business, it's just the way of the world) if you are not comfortable looking at them yourself. If you were nearer I would offer to do it myself.

The causes of service brake issues and parking brake issues could even be the same issue (if the caliper, or calipers, has/have an issue then this will affect the overall braking ability. But it could just as equally be two different issues. Brakes are more complex than they need to be these days, but they are also critical so don't leave it to chance.

Excellent knowledge there buddy.

Thanking you 👍
 

Bamberdele2.0

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Just a update.

I ended up taking my car to another garage explaining the situation. They said book it in for an MOT and we’ll check it over.

Turns out all I needed was a coil, bearing and bulb all for 1/3 of the cost of the other garage.

What is that about?
 

Bunkermagnet

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Just a update.

I ended up taking my car to another garage explaining the situation. They said book it in for an MOT and we’ll check it over.

Turns out all I needed was a coil, bearing and bulb all for 1/3 of the cost of the other garage.

What is that about?
For the very reasons you're now questioning the first results, I only take any of my vehicles to somehwere that is only an MOT testing station.
 

MadAdey

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I think you've received some good advice so far, what I will add is do not be frightened of aftermarket parts. Best example I can give is my BMW 550. Needed new ignition coils, BMW wanted $105 each. Local car parts shop sold me Bosch ones for $40 each. Took the ones out of my car and they were the identical part as the ones I got from a local shop. The only difference is the Bosch ones in the car had a BMW badge on them.
 
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