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MOT Failure - Foot brake 'efficiency'

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Old May 25th, 2020, 19:25   #31
oragex
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I believe the expanders were standard on P1 cars such as S70 850. Basically for free at the breakers, as long as you can remove a well rusted brake caliper and disk. I also lubricated nicely inside the expander sleeve, and these need adjusted after placing back the brake drum, by inserting a slim flat screwdriver through a hole to reach the small gear : not exactly easy and has to be redone once in a while.
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Old May 26th, 2020, 03:26   #32
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Originally Posted by john langrick View Post
And also note frf Swansea is up and working.

For me the last part ordered last week arrived with two days and a decent discount as a forum member.

Thumbs up from me..
Thanks. How do you order? I have only managed yo get through on the phone once in the last 3 weeks and that was by going through reception. Still waiting on parts since March :-(
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Old May 26th, 2020, 03:30   #33
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Great question! I have located the adjuster in the passenger footwell but haven't had a chance to tackle the job yet.

My foot brake clicks 8 times to fully engage. If i adjust this (assuming that's possible) to 2 clixks would that be enough to get from 13% efficiently to over the 16% required for my MOT retest this week?

New pads, clips / springs and rotors on order from FCP but won't get here before the retest date unfortunately.


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If you are maintaining your car yourself, how do you check the parking/emergency efficiency?

To do the road brake test, I believe they use some sort of decelerometer. Given that mobile phones have all sorts of sensors, I thought I'd find "an app for that", but failed. Instead I did find one that just records the 3 accelerometers and then stuck the output of that into Excel. Fortunately we live on a mostly flat, straight country road, so got the car up to 20mph, and then stamped on the parking brake. The attached graph shows my results.

The grey "mazda" line is just for comparison with our little Mazda 2. Time in seconds on the X axis, and some measure of acceleration in the Y (perhaps in "G"). I didn't suppose the units really matter, as long as I can see an improvement before and after adjusting the brakes.

Volvo 1 and 2 are two runs before any fiddling (and just after the MOT fail), one would be slightly up hill, the other slightly down. And shows that it look between about 5.2s and 6s to stop the car.

Volvo 3 to 6 are after some adjusting, and all within 2mins or so. And that shows the brake now stops the car between 4.5s and 5.5s. If I choose to ignore that Volvo 6 (5.5s) as it was slightly downhill and by now the brakes would be rather hot, then down to between 4.5s and 4.8s. Which is better than I started off with.

I just need to replace an track rod end, and then I'll be taking the car back for another MOT, then I'll find out how my results translate into "parking efficency".

Anyway back to my original question, how do others measure their braking efficiency? Do you just go and buy an expensive gadget?

Neil
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Old May 26th, 2020, 13:09   #34
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Hi, I just called the number and asked for parts department.
The call went straight through. Looking at my invoice, the number is

'441792 31099fax +441792 701084
www.frfvolvo.co.uk

Cheers John l
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Old Jun 18th, 2020, 14:57   #35
spiralarms
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Default MOT parking brake test should only be for parking

Yet again our XC90 has failed its MOT on parking brake efficiency. This got me looking at the Gov's own docs on MOTs and testing of the brakes. Having done so, it seems to me you could argue that the parking (foot operated) brake shouldn't be tested as an "emergency" brake, and only as a "parking" brake in conjunction with the "P" on auto gearbox car.

Two web pages to make my case:

1. https://mattersoftesting.blog.gov.uk...formance-test/

on which is states:

"Those few vehicles still around with a single line braking system will be subject to some additional checks. This is because the parking brake on such vehicles also performs the secondary brake function ..."

The Volvo is a modern car with dual line braking system, two hydraulic circuits. Not a single line braking system.

and secondly, section 1 of the Car MOT tests

2. https://www.gov.uk/guidance/mot-insp...icles/1-brakes

There's a few subsections from this to support my argument.

From section 1.1.6 -

"If the parking brake is the ‘P’ position on the gearbox, the efficiency of the brake cannot be tested. The tester must therefore assess the brake by using a gradient (ideally 16%), or by attempting to push the machine when ‘P’ is selected."

From section 1.3 regarding "Secondary brake performance and efficiency"

"This inspection is only for vehicles with a single line braking system. If the secondary brake is also the park brake then there is no need to carry out a separate park brake test."

The XC90 has a dual hydraulic braking circuit, so the test in section 1.3 does not apply. However we still do need to meet the "separate park brake test".

Section 1.4 - "Parking brake performance and efficiency"

"You only need to inspect vehicles that have not already had the parking brake system tested as the secondary brake."

which is us, as section 1.3.2 doesn't apply. Various methods are described on how to test, but as 1.1.6 said at the beginning "If the parking brake is the ‘P’ position on the gearbox, the efficiency of the brake cannot be tested. The tester must therefore assess the brake by using a gradient (ideally 16%), or by attempting to push the machine when ‘P’ is selected."

So for me the only brakes that need tested on the XC90 are the normal hydraulic service brakes, and the parking brake (not secondary/emergency brake), and the only way to test the parking brake on the XC90 is with the footbrake depressed AND the gearbox in P, either on a suitable gradient or by then trying to push the car. Which, unless you have a problem with the gearbox, it should pass no problem.

Perhaps some MOT inspector will point out the flaw in my logic (but hopefully not!)

Neil
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Old Jun 18th, 2020, 15:45   #36
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Neil , honestly I'm not trying to be clever here but why not simply make the existing parking brake efficient enough to pass the MOT?

In it's basic form it is a poor design but there are literally dozens of threads on here as to how to get an older XC90 parking brake up to and beyond the required MOT level.

Manual adjusters in the rear drums coupled with correct cable adjustment will work wonders particularly with a new set of VOLVO brake shoes.
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Old Jun 18th, 2020, 16:06   #37
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Neil , honestly I'm not trying to be clever here but why not simply make the existing parking brake efficient enough to pass the MOT?
I agree, but short of new rotors and shoes (I've had them all done twice in the 8 years we've had the car), I've done all those things.

I think they are currently performing about as well as they ever have. I can fully tighten and loosen the wheel studs with the wheel off the ground (using a socket and wrench, not a gun), which I can't remember being able to do before.

I think the actual problem, given the age of the car, is the cables are now too stretched to adjust for.

And though I agree, with "why not fix it", it would be frustrating to spend time, effort and money on something that wasn't actually necessary.

We've moved house, which is why I've not taken it to the garage that used to MOT it, but it might be worth the extra journey.
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Old Jun 18th, 2020, 16:40   #38
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Did you fit the manual adjusters inside the drum assembly to replace the solid H bar?

That gives a huge improvement for less than £15 and not a bad job to do.


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Old Jun 18th, 2020, 18:20   #39
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Did you fit the manual adjusters inside the drum assembly to replace the solid H bar?
Yes, done that. With 2 clicks of the peddle, they already binding. You can still turn the wheels with a bit of effort. I can't press more than 9 clicks, does anyone know how many clicks there are? It doesn't feel like there's much room for more.

Though there seemed to be plenty of material left on the shoes, I'll order some new ones, but I forgot to measure the diameter of the inner hub, so I'll need to get them off again before I can.
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Old Jun 18th, 2020, 18:48   #40
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The problem with what you describe above is that those of use with Manual gearboxes do not have a P position however we do have to use our parking brake all the time. I added the adjusters along with new pads when I got mine (at 172k miles) the car has been passing the MOT each time since. They were fitted in 2014 and the car has cover 254k now.
It really is a case of use it or lose it as I suspect that many automatic drivers (not just XC90 ones) don’t both using the parking brake and just stick it in P. This is less of an issue in cars with auto brakes as it applies it for you.
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