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miker916

Member Since: 25 Oct 2022
Location: Fife
Posts: 52

diagnosing brake servo

Hi,

The brakes on my 2010 Puma have always been a bit rubbish since i bought it. The rear pads and discs were replaced as they were a bit worn but this made no difference (already had new front discs & pads).

I'm wondering if i have an issue with the brake servo, I tried the usual pump brake pedal 3 times then start engine. The brake pedal doesn't move after the engine has started - that's not normal is it?
Is there anything else i can do to diagnose the servo being at fault?

Cheers
Mike

10th Apr 2023 10:34am

I Like Old Skool

Member Since: 23 Feb 2015
Location: Manchester
Posts: 812

1994 Defender 110 300 Tdi ST Coniston Green

Pull out the vacuum hose from the servo and check the vacuum pump is working with the engine running (put your thumb over the end and it should get sucked on). If this is ok then put it back in and run the engine for a minute before turning off and pulling the pipe out. The servo should hold vacuum for a while and if you don't get a whoosh/hiss of air rushing in when you pull the pipe then the servo is leaking.

The servos are a bit crap and do split where the master cylinder mounts but the cracks are usually hidden so only really visible when you pull the cylinder away. Just had to replace mine on my old TDI last year after thinking for a year or two previously that the brakes perhaps weren't 100% (still passed MOT though!) and it was much better after the new servo.

10th Apr 2023 2:26pm

miker916

Member Since: 25 Oct 2022
Location: Fife
Posts: 52

thanks for the help, so it looks like i have some sort of problem but not with the servo:

With the engine running and vacuum hose disconnected from the servo i can feel it sucking when i put my finger over the end.

Connected the hose back to the servo and left the engine running for a minute, switched engine off and pulled the hose out - air came rushing out the servo.

But when i pump the brake pedal and hold it down as far as it'll go then start the engine the pedal dosent move down at all. I tried this about 10 times and it was the same for 9 tries but one try after starting the engine, the pedal did sink.

10th Apr 2023 2:53pm

geobloke

Member Since: 06 Nov 2012
Location: Nottinghamshire
Posts: 4410

Your brake servo is failing or has failed internally I am afraid. By replacing it you will have your pedal back again.

I have recently been through a similar fault finding experience in Miffy which led to the replacement of the servo.

To give you an idea now Miffy's brakes are good enough to hang you from the seat belts.

11th Apr 2023 6:33pm

miker916

Member Since: 25 Oct 2022
Location: Fife
Posts: 52

thank you, a new TRW booster is on its way. Fingers crossed it fixes the issue

12th Apr 2023 7:12pm

landy andy

Member Since: 15 Feb 2009
Location: Ware, Herts
Posts: 5720

2006 Defender 110 Td5 USW Zermatt Silver

How much is the servo costing?

Is there an uprated option that others have used?

12th Apr 2023 7:22pm

geobloke

Member Since: 06 Nov 2012
Location: Nottinghamshire
Posts: 4410

There is not really an uprated version. But... there is one that has a slightly bigger internal volume made by County. The housing is more square than the LR item. This is the one that I bought as I was curious that others had said the extra internal volume provided better braking efficiency. I am not sure about that, but thought I would give it a go and Miffy's brakes are superb.

https://www.ebay.co.uk/itm/114248028555?ha...R6bf6O_uYQ

12th Apr 2023 7:42pm

landy andy

Member Since: 15 Feb 2009
Location: Ware, Herts
Posts: 5720

Thanks. Notice that is non abs so may give them a call. Just not happy with my brakes, and have swapped most other things. Servo appears ok, but may swap out

12th Apr 2023 9:26pm

geobloke

Member Since: 06 Nov 2012
Location: Nottinghamshire
Posts: 4410

Hope you get it sorted

13th Apr 2023 8:49am

Porny
Site Sponsor

Member Since: 31 Aug 2009
Location: Sutton Coldfield - West Midlands
Posts: 809

£192 + vat inc UK postage for a TRW/OEM ABS spec brake master cylinder

They do fail internally, but most commonly they spit where there master cylinder bolts on (more common on none ABS) IRB
The home of the first modified Keswick Green 90 - and the first 2.4 Puma through both the 200bhp and 550Nm barriers.

www.IRBdevelopments.com

www.facebook.com/irbdevelopments

www.integrated316.com

www.facebook.com/integrated316

17th Apr 2023 12:03pm

miker916

Member Since: 25 Oct 2022
Location: Fife
Posts: 52

it was the TRW one i went for, only cause autodoc are doing it for 97 + VAT just now

17th Apr 2023 12:20pm

Porny
Site Sponsor

Member Since: 31 Aug 2009
Location: Sutton Coldfield - West Midlands
Posts: 809

That's cheap! IRB
The home of the first modified Keswick Green 90 - and the first 2.4 Puma through both the 200bhp and 550Nm barriers.

www.IRBdevelopments.com

www.facebook.com/irbdevelopments

www.integrated316.com

www.facebook.com/integrated316

17th Apr 2023 12:24pm

miker916

Member Since: 25 Oct 2022
Location: Fife
Posts: 52

it wa the servo, was cracked where the master cylinder bolts to it

20th Jun 2023 2:56pm

I Like Old Skool

Member Since: 23 Feb 2015
Location: Manchester
Posts: 812

I win

20th Jun 2023 10:46pm

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