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Vagabond911
Newbie


Joined: 17 Jul 2018
Posts: 6



PostPosted: Tue Jul 17, 2018 4:22 pm    Post subject: Triumph Daytona throttle bodies - servo assist/vacuum advice Reply with quote

Hi all,

I recently got my SC back on the road after a rebuild, I am now running triumph Daytona throttle bodies and Omex management

I’m trying to diagnose a problem I’ve been having with the brakes since being back on the road, I’m thinking it may have something to do with the way I have connected the vacuum for the servo to the inlet. Although I have also fitted new brakes and lines and re-bled the system so could also be a fault there

The problem I’m experiencing is the brake pedal feels overly soft. The brakes do work and I have bled the system properly twice to be sure. There are no leaks in the system. The disks and pads are new but have done sufficient miles to bed in.

On a recent testing day I was unable to lock the front brakes on a damp test track no matter how hard it tried!

I have run the servo lines off each individual body as they all had a take off, the lines join and run to a one way valve in the engine bay and object to the original servo pipe work

Attached is a pic that hopefully shows how I’ve run it.

Any advice/experience would be greatly appreciated!!!

Cheers

Paul
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Johnd52
Montreal


Joined: 06 Oct 2014
Posts: 580
Location: North Yorkshire

2011 Porsche Cayman 987

PostPosted: Tue Jul 17, 2018 10:25 pm    Post subject: Reply with quote

It does sound as if the servo is not working effectively. If you turn the engine off and work the brakes so that the servo vacuum is expended, is the pedal then solid? If so, I would guess that the servo arrangement is at fault, if the pedal is still soft I would start looking at the master cylinder.

Can you connect a vacuum gauge into the system between the junction of the separate feeds and the one way valve?
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2015 Cayman GTS. No more PDK but still red.
 
  
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Vagabond911
Newbie


Joined: 17 Jul 2018
Posts: 6



PostPosted: Tue Jul 17, 2018 11:18 pm    Post subject: Reply with quote

Johnd52 wrote:
It does sound as if the servo is not working effectively. If you turn the engine off and work the brakes so that the servo vacuum is expended, is the pedal then solid? If so, I would guess that the servo arrangement is at fault, if the pedal is still soft I would start looking at the master cylinder.

Can you connect a vacuum gauge into the system between the junction of the separate feeds and the one way valve?


if I build pressure in the brakes with the engine off the pedal is solid and stays solid. I can use a t piece and connect a guage in the junction. What sort of reading am I looking for?

Thanks for your help Thumb
 
  
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Johnd52
Montreal


Joined: 06 Oct 2014
Posts: 580
Location: North Yorkshire

2011 Porsche Cayman 987

PostPosted: Wed Jul 18, 2018 6:01 am    Post subject: Reply with quote

There is a useful eBay ‘how to diagnose a faulty brake booster’ which sets out basic tests that you can do. This may help.
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jev911uk
Trainee


Joined: 06 Mar 2011
Posts: 51
Location: Berkshire


PostPosted: Wed Jul 18, 2018 7:58 am    Post subject: Reply with quote

When you say new brakes what did you actually change? New calipers too?

Is the pedal travel long as well as soft?
 
  
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deMort
Long Beach


Joined: 21 Mar 2015
Posts: 6803
Location: Brighton


PostPosted: Wed Jul 18, 2018 7:07 pm    Post subject: Reply with quote

Engine running and press the brake pedal several times quickly .. it should stay soft .. if it goes hard then you are running out of vacumn for the sevo .

By hard then engine off and pump the pedal .. it should go rock hard .

Engine running and press and hold the brake pedal .. any creeping and you could have a deffective master cyl.

The servo is only there to increase brake pressure .. you can in theory use 2 feet and press as hard as you can and get a similar effect to light brakeing with a functioning brake servo .

So .. do you have steel braded brake pipes fitted ? you could well have a flexi pipe thats swelling / balooning on brakeing .

Do mainly the front caliper pistons move freely ( rears to a lesser degree as fronts are 75% of the stopping power ).. are the pads nicely greased and again can move freely .. sticking piston in the caliper or stuck pads will cause a poor brakeing effect .

Nice job with the servo pipes though .. no way you can get any more vacumn at the servo that that setup Thumb
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