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Spongy Brake Pedal


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#1 AlexHillTVR

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Posted 02 October 2019 - 03:53 PM

Hi gentlemen,

 

Picked up a beautiful Stage 2 Turbo just over a week ago and I'm loving being back in a VX. I noticed from the history the brake fluid hadn't been changed since 2015 and the brakes felt quite spongy so this weekend just gone, I bled the system using my trusty Eezibleed at 15PSI.

 

I used around 750ml of DOT4 to perform a partial flush and bleed. Bled the 4 calipers from rear left to front right, a couple of small bubbles through and some slightly skaggy looking fluid in places but still relatively clear. 

 

Driven the car today and the brakes feel a bit better but still a bit spongy. Don't get me wrong, they are fine for stopping the car at normal speeds, but not particularly confidence inspiring in a car that makes around 265bhp/tonne. 

 

Just wondering if there's anywhere else air could be trapped in the system? Anything I've forgotten? 

 

For the record, the pedal does firm up when I pump the air out of the servo with the engine off, but it doesn't go completely rock hard. Fluid wasn't brand new but was opened first around 3 months ago, used and then sealed up and stored in the garage.

 

Any pointers would be massively appreciated!

 

Alex

 



#2 martinroger

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Posted 02 October 2019 - 04:37 PM

Could be air build up in the calipers, especially at the back. Try turning them upside down then purging the fluid. Also the clutch shares the same fluid, so flush it too!

#3 Talk-torque

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Posted 02 October 2019 - 04:45 PM

If you look at the front callipers you will see that the pipe connecting the inner and outer pots runs under the callipers. This means that air can be trapped in the side away from the bleed nipple. The process to clear any possible trapped air is to apply bleed pressure with the calliper unbolted and slid around the disc until it is upside down. Tapping with a plastic hammer will encourage any reluctant air through the pipe.

A more detailed description can be found here:

 

https://wiki.seloc.o...leed_the_brakes

 

 



#4 AlexHillTVR

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Posted 02 October 2019 - 06:59 PM

If you look at the front callipers you will see that the pipe connecting the inner and outer pots runs under the callipers. This means that air can be trapped in the side away from the bleed nipple. The process to clear any possible trapped air is to apply bleed pressure with the calliper unbolted and slid around the disc until it is upside down. Tapping with a plastic hammer will encourage any reluctant air through the pipe.
A more detailed description can be found here:

https://wiki.seloc.o...leed_the_brakes


Awesome I will try that this weekend! Are the callipers easy to unbolt? I mean the brakes aren’t horrendous, I can still run into the ABS in the dry if I stand on them, just expected them to take my face off!

#5 martinroger

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Posted 02 October 2019 - 07:09 PM

Literally two bolts on the front, super easy. Rears are on the back of the caliper, and one slider.

#6 Pidgeon

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Posted 03 October 2019 - 08:01 AM

If the system has been bled dry, any air in the ABS pump is difficult to displace.  Operate the ABS (on the road) before you bleed is the remedy.



#7 AlexHillTVR

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Posted 03 October 2019 - 11:47 AM

If the system has been bled dry, any air in the ABS pump is difficult to displace. Operate the ABS (on the road) before you bleed is the remedy.


May have been bled dry in the past but certainly not by me. I activated the ABS twice last night so will re-bleed this weekend with the above method and report back 😁

#8 AlexHillTVR

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Posted 06 October 2019 - 07:14 PM

Bled the front brakes using the inversion method above on Seloc, not seeing much in terms of bubbles coming through. Brakes felt much the same.

Bled the clutch a small amount as I only have 9mm in a socket and not a ring spanner so I didn’t want to pee fluid down the gearbox for too long. Pedal feels much the same. I’m out of ideas now. Maybe this is how the brakes are and I’m not used to it. I can just about run into the ABS in the dry with an emergency stop from 30mph but it doesn’t feel fitting to a car of this weight. 🤔

#9 ayresyy

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Posted 06 October 2019 - 08:01 PM


Maybe you just need to meet up with another owner and try each other’s brakes.

#10 smiley

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Posted 06 October 2019 - 08:14 PM

I had very solid braking before i got the braided brake hoses.

Not been able to get those back since. Tried easybleed, invert calipers and bleed clutch. Nothing.

Only thing i can think of, is the abs holding air.

 



#11 NOSBandit

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Posted 06 October 2019 - 09:02 PM

I had the same problem when I changed the abs unit, I used a diagnostics tool to cycle the abs unit which resolved the issue.

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#12 AlexHillTVR

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Posted 06 October 2019 - 09:16 PM

I had the same problem when I changed the abs unit, I used a diagnostics tool to cycle the abs unit which resolved the issue.

Sent from my SM-G935F using Tapatalk


Hmm, would this have not been ironed out from me braking hard and running into the ABS myself a couple of times then bleeding? Or do I need to get hold of a USB to OBD cable so I can trigger the ABS with OPCOM and bleed that way?

I don’t remember my old NA’s brakes feeling as uninspiring but then the NA only made 140bhp 😄 Certainly just left a TVR as a daily and the brakes on that were fantastic, that’s with a heavier car and smaller brakes.

#13 smiley

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Posted 06 October 2019 - 09:20 PM

I had the same problem when I changed the abs unit, I used a diagnostics tool to cycle the abs unit which resolved the issue.
 

 

Was that with the official tech2?
I was thinking to get a china tech2, but a bit expensive for a gamble.



#14 NOSBandit

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Posted 06 October 2019 - 09:24 PM

I used a autel unit, can't remember what model it was but I can have a look tomorrow if you want.

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#15 smiley

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Posted 06 October 2019 - 09:38 PM

yes please.



#16 Nev

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Posted 07 October 2019 - 07:20 PM

Does the Tech2 plug into the ABS unit directly, or connect via the ODB2 port?



#17 NOSBandit

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Posted 07 October 2019 - 07:26 PM

It was an Autel maxicheck pro, there is no autobleed but you can cycle the abs on each wheel. It worked for me by using a pressure blender and cycling the abs on each corner.



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#18 AlexHillTVR

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Posted 08 October 2019 - 11:53 AM

Decided I’m going to take the car to Back on Track when Jez has a free minute. I can sod about repeating and triggering the ABS myself but they’ll have it sorted much quicker. That’s if I have a problem at all. I expect I do.

#19 AlexHillTVR

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Posted 09 October 2019 - 05:08 PM

Fixed!

Went and saw Jez and Sam today at BoT. Turns out the rear left caliper was stuck on as the handbrake cable was not returning. Lots of aggressive yanking and lubrication and the guys managed to loosen it up. Car now stops very very well! Easy to run into the ABS in the dry so I’m going to have to disable that.

New problem though. My locking wheel nut key is somewhere down the A3 I reckon 🙄 Was in a rush the other night after inverting the fronts!

#20 LY_Scott

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Posted 09 October 2019 - 08:06 PM

Does the Tech2 plug into the ABS unit directly, or connect via the ODB2 port?


OBD2 port Nev




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