Advice on a soft pedal after bleeding master / upgrading brakes

Hi all,

After a couple months, got the car back on the road now, had to remake a couple brake hard lines, but all back on the floor now. I upgraded the front brakes to a 280mm setup with G60 calipers; rears are still the same discs and EBC Greenstuffs all around.

Bled the system including the master cylinder (bled the master by taking off the brake lines from the two connections it has, connecting up two short pieces of hardline from these connections which routed back into the fluid in the master cylinder and pumped through until only liquid coming through the lines back into the reservoir. Like a closed system).

Then bled the brakes twice starting at the rear; no bubbles etc

The pedal itself still feels soft though, doesn't quite go to the floor, but is definitely "mushy". Took it for a test drive and the brakes do work (the fronts will lock from 20mph, and tested hard braking from 40mph and it'll stop - just need to depress the pedal quite a distance to get full force). So, the brakes work, they just aren't confidence inspiring.

only weird thing while bleeding is that the rear right caliper seems to struggle compared to the rest with getting fluid through the bleed nipple. So where a brake depress on the other corners would shove through "half a hose" of fluid, the rear right would only get half that.

Not sure if you've got any advice on this. Given the larger piston diameter on the corrado front calipers, do I need to change the master cylinder?

Thanks all
 

Yes,,  22mm is the norm, think a 25mm is available, maybe lots more,,

But would a larger MC actually be required here?

Well I would say remove the rear bleeder and clean it.
That is it I just had a similar issue and rebuilt the Calipers and wheel cylinders, two of the bleeders were rusted and clogged.

Power bleeding is a godsend for making sure that all the air is out.  

Google Home Made power brake bleeder as there are good tips on making one out of a 2 quart garden sprayer.  I love the one I made.

Then if you replaced the mc, make sure that you have the free-play set correctly, that can make a world of difference.  I don't have the rube goldberg set up that you guys that drive on the wrong side do.

Don't discount a bad brake booster. If you can pump up the pedal and it is stiff and doesn't move then it may be your booster or a vacuum leak at the check valve.

I think that the bigger front brakes require more fluid movement to move the piston than the original smaller piston in the VW11 calipers.

If you've kept the original MC then you'll have to push virtually all the fluid out of it to make the bigger pistons move the required distance.

It's all about the fluid transfer between the MC and the brakes.

I'd suggest a bigger MC would be the way forward.to get the pedal to move less.

I have one from Leaon Cupra R on my system and my pedal moves about  3/4 of an inch, from off to total lock up.

I'm not using assistance though!

Ian

Thanks,

borednow : The MC you're using, does it have 2 ports or one? My MC has two ports, with a T-piece being used off either to split the brake lines to the 4 corners. I don't want to have to bother with remaking all the hard lines, so would be looking for a MC with two ports that are of a similar orientation to the existing mk1 cylinder.

They come with 4 ports or 2 ports, so you have a split system, 1 port would,nt allow this. 4 ports are better as no T pieces required..

abfmk1 said

They come with 4 ports or 2 ports, so you have a split system, 1 port would,nt allow this. 4 ports are better as no T pieces required..

Wasn't looking for 1 port… Not sure where you got that. Current mk1 MC has 2 ports, each using t-pieces.

Yeah, I know a 4 port would be better, but honestly I don't have the will to remake all the hard lines for the car

I got that from your question to borednow

abfmk1 said

I got that from your question to borednow

Well, I am an idiot lol. I meant to ask whether it was 2 ports or 4! My bad!!

2 ports mucker.

Ian

I have g60  front brakes on my golf and rear disc brakes also and my car will stop on a penny. For sure you need a bigger servo and 22mm master cylinder minimum, braided hoses also a great addition.My m.c has 4 ports . I wouldn’t be half doing brakes or settling for there ok you just have to push harder.


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gafo So which booster and MC are you using? Where are they from?

Booster is from an early 90s Passat and m.c is from a mk2 golf 16v I think . Booster I bought second hand ,new m.c from gsf. Then I used two  T pieces for brake light switch again from gsf.I know later Cabby’s have the switch on the pedal. 22m.m master cylinder will be grand, not expensive either but buy a new one so I’ve always heard


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Seems I've got a few options! Think I will probably go for the 2 port option from the SEAT mebbe; without changing my booster.

Well…apparently I already have the 16V booster and MC upgrade…so it shouldn't be booster or MC related

In that case I'd go and have a word with your brake comensator and suggest it starts behaving itself before you hit it with a hammer.

I'm presuming you have a GTI and it has one of course………..

I believe you have to be careful about having the car flat and level when bleeding the brakes when you have a compensator on it or otherwise; if it's in the air; the comensator, well, compensates and doesn't let fluid through the system.

I had a bias valve that ended up in the bin due to not letting fluid through and I couldn't bleed the system.

This has been going through my head for the past few days btw!

 

Ian

Nope, not a gti. It was a golf C 1.1 but has had an R32 engine put into it now

Haha, sorry to add to your brains workout for the week xD Trust me it's working out my brain too!

Hmmmm R32 engine in it? I see why you may be concerned about the brakes then.  

So to confirm:
You have G60 front brakes.
You have Rear disc brakes
You have bigger M/C
You have bigger servo
You have EBC green stuff pads (personally I'd throw those away and go with 'normal' spec pads cos they always felt 'greasy' to me).
You don't have a bias valve

Brakes will lock up but pedal moves a long way.

Do you have braided line anywhere?
Do you have one or two flexis on the rear system?
Have you checked your lines for kinks?
Have you replaced the bleed nipples on the back brakes?
Do you have a good seal at the M/C tank interface?
What brake fluid reservoir are you using?

Did you use a vac bleeder or just pedal pushing?

My head hurts!

Ian

Hey Iain,

Ok, answers below Also some pictures attached, not great ones, taken when the old 1.8t was coming out.

You have G60 front brakes: Yes
You have Rear disc brakes: Yes
You have bigger M/C: Yes
You have bigger servo: Yes
You have EBC green stuff pads: Yes (brand new, so gonna use them)
You don't have a bias valve: Correct

Brakes will lock up but pedal moves a long way: Yes, pedal has a lot of travel, but I can lock the brakes up

Do you have braided line anywhere? Yes, front and rear
Do you have one or two flexis on the rear system? One
Have you checked your lines for kinks? Yes, and seems ok to me
Have you replaced the bleed nipples on the back brakes? No
Do you have a good seal at the M/C tank interface? Can't see any weeping or leaks
What brake fluid reservoir are you using? See pictures

Did you use a vac bleeder or just pedal pushing? Just pedal pushing. But getting 100% fluid from each corner and I bled the MC

I was also advised to check if I has weeping piston seals at the rear but haven't seen anything yet.