brake issues

[nicolas]

i have experienced some troubles with my rear brakes lately. they are soft, almost non-existant and i am scratching my head on this one, so maybe someone can help out.

i have a CSP 21mm dualcircuit master cylinder and talbot calipers on the front with pressure valves on both sides. these work fine, almost too good.
in the back i have type3 drums and no pressure valves. these are no good. i always bottom out on the first push and i have to pump the brakes a few times to get them to work. as soon as i release the pedal for a few seconds they are gone again. i have bled the brakes a few times and after that is done they are hard and seem fine, but after a short ride they are gone again.
i was thinking about a leaking cylinder in the wheels or a leak, but so far nothing can be found, everything is dry from the master cylinder to the drums.

so what could cause this? bad brakefluid? weak flexible lines? ...

[fredy66]

collapsed brake lines is my first guess

[Diederick/DVK]

i have the same CSP 21.64mm master cylinder and rear disc brakes. and i am also having trouble with the rear brakes, i am hoping to install a 2lbs residual pressure valve soon when i can find one. my only source is Summit... won't a 10lbs (given they are drums) help with your issues?

[Sarge]

I have CSP discs up front and Type III drums out back with a standard old rusty stock master cylinder and NO VALVES of any sort.... no problems and plenty of brakes.  Years ago, I put a Neal disc brake kit (rears only) on the sandrail and was told I would need residual brake pressure valves.  I had a miserable time until I got rid of the valves.  My $.02

[nicolas]

i'll have a look at the brakelines again
and maybe the pressure valves could cause some trouble, i have been thinking of getting rid of them before, but since it only affects the rear drums which don't have them i wasn't sure what to make out of it...
can you tell me Sarge what the problem was with the valves?
thanks for the replies allready.

[Bruce]

what the problem was with the valves?

Production cars don't use such valves.

[Peter]

So what is the solution?
I think I have the same issue..

[Sarge]

   ...."can you tell me Sarge what the problem was with the valves?"

There was nothing wrong with the valves themselves... they just weren't needed.

[nicolas]

what the problem was with the valves?

Production cars don't use such valves.

   ...."can you tell me Sarge what the problem was with the valves?"

There was nothing wrong with the valves themselves... they just weren't needed.

i see your point(s). i'll look at it, and i hope it will cure the problem as it has no use in driving a car that has not got good brakes. stop before go. the valves were put there because the talbot brakes use bigger pistons and need more oil to make them work, so keeping them closer to the discs is a good idea.
but somehow it seems unlogical if it only affects the rear brakes and there are no valves on the rear... i got my sherlock holmes hat out and i hope to find out what works and what not soon.

[TexasTom]

My '69s brake setup isn't quite the same as yours ... 4 wheel discs with single piston calipers in the back and 4s in the front, Yep OVERKILL! ... anyway, STOCK master cylinder & no valves of anykind outside of the linelock.
Pedal is very good!
Do need to seriously consider backing down to 2 piston calipers in the front ...

I don't suppose it's possible the valves were installed backwards??? Just an idea ...
TxT

[christophe]

How are you back brake adjust?
If you adjust them more tight do you still have exactly the same problem?
You can check your wheelcylinders.Lift the pistons rubber and check if there is brake fluid there,if so there are leaking.Sometime they are dry outside but leaking a bit and the fluid stay in the rubber.

[Bruce]

what the problem was with the valves?

Production cars don't use such valves.

   ...."can you tell me Sarge what the problem was with the valves?"

There was nothing wrong with the valves themselves... they just weren't needed.

...the valves were put there because the talbot brakes use bigger pistons and need more oil to make them work, so keeping them closer to the discs is a good idea.

What is the bore dia of these talbot calipers?  Two pistons per caliper like stock?  Why do you think stock calipers aren't good enough?

[PH1303]

The Talbot calipers is indentical to the ATE stock caliper, however they have a piston diameter 48 mm, whereas the stock has 40 mm (type 3 is 42 mm). So you get 20 % increase, with almost stock looks. Only difference is that the Talbot caliper is a little bigger. But it's a straight fit

I have an identical setup on my 1303 (oh no.... not cal look ), an had similar problems to begin with. Then I changed to the 20.64 mm master cylinder, with only little difference. But after readjusting the brakes, and had the brake shoes and pads properly weared in - and I know this sounds stupid - the problem slowly disappeared. Now the pedal is perfect, and the car brakes realy good.

This brake setup is very recommendable for those who want a little extra, without going to full Porsche 4 wheel discs etc...

Btw - I don't have any prepressure valve mounted.

/Peter

[Rick Meredith]

Sounds interesting. What are those Calipers off of? Part numbers if you have them.

Rick

[LuftsickTero]

What are those Calipers off of?

Off from this:


Dodge Omni or Plymouth Horizon in US?

[LuftsickTero]

4 wheel discs with single piston calipers in the back and 4s in the front, Yep OVERKILL! ... anyway, STOCK master cylinder & no valves of anykind outside of the linelock.

Sorry for off-topic, but what disc brake kit are you using?

[Rick Meredith]

What are those Calipers off of?

Off from this:


Dodge Omni or Plymouth Horizon in US?

Hmm.. yes they would be the omni or horizon

[Bruce]

The Talbot calipers is indentical to the ATE stock caliper, however they have a piston diameter 48 mm, whereas the stock has 40 mm (type 3 is 42 mm). So you get 20 % increase, with almost stock looks.

Nicolas, what are your wheels and tyres?
Why do you think you need bigger calipers on the front?

[PH1303]

Because I upgraded the rear brakes to type 3 (4x130), so I needed a upgrade up front which could match the rear.... The type 3 rear brakes really made a difference, and the last thing you want, is a car that locks the rear wheel before the front.

Btw, do not use the 24 mm wheel cylinder on the rear brakes from the type 3 variant. Use the 22 mm from the hatch back, or the 19 mm porsche size. Otherwise it will easily get to much brake force on the rear wheels.

/Peter

[nicolas]

i never bothered redoing the old ones i had on the car (orginal discs from 66 on a type 3, stock setup as you probally know). i had the chance to find a set on a hunt for carbs while on vacation in France years ago, before the car was even finished. i read about it in one of Keiths books => therefore blame him  ) and they were refirbished and seemed to be a good idea. they promised a better braking for a beetle and since a type3 is heavier that sounded even better to me. they work great and do indeed brake better then the stock system on my 67 squareback. i would recommand it, but if it is worth all the trouble to find them and pay the price of rebuilding them insted of new stock callipers is maybe up for debate, but i am happy with what i got.
as for tyres i run 165/60 at the front and 185/70 on the back, wheels are empi 8 spokes.

i have now 'tested' the pedal with the car at rest and i hear noises 'in the back of the car' which indicate somthing is wrong there, but i will look into it and i am going to fit all the lines without the valves just to see what happens.

[nicolas]

a quick update. i have better brakes now on the back, but it was a problem of air that kept getting traped in the lines and couldn't really be taken out with just a few strokes on the brakes. but it just brakes like before.

BUT, what system would be better to bleed the brakes on a beetle. i have heard of a pressureising system, but i haven't seen one that fits a VW yet...

BTW the valves stayed on as they seem to be OK and no leaking or problems were found at the front. like NOFX once said, the voice of reason comes from the PA, Leave it alone!

[Donny B.]

I bought one of these a short while back and it works great!  Check it out...

http://www.cbperformance.com/catalog.asp?ProductID=1184

[PH1303]

This is what can be done, if you do not have any special bleeding equiment at hand  ;o

The screw cap of a ½ liter Coke plastic bottle fits the brake reservoir  Then mount a standard wheel air valve in the screw cap from the coke bottle, and then use the standard VW sprinkler plastic tube (from a 1303 for example), and connect it to the spare wheel. Then you have pressurized your system, and can bleed the brake alone 

I haven't done it myselt yet, but I've seen it done...

/Peter

[nicolas]

well after a few hectic weeks and weekends i found some time to fix the leaking oilseal in the drumbrakes and fix the brakes.

for now they seem to hold up fine and they are very hard and don't flex or bottom out.

i found that the valves that are used to let the air out may be leaking or at least they suck in air when the pedal was released. i also mad a botllecap with an stem from a tyre to pressurize the brakefluid reservoir a bit and bled the brakes that way. it worked like a charm with a litlle help from my son