clutch hyd question

[steveo3002]

ah i see ...like i say i dont have the genuine bits to look at , would be an easy fix if i need 1/4 line

will get the old slave and m/c and see what dia outlet they are, does make sense the fluid cant move fast enough on return

 

[Melvyn Best]

Try slackening the outlet from the master cylinder to start with, check that you have fluid coming out when the pedal is pressed or the pressure bleeder is attached , if not check that fluid is getting to the master cylinder., when you have fluid coming out of the M/C bleed the slave . Using a bleed hose from a brake bleed nipple to the clutch bleed nipple and pumping the brake pedal has got me out of trouble a few times

I had problems years ago with a VAG car that I had fitted a new clutch on and had to bleed the hydraulics, nothing worked even fitting a new M/C , turned out the outlet from the reservoir was sealed not allowing fluid to the M/C , worth checking

 

[mtt.tr]

Restrictions would cause a hard pedal, I'd be looking for trapped air

 

[m_c]

Restrictions would cause a hard pedal, I'd be looking for trapped air

Depends on the restriction.
The big problem with bleeding clutches is there are often high points in the middle of the pipe run, so unless you get enough flow to carry the air downhill, they just won't bleed.

And some just won't bleed without the use of a pressure bleeder set to a reasonably high pressure.
Personally, I'd put a pressure bleeder on set to at least 1bar, and see how much fluid flows.
If you've not got a pressure bleeder, open the bleed nipple, hold your finger lightly over the end of the nipple to act as a one way valve, then get somebody else to pump the pedal at a reasonable speed. It will be messy, but it'll often work to get enough fluid flowing to carry air out the system.

The clutch pedal being slow to return, may well just be because the air in the system is preventing it getting the full force of the clutch releasing to help it return. There are often restrictors in the system to control pedal return speed, so without the additional pressure from the clutch cover, they're slow to return.

 

[mtt.tr]

Depends on the restriction.
The big problem with bleeding clutches is there are often high points in the middle of the pipe run, so unless you get enough flow to carry the air downhill, they just won't bleed.

And some just won't bleed without the use of a pressure bleeder set to a reasonably high pressure.
Personally, I'd put a pressure bleeder on set to at least 1bar, and see how much fluid flows.
If you've not got a pressure bleeder, open the bleed nipple, hold your finger lightly over the end of the nipple to act as a one way valve, then get somebody else to pump the pedal at a reasonable speed. It will be messy, but it'll often work to get enough fluid flowing to carry air out the system.

The clutch pedal being slow to return, may well just be because the air in the system is preventing it getting the full force of the clutch releasing to help it return. There are often restrictors in the system to control pedal return speed, so without the additional pressure from the clutch cover, they're slow to return.

Advocate for vacuum bleeders

 

[m_c]

Advocate for vacuum bleeders

I've never really gotten on with vacuum bleeders.
Modern systems generally get bled at 2bar (some ABS systems now need 2.5bar and a couple litres of fluid for a full bleeding cycle), so a vacuum bleeder isn't much use.

For home use, you can't really go wrong with an Eezibleed kit, especially since they're only £20 from Halfords. Just remember to let your donor tyre/wheel down to a suitable pressure before using it.

 

[steveo3002]

Try slackening the outlet from the master cylinder to start with, check that you have fluid coming out when the pedal is pressed or the pressure bleeder is attached , if not check that fluid is getting to the master cylinder., when you have fluid coming out of the M/C bleed the slave . Using a bleed hose from a brake bleed nipple to the clutch bleed nipple and pumping the brake pedal has got me out of trouble a few times

I had problems years ago with a VAG car that I had fitted a new clutch on and had to bleed the hydraulics, nothing worked even fitting a new M/C , turned out the outlet from the reservoir was sealed not allowing fluid to the M/C , worth checking

are you saying a pipe from the brake caliper to the slave , crack them and pump the brake yes?

i have a selection of bleeders , vac pump , pump up pressure thing like a garden sprayer , and ive tried a large syringe

the m/c also has a nipple...whould that gravity bleed? or what

 

[steveo3002]

okay anyone still with me ...

master fluid inlet is 2.8 mm (ish) and slave is 4.2mm or so ...are we happy its probably 4.75 mm brake line ?(its about 3.2 i.d)

 

[Gareth_16V]

M/C having a nipple is a good thing, as you can get the air out of the end of the master (sometimes the highest point on the system if the bulkhead/cylinder is leant back. Try a manual bleed from the master, then go back to the slave.

 

[Melvyn Best]

are you saying a pipe from the brake caliper to the slave , crack them and pump the brake yes?

Yes, it works a treat but it’s better to hold the pipe on each nipple while someone pumps the brake pedal .

 

[mr haynes]

okay anyone still with me ...

master fluid inlet is 2.8 mm (ish) and slave is 4.2mm or so ...are we happy its probably 4.75 mm brake line ?(its about 3.2 i.d)

That would tie in with my dodgy memory

 

[steveo3002]

so no progress

ive spoken to a maker that can do a custom line if i want ...they say they do all thiers in dash 3 but i can have dash 4 if i want , he suggests no difference whatsoever

so why would some cars /vans have 1/4" brake /clutch lines if its all the same ? any thoughts

 

[Tinbasherdan]

I wouldn’t get one made, I’d buy some -4 ptfe lined hose and some fittings and have at it

 

[steveo3002]

I wouldn’t get one made, I’d buy some -4 ptfe lined hose and some fittings and have at it

whats your thinkng on -4 ...why might i need it /what will it do different ?

 

[Tinbasherdan]

Wel -3 or -4, whichever is the right diameter

 

[Bornfree]

what are you thinking the purpose of that coiled part is ? i dont have it at present , just a straight bit

Iam not sure that it's just for vibration purposes. I've seen several car's and trucks with a long loop of pipe going right across the bulkhead and back again. No Idea why

 

[m_c]

Iam not sure that it's just for vibration purposes. I've seen several car's and trucks with a long loop of pipe going right across the bulkhead and back again. No Idea why

If it's a vehicle that's designed around LHD (which most are), they'll simply extend the pipe in the most convenient way, which means you can end up with weird routings.

Also, the longer the pipe, the more damping effect you'll get from the fluid to reduce vibration through the pedal when you press it. As the OP's car is LHD with not much distance between slave and master's, some engineers probably spent a lot of time deciding how many loops to add to give optimal damping.


As for the OP, disconnect the pipe from the master and slave cylinders. Clamp the hose on your pressure bleeder (pump up one like a garden sprayer as you describe it) using a brake pipe clamp, pump the pressure up to about 1 bar, and attach it to the master cylinder. Release the clamp and make sure fluid flows out under pressure and at volume (you should be getting a jet). If that's OK, attach the new pipe to the master, and again release the clamp. Again you should be getting a jet. If that works, attach pipe to slave cylinder, and remove the bleed nipple completely. Again you should get a jet.
Doing that will result in lots of brake fluid being sprayed around, but it'll tell you where any restrictions are.

If there are no restrictions, I'd then be attaching the pressure bleeder at the slave cylinder end, removing the inlet hose from the master cylinder, and jamming the clutch pedal down. Apply pressure to the system, and while slowly lifting the clutch pedal, check no fluid was leaking back through the master cylinder until it got near the top of it's travel.

And if that still didn't show any issue, have a close look at the slave cylinder itself to make sure there's nothing stupid like a plastic bung wedged in the pipe connection. In fact, probably worth doing that while the pipe is off to begin with.

 

[steveo3002]

right update...not alot of progres

felt both the slave and master off the car..both have a firm spring feeling to return to rest

clutch pedal is sprung and pings up

ordered a new 3.5mm bore hose

assembled it all on my workbench with a motorbike reservoir, it bled up in seconds , a clamp holding the slave rod from popping out , and the master is stiff telling me theres no air?

went back to the car and fitted it undisturbed so for the time being i have a motorbike reservoir- much the same , pedal is too slow to return

could the seals be a bit tight and loosen up ?..its drivable but not right

 

[steveo3002]

add to the above , ive found the old rotten slave its the orig vw part it measures 22mm and has 22 stamped on it , replacements are all 23.8 mm

would the 2mm effect it ?

 

[T5 TDI]

assembled it all on my workbench with a motorbike reservoir, it bled up in seconds , a clamp holding the slave rod from popping out , and the master is stiff telling me theres no air?

Yes. If it feels more or less solid with almost no movement except for the tiny mechanical slack of say the clevis pin, there is no air in the system.
I can't think that the slightly larger bore size wouldn't make the return slow but I suppose it is possible. It's also worth having a good look at the pedal box with a good light just to eliminate any problems there. Does the master cylinder rod press in centrally? Look out for any missing or bent parts, cracks or accident damage of the pedal box. The parts diagram shows shows a return spring.

The supply hose from the reservoir to the master cylinder is worth checking because it could cause a problem if it is collapsing and stopping the master cylinder recuperating properly.