Bleeding brakes

[Gmg31]

I started a thread on this a while back but can’t find it to update, sorry for starting again.

During my restoration project I’ve replaced every single component in the braking system but despite my best efforts I cannot get the system bled.  There are no leaks, I have double checked.  I’ve bled the master cylinder, I’ve tried the traditional manual way and I bought a vacuum bleeder. I’ve done it a dozen times over several weeks and absolutely no brake pedal, not even half a spongy pedal, absolutely nothing. I am coming to the conclusion that the new master cylinder must be duff.  I cannot bare the idea of replacing it now that the body shell is back on, it actually looks impossible. 

My last effort is, I have bought a male to male connector and I’m going to join the master cylinder brake pipe directly to one front wheel and see if I can get that to work by eliminating everything else.

Any other pearls of wisdom would be very welcome please.  Especially how to replace a master cylinder when there is absolutely no access the bolt heads inside the chassis.

[4129R]

The M/C on TCS are held in place with 5/16" studs and 1/2" diameter self locking nuts. What is different on yours?

I have the same problem bleeding the brakes on 4688R.

I am thinking of taking the car on a trailer to a local garage where they have a machine which pressurises the header tank with fliud, so all the air is pushed out direct from the reservoir. 

[Grumblebuns]

Have you done a bench bleed of the master cylinder before installing it? How did the pushrod feel on the vise when pushing it in?

[EuropaTC]

Removing the m/cyl looks bad but in truth it's fairly straightforward (or perhaps I've just had way too much practice with trying out different ones    )

I normally remove the closing plate which gives great access from both sides although I suppose you can get by without doing so. Release the connecting rod and then it's just a the m/cyl bolts and it's free.

But before doing that, if you really do have no pedal at all from the m/cyl, then firstly I'd crack the outlet and see if any air comes out there, sort of "bench bleed on the car" if you like.    Personally I can't see a new m/cyl being having duff seals but if I did suspect it then I'd just block off the outlet (bleed nipple same thread ?) and see if I could get a pedal on the cylinder alone.

I can't say I've had serious problems getting the brakes to work but I've certainly got better results with pressure bleeding. I've got a modified cap which I can pressurise but the old fashioned Gunsons Ezibleed using a spare tyre would be equally good enough to blow fluid in a continual stream through the individual lines. That is better than using the brake pedal alone, you get a good volume coming out in each "push" and less chance of bubbles drifting back to high points.

Brian

[Gmg31]

I didn’t bench bleed it before fitting it, I didn’t know that was recommended but having been given that advice the last ime I posted this I have since tried to do it in situ.   My presssure bleeder goes on the bleed nipples and sucks fluid through. So I disconnected the outlet pipe from the T piece and bled it that way.

I like the idea of screwing a bleed nipple straight into the outlet on the MC that will either work or not and it will be very clear what the fault is if that doesn’t work.

My MC is bolted on from inside the chassis with absolutely no acces point once the shell was refitted.  Had I known I was going to have this problem I would have tried to weld the bolds in place.

 I’m considering opening up an access port on the bottom of the chassis just big enough for a spanner and then welding a disc over it when I’m done.

[jbcollier]

Sometimes you can access the m/c nuts/bolts through the hole in the chassis for the m/  pushrods.  It isn’t easy but it is possible.

[EuropaTC]

I didn’t bench bleed it before fitting it, I didn’t know that was recommended but having been given that advice the last ime I posted this I have since tried to do it in situ.   My pressure bleeder goes on the bleed nipples and sucks fluid through. So I disconnected the outlet pipe from the T piece and bled it that way.

Bench bleeding isn't in the manual and although you'll find lots of Youtube videos on the subject, I wouldn't say it's common practice. With a single system I've never bothered myself and the first time I tried bench bleeding was with the tandem m/cyl, mainly because I was unsure as to how well it would fill with fluid. With the positioning of the m/cyl on the Europa I'm not convinced it's any advantage as fluid drips out as soon as you try to connect the lines, the alternative of trying to fit the m/cyl with lines connected seemed impractical as I wanted a single run for the rear system.

My MC is bolted on from inside the chassis with absolutely no acces point once the shell was refitted.  Had I known I was going to have this problem I would have tried to weld the bolds in place.
I’m considering opening up an access port on the bottom of the chassis just big enough for a spanner and then welding a disc over it when I’m done.

That's tough. If you do go the access port route then rather than try to tack the bolt heads in place I'd be tempted to make the hole slightly larger and fit a backing place with studs, like the image from the manual.  If there's no way you can get a spanner to the bolt heads through the central hole then I'd do the modification. It will be easier now while the car/chassis is clean and at some point either you or the next owner will want to service the m/cyl, if only to replace the seals.

[Grumblebuns]

Before trying to remove the M/C, I would block off the outlet port on the master cylinder as Brian recommended and see if you have a solid pedal first. At least you would know for sure that the M/C is bad.

[Clifton]

Are you sure the rod is adjusted so the master cylinder plunger returns all the way, opening the inlet port? If not it will never take fluid in.

[Grumblebuns]

My MC is bolted on from inside the chassis with absolutely no acces point once the shell was refitted.  Had I known I was going to have this problem I would have tried to weld the bolds in place.

 I’m considering opening up an access port on the bottom of the chassis just big enough for a spanner and then welding a disc over it when I’m done.

The federal S2s have an access port in the middle of the front "T" section of the chassis where I was able to reach in and remove and replace the M/C backing plate. Do the non federal S2s have the same setup?

 

[Gmg31]

Yes mine does have that but surely it’s impossible to reach the bolt heads from there....

[Gmg31]

Are you sure the rod is adjusted so the master cylinder plunger returns all the way, opening the inlet port? If not it will never take fluid in.

If I’m reading that right are you suggesting the rod could be adjusted too long or too short to pick up fresh fluid.  I adjusted mine to be long to get maximum travel along the cylinder but you seem to be suggesting that is wrong?

[EuropaTC]

I can see what Clifton is on about with the stroke on the cylinder and there's an optimum range.  When I changed to a tandem m/cyl, I took this photo of the old pushrod to establish the length for the new one.  That's assuming you have the UK set-up with single circuit, if you have the Federal set-up with a pivot arrangement then I can't help with those measurements.

It's difficult to set the length while installed, but surely all you have to do is remove the pin from the brake pedal end and that insures that the piston is returning to it's stop and you have maximum travel ? If the pushrod is too long then I'm not sure how you'd manage to bleed the brakes at all, but I could see the incorrect length affecting brake performance, maybe causing them to bind or apply the servo.

FWIW I only used those dimensions as a guide to making a new pushrod. As you can see I favour an adjustable end by the brake pedal which you can reach easily from the footwell so I just tighten it up until there's only a tiny fraction of movement at the pedal before the piston starts to move. And of course it makes it easier to adjust the pedal position.

Brian

[Gmg31]

Mmmmm that’s alll very interesting. Thanks. I’ll start with that this weekend and see what happens. 

Thanks everyone.

[2483R]

I second EuropaTC on pressure bleeding. I can pressure bleed all 4 wheels on my federal TC in 30 minutes.

You didn't say if you are using boosters. On the federal cars the stock setup was dual boosters, removing them along with the all the associated brake lines makes a huge difference in bleeding difficulty.