Master Cylinder Confusion

[cliff.b]

27 minutes ago, johny said:

The official tools use round rod of fairly small diameter as the clamping surfaces to spread the load and ensure good close off but its not critical...

I will have a rummage in the garage and see what I can find.

[cliff.b]

1 hour ago, johny said:

The official tools use round rod of fairly small diameter as the clamping surfaces to spread the load and ensure good close off but its not critical...

I will have a rummage in the garage and see what I can find.

[cliff.b]

Ok, before clamping any pipes I have disconnected both of the flexibles to the calipers and capped them with spare bleed nipples. The brake pedal is now as hard as a teenage boy who has just woken up 😁. So I am assuming the MC is ok, the rear brakes are not causing the issue, I don't have any leaks and it must be either the calipers or connection to them. So now to fit the new calipers 👍

[cliff.b]

Correction, I meant capped the ends of the metal pipework

[Pete Lewis]

as you have a non std master cyl have you checked there is some free play between the pushrod and the piston as this will block recuperation and upset pedal travels .  a  simple fault with major consequences 

whilst hose clamps are used they are not advised as ok by any reinforced hose manufacturer

Pete

[cliff.b]

4 minutes ago, Pete Lewis said:

as you have a non std master cyl have you checked there is some free play between the pushrod and the piston as this will block recuperation and upset pedal travels .  a  simple fault with major consequences 

whilst hose clamps are used they are not advised as ok by any reinforced hose manufacturer

Pete

Just checked & it feels pretty tight to me. What sort play should I be seeing?

[Pete Lewis]

any  a couple of mm thiis ensures with foot off the piston does fully return 

seized pedals can also cause the same problem do test the pedal does fully return to its stop

you need the rod to have a bit of a rattle ,foot off 

Pete

 

[cliff.b]

Just now, Pete Lewis said:

any  a couple of mm thiis ensures with foot off the piston does fully return 

seized pedals can also cause the same problem do test the pedal does fully return to its stop

you need the rod to have a bit of a rattle ,foot off 

Pete

 

Ok, that makes sense, thanks. I assume there is no adjustments available to adjust the play? Anyway, I have the correct master cylinder now so I may fit it as a matter of course. 

[johny]

I wouldnt change too much yet as itll confuse the issue. As Pete says check the MC actuator rod is free to rock with your fingers and not under load. No adjustment available but the end of the piston where the rod locates is conical so the rod wont fall out of place but is free to move around a little...

[cliff.b]

35 minutes ago, johny said:

I wouldnt change too much yet as itll confuse the issue. As Pete says check the MC actuator rod is free to rock with your fingers and not under load. No adjustment available but the end of the piston where the rod locates is conical so the rod wont fall out of place but is free to move around a little...

Yes, agreed. I wasn't going to change it all at once. One thing at a time then test ☺️. I have replaced the caliper with the seized piston now, bled it and the pedal feels much better. Will replace the other one after lunch.

Incidentally, I am using Rimmer supplied caliper, pads & fitting kit and the clip can't be fitted on the retaining bars because the hole is still covered by the caliper. I have had to use a drill slightly larger than the retaining bar head to recess the opening a couple of mm so the bars sit further in and the clip hole can be accessed. 

 

[cliff.b]

4 minutes ago, cliff.b said:

Yes, agreed. I wasn't going to change it all at once. One thing at a time then test ☺️. I have replaced the caliper with the seized piston now, bled it and the pedal feels much better. Will replace the other one after lunch.

Incidentally, I am using Rimmer supplied caliper, pads & fitting kit and the clip can't be fitted on the retaining bars because the hole is still covered by the caliper. I have had to use a drill slightly larger than the retaining bar head to recess the opening a couple of mm so the bars sit further in and the clip hole can be accessed. 

 

Ha Ha, I've just realised my "school boy error I was putting the bars in from the wrong side 😀. In my defence, it's a long time since I have done this sort of thing.

Will need to start engaging brain before taking action.

[Pete Lewis]

there is no club for getting the Tee shirts for Oops moments 

weve all got some 

Pete

[cliff.b]

Both calipers replaced now. As I explained previously, the NS caliper had a seized piston. The OS pistons are not completely seized but very "sticky" and co-incidentally, the retaining clips that I had a problem with were missing and one of the bars had backed out to the extent that the pad was no long properly seated. 

Anyway, I bled just the calipers and tested it. The pedal is still spongy but even so the braking is much better and a 2nd hard pump dips the nose sharply.

I am thinking bleed the whole system again, (following advice regarding rear brakes) and drive a bit more to bed the new pads in.

If still spongy, I will then put the new original spec MC on as I cannot detect any play in the actuator rod. Or would it be feasable (or even sensible) to temporarily place a couple of washers between the MC & the mounting bracket to gain a little play and see if that resolves the problem?

 

 

 

 

 

[johny]

Yes the pads bedding in could improve the pedal and braking a lot plus bleeding again if necessary isnt a bad idea.

You could take out the split pin and separate the brake linkage to see how much difference there is between the pedal hole and clevis pin. Actually at the same time you could change over the clutch and brake MCs mounting brackets as I believe they have been swopped - the reinforced one should be for the brake.... 

[cliff.b]

44 minutes ago, johny said:

Yes the pads bedding in could improve the pedal and braking a lot plus bleeding again if necessary isnt a bad idea.

You could take out the split pin and separate the brake linkage to see how much difference there is between the pedal hole and clevis pin. Actually at the same time you could change over the clutch and brake MCs mounting brackets as I believe they have been swopped - the reinforced one should be for the brake.... 

I didn't even notice the brackets were different and I'm guessing whoever put the car back together didn't either.

 

[johny]

yes and there can be quite a bit more force applied to the brake MC, especially in an emergency!

[Pete Lewis]

all new pads need a fairly hard use to bed them in but new pads on old disc  needs a bit of care to start with 

i have found if the anti squeal shims are the plastic version you never get a good pedal the stiless shims are the better 

mintexx 1144 have a procedure which would also suit most pads but this is based on new disc and pads  

the plan is to get them pretty hot but never stop whilst allowing to cool 

mintex bedding.pdf

[cliff.b]

27 minutes ago, cliff.b said:

I didn't even notice the brackets were different and I'm guessing whoever put the car back together didn't either.

 

Do you know if the bolts holding the brackets go into captive nuts or do you need to find the non captive ones?

[cliff.b]

6 minutes ago, Pete Lewis said:

all new pads need a fairly hard use to bed them in but new pads on old disc  needs a bit of care to start with 

i have found if the anti squeal shims are the plastic version you never get a good pedal the stiless shims are the better 

mintexx 1144 have a procedure which would also suit most pads but this is based on new disc and pads  

the plan is to get them pretty hot but never stop whilst allowing to cool 

mintex bedding.pdf 86.89 kB · 0 downloads

The shims supplied in the Rimmer fixing kit are stainless. I'm sticking with standard pads for now because I want to make sure the stock setup is as good as it can be before deciding if I want to try and improve it. Partly this is because I hadn't driven a Spit for 40 years and it's difficult to remember how good (or bad) the stock brakes actually were. 

I'm certainly open to the idea of improving the brakes eventually, but not to try and make up for something that isn't working optimally.

 

[Pete Lewis]

sure the pedal brackets have weld nuts not loose nuts 

[cliff.b]

26 minutes ago, Pete Lewis said:

sure the pedal brackets have weld nuts not loose nuts 

That will make things easier 👍

[cliff.b]

18 hours ago, johny said:

Yes the pads bedding in could improve the pedal and braking a lot plus bleeding again if necessary isnt a bad idea.

You could take out the split pin and separate the brake linkage to see how much difference there is between the pedal hole and clevis pin. Actually at the same time you could change over the clutch and brake MCs mounting brackets as I believe they have been swopped - the reinforced one should be for the brake.... 

I have just removed the clutch & brake cylinder brackets to swap them over and there are other differences apart from the re-inforcement (see pics). I'm wondering if this might account for the lack of play in the actuator rod 🤔

[cliff.b]

Just now, cliff.b said:

I have just removed the clutch & brake cylinder brackets to swap them over and there are other differences apart from the re-inforcement (see pics). I'm wondering if this might account for the lack of play in the actuator rod 🤔

 

[Pete Lewis]

quite possibly  but yours is a very non std unit thats probably more the culprit 

seeing as clutch and brake are pretty much the same cylinders and actuation

but the slight angular difference wont help

your about to prove it  !!!!

Pete

[cliff.b]

I have refitted the old, non-standard brake MC on the reinforced bracket and the actuator rod still has no movement, but it's not because of the distance from the brake pedal. In fact I had to move the top of the brake pedal about 5mm towards the MC to get the pin in.