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Bleeding brakes again sorry


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Sorry to ask. I have spent the last hour or so looking through past posts but am still confused. I have just re-fitted my brake master cylinder after a rebuild by past parts. Bled the rears no problem but nothing at the front. I undone the pipe connection from the master cylinder and there is nothing coming out of the cylinder even if the pedal is depressed. I have read the other posts and it looks like I should have bench bled the master cylinder before fitting? I have now wedged the pedal to the floor and will leave over night as suggested in other posts. Is this all I can do? And is this correct though I would have thought I would have fluid coming out of the master cylinder with the pipe disconnected? Anything else I should know please? Should I take the cylinder of and bench bleed and start again? Sorry for the repeat question if I have missed the answer elsewhere.

Regards Richard

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Hi Richard

In all my years as a mechanic never have I bench bleed a master cylinder, anyway what you should do is with some one in the car slightly undo pipe first pipe at master cylinder press pedal to floor hold  nip up pipe release pedal slacken pipe again pedal to floor hold do pipe up repeat until fluid seeps from joint repeat for other pipe then move to three way union at front near side of chassis repeat the process once you have fluid at all three unions bleed brakes starting from the furthest one from master cylinder which I think is drivers side rear then passenger rear, passenger front, lastly drivers front no need for engine to be running hope this helps

Chris      

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Does the car have a PDWA fitted? - it was standard on LHD cars and is a brass block with 4 brake pipes going into it and an electrical wire connection.

The shuttle in PDWA, if fitted may need centralising if you have bled one circuit only and it has pushed across and blocked the other circuit.

Cheers

Peter W

have a read of this it explains the function  http://www.mossmotoring.com/triumph-tr6-brake-tech/

 

image.thumb.png.f93ce2daec29beb1f00ebe9e56ffa2a2.png

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My cylinder was also reconditioned by PP and I just installed it “dry” and then filled and bled the system.

Have you used a vacuum bleeder or the pressurised cap? This may help. (but I did not do that).

Waldi

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Ok so I tried to bleed at the cylinder and I was not getting any fluid through. I rang Pastparts and they suggested the push rod maybe was not fully returning to the closed position. So I loosened of the master cylinder fixing nuts to allow the master cylinder to move forward and sure enough I can now get fluid to pump out of the master cylinder brake pipe connection. I have seen on previous posts that some people have packed out the cylinder from the servo to achieve the correct setting however they have also been slated for doing this. Looking in the haynes manual it says the push rod can be adjusted with a nut that I can't identify on the diagram and setting with lock tight. However it does say that this is only necessary if installing a new push rod. I'm at a bit of a loss on how to get over this problem properly so any advice welcome and if I need to adjust and set the nut how I find and I go about doing this please

IMG_20200928_124422992.jpg

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Its item 17 in your drawing, you will need to take the master cylinder off, place a straight edge between the 2 mounting studs of the servo, the push rod should be just below the straight edge, less than 0.010"  ten thou.

I think its written in the manual.

John

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Hi Richard , welcome to the wonderful world of TR6 Master cylinder problems.

As John has said it's the rod protruding from the servo that's adjustable and it is very tight.

Gave mine about 1/8 - 3/16 free play as it slowly put the front brakes on as the fluid warmed up and expanded.

Loads of stuff on here about this type of problem.

Looks like your on the right track good luck.

Mick.

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Thanks John. It suggests in the Haynes manual to do this with the engine running. Is this necessary? Also I have quite a bit of play in the push rod I can pull and push it at a guess 5mm back and forth so its not locked as such and I can turn it with my fingers as well should it be loose like this?

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You have push the rod into the servo to get the clearance, make sure the pedal is not pushing on the push rod, have you got a return spring on the pedal?  You don't need the engine running

John

Edited by John L
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3 hours ago, John L said:

Its item 17 in your drawing, you will need to take the master cylinder off, place a straight edge between the 2 mounting studs of the servo, the push rod should be just below the straight edge, less than 0.010"  ten thou.

I think its written in the manual.

John

 

2 hours ago, Michael Mckiernan said:

Hi Richard , welcome to the wonderful world of TR6 Master cylinder problems.

As John has said it's the rod protruding from the servo that's adjustable and it is very tight.

Gave mine about 1/8 - 3/16 free play as it slowly put the front brakes on as the fluid warmed up and expanded.

Loads of stuff on here about this type of problem.

Looks like your on the right track good luck.

Mick.

Thanks for all the help. Big difference between .01 and 1/8. If its not critical I'm thinking a bit of free play is a good thing?

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Sorry call me stupid I have read previous threads and I still don't get it. My push rod has a nut at the top and what looks like a tapered edge further down the thread?? I'm guessing I have to some how hold the push rod on the tapered edge and screw the push rod down further into it or turn the domed nut further down? But thats easier said than done. But first I have to get it of to put some lock tight on it and all the while I have greater than .012 gap anyhow?

IMG_20200928_133331038.jpg

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I checked the clearance between the push rod tip and the plunger which is spherical by calculating from the 2 measurements. Then gave it minimal clearance, like 0.2 mm because more will increase foot pedal travel unnecessary.

Waldi

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Hi Richard

It seems that the push rod is to long not allowing the master cylinder valve to fully close I take it its the first outlet you cannot bleed if so shorten the servo push rod ie screw the nut in slight and re-try until you have success. The manual is only a guide when new or reconditioned factory units are fitted yours has been reconditioned differently to how you would normally do with just a seal kit so take that into consideration.

Chris       

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Thanks guys for trying to help me but now I'm struggling to move the nut by holding the serrated part of the shaft with pliers and just succeeding in tearing it up. I guess its on with lock tight so I decided to launch my spanner across the garage, lock the door and open a beer. I'll look to see if I can buy a large bag of mixed inspiration and willpower and come back to it another day. Poxy heap of s### I only started with a leaking wheel cylinder. 

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Spot on Chris, it seems that no two M/Cylinders are the same.

I had no problem at all bleeding my brakes after fitting a new M/C but after a fast run it pulled on the front brakes.

Richard i held my push-rod with big long nose mole grips and turned the nut with a socket and ratchet.

As i said it was murder tight. It's probably not been moved since the car was built.

Just be "careful" and dont snap it off.

May-be someone will be on with a better solution !!

Mick.

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Sorry Richard if I appear to be hi-jacking your thread.

I had my servo rebuilt by Past Parts this year, I've now re-installed it and find that although the car passed an MOT and the brakes are fine(ish) the stopping distance is somewhat further than I'm 100% comfortable with.

I never checked the pushrod clearance before fitting, so I'm now wondering if that could be the root of my problem, hmmmm!

Richard.

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Richard

Use something to hold the brake pedal down that will push the pushrod out and will make it easier to adjust.

You need to hold the serrated part of the push rod with some small grips and then adjust the nut down, its a tight fit so I dont  think you need to worry it coming loose.

Just place a steel ruler across the opening between the 2 studs, but remember to release the brake pedal to allow the rod it go back into the servo. The rod needs to be just below the ruler.  How much protrusion do you have at the moment?

Sorry I didnt press submit earlier.

How far does the pin protrude, could you grind a bit off the top to give the right clearance you need.

John

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