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Brake Master Cylinder problems


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Hi all, i was just wondering if there is still a problem with TRW brake master cylinders.

The reason for asking is that i fitted a new one about 3 months ago and all appeared to be ok.

Set off for Brooklands Sunday morning got about 14 miles down the A303 and the front brakes locked on ( set fire to the o/s/f outer pad )

Now having checked the dimensions of the old M/C  with the new one it would appear to be about 4mm slimmer so will close the gap on the servo push rod.

With this in mind i have increased the gap a extra 6mm  ( just to be sure )  Then replaced pads bleed brakes and road test .So-far so good.

Do you think that i have found the problem or is it more likely to be the tipping valve sticking.

Bit reluctant to go to far  ( 8 miles for road test ) Also got new discs and pads to fit when i am positive i am not going to burst into flames again.

Any help much appreciated

Mick.

 

 

 

 

 

 

 

 

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Had exactly the same issue although it showed up immediately, and resolved the same way.

I made sure I carried a spanner around (as the pressure would release upon loosening the MC from servo when I first discovered the issue), just in case, but since the servo rod adjustment it's been fine. 

It's not good that you have to find out the hard way though. 

Gareth

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4 hours ago, Mk2 Chopper said:

Had exactly the same issue although it showed up immediately, and resolved the same way.

I made sure I carried a spanner around (as the pressure would release upon loosening the MC from servo when I first discovered the issue), just in case, but since the servo rod adjustment it's been fine. 

It's not good that you have to find out the hard way though. 

Gareth

Cheers for that Gareth, nice to know that it's happened before.

Odd that i did not have a problem on shortish runs, i can only surmise that a steady

65/70 MPH for 14miles built up a bit of heat or maybe a bit more vacuum that allowed the servo to push on the master cyl.

Feel a lot better now about fitting the new discs & pads.

Mick.

 

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1 hour ago, Michael Mckiernan said:

Cheers for that Gareth, nice to know that it's happened before.

Odd that i did not have a problem on shortish runs, i can only surmise that a steady

65/70 MPH for 14miles built up a bit of heat or maybe a bit more vacuum that allowed the servo to push on the master cyl.

Feel a lot better now about fitting the new discs & pads.

Mick.

 

Thinking about it the first symptom was I couldn't bleed the brakes, when I undid the MC to try and figure it out it obviously released the push rod and allowed fluid through and bled just fine. 

A couple of test drives and it worked but then one time it locked on, once I'd realised that undoing the MC cured it I knew what the cause was. I actually put a dab of paint on the rod and kept adjusting and refitting the MC until there was the lightest hint of paint visable on the inside of the MC so I had my 'air' gap between them.

Gareth

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Was there not a problem with these new ones a couple of years back which i seem to remember was the tipping valve.  

Roger may have details.  NTC and others had failures which as it's brakes the forum had a lot of activity.

ROY

 

Found details on google search  august 2016

Edited by roy53
new info
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Hi Roy, there was indeed a lot of trouble 3ish years back with faulty TRW Master Cyl.

But as there is no later posts with this problem i was hoping it had been resolved.

Maybe Roger can help or indeed head me in the right direction.

Really don't want to fit new discs & pads and have it happen again.

I have the old Master Cyl maybe i should rebuild that ? seems such a shame to bin a " new " part.

Mick

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I have just had a problem with this master cylinder,  I was having a slightly longer pedal travel than I used to have, bleeding didn't seem to cure it, with the cap off the reservoir when the brake was depressed the fluid would rise in the front compartment.

On dismantling I found that the  plastic/nylon  part at the very end had distorted and was stopping the plunger sealing against the end of the cylinder, and so bypassing fluid back to the reservoir.

Luckily having not thrown the old MC away I was able to get the nylon part out of the old cylinder, this hadn't shrunk like the new one, and system restored.

The MC is on the side of the manifold and does get hot on a good run and wonder if this is cause of the white plastic part deforming, is it worth contacting TRW with this info?

IMG_2301 (2).JPG

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I have had this problem, blodey annoying,  I cured it by putting  a couple of washers between the servo and the master cylinder (were it bolts on )

Thicknes of washers, Approx 1/8 of an inch,  this allowed more play for the tipet valve to operate , 

Pink 

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Thanks for that Pinky, checked the gap from the servo push rod to the Master cyl with play-doh

and its now 3/16 so now hopefully will be more than enough.

Also made hardly any difference to the pedal travel. Thank you all for your input, feel a lot better about fitting new stuff.

Off to Silverstone in a hour or so for the classic. As we are there all weekend we are taking the Motor-home. ( 1994 talbot express ) glutton and punishment spring to mind.

So i will be seeing some of you there.

Mick.

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It was years ago that myself and Guy found these bad batches and most was removed from sale ( it took hard work with no help from the club)some may have slipped

the net.There is NO way you should have to pack with washers I would fail that outright as should any Mot tester, adjust the rod that is inside the servo to the correct length it is in the workshop manual.If that is not right you have a bad master,rant over.   

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Hi Mick,

One of the problems was the leaking reservoir on the brake master cylinder. Guy in Jersey and Neil gave lots of updates on what wasn;t happening by the supplier.

Eventually a supplier sent a sample back to the manufacturer and hey presto the problem seemed to disappear over night.

TRW never gave a reason of the fault.

This current problem sounds like an adjustment problem. I haven't seen or been involved with it.

If there is a problem then return the item back to the supplier for them to return it to the manufacturer.

 

Roger

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Hi Roger, I know the leaking brake reservoir problem well, I fitted three new master cylinders and reservoirs in 2 months until I got one that did not leak, it is still on the car. I was told repeatedly that it was a batch problem. I agree, this sounds like adjustment or a tolerance build up issue.

Mick

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There was more problems than just reservoir leaks with those cylinders.

Stuart.

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I fitted a brand new TRW master cylinder unit to my TR6 when it went on the road earlier this year after a full restoration. Leaked from where the reservoir joined the cylinder itself, although it took a few miles and a repeatedly emptying reservoir before I worked out what was wrong.

Easily fixed with a replacement rubber O-ring/seal between reservoir and master, but seems like the problem is still, well, a problem. Potentially a batch issue, as Mick states above, but I thought it worthy of a mention.

Matt

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This is why I had my original cylinders sleeved and reconditioned. Yes, it is more expensive, but I have no problems like above. Well recommended.

Regards,

Waldi

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Thanks for all the information, looks like there might be a on-going problem.

I will take a chance tomorrow when the weather clears and drive the same route now i have a gap on the servo push rod.

Borrowed a digital temp gauge to see what is happening  ( Hopefully nothing )

If it still overheats i will contact Rimmers return the unit and get a refurbish kit and overhaul my old unit.

Lovely to see so many TR's at the classic we had a look round but as the tent was very crowded we did not say hello ( it was pouring down )

With a bit of luck i will try to get up to the Inter- club weekend.

Mick.

 

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Amazingly enough my front brakes locked on this evening after sitting in traffic for awhile. I logged into this forum to ask for advice and I found this post. I have a new master and booster which I fitted a few years ago and have not had any issues until now. Even driving in hot conditions. I’ll investigate further over the weekend.

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