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New TRW brake master cylinders - sticking piston


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Hi Folks,

I recently fitted a new TRW master cylinder to my 5. Having filled the reservoir and starting to bleed the brakes, the first few depressions of the pedal failed to pump any fluid. On taking the cylinder off again, the piston was stuck in the bore, obviously not having returned from the first push on the pedal.

With gentle persuasion (tapping on the end of the cylinder) I eventually managed to get the piston to return. However, on pushing it back in the bore manually it stuck again. Repeated this a few times before giving up and returning the unit to Moss. They kindly couriered a replacement out to me promptly. I tried this one on the bench and the piston appeared to be moving smoothly in the bore. However, on fitting to the car exactly the same problem occurred as with the first unit. After removal, again I managed eventually to get the piston to return but on pushing it in again manually it stuck again and no amount of persuasion has released it again.

Is anyone aware of a similar problem with any recent TRW units or have any advice to offer?

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Hi Jon,

 welcome to the forum.

This is a new defect to me.

Have you spoken to Moss regarding the second MC. It could be a batch problem - replacements off the shelf may all have the same problem.

I have sent you a PM - look for Red letter in top right hand corner and click on it.

 

Roger

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Thanks Roger / Rich,

Roger - I had been trying to speak to Adam Chignall at Moss for a few days and we finally caught up today. He agreed that it sounds highly unusual and therefore potentially a batch problem. Obviously they will check the returned units in due course but this may take a while. We agreed it doesn’t seem worth having another from their existing stock until it is known if it is a batch fault.

Re. the PM, I can’t see the red letter you mention, can you clarify?

Rich - thanks for the link, I had not heard of Past Parts. I will be dismantling my old master cylinder and if the bore is ok I will probably rebuild it myself but goood to know of PP anyway.

Cheers,

Jon

 

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39 minutes ago, Jon Clark said:

Thanks Roger / Rich,

Roger - I had been trying to speak to Adam Chignall at Moss for a few days and we finally caught up today. He agreed that it sounds highly unusual and therefore potentially a batch problem. Obviously they will check the returned units in due course but this may take a while. We agreed it doesn’t seem worth having another from their existing stock until it is known if it is a batch fault.

Re. the PM, I can’t see the red letter you mention, can you clarify?

Rich - thanks for the link, I had not heard of Past Parts. I will be dismantling my old master cylinder and if the bore is ok I will probably rebuild it myself but goood to know of PP anyway.

Cheers,

Jon

 

Jon - as I understand it, Past Parts ream out the bore and fit a stainless steel liner, bead blast the outside and rebuild with known quality seals and new parts as necessary, so a refurbed unit should be as good if not better than an original new unit. Cost is obviously more than your TRW repro but how much hassle have you already had and the historic evidence of the longevity of these repros is not that encouraging, but ultimately the choice is yours.

If the bore is corroded, don't throw it away. just put it on here and someone will snap it up!

Cheers Rich  

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  • 2 years later...

Coming to this thread a bit late. In the process of finishing full refurb of my TR6. Fitted new brake master cylinder and tried to bleed. First press OK then goes soft. Piston stuck in barrel. Managed to free with air line but stuck again. Replaced unit and same thing happened with new one. Both were TRW units. Did a lot of searches but found nothing to explain problem. Then when I was looking to get my 3rd unit found this on TRGB web site.

BRAKE MASTER CYLINDER FOR TR5/6.

**IMPORTANT**      PLEASE READ THE FOLLOWING FITTING DISCLAIMER...

THERE IS ONLY ONE MANUFACTURER OF BRAKE MASTER CYLINDER FOR THESE MODELS - TRW.

THESE ARE CHEAP UNITS WHICH, 3 YEARS AGO WE WERE SELLING FOR NEARLY £200 +VAT.

WHEN FITTING, THERE IS A VERY HIGH POSSIBILITY THAT, IF THE PEDAL IS DEPRESSED COMPLETELY TO THE BULKHEAD, THAT THE SHUTTLE INSIDE THE MASTER CYLINDER CAN STICK AND MAKE THE UNIT UNUSABLE.

IF THIS HAPPENS THEN IT IS NOT COVERED BY ANY WARRANTY.

WHEN BLEEDING THE SYSTEM THE BRAKE SYSTEM NEEDS TO BE PARTIALLY BLED ALTERNATIVELY BETWEEN THE FRONT AND REAR HALVES OF THE SYSTEM USING 1/2 PEDAL PRESSES UNTIL THE SYSTEM IS "FULL" OF FLUID.

AFTER THIS PROCESS, THE BRAKES CAN BE BLED NORMALLY, STARTING AT THE N/S REAR, BUT ONLY BY PRESSING THE PEDAL 2/3rds OF THE FULL STROKE.

THESE INSTRUCTIONS SHOULD COME WITH THE UNIT WHEN IT ARRIVES AND NEED TO BE FOLLOWED, TO THE LETTER.

So basically TRW unit is pretty useless but is the only one available. Has anyone else had the same issue?

 

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Past Parts are the best choice and have done all my hydraulics. The problems have now gone away.

Give them a try.  We are talking about brakes which can cause serious damage if the cylinder fails in use.

Good luck Richard & B

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I have had a 2 year old TRW master cylinder fail! Which was something that I don't want to re experience :o so now will only use Past Parts refurbished components.

As has been mentioned its a little bit more expensive to go this way and it's not an off the shelf replacement so you have to wait, but it's quality parts that are reliable.

I have no connection with Past Parts apart from being a customer.

George 

 

 

 

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2 hours ago, harlequin said:

I have had a 2 year old TRW master cylinder fail! Which was something that I don't want to re experience :o so now will only use Past Parts refurbished components.

As has been mentioned its a little bit more expensive to go this way and it's not an off the shelf replacement so you have to wait, but it's quality parts that are reliable.

I have no connection with Past Parts apart from being a customer.

George 

 

 

 

Aside from the waiting time, can anyone quantify what is a "little more expensive" please?

If appropriate, and the wait is not months, this task could go on the 'Winter layup' list.......

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8 minutes ago, John Bracher said:

Aside from the waiting time, can anyone quantify what is a "little more expensive" please?

If appropriate, and the wait is not months, this task could go on the 'Winter layup' list.......

FWIW Past parts will only refurb original cylinders and wont touch the TRW ones.

Stuart.

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Hi John,

I ordered mine from PP a couple of years ago, they came back within 3 weeks….to Holland! And this was including “yellow zinc” plating.

Think they have some stock as well for  exchange.

Think I paid 80-100 pounds each.

Waldi

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2 hours ago, John Bracher said:

Thanks Gents. That seems 'acceptable'.

I think I have a Girling one in a shed, so maybe send that one away??

If you have a Girling original then yes thats whats needed.

Stuart.

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Hi John

I bought one from Conrad a few years ago now which had being reconditioned by Past Parts. Try contacting him he might just have one on the shelf.

Out of interest I have the one that came with the car how do you tell if its an original rather than a TRW repro?

Andy

 

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On 12/10/2022 at 8:19 PM, ntc said:

Odd this I have fitted three of these in the last four years and not had any problems.

The one I had was fine for about 2 years, I then had some brake work done which must have altered the travel of the master cylinder piston. Within 100 miles of having this work done the master cylinder failed.

When I stripped it down I found the seal was stuffed and there was a distinct step in the bore. My assumption was that the cylinder material was to soft and was wearing, then when the stroke changed the seal was crossing the wear step which wreaked it. End result no brakes.

George 

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  • 3 weeks later...
On 9/16/2020 at 10:17 AM, rcreweread said:

Jon - Have you still got the original master cylinder? If so, send it to these guys who will recondition it - http://www.pastparts.co.uk/index.php?route=information/contact

No connection other than a satisfied customer

Cheers Rich

+1. I  would not buy a new TRW master cylinder. Problems with their M/Cs extend into other marques. There seems to be a lack of QA in that company.

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11 hours ago, astontr6 said:

+1. I  would not buy a new TRW master cylinder. Problems with their M/Cs extend into other marques. There seems to be a lack of QA in that company.

Last time this problem came up a few years ago it was traced to a rogue batch of Chinese fakes, I suspect thats probably the case this time too. There is a lot of genuine TRW ones in service doing fine.

Stuart.

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