sized front brake piston

[david c]

Out driving recently and became aware of a noise from front n/s brake, on examination noticed the brake was rather warmer than I feel it should be. Today I removed the calliper and found one of the pistons to be sized solid, to cut a long story short I worked out that the only way to get the offending piston out was to put back the free piston (as best I could.....about halfway) and blow them out with the airline, this worked a treat.

My questions are should I now replace both front callipers?  if so any recommendations?

Is it feasible to replace the rubber seals?  If so any tips?

Obviously to get the pistons back in the callipers they have to go in 100% square any tips on achieving this would be really helpful.

Thanks for taking the time to read this.

David

[RogerH]

The TRShop are doing a good deal on calipers

 

Roger

[Lebro]

Perfectly possible to refurbish.

New seals & new pistons, plus a bit of cleaning up.

Bob

[david c]

Thank you both for your replies, and to Richard C R  for calling me.

It seams to me that for the sake of £20.00 ish. I should give refurbishment a go, after all I have plenty of time. If I don't feel happy with the result then I'll go for the new / refurbished  callipers.

Thanks again David

[John Morrison]

David fit stainless steal pistons, that's fit and forget, the plated ones lasted me just 15 months, (Just out of guarantee)

As Bob says, very straight forward job.

John.

[Hamish]

Definitely try a refurb first. I did this on a Daimler sp250 that was a new to me car. Before I had the tr. 

You don’t have to split them to do it as there is a sealing “O” between the halves that can be difficult to find/replace. 
 

with mine the piston had rusted, inside the caliper was ok and there is a seal tolerance “gap” which means the piston is not metal on metal anyway. 

Edited November 5, 2023 by Hamish
Pics

[Lebro]

Quite so !

Bob

[BlueTR3A-5EKT]

10 hours ago, John Morrison said:

David fit stainless steal pistons, that's fit and forget, the plated ones lasted me just 15 months, (Just out of guarantee)

As Bob says, very straight forward job.

John.

Plus one for stainless pistons.   I also use silicon fluid but that is another thread elsewhere.

As stated by Hamish do not split the caliper unless you have the new o ring to seal the two halves in your hand and you know the torque the bolts get reset to.

[Hamish]

19 minutes ago, BlueTR3A-5EKT said:

Plus one for stainless pistons.   I also use silicon fluid but that is another thread elsewhere.

As stated by Hamish do not split the caliper unless you have the new o ring to seal the two halves in your hand and you know the torque the bolts get reset to.

The torque figures are in the Daimler manual. Posted before but just in case the calipers are already split !!
 

[BlueTR3A-5EKT]

1 hour ago, Hamish said:

The torque figures are in the Daimler manual. Posted before but just in case the calipers are already split !!
 

I have copied these pages to the Technical Section. Pinned Bonanza Collection of tech info etc.

[John L]

From the pictures of the caliper pistons, there doesn't seem to be the cut outs in the piston facing the pads, I understood this helps with the wear rate on the pads, more pressure on the outside, so equaling the pad wear.

John

[Chris Hubball]

If you are using Silicon Brake Fluid make sure the seals are compatible .

Cheers Chris

[Michel Higuet]

5 hours ago, BlueTR3A-5EKT said:

Plus one for stainless pistons.   I also use silicon fluid but that is another thread elsewhere.

As stated by Hamish do not split the caliper unless you have the new o ring to seal the two halves in your hand and you know the torque the bolts get reset to.

In the past I have split the calipers and using the same O ring without any problem... But of course  is better if you have new one. In the past there was a rumour of never split the calipers... :-)

As a doctor friend told me, “you have to avoid believing everything the doctors tell you.” :-)

[Lebro]

I rebuilt mine (late TR3 ones) did not split, & used non stainless pistons (I presume as I did not ask for stainless) that was 10 years ago & many miles, no problems to date.

Bob

P.S. If doing them again I would specify stainless ! 

[david c]

My goodness 

That's a lot of information, thanks all.

I had no intention of splitting the callipers, so that is one problem solved. having seen Hamish's photos I think my problems are fairly small  I cleaned up all the parts today and found only very minor pitting on the non business ends of the pistons if this is a problem I will obviously spend the few extra quid and get stainless.

Thank you all again David

[david c]

Well it looks like both Hamish and Lebro were right, it was quite straightforward to rebuild the callipers, even getting the pistons back in was fairly easy.

Then I went and mucked it all up refitting the copper calliper brake pipe fitting (one side only) I overtightend and stripped the copper thread, I assume it is only the copper thread I stripped, there is no way I can have stripped the thread in the calliper.............is there?

On that subject I'm having some trouble finding some new replacement items (calliper to brake pipe) the original and the spare I messed up are pre bent but I can't remember where I got the spare from. 

Any ideas?

[stuart]

17 minutes ago, david c said:

Well it looks like both Hamish and Lebro were right, it was quite straightforward to rebuild the callipers, even getting the pistons back in was fairly easy.

Then I went and mucked it all up refitting the copper calliper brake pipe fitting (one side only) I overtightend and stripped the copper thread, I assume it is only the copper thread I stripped, there is no way I can have stripped the thread in the calliper.............is there?

On that subject I'm having some trouble finding some new replacement items (calliper to brake pipe) the original and the spare I messed up are pre bent but I can't remember where I got the spare from. 

Any ideas?

Automec do pipes ready made but you do have to bend them yourself, 

Stuart

[david c]

Thanks Stuart, TRGB do the straight pipes too, I was just hoping I could get them ready made.

[BlueTR3A-5EKT]

1 hour ago, david c said:

Well it looks like both Hamish and Lebro were right, it was quite straightforward to rebuild the callipers, even getting the pistons back in was fairly easy.

Then I went and mucked it all up refitting the copper calliper brake pipe fitting (one side only) I overtightend and stripped the copper thread, I assume it is only the copper thread I stripped, there is no way I can have stripped the thread in the calliper.............is there?

On that subject I'm having some trouble finding some new replacement items (calliper to brake pipe) the original and the spare I messed up are pre bent but I can't remember where I got the spare from. 

Any ideas?

If you have TR6 calipers……..There are two types.    Imperial threaded and metric threaded end to fit in the caliper.  Get it wrong and ruin the caliper/pipe.

[david c]

After much faffing about all back together now without leaks, with the callipers on the bench it was very much easier to fit the bent copper pipes (thanks TRGB  for really quick fuss free service). System blead twice as instructed by the workshop manual...........but I have about an inch of travel on the pedal before I get any resistance the first time I press the pedal down. I don't remember that happening previously, is it normal?

[Ralph Whitaker]

10 hours ago, david c said:

After much faffing about all back together now without leaks, with the callipers on the bench it was very much easier to fit the bent copper pipes (thanks TRGB  for really quick fuss free service). System blead twice as instructed by the workshop manual...........but I have about an inch of travel on the pedal before I get any resistance the first time I press the pedal down. I don't remember that happening previously, is it normal?

I would say that is normal, before with the pistons seized the pedal would have felt abnormally high.

Ralph

[stuart]

16 hours ago, david c said:

After much faffing about all back together now without leaks, with the callipers on the bench it was very much easier to fit the bent copper pipes (thanks TRGB  for really quick fuss free service). System blead twice as instructed by the workshop manual...........but I have about an inch of travel on the pedal before I get any resistance the first time I press the pedal down. I don't remember that happening previously, is it normal?

Check the pedal lever clevis hole for ovality and also wear on the clevis pin itself.

Stuart.

[Efuentes]

Hi, David. I refurbished one caliper some years ago as the other one seemed to work perfectly, and I have recently refurbished the other, as the car was steering to one side when braking. While the first time everything went great, this second time I had the issue that, after the change of caliper pistons, my brake pedal was going down all the way and no matter how much I pumped, I was not getting fluid pressure from the master cylinder, so I could not bleed the brakes (even if I pushed the pedal repeatedly, I never got fluid out from the caliper bleeder). I remembered that I had an easy bleed type brake bleeder, which essentially is a hand vacuum pump that you plug, with an intermediate receptacle, to the bleeder in the caliper. You then apply vacuum and open the bleeder and repeat until you get fluid out. It worked and I managed to get pressure at the pedal. You can get those cheaply at Amazon. I attach a picture 

[david c]

That's a nice looking piece of kit, but I think I have possibly found the answer to problem.

Being "clever" when refitting the brake pads I pushed them back as far as I could, makes sense to me so much easier to slide the callipers over the disks?

I think the problem is now I have a situation where I have to push the peddle about an inch just to get the pads to contact the disks, hence the "dead" space.

Does this theory make sense?

If so what can I do about it.?.............without removing the callipers preferably.

[Efuentes]

OK, so I understand that you have pressure in the master cylinder, but the brake travel has increased… I am not sure that the issue is the travel before the pads contact the discs, as, normally, once you have pressed them against the brake, they should not come back all the way (for example, when the brake pads wear out, the pedal travel does not increase that much). There may be circumstances where that separation can happen, if there is aggressive driving in a bumpy road,  i rations due to an unbalanced wheel or if the brake disk is not straight, but that’s uncommon. I believe that there was a valve in the brake distributor fixture (a piece where the hose coming from the master cylinder splits into the two hoses for the front wheel and a hose for the rear wheel) to prevent the pads going back, but it creates more problems than it solves, so most owners remove it (my car didn’t have it), which is also a sign that the pads going back all the way is not something that should happen normally. I would be inclined to think that you may still have some air trapped in the system and, as air is compressible, you need to press the pedal more than if there would be no air. There are other participants in this forum that have much more know how than me, but I would try a proper bleeding.