1 hour ago, Wino said:

There are a few fasteners like that - with tool size sounding wrong relative to the thread size but actually being correct.  It doesn't surprise me to see such a mismatch.  

 

 

 

So my next question.

 

On the skoda.7zap site, there lists two different caliper carrier bolts, they both have the same description , how do you tell which ones you need, for example, so you get 16 and (16). 

 

 

 

16	N  91006802	socket head bolt with inner multipoint head (kombi)
(16)	N  91081501	socket head bolt with inner multipoint head (kombi)

 

1 hour ago, Aj77 said:

Any idea why the caliper carrier bolts are referenced as M12 bolts when they need and M14 spline socket?

 

From this page, https://skoda.7zap.com/en/cz/octavia/oct/2008-419/6/615-615065/

 

N 91006802 brings up 

https://www.onlinecarparts.co.uk/febi-bilstein-9799886.html

 

Which says, Outer thread [mm]:M12 x 1,5.

 

 

 

That's perfectly normal. It's an M12 thread, but takes an M14 spline socket to fasten it. Most M8 bolts have a 13 mm hex head on the car, same diff.

3 minutes ago, Aj77 said:

 

So my next question.

 

On the skoda.7zap site, there lists two different caliper carrier bolts, they both have the same description , how do you tell which ones you need, for example, so you get 16 and (16). 

 

 

 

16	N  91006802	socket head bolt with inner multipoint head (kombi)
(16)	N  91081501	socket head bolt with inner multipoint head (kombi)

 

Look in the next box along

 

Edited 18 December, 20205 yr by Tech1e

Duplicate of Tech1e's post

Edited 18 December, 20205 yr by Wino

Personally I would have just gone for this over all the faffing about...

 

1 Pair of reconditioned calipers

Warrantied and guaranteed to work. Car is back on the road, minimal fuss and safe.

9 minutes ago, Tech1e said:

Personally I would have just gone for this over all the faffing about...

 

1 Pair of reconditioned calipers

Warrantied and guaranteed to work. Car is back on the road, minimal fuss and safe.

 

Yep this is doing my head in, previous cars have been simple finding parts.

1 minute ago, Aj77 said:

 

Yep this is doing my head in, previous cars have been simple finding parts.

Been repairing Skodas for 25 years, not had a problem finding parts. Maybe that's just practise.

Does anyone know if it matters what way around these O seals go in, it can only be two different ways, I read there may be a lip on some of these seals that has to sit a certain way, i.e nearest the top or bottom?

Bump, should be getting parts tomorrow, does anyone know if it matters which way round these caliper piston seals ho in?

I was taught that the (not quite square) square seals went in with the thickest face facing the inside of the cylinder so when the piston was pushed forward towards the pads the thick/lip bit acted as a kind of return spring that helped to push/pull the piston back into the cylinder when the brake pedal was released. It also ensured a better seal round the piston.

Edited 21 December, 20205 yr by erindad

On 15/12/2020 at 08:11, Aj77 said:

So my rear piston won't wind in. I have the tool and had removed the caliper from the car.

 

Now the piston screws in fine when the O ring(or I think it's actually called a square seal even though it's round) seal is removed and I've cleaned the bore and groove where the seal sits thoroughly but no change. The piston still will not wind in at all the seal is causing to much resistance/friction.

 

I've ordered a new seal but the current seal looks ok it doesn't looked damaged or distorted.

 

But then these are fine fits so maybe a new seal will sort the problem, I'm kind of doubting it will but I can't see any other option and it's obviously the seal that's preventing the piston winding in.

 

Any ideas?

The rubber boot is age hardened and is therefore preventing your piston winding back, it happened to me. Remove the piston and try it without the boot and it will wind back with ease. A new repair kit will sort ir out

Rear Caliper Overhaul - When carrying out a full overhaul of the rear calipers, sometimes it is difficult to re-fit the internal spring assembly circlip, nay impossible. The metal fingers of the assemby can become weakened over time, allowing the assemble to expand slightly when removed from the caliper making it impossible to replace the assembly. Remedy-  the spring assemble must be compressed in a vice and the metal fingers need to tightened with a hammer and a punch, this will allow the spring assembly to be refitted.

12 hours ago, TonyOB said:

Rear Caliper Overhaul - When carrying out a full overhaul of the rear calipers, sometimes it is difficult to re-fit the internal spring assembly circlip, nay impossible. The metal fingers of the assemby can become weakened over time, allowing the assemble to expand slightly when removed from the caliper making it impossible to replace the assembly. Remedy-  the spring assemble must be compressed in a vice and the metal fingers need to tightened with a hammer and a punch, this will allow the spring assembly to be refitted.

 

I only replaced the O seal, that was what was preventing the piston winding back in, not the dust boot though I changed that also. I didn't want to mess around with replacing the spring etc.

 

The old seal didn't look damaged or warped but something must have happened(expanded or something) to it as when new seal was put in then the piston wound back in fine, although I did use the red grease on the new seal but never tried it with old seal though I'm pretty sure that wouldn't have made a difference with the old seal, I'll guess I'll never know but maybe I'll take it apart one time and find out because I'm curious to know the effect of the red grease, it's good stuff whatever it is.

It has the same effect as KY Jelly.

8 hours ago, Aj77 said:

 

I only replaced the O seal, that was what was preventing the piston winding back in, not the dust boot though I changed that also. I didn't want to mess around with replacing the spring etc.

 

The old seal didn't look damaged or warped but something must have happened(expanded or something) to it as when new seal was put in then the piston wound back in fine, although I did use the red grease on the new seal but never tried it with old seal though I'm pretty sure that wouldn't have made a difference with the old seal, I'll guess I'll never know but maybe I'll take it apart one time and find out because I'm curious to know the effect of the red grease, it's good stuff whatever it is.

No, you can't replace the springs, but you can replace the inner O Ring and the spline seal on the actuating rod. One of the inner spring assemblys went back ok, the other didn't, I couldn't get the circlip back in. I didn't give up until I discovered the reason, and fixed it.  Replacing the piston seal and boot is the same as using a repair kit. On my daughter's caliper it was the boot which was aged, 93000 miles. A new repair kit fixed it, but I had to make sure that the piston would wind back without any seizure before fitting the kit, which I did by winding the piston back with the boot removed

4 minutes ago, TonyOB said:

No, you can't replace the springs, but you can replace the inner O Ring and the spline seal on the actuating rod. One of the inner spring assemblys went back ok, the other didn't, I couldn't get the circlip back in. I didn't give up until I discovered the reason, and fixed it.  Replacing the piston seal and boot is the same as using a repair kit. On my daughter's caliper it was the boot which was aged, 93000 miles. A new repair kit fixed it, but I had to make sure that the piston would wind back without any seizure before fitting the kit, which I did by winding the piston back with the boot removed

 

Interesting, I can't imagine the boot, no matter how aged, preventing the piston sliding in are you sure it wasn't the O seal preventing it as in my case?

 

 

Yep I bought a repair kit on eBay for £5. The only question I couldn't answer was, does it matter which way the seal went in, it could only be one of two ways and there didn't seem any difference on either edge on the seal such as width or markings. I know this seal contracts and expands allowing the piston to move in and out so a point like this could be crucial. Maybe you know?

19 hours ago, Aj77 said:

 

Interesting, I can't imagine the boot, no matter how aged, preventing the piston sliding in are you sure it wasn't the O seal preventing it as in my case?

 

 

Yep I bought a repair kit on eBay for £5. The only question I couldn't answer was, does it matter which way the seal went in, it could only be one of two ways and there didn't seem any difference on either edge on the seal such as width or markings. I know this seal contracts and expands allowing the piston to move in and out so a point like this could be crucial. Maybe you know?

This brake overhaul was on our daughter's 2007 Octavia with 93000 miles, the rubber boots are locked into the caliper groove and the piston groove, the rubber was age hardened and would'nt compress and attempts to wind the piston back resulted in a bent wind back tool handle. With regard to the piston seal, the overhaul kit I got from EBay, the seal had a square profile so it could be fitted either way. If the seal has an angled profile then the thicker edge should face inwards.