Technical brake caliper seal - replacement issue

[sprie]

I have an issue reinstalling replacement calliper seals.

I have removed callipers, given them a good clean.
I have wiped some brake fluid inside the calliper, put some brake fluid over both seals. I have reinserted inner seal. As a test, if i ignore the outer boot, i can insert the piston, but it is very tight and takes some real careful pushing to get it in.

According to the elearn:
"Before fitting the piston (1a) in the caliper casing, position the protective boot (1b) in the housing in the caliper casing. Insert the piston gradually, taking care not to damage to the protective boot or the seal.

I can understand that this makes sense. As you can see in the photo below, that's when the protective boot is not put in the calliper housing first, and there is no way you can get the rubber rim into the casing when the piston is in place.

So, the instruction from elearn makes sense, but when i followed the instruction (i.e. inner seal in first, outer protective boot next, then inserting piston), i was not able to get it nicely past the protective boot and then past the inner seal and I finished up trashing the protective boot seal.

Is there a knack or technique to get the piston in without damaging the seal.

 

[AsdaPricey]

I have an issue reinstalling replacement calliper seals.

I have removed callipers, given them a good clean.
I have wiped some brake fluid inside the calliper, put some brake fluid over both seals. I have reinserted inner seal. As a test, if i ignore the outer boot, i can insert the piston, but it is very tight and takes some real careful pushing to get it in.

According to the elearn:
"Before fitting the piston (1a) in the caliper casing, position the protective boot (1b) in the housing in the caliper casing. Insert the piston gradually, taking care not to damage to the protective boot or the seal.

I can understand that this makes sense. As you can see in the photo below, that's when the protective boot is not put in the calliper housing first, and there is no way you can get the rubber rim into the casing when the piston is in place.

So, the instruction from elearn makes sense, but when i followed the instruction (i.e. inner seal in first, outer protective boot next, then inserting piston), i was not able to get it nicely past the protective boot and then past the inner seal and I finished up trashing the protective boot seal.

Is there a knack or technique to get the piston in without damaging the seal.

I’ve always use brake grease so that all surfaces are as slippery as a slippery thing - makes it a chuff to hold but stops the chaffing you are experiencing causing the rubber boot to tear - out of interest, was the boot a new unit or the old one?

 

[Jockstrap]

Brake fluid is not a lubricant.

A smidgeon of silicone lube .

 

[sprie]

I’ve always use brake grease so that all surfaces are as slippery as a slippery thing - makes it a chuff to hold but stops the chaffing you are experiencing causing the rubber boot to tear - out of interest, was the boot a new unit or the old one?

It was a new one i trashed. I have to order parts to refresh the rear brakes, so i will order another set of seals for the front at the same time - no point getting this far if i just re-use an old seal.
I will use some silicon grease and see if that makes it easier.

 

[sprie]

I am so confused, I have done calliper seals on a couple of cars, and i can't remember any issue like this.

1) If i remove both seals, I can put the piston in the calliper and it moves up and down nicely, as you would expect. Nice and snug but moves easily.

2) If i just put the inner seal in, it is really difficult to get the piston in, using all my strength in my hands (don't want to force it with a tool) and once in, it is really tight. It does move in, but not easily. I have tried this with the new seal and the old seal, and they feel the same. I am using silicon grease to lubricate.

3) If i remove the inner seal and just put the protective boot seal in place in the calliper, I cannot get the piston in. I can feel it pushing against the inner ring of this seal, but not pushing past it. I think it is squeezing the inner ring against the wall of the calliper and it doesn't have a hope of getting past.


I have tried putting the piston in the freezer, no difference.

I have not tried either heating the calliper or freezing the calliper. It is a very hot day today, but i would have thought that would make it easier to get the piston in.

If i could get the protective boot seal sorted, i might then be able to get the piston past the inner seal.
I did wonder if i had a plastic tool with a delicate hook - so i squeeze it down between the piston and the seal, and try and pull/hook out the inner ring of the protective boot - but it would have to be soft to avoid damaging the seal.

any ideas or suggestions appreciated - spent hours on this and have 2 trashed new seals.

 

[AsdaPricey]

It’s difficult to assist over t’interweb.

Things to try/check…

Check the seals you’ve been supplied are the correct inner and outer diameter and profile for the calliper type & piston sizes.

Are you resembling with supply and bleed ports open so there’s no pressure.

Piston only in the freezer overnight not just a few hours

Honing the glaze from inside the caliper and check it’s not oval.

….with gritted teeth throw the towel in and obtain recon units with a 12month warranty

 

[bugsymike]

If piston and caliper in good condition then without seals the piston should slide in and out fairly easily without freezing or heating anything.
If seal kit is good quality correct parts then normally a good lube with brake grease or silicon grease and a bit of a wriggle it should slide in.
Maybe just be a bit more generous with the lube.

 

[AnthonyH]

A new caliper costs £40, or thereabouts. How much do the seals cost? Is it really worth reconditioning damaged calipers when you have to fight with them? Of course give it one more chance, then if no good buy another.

 

[Jockstrap]

A new caliper costs £40, or thereabouts. How much do the seals cost? Is it really worth reconditioning damaged calipers when you have to fight with them? Of course give it one more chance, then if no good buy another.

Where are you getting a new caliper for £40?
Sorry, you do say "thereabouts".

 

[AnthonyH]

Where are you getting a new caliper for £40?
Sorry, you do say "thereabouts".

Ebay has the cheapest at £30, no more than £100, depending on the model which i can't tell.

Seal kits are £10-£30. So depending on the model its possible to get a new caliper for the price of an expensive kit.

 

[bugsymike]

It is possible to get pattern aluminum brake calipers for around £30-£40, but they are a long way from Original Equipment Spec. more a case of, to get an Mot if you are selling the vehicle.

 

[AnthonyH]

It is possible to get pattern aluminum brake calipers for around £30-£40, but they are a long way from Original Equipment Spec. more a case of, to get an Mot if you are selling the vehicle.

I have one of the painted steel brake calipers, its not made of aluminium, just painted in that colour. Maybe its not an exact OEM part *shrug*. I'd rather buy that than be on my third set of seals for an old original caliper.

 

[bugsymike]

I have one of the painted steel brake calipers, its not made of aluminium, just painted in that colour. Maybe its not an exact OEM part *shrug*. I'd rather buy that than be on my third set of seals for an old original caliper.

Generally unless the outer dust cover has split letting water and dirt in so that the piston seizes, in my experience it is very rare for brake caliper seals to start leaking, unlike in the past brake wheel cylinders which we were often replacing.

 

[sprie]

I found a way to get the seals on.

Ignoring the elearn instructions, i put the protective boot seal on the piston first. I then put a cable tie over the end nearest the top (open end) of the piston, and slid the seal about 5/6 of the way down the piston - the cable tie holds it in place and stops it sliding any more.
I then had quite a bit of the bottom end of the seal free. I was able to get this into place in the calliper. Then i was able to insert the piston into the calliper, pushed/wiggled it part way in, removed the cable tie, and then slid the piston all the way in.

I think i may inspect the other calliper and leave it as-is unless i see any damage.