Brake caliper refurb

[123hotchef]

This has a familiar ring to it!

I usually play with older vehicles where parts are scarce and/or expensive, so always try refurbishing first.

All my boys have MX-5s and accumulated many spares from dead ones or ones they specifically bought to break.

At one point there where 6 pairs - 3 cars' worth - of calipers in my shed. I thought it would be a good plan to clean them all and other odd small parts and have a painting session.

Spent ages doing so and felt rather chuffed with the end result. Much like @armalites but beige.

No 2 son then pointed to the clearance page of a well known supplier - brand new ones were about £35 each!

£35 for a new caliper wow! mine are well over £100 refurb costs about £50 for both so quids in me thinks

 

[123hotchef]

Build a lamp box to control the current.

Old bulb holders with 5 or 21 W bulbs in. Re-purposed old switches. Then switch into circuit however many are needed to achieve the current you want.

Or is a small PSU just permanently put the requisite number of bulbs in series with your tank.

ha ha that is what I did last time @WorkshopChris told me to do that I am sure. I didnt make a box though just used bullet connectors soldered to the lamps with short fly leads

 

[rcx132]

I have found with heavily corroded calipers blasting doesn’t get in the pitting and they start rusting again. Last ones I did, blasted them first then stuck them in the electrolysis tank to highlight and neutralise the pitting then repeated the process until they were clean.

Blasting doesn't get into the smallest pits. It is much better than wire brushing which can just 'polish' the corrosion.

I don't have access to blasting so finish with Bilt Hamber.

If I had a blast cabinet I would:

1. high pressure water jet to remove loose muck (or dishwasher if brave, bachelor or have an old one in the workshop)
   
2. electrolysis
3. water jet to remove the loose black oxide and any loosened 'muck'
   
4. leave to dry
5. blast
6. paint

Do you mean how when you blast very pitted areas that rust spots quickly reappear? I always thought that was moisture in the compressor air getting stuck in the pits and making things re rust.

So people who have dealt with very rusty calipers, how did the cylinders look and did you have to repair the cylinders?

 

[123hotchef]

my cylinders were just fine they usually are as they have brake fluid still in them

cany you re hone them if they are rusty

 

[armalites]

I do it because I like doing it, and on the last two sets I've done I've used stainless pistons, I actually machined them up myself for one set as they weren't available.

If you look at Brakeparts.co.uk then it's scary how cheap an exchange caliper is, in many cases you can't even buy the pistons and seals as cheap as a caliper.

My blast cabinet is using chilled iron and I've never had calipers come out anything other then pristine even on calipers that have lots of complex shapes and heavily rusted. Nothing ever goes in my cabinet if it has grease/oil/damp so they are ready to paint immediately. I can leave bare calipers in there for a few days and they do not flash rust. That said it is big industrial unit fed by 130CFM compressor.

If I had to wash.pickle,blast and use an electrolysis tank I probably wouldn't even consider doing them.

 

[armalites]

So people who have dealt with very rusty calipers, how did the cylinders look and did you have to repair the cylinders?

I blast them all over and in the bores, with the seals out pistons are a easy sliding fit in the bore so no issues. Due to the shape of the bore the media tends to glance off and they generally come out smooth and clean. I have some small brake hones that I've used for a quick fix on a semi seized caliper still fitted to vehicle. Even if they look like they've been in the sea the bores tend to clean up fine.

I use silicon grease on the seals and the bores, you only need to a small dab on your finger, the pistons then slide in really nicely. The only downside is when the rubbers have been lubed the dust seal can be a pain, there are different variants and there is a trick to doing all of them.

I've seen stuff on the web where people are poking dust covers in with screwdrivers after the piston is fitted. What I tend to do is slide the dust cover on to the piston, extend it so it hangs below the piston then you can ease the cover into the groove , rotate it to seat it then slide the piston into the bore. This only works for piston which have bellows type dust shields fitted to individual pistons.

I've recently done some old Girling units that had 3 pistons, the half with two has a figure 8 dust boot covering two pistons and the only option is to fit the boot first and manipulate it to fit the pistons. Like all things first time your swear box will be full but it's actually really easy once you sorted a process that works for you.

 

[armalites]

Blasting doesn't get into the smallest pits. It is much better than wire brushing which can just 'polish' the corrosion.

I don't have access to blasting so finish with Bilt Hamber.

If I had a blast cabinet I would:

1. high pressure water jet to remove loose muck (or dishwasher if brave, bachelor or have an old one in the workshop)
   
2. electrolysis
3. water jet to remove the loose black oxide and any loosened 'muck'
   
4. leave to dry
5. blast
6. paint

If you have a blast cabinet set up with right media then there is absolutely no to do anything other than degrease,blast and paint.

 

[CompoSimmonite]

I need to refurbish the calipers on my Smart - they are too dear to replace with new. Intention is to blast and then fit new pistons but aren't sure what to paint the actual body. Is it worth using black stove paint (and then curing in the kitchen oven when wife is out ) as I have numerous cans from when on offer at Aldi.

 

[armalites]

Calipers for a Smart are about £60-£73 from brakeparts depending on model.

I use POR-15 caliper paint and I really like it. I'm not convinced the results would be so good if you didn't have access to blasting.

In fairness probably any metal paint is better than no paint and in normal road use the temperatures won't be that high. Even Hammerite would probably work just fine.

 

[123hotchef]

They are out the rust tank and been jet washed just debating weather to blast or not

 

[123hotchef]

Looking at them now they r dry I might pop them back in the tank

 

[Wallace]

They look better than some I have done. I would seal the bores up, give them a light blasting and another dunking to see how deep the pitting is.

 

[123hotchef]

They look better than some I have done. I would seal the bores up, give them a light blasting and another dunking to see how deep the pitting is.

Well the psu died again so I moved the pc one in 7.3amps bubbling away nicely now

 

[armalites]

Just blast them, you don't need to seal bores just blast them too.

I still struggling with the concept of spending time messing about with electrolysis tanks when 10 mins in the blast cabinet and they'd be like new and ready to paint. I've done quite a few and I've never been in a situation where blasting didn't get all the rust off.

 

[123hotchef]

Just blast them, you don't need to seal bores just blast them too.

I still struggling with the concept of spending time messing about with electrolysis tanks when 10 mins in the blast cabinet and they'd be like new and ready to paint. I've done quite a few and I've never been in a situation where blasting didn't get all the rust off.

Yes next set are getting blasted that's it

 

[Wallace]

Only reason I’ve been using electrolysis is the soda crystals are cheap otherwise I would use Deox-C which has given excellent results but is expensive. I’ve not had the time to experiment with citric acid in place of the Deox-C but that may happen shortly as I have another Chrysler engine to do which would give a back to back comparison against a previous engine done in 50 gallons of Deox-C.

 

[123hotchef]

now i have 7 amps going through them it looks to be shifting the rust a lot better i will give them 24 hours and take a look

 

[Wallace]

Also, I prefer not to blast the caliper bores or machined seal faces especially on alloy calipers, not poo pooing what any of you are doing just personal preference.

 

[123hotchef]

Only reason I’ve been using electrolysis is the soda crystals are cheap otherwise I would use Deox-C which has given excellent results but is expensive. I’ve not had the time to experiment with citric acid in place of the Deox-C but that may happen shortly as I have another Chrysler engine to do which would give a back to back comparison against a previous engine done in 50 gallons of Deox-C.

citric acid works well works even better if u can keep it warm/hot with a element

 

[brightspark]

I have found with heavily corroded calipers blasting doesn’t get in the pitting and they start rusting again. Last ones I did, blasted them first then stuck them in the electrolysis tank to highlight and neutralise the pitting then repeated the process until they were clean.

do them with kiln dried sand and there is no pitting obviously the stuff you were using was 2 course