Lotus Elan

Brake have been sitting since 1990 - replace or rebuild?

PostPost by: tdskip » Thu Jan 09, 2020 2:34 am

Thanks for all of the responses.

I was able to get all four pistons out but, man, that was work.

I used heat in the pistons and then cut a grove and used a chisle to rotate the pistons with compressed air being applied periodically.

Hope the rears are more cooperative but I doubt they will be.
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PostPost by: tdskip » Sun Feb 16, 2020 4:26 pm

Got all four rear pistons out without having to split the calipers.

How would you recommend;

1) making sure the piston bores are clean and ready for new rubber seals and pistons

2) cleaning and preparing the exterior caliper metal for paint? Can blast and the clean them extensively.

3) how best to clean the interior fluid passage ways?

Hope everyone is having a good weekend. Thanks!
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PostPost by: nmauduit » Sun Feb 16, 2020 4:56 pm

1) it's the rubber seals that do all the hard work, but it's better to reasonably clean the whole inside. I would get new pistons if they are not in top condition (esp. the steel / chromed ones, which tend to lose chips with conventional brake fluid that has absobed water, then the chip may score the rubber and create a leak)

2) I would not blast with media that can get stuck and create problem later (sand, iron grit etc) - some people use soda (water soluble for an easy clean), some organic media (wall nut shell etc)... depending on the condition and what you expect of the end result, a good clean with degreaser and brush may give you a good start. ps: I usually don't paint my calipers (as per original)

3) when the pistons are removed, you'll see the bore that connect inlets or purge to it (if need be using a flash light) : after a good soak in degreaser etc one can use compressed air to clean and assess result.

ps: I use dot5 (hygrophobic silicone) on vintage vehicles and apply some after rebuild; if to be stored and eventually used with regular brake fluid, applying brake grease to avoid oxidation may be advisable

pps: if in doubt, it is not difficult to split the 2 halves for better access - but make sure you can source the proper square section rubber gasket before.
Last edited by nmauduit on Mon Feb 17, 2020 9:56 am, edited 1 time in total.
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PostPost by: Donels » Sun Feb 16, 2020 6:09 pm

I lightly blasted mine with crushed glass while still assembled, then split the callers and throughly cleaned with methylated spirit. Painted the outside with a suitable paint and reassembled with new pistons and seals. I could have zinc plated but painting is more controlled.
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PostPost by: tdskip » Wed Feb 19, 2020 12:49 am

Question gentlemen - how prefect does the bore where the rubber seal and piston reside need to be?

I would imagine that putting on the sides would be more problematic than at the bottom of the bpre,yes?

Pistons would be new of course...

Thanks!
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PostPost by: nmauduit » Wed Feb 19, 2020 1:37 pm

Reasonably clean and smooth would do for me, as there is a bit of clearance between the bore and the piston for it to move without touching the caliper: no need to replace everything with new at the slightest discoloration...
The slot where the rubber seal should be also reasonably clean so that the the seal can seat properly.

If in doubt pressing hard on the pedal for a while with a piece of wood between the pads before completing the reassembly before close scrutiny for leaks would give confidence that the overhaul is satisfactory - then a follow up of brake fluid level and potential leaks after a bit of use to make sure, before reverting to regular maintenance schedule.
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PostPost by: tdskip » Wed Feb 19, 2020 2:56 pm

Thank you for the follow on reply, very helpful.
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