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Post by tucksie on Nov 18, 2020 16:37:02 GMT
I have recently acquired a used oem master cylinder with a seized piston which appears to be seized fully in. Would someone be able to advise the best way of removing the piston please?
Many thanks.
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Post by buster on Nov 18, 2020 16:58:59 GMT
I'd say any method you use needs to be very gentle, its really important not to damage the bore otherwise it will be fit for the scrapheap. if you get a full rebuild kit (I'd recommend it if its seized) you should get a new piston/plunger in the kit so you could try lots of penetrating oil and see you can gently get it to twist free with suitable grips. they usually pop out on the spring when you take the (b*st*rd) circlip out. the other thing you could try (bad bodgers method) is reaching in through the banjo bolt hole and 'helping' the spring but very easy to damage the bore that way
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Post by tucksie on Nov 18, 2020 17:05:15 GMT
The added problem is there is no piston to grip as it appears to be stuck in. I have considered going in through the banjo bolt hole but it looks very easy to damage the housing as you say. Not sure if there is any choice but the banjo bolt hole route?
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Post by comstar on Nov 18, 2020 17:33:46 GMT
Perhaps an option would be to lie it on its side and soak it with some plus gas or similar for a few days?
This may free the piston Neil.
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Post by tucksie on Nov 18, 2020 17:41:55 GMT
Perhaps an option would be to lie it on its side and soak it with some plus gas or similar for a few days? This may free the piston Neil. yes I agree Nick, I think that’s a good idea. Not like there’s any urgency, only my own impatience  |
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Post by tucksie on Nov 19, 2020 11:50:39 GMT
The piston has finally been removed. Soaked in penetrating oil overnight and it eventually started to move. The next job is to remove the aged oil cup. Any advice regarding this please? It seems incredibly well set.
Thanks.
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Post by buster on Nov 19, 2020 12:43:04 GMT
I grabbed mine in a rubber jawed vice/clamp (superjaws, toolstation) and twisted the master cylinder itself, got it going back and forth a fraction first then eventually it came. took a fair bit of shifting though, I was cringing thinking I was going to break something
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Post by tucksie on Nov 19, 2020 13:21:58 GMT
I grabbed mine in a rubber jawed vice/clamp (superjaws, toolstation) and twisted the master cylinder itself, got it going back and forth a fraction first then eventually it came. took a fair bit of shifting though, I was cringing thinking I was going to break something Ok buster thanks. |
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Post by tucksie on Nov 19, 2020 16:42:50 GMT
The oil cup has now been successfully removed. Can now order the required parts for a re build |
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Post by duffer on Nov 19, 2020 16:47:04 GMT
I removed one using a hot air gun to soften the base up a bit. You get a little more give when it warms up. Gloves required ! Elf n safety y-know.
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Post by Chris P Duck on Nov 19, 2020 17:52:42 GMT
Once I sprayed amounts of the excellent toolstation brake cleaner in the reservoir and in the works.....the following day i found that the piston had completely freed up and was moving as smooth as silk. I sprayed silicon in the reservoir and flushed out the end of the cylinder through the banjo bolt hole with the same.....yours may get away with just a clean up.........what a pity the rubbers aren't available separately
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