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Post by chippie on May 10, 2023 16:05:30 GMT 1
Ordinarily I don’t have an issue when it comes to bleeding clutches or brakes…. But, having removed the front calipers, for some basic maintenance, on my 19 Passat est…I find that on bleeding I’m getting bubbles in the bleed tube on the o/s caliper…. I should add that the pistons have been fully retracted, so the chambers are empty of fluid…. I can get a hard pedal, but if I leave the nipple cracked, there are bubbles still appearing in the fluid…. I’ve gone thru 3/4 litre trying to sort this… Bubbles suggest an air source but where?….I’ve tried with the engine running and off…,no difference… Any suggestions? ( apart from torching it….  ) |
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Joepublic
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Posts: 3,951
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Post by Joepublic on May 10, 2023 17:28:48 GMT 1
Air entering via nipple threads - Venturi like a carb.
Grease yer nipples
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Post by sorted on May 10, 2023 17:56:13 GMT 1
Air entering via nipple threads - Venturi like a carb. Grease yer nipples +1 on this, been caught before. If the pedals hard and the brakes work, it’s fine! |
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Post by chippie on May 10, 2023 17:59:11 GMT 1
Air entering via nipple threads - Venturi like a carb. Grease yer nipples Ooooer...misses....  Yeah, thanks for that... the thought had crossed my mind.. I had the nipple out earlier and ran an M10 x 1 die down it to clean up the threads... so your thinking is probably right.. |
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Post by remmington on May 10, 2023 18:53:12 GMT 1
Air entering via nipple threads - Venturi like a carb. Grease yer nipplesYeah good simple basic advice... Well done Joepublic |
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Post by valhalla on May 10, 2023 22:51:57 GMT 1
Whenever I fit a new caliper, I remove the bleed-nipple and grease the thread with red-rubber grease, or something similar and thick. It has two jobs; first is (obviously) it helps prevent it seizing during the lifetime of that caliper, but secondly it overcomes the natural tendency of a new thread to pull air into the nipple.
It can also help if the hydraulic line needs a helping-hand to start flowing with a Mityvac vacuum-bleed, as I tend to let the bulk of the air come out first under gravity-bleeding (whilst I do something else) rather than fitting a pressure-bleeder straightaway. |
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Post by Rhubarb on May 11, 2023 9:16:10 GMT 1
I always grease my nipples  |
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Post by chippie on May 11, 2023 10:27:44 GMT 1
Ok, an update…, Both sides, nipples removed and cleaned up, (o/s I was a bit more meticulous…ran a die down the threads and put a tap down the caliper…) greased with Coppaslip and refitted. Both bled and now ok… Should be good for an MoT now..in 2 weeks time.. (I’m forever blowing back bubbles…….. . ) |
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