Popular Post Hunter Posted October 20, 2020 Popular Post Share Posted October 20, 2020 (The name of my new band) This post is a mix of post-stress relief, and perhaps food for thought. The situation My Cayman was due a brake fluid change, and some pipes were badly corroded so I booked to get them changed as well: Full credit to the specialist: they took me aside ahead of time and said that there was a worst case scenario in which the bill would be pretty large. In a portion of these cars ("maybe one in twenty"), the various fitting points on a caliper can corrode to the point of seizure and snapping upon attempted removal, especially where they haven't been removed in a long time. Part of the cause is poor material choice by Porsche: aluminium calipers with mild steel inserts, resulting in galvanic corrosion. The pictured line has been an advisory on my car for 3 consecutive MOTs. The previous owner was otherwise reliable when keeping on top of repairs, so with hindsight I see that this was an iceberg just waiting to be struck. Friday I dropped the car off Thursday evening, still innocently hopeful of an uneventful service. I was wall to wall with work Friday, so not once did I look at my phone until about 6pm. Turns out, the specialist had had a hectic day. The car had been on stands since the morning, when they discovered that corrosion was indeed a problem. Generous quantities of penetrating oil and heat cycling allowed a couple of fittings to be freed, but by 3PM several had already snapped and almost all are threatening to snap. In total, there are 5 insertion points per caliper: 2 bleed nipples (inner & outer) 2 link pipe fittings 1 brake supply fitting By end of day, they had successfully removed all outer bleed nipples and some pipe fittings. Only the outer bleed nipples: that's important, because it suggests the specialist used by the previous owner for 6+ years did a half-ass job when changing brake fluid, only utilising the outer nipple. The really bad bit? The brake fluid which has been sitting in the other side of the caliper has therefore not been changed in the better part of a decade. Brake fluid is hygroscopic, so imagine what a decade of water absorption means for mild steel? Monday Over the weekend, the calipers were stripped from the car and taken to a local engineer. The fittings which had snapped (the majority, it turns out) or seriously corroded were machined and stainless steel inserts with stainless steel fittings were put in place. In theory, stainless fittings will avoid future dramas. I had requested braided stainless steel hoses be put on too (which, by that point, was a drop in the bucket). Picked up Monday evening after a successful MOT. For the sins of another specialist/previous owner, these guys put in more work than could have been reflected by the bill, and I feel pretty well looked after. The brakes are rock solid too, and now I have one less worry on my mind (besides the perpetual risk of catastrophic engine failure). Conclusion The obvious stuff: if there's a repeated advisory on a car you're buying, be skeptical. It might be a big bill. The less obvious: if you're having a brake fluid change, consider asking your garage to check corrosion on all the caliper fittings. You could also prod your garage to see if they use both inner and outer bleed nipples. Apparently, even some specialists cut corners. That said, if a fluid change/brake bleed is all you need (i.e. the pipes/hoses do not need changing), you can get away with leaving corroded fittings in place... until said pipes/hoses do need changing. Finally, if anybody needs a recommendation for an indy in the south, I've now got one for you. Give me a message. 2 Link to comment Share on other sites More sharing options...
alexjc4 Posted October 20, 2020 Share Posted October 20, 2020 I feel your pain. I have been afflicted by this complaint many times over the years. In just replaced all eight bleeders on mine last week, with a great deal of "ginger carefulling". When I bled the brakes prepping for Silverstone in August and noticed a couple were very tight so I wanted to address it before disaster stuck. I once snapped a bleeder off in the pits at Spa... on someone else's car.. less said the better. Link to comment Share on other sites More sharing options...
Aaron Posted October 20, 2020 Share Posted October 20, 2020 I bleed the brakes and change the oil and filter in between the two year services myself. Just because you need the stamps to maintain value and you expect it to be done properly, doesn't necessarily mean going that extra mile isn't worth it. When I bleed the brakes, I remove each nipple and clean it up. Never had an issue with any corrosion myself, but there has been a significant amount of effort to keep moving the fittings. The inner nipple never being used is unforgivable. There's no worthwhile excuse to justify it... How much was the bill for all of this, if I may? I'm intrigued. Link to comment Share on other sites More sharing options...
Hunter Posted October 20, 2020 Author Share Posted October 20, 2020 29 minutes ago, Aaron said: I bleed the brakes and change the oil and filter in between the two year services myself. Just because you need the stamps to maintain value and you expect it to be done properly, doesn't necessarily mean going that extra mile isn't worth it. When I bleed the brakes, I remove each nipple and clean it up. Never had an issue with any corrosion myself, but there has been a significant amount of effort to keep moving the fittings. The inner nipple never being used is unforgivable. There's no worthwhile excuse to justify it... How much was the bill for all of this, if I may? I'm intrigued. Seems super sensible. I was on the fence about tackling the fluid change myself, would've tried if I didn't need the pipes doing. Is it particularly difficult? The "label" price was around £1700-2000 - unclear because I think the machinist did more than he was actually paid for. Link to comment Share on other sites More sharing options...
Aaron Posted October 21, 2020 Share Posted October 21, 2020 1 hour ago, Hunter said: Seems super sensible. I was on the fence about tackling the fluid change myself, would've tried if I didn't need the pipes doing. Is it particularly difficult? The "label" price was around £1700-2000 - unclear because I think the machinist did more than he was actually paid for. Bleeding is pretty easy. I use a vacuum pump and clear hose: Attach vacuum pump to nipple Crack open nipple Pull vacuum until fluid is clear Close nipple whilst holding vacuum Rinse and repeat for all 4 corners Drive car, activate ABS a few times Repeat above If you have access to Durametric or PIWIS, you can activate the ABS pump to bleed instead. Looking back at your picture, your caliper doesn't look in great shape in itself. Have they really lost that much of their colour and finish around the nipple? Link to comment Share on other sites More sharing options...
Hunter Posted October 21, 2020 Author Share Posted October 21, 2020 9 hours ago, Aaron said: Bleeding is pretty easy. I use a vacuum pump and clear hose: Attach vacuum pump to nipple Crack open nipple Pull vacuum until fluid is clear Close nipple whilst holding vacuum Rinse and repeat for all 4 corners Drive car, activate ABS a few times Repeat above If you have access to Durametric or PIWIS, you can activate the ABS pump to bleed instead. Looking back at your picture, your caliper doesn't look in great shape in itself. Have they really lost that much of their colour and finish around the nipple? Sadly no Durametric/PIWIS, but that does sound fairly straightforward (with a little equipment). The caliper is generally okay. A few little chips in the paint here and there (most of the rear is just dusty), but yes a fair bit of corrosion around the nipples. Any DIY suggestions on fixing them up? Can't bear another bill right now. Link to comment Share on other sites More sharing options...
Woodhouse Posted October 21, 2020 Share Posted October 21, 2020 I can personally attest to the fact that some Official Porsche Centres only bleed through one nipple too. I wonder how many people religiously stick to OPC servicing in the mistaken belief they are getting the gold standard? Link to comment Share on other sites More sharing options...
Mavrik Posted November 14, 2020 Share Posted November 14, 2020 (edited) I recently had a similar scenario!! ... & another reason why I do ALL my own servicing/repairs!! I fitted SS braided lines & as eluded to the caliper to flexi hose unions all seized (I posted about this previously) I had to make new hardlines myself from Kunifer but I always use Silicone grease on the threads/fittings to inhibit galvanic corrosion... Edited November 14, 2020 by Mavrik 1 Link to comment Share on other sites More sharing options...
Maxheadroom Posted November 14, 2020 Share Posted November 14, 2020 54 minutes ago, Mavrik said: I recently had a similar scenario!! ... & another reason why I do ALL my own servicing/repairs!! I fitted SS braided lines & as eluded to the caliper to flexi hose unions all seized (I posted about this previously) I had to make new hardlines myself from Kunifer but I always use Silicone grease on the threads/fittings to inhibit galvanic corrosion... Now that is a good tip on using silicon grease on fittings @Mavrik, never thought about this, just in time for rebuild of my last two callipers, bit too late for my two offside callipers Dam ! This looks like a good excuse for getting me out of decorating spare bedroom as we all know it’s more important to spend as much time as possible in a cold damp garage during winter doing blokes stuff 🤭 1 Link to comment Share on other sites More sharing options...
Mavrik Posted November 15, 2020 Share Posted November 15, 2020 (edited) Yeah, Silicone grease (or dielectric grease) is a good corrosion inhibitor & helps with this common issue of galvanic corrosion... I've used it for donkeys! I also ride Superbikes & I use ACF50 corrosion inhibitor & every year when I service my CS I jet wash the arches & suspension components etc & douse with a generous coating... It was originally developed for the aerospace industry 😉 https://en.wikipedia.org/wiki/Silicone_grease http://www.acf-50.co.uk/ Edited November 15, 2020 by Mavrik Link to comment Share on other sites More sharing options...
andygo Posted November 15, 2020 Share Posted November 15, 2020 3 hours ago, Mavrik said: Yeah, Silicone grease (or dielectric grease) is a good corrosion inhibitor & helps with this common issue of galvanic corrosion... I've used it for donkeys! I also ride Superbikes & I use ACF50 corrosion inhibitor & every year when I service my CS I jet wash the arches & suspension components etc & douse with a generous coating... It was originally developed for the aerospace industry 😉 https://en.wikipedia.org/wiki/Silicone_grease http://www.acf-50.co.uk/ That corrosion block inhibitor looks as though it was made for the front crossover pipework! Link to comment Share on other sites More sharing options...
Mavrik Posted November 16, 2020 Share Posted November 16, 2020 @andygo It's mega stuff & protects a mulitude of machinery, cars & bikes etc. I've been using it for quite a few years & does what it says on the tin 😂 Link to comment Share on other sites More sharing options...
Andyoz Posted November 17, 2020 Share Posted November 17, 2020 (edited) Why I do as much work on my Cayman as I can. Putting a Porsche mechanic on a timer can be dangerous...these cars throw up 'issues' and some take time to work through. Edited November 17, 2020 by Andyoz Link to comment Share on other sites More sharing options...
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