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Coffin arms and tuning forks - replacement

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This is a bit of a summary of a job that I have now finished and thought that I would write-up for the sake of other forum users; the replacement of the coffin arms and tuning forks on my 987.1 Cayman, as well as ARB drop links and front suspension top mounts. The work will almost certainly be the same for 987.2 cars and Boxsters (and probably for 981's as well). This has also been posted on Boxa.net but is relevant to Caymans as well; I hope that cross-posting is OK. 


My 987 has ticked over 110k miles and the suspension was a bit klunky; it knocked and I had changed a few parts over the last couple of years, but now was time to bite the bullet and fully overhaul the thing. I have always been more into delicacy of handling in my cars rather than outright power so gaining some extra precision appealed. I'll not write the whole job up here as it's not technically that difficult and someone who is able to do it doesn't need to have the detail spelt out. However some things that I wished I knew before I started are as follows; 


- You will need a good collection of 18mm, 19mm, 20mm and 21mm spanners and sockets to do the job. Yes, 21mm. No, I know it's not a common size and you may need to buy some specially if they aren't in your socket set. You will also need some large hammers, pry bars, a Dremel (or similar) and a reciprocating saw with some metal blades. 


- ARB drop links are worth replacing if knocking starts. These are steel pins in an alloy casting and often seize due to electrolytic corrosion. As has been stated on here many times, the best bet to get them out is to cut off the ball joint from the head of the pin with an angle grinder with a thin blade, then apply a 19mm socket to the hex head that remains. Turn this with a long breaker bar (it will be very stiff at first) until it is loose-ish and hit hard on the other end of the pin with a large hammer while twisting it. It will eventually yield and reluctantly come out but it is a fight. If it is really stiff then applying heat helps as does drilling a hole axially along the pin, but make sure that you don't wander with the drill and end up in the alloy casting of the upright. Apply lots of copper grease to the new pin before inserting it. 


- Coffin arms are a pig to get off as the hinge bolt at their base corrodes in the same way as the pin in the ARB drop links (when will Porsche learn that steel fasteners through alloy castings WILL cause problems?) A reciprocating saw is an essential tool; I ended up cutting all four arms to get access to the hinge bolts and then using the reciprocating saw to cut each hinge holt, once at each side of the coffin arm. Access to do this is difficult but not impossible. It is possible to get an angle grinder in for the front coffin arms but not for the rears; the angle grinder cuts more quickly than the reciprocating saw but you need to take care not to cut into the subframe below the coffin arm, which would be bad news. 


- The rear coffin arms are held on with special bolts with eccentric washers that allow adjusting the rear camber. Buy new bolts and replace them - it's not worth the grief of trying to get them out. (Note that you can salvage the eccentric washers and re-use them and save some pennies. Those bolts and washers are indecently expensive to replace). This aside, the rears are a little easier than the fronts as there is better access around the bits that need cutting. 


- If you aren't replacing the rear dampers then you won't need to remove the interior trim around the top of them, but dropping the struts does make access a lot easier. Getting this trim out is far more involved on the Cayman than it should be and there are various YouTube videos about it. Here's one: 



- When cutting through the hinge bolts for the front coffin arms then beware of the coolant pipes that run right behind them; your reciprocating saw will quite quickly punch a hole in those pipes (don't ask me how I know this. I patched the hole with some high-modulus sealant, a bit of inner tube rubber and a jubilee clip and am keeping my fingers crossed.) 


- You will need to cut some other nuts off in the process; the nut on the top of the lower ball joint at each corner, most likely. A Dremel is your friend here. Have some good cutting disks to hand as you will need them. It may be easier on the Boxster.


- Same goes for the top nuts on the front dampers. It is quite possible to cut the top nut off a damper with a Dremel without damaging the damper if you are careful. You will need spring compressors (for obvious reasons). You will need to replace these nuts but your friendly local fasteners merchant will supply them for pennies. 


- You DO need to take the front damper assemblies out as you DO want to remove the top bearings and clean them up. They are supposedly sealed but one of mine had clearly leaked and rusted slightly. I didn't have a spare so cleaned it out as best I could and rubbed down the bearing faces and re-assembled with a lot of grease. When I had finished then it wasn't quite as smooth-running as the one that hadn't leaked but there wasn't much in it. (Interestingly, the components on the near side of the car were noticeably more corroded than those on the off side. I guess it makes sense when you think about it.)


- Controversially I didn't replace the dampers or springs on mine. Springs don't lose much functionality with age and I reckon that tales of them going soft by 100,000 miles are hype. The dampers are a different matter; my 987 has PASM and the price of four new PASM dampers was simply stupid (around £800/corner. Yes, bonkers.) I took my car apart and closely inspected the existing dampers and they seemed OK; they were still very stiff to compress and showed no sign of wear, so I re-used them. How much performance have I lost by doing this? I don't know, but I suspect very little. For reference, the PASM dampers are made by Bilstein and the standard ones are NOT re-buildable (despite what you may read on the internet) as they are single tube models with crimped ends. However Bilstein make excellent quality kit which lasts very well for many thousands of miles so I'm happy to keep the existing ones on my car and over £3000 in my pocket. 


- I hit a major snag with the bolt that holds the front bush on one of the rear tuning forks in place. This runs vertically up just behind the side vent, though the tuning fork bush and into a captive nut deep in the bodywork. The captive nut is held captive with a mild steel clip, which failed on the offside and allowed the nut to turn and thus prevented the bolt from coming out. Access to the bolt head is extremely limited and is in the middle of a nest of air con pipes. If this happens to you then don't panic; you can remove the engine bay cooling fan from above and drop it out downwards, which gives you access to the offending nut and clip. I imagine it's the same on the nearside although you will have to remove the intake box in that case. The fronts probably work in a similar way. However this is a MAJOR headache and best avoided if you can (some release spray on the nut to help it come loose would be a good thing to do. You can access this from underneath but it's a fiddle and you need to be right under the car to do so.) 


- I replaced my arms with the polybushed ones from Spyder Performance. These seemed to be well enough made and were well-priced, although they were notably lighter in design than the original ones (compare how the clip-on air ducts are the front fit for reference.) I had slight reservations about fitting polybushed items to a daily driver but it doesn't seem to have affected NVH much, if at all. 


- You NEED to have an alignment done after the work is complete and I had my car aligned yesterday by Cotswold Porsche. They were extremely helpful and very well priced indeed. I met Chris and Lee, both of whom were excellent and whom I would happily recommend. They both seemed to know their Porsches very well, particularly Lee who has had some dalliance in the world of transaxles - as have I! Thanks to the pair of them for their help. 


- For reference, the job took me about 3 days working fairly full-on. I have a garage and air tools but was working on stands as I don't have a pit or a hoist. This isn't a job to be attempted in a rush but wasn't particularly difficult. A lot of the time was spent cutting and grinding things, which is tiresome; if you had a car that came apart easily then you could halve this time pretty readily. 

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That's excellent. I recently had my front end rebuilt (everything apart from shocks/dampers).


I decided to hand it to Indie as I don't have a lift and the time really. As you found, there's a few showstoppers and it would have taken me weeks off and on as I'd have to add to my tools. 


Out of interest, how was your steering rack? When they took the boots off mine, there was a good bit of fluid in one and it did correlate with me having to top up the fluid reservoir slightly so I wasn't that surprised really. I got it reconditioned for £400 versus £1500 new which is silly price when it's just the seals that go. My cars on 58k miles.

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20 hours ago, Andyoz said:

Out of interest, how was your steering rack? When they took the boots off mine, there was a good bit of fluid in one and it did correlate with me having to top up the fluid reservoir slightly so I wasn't that surprised really. I got it reconditioned for £400 versus £1500 new which is silly price when it's just the seals that go. My cars on 58k miles.


Interesting Q: I've read a few comments about failing steering racks of late (although they could all have been from the same person on different forums!) 


I'm not aware that there is any problem with mine; it doesn't use fluid and when I changed the tie rods a couple of years ago there was nothing untoward in the boots. Do you have any idea why yours failed (had someone put the wrong fluid in or something)? 

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Yes, if you see any change in fluid level then that's the hint I guess. It's just one of those things, it's only the seals that go and mine was sent to this crew who are well regarded.




Mine was only using very little as when I bought it in Sept it was slightly low. I topped it up and it barely used any since so the rate of leak was slow and probably fine for ages if they hadn't discovered the fluid in the boot.  Whilst they were at the front end, easy to get subframe dropped and do it as well as coolant pipes. It needed an alignment anyway after suspension work so no point going in there later and triggering another alignment.  Coolant pipes only cost £350 doing it now compared to say £600 as a solo job?

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