Variocam Sliders without Engine Removal - Here we go!

Hi All, I do all the maintenance on my 996 myself and ever since I have owned the car - over 6 years now! - I have been finding small brown plastic shavings in the oil filter. Consensus is that this is variocam slider material wearing away - Not something you want to continue indefinitely. What is Variocam? The variocam system is a simple solenoid controlled on/off inlet camshaft advance mechanism fitted to early "5-chain" 996 and 986s alongside some earlier transaxle Porsches. It works by altering the phasing of the inlet camshaft relative to the fixed exhaust camshaft. To do this two plastic sliders are required which take up the excess length in the cam chain. It is these sliders which wear, causing plastic material to shed off and collect in the oil filter. The status of your vairocam sliders condition is monitored by the car via 'camshaft deviation' which will cause a check engine light at +/-8 degrees or so. As these wear away the chances of them breaking increases and should they break the engine is likely toast. You can see these at top left and bottom right of this image: This pic gives a better idea of how they work: Why is doing it in the car a big deal? As these engines are shared with the Boxster platform replacing the variocam sliders with the engine in the car is a major job but isn't unheard of. There are various threads you can follow that detail the steps to take, but fundamentally it is doable. This is not the case with the 996 with the engine placement in the rear of the car. However, there are discussions online saying it is doable alongside some slightly shady Youtube vids which don't really explain what to do. I've decided to take the bull by the horns are try it myself to see if it can be done. What makes you think you can do this anyway? ELA (of Project Leichtbau fame) has a guide here for replacing the tappets on the left bank (cyl. 1-3) of the engine: https://911uk.com/porsche/clr-project-leichtbau-adding-lightness-to-the-tune-of-250kg.79527/post-1102230. Which is the same procedure for replacing the variocam sliders. He makes it look fairly easy here and it's a big job but there is nothing here that is completely impossible. The left bank of the engine is the easier side to do as when the engine is timed there is ample clearance to fit the rather bulky timing tool to the non-flywheel side of the engine. The issue is the right bank (cyl. 4-6) where due to the rather odd shared cylinder head arrangement on our engines the timing tool needs to be fitted to the flywheel side of the engine. This Is tricky as the right rear subframe is in the way of the timing tool. So what if we... just removed the rear subframe? There's only one way to find out! Enough talking get on with it: BANK 1 - Cylinders 1-3 First step is to remove all this stuff: If this gives you the heebie-jeebies this job probably isn't for you. Note that I have previously replaced the exhaust manifolds on this car so didn't have to worry too much about the manifold bolts - except one of my stainless fasteners snapped which is a huge pain and unwanted side-quest. Anyway will have to come back to that particular nightmare. Only part of this job I hadn't done before was removing the exhaust brackets. This was a bit of a pain the in arse as the top most bolts are tricky to reach but not the end of the world. This is what you're faced with. Next step is to give the whole area a scrub down to remove 26 odd years of oil leaks and grime buildup. I decided to tackle the bank 1 (cyl. 1-3) first as thanks to ELA's documentation (above) I knew this was doable. The only deviation from the workshop manual was limited access to the scavage pump bolts which meant the pump needed to come off with the cam cover not separately as described in the manual. A minor concern. Need to lock timing with the appropriate dowel with the exhaust cam oriented like so. the green cam cover caps need to be removed to view the cams. Very dirty in this pic! Inlet cam slot needs to be pointed away from flywheel on bank 1 Cleaner head! The cam hold-down tool needs to be fitted using a spare M8 fastener (you will have plenty at this point - I used one from the exhaust brackets). Next it is just a question of undoing the (many!) 10mm bolts. Note that the cam cover bolts are longer than the bolts which hold down the variocam solenoid seal (x2) and oil scavenge pump (x4). Take note of the scavenge pump orientation - "1-3" should be facing the flywheel. Note that the scavenge pump can be rotated slightly to remove the fixings. Then it's a question of putting on your big boy pants and carefully levering off the cam cover. This will be adhered to the cylinder head due to the sealant used at the factory. This has started to get a bit serious! The next steps are pretty much per the workshop manual - undo chain chain tensioner, cam sprocket bolts, cable tie chain to sprocket, undo remaining cam caps (DO NOT MIX THESE UP) and carefully remove the cams. I used a drip tray lined with paper towels to place the cams into. Once the cams are removed you can refit the cam cover which limits contamination of the inside of the engine while you work on the cams. Replacing the variocam pads on the workbench is a pretty simple job. I didn't use the specific Porsche tool to compress the tensioner, I found that a hand clamp did an excellent job then I just used wire to hold the tensioner in the compressed state. I did try using a zip tie but you need thin ones to fit in the hole and they broke very easily. The pads were extremely badly worn - most likely this wear was due to an incorrectly installed o-ring from the factory (see pic - it was stuck in this shape after 25+ years of being baked in the engine!) which meant that sufficient oil wasn't getting on the cam chain. Very glad to have changed these! Note that the whole slider is worn - the centre chain rollers were dragging on the surface of the slider. I found reinstalling the vaiocam unit was easy if a) it was fully compressed and b) slightly counter-intuitively the solenoid was passed through the cam chain first. Retiming the cams is covered in detail in the workshop manual and I would encourage anyone attempting this job to read and re-read this document. At a high level align the marks on the cams with the lighter coloured links on the cam chain, ensure this is all pointed away from the cylinder head and refit using cam hold down tools. once cams are installed cut the wire holding the tensioner compressed and refit the cam cover. Next is bank 4-6!

well done sir. Big boy pants and brave pills obviously worked.

I did this job last year it’s not too bad really once you get over the fear, shame about the snapped stud is it an end one? My cam pads were nearly worn through about to snap , what’s the mileage on yours? Great write up btw and well done mate

Thanks guys the exciting bit is the right bank which I have now completed - not too bad really, will add the write up this evening.

With bank 1 successfully replaced I moved on to bank 2. This is the troublesome side. The oil pump is easier to access unlike bank 1, but the timing tool needs to fit on the back of the head by the flywheel and this is hard up against a chassis rail and rear subframe. I've never seen this documented so I was going in blind here, but the first step is to remove the rear subframe to see if there was any chance of the timing tool fitting. Removing the rear subframe is not that common but it's not too bad of a job, I didn't want to wrestle with the various tapered fitting (coffin arms and toe links) so elected to leave those attached and remove those suspension arms from the subframe instead. Luckily all the eccentric bolts came out easily, although the bolts were bloody tight! big old breaker bar definitely needed here. I had in the past replaced the coffin arms and tuning forks but had never removed the top 'dog bone links but they all came out fine. Result was that even with the subframe removed the timing tool doesn't fit, but only just. I had expected this might be the case, so I opted to drop the right side of the engine slightly, and remove some material from the timing tool itself to allow fitment. I used some threaded m10 studding to drop the engine on the existing engine mounts which worked very nicely. To fit the timing tool you need to turn the engine over one full revolution at the crank and lock the crank again, you can check timing by looking at the inlet cam position in the same way as bank 1. result - with a small 25-30mm drop the timing tool fitted very nicely enabling the engine to be properly timed. With that excellent news that I hadn't completely wasted my time stripping down the right rear suspension I cracked on with the next step which was removing the A/C compressor. This is required to access the timing chain tensioner on bank 2. This is a bit of a pain as the rear most 13mm bolt is pretty well hidden, but removing the PS fluid reservoir, throttle body and primary plenum tube gives enough space to get a 13mm spanner on to the bolt. Access to the 32mm hex on the timing chain tensioner is not great and it is bloody tight so that's a bit tricky. Then it's a copy paste from the other bank. fit the hold-down tool to the cams before removing the cam cover and oil scavenge pump: Again big boy pants fully installed/brave pills taken: This time interestingly the O-ring was in the proper position and variocam pad wear was much reduced, albeit still not great: You can see that the centre of the chain links haven't started dragging on the centre of the slider on the right yet as the main wear lines haven't got deep enough. Anyway, bin those off and fit new pads: Then it's simply a question of timing the engine and bolting everything back up!

In terms of replacement parts I needed the following: 2x sets of variocam pads 2x variocam o-rings 2x variocam solenoid seals 2x timing chain tensioner sealing washer 2x timing chain tensioner O-ring 2x scavenge pump O-rings 8x scavenge pump bolts - Porsche recommend replacing these as the threaded holes are through holes into the engine so need to be oil-tight. The problem with this is that the replacement bolts (which I bought for £7 each!) are torx heads which are a pain to fit to the left bank. So I carefully cleaned the existing bolts and blobbed on some thread sealant. 6x green cylinder head plugs 6x upper spark plug tube O-rings 6x lower spark plug tube O-rings I also took the opportunity to replace the spark plug tube O-rings - I replaced these five or so years ago and they were leaking pretty badly into the spark plug tubes. When I tried to remove them they had gone hard so definitely an excellent 'while you're in there'. I used loctite 5900 to seal the cam covers per Porsche's recommendation. On top of the above the manifold exhaust gaskets will need changing. Additionally I'll do a oil and filter change after 500 miles or so - little bits of flaking sealant etc will be sloshing around in the car for a while so that will be very worthwhile.

A great write up and quite relevant to what I have unfortunately discovered in my filter this week!

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Mileage is 85k I think, so pretty low given that plenty of 100k mile + cars don't seem to have had their sliders replaced. Although the dodgy o-ring is possibly a smoking gun as to why I was seeing the brown plastic flakes. my cam deviation was around 7 degrees which is right on the cusp of a check engine light I believe, and as this is a very early engine it only has a single cam sensor so there was no monitoring of the 'other' cam. I'm not sure if the single sensor is monitoring bank 1 or 2 though, I think it's bank 1 (which was the worst worn one).

I'm hoping to get the engine fired up this weekend if I can get the stupid exhaust manifold bolt drilled out. Timing the engine hasn't been too tricky with the proper tools, although I don't want to count my chickens quite yet. The issue with timing (once there is space to fit the timing tool on bank 2) is that you can't remove the scavenge pump from the head with the cam cover fitted to adjust exhaust cam sprocket bolts on bank 1. I got around this by refitting the cam covers (with some assembly lube) without sealant or oil pump fitted on both sides which let me time the engine properly as I could access the bolts all round to tweak the camshaft position. You also need to loosen the shear plate on the rear of the engine to fit the timing tool to bank 1 but this is simple enough. You could just fit the cam hold down clamps on bank 1 but I wasn't happy with leaving the engine exposed to the elements for any longer than strictly necessary while faffing around with the timing. Once everything is timed and you've spun the engine over a few times by hand to check the timing still lines up you can remove and seal up the cam covers + oil scavenge pumps. Removing the old sealant is easiest I found with the cams removed as it flakes away pretty easily. clearly you need to do some additional cleaning with brake cleaner before finally sealing it up. Definitely worth doing another torque check at this point too.

Very valuable write up for future work as these cars will all need this sort of attention and £200+/hr for a Porsche tech means DIY is the only valid option (for me at least) . Regarding O rings, I don't think I've ever bought one from Porsche mainly due to cost, they're all very easy to obtain from other suppliers , sizes of the OEM are usually all readily available from D911. We should make a list actually , I've just done some on my Turbo coolant system.

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Thanks hopefully it will be useful for people in future! Funnily enough I was looking for some o-rings (for the chain tensioners I think) which were in a very funny size which turned out to be imperial ones. There are plenty of places to buy them but I couldn'f find them in HNBR so i just went with Porsche in the end.

Great write up Thanks for taking the time to post it up. What did you use to read cam diviation ?

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My Autel AP200 reads cam deviation amongst other bits n bobs, would highly recommend.

Excellent work, thanks for the write up, this will be invaluable to so many as brave as you.

Thanks for the likes and kind words all. Was too rainy yesterday to get much done so ended up tidying up the garage. Took some better pics of the stars of the show... Bank 1 sliders - definitely the worst, getting very thin towards the centre, no doubt due to the mis-installed o-ring. Bank 2 sliders, definitely better but not great. Probably more typical of an 85k mile car.

Here’s a picture of mine these had done 117 k