What''s this? (On the underside of the M96 engine)

At the risk of looking a bit foolish, can anyone tell me what this 'drain plug' 'looking like' big nut is for? ..... had the car (C2, 996, 2003) on a ramp yesterday for half an hour (thanks Neil), for bit of a general inspection/ minor maintenance and noticed a bit of oil around this big nut, possibly coming from higher up. Not enough to make a drip but just a bit oily all around. Ps the picture is not my actual car .... forgot to take a pic.

That's not something you want to be undoing .. it's the chain tensioner . The seal can leak but the engine needs to be set up in a certain way before you remove it .. or else your in trouble .

You beat me to it !! As De Mort says, steer clear unless you know how to lock the engine My 997 was weeping from there, but a change of washer sorted it Cheers K H

Personally, get an Indy to change it..... ac it requires a certain amount of knowledge & expertise

Quick draw deMort lol Either way i think the owner will know not to just undo it

On a slightly related matter, mine looks a bit grimy around the component circled below and occasionally drops a bit of oil - did when laid up for 3 weeks whilst on hols. What is it? Sorry for the thread hijack and hope you dont mind me screen grabbing the original photo. Ian

Chain tensioner oil leak Thanks to demort and mr911 for identifying this ..... now I know what's going on. As I understand it the crank needs to set at tdc and possibly the cam locked with the special bracket. (Which I can make easily) Some ask whether just setting at tdc is enough, because there is no tension at this position, but I suspect the cam lock is advisable/essential. Is it ok to lock only the one side in question? Am not phased by having a go at this (am probably a bit more engineering savvy that I am letting on) ..... unless the location of the cam lock holes is beyond the reach of diy. Am more irritated (with Porsche) that it will cost half an hour of top quality Indy time to change a £1 Ali washer. I would rather use them to do the really specialist diagnosis/fix jobs Welcome to the world of 911 ownership, I am sure most will say! Paynewright .... no problem to add on to this thread .... am interested in the answer .... and will be checking same location when next underneath.

@ Paynewright .. That would be a core plug and if it's damp then it has rusted through and as such needs changing , there are a few others that can also suffer this . Op .. There is the way i would do this job and the way that on here i have to tell you how to do this job ! With the crank locked with a pin then one bank will have the cams on the lift .. balancing shall we say .. turn it 360 and the other side will be at this point . You have a 50/50 chance as to which bank will be in this position but if the bank with the tensioner to be removed is on this position then in theory it could slip . How i would do it .. i would pin the crank then take out the tensioner .. i've never had one slip BUT i'm not telling you to do it this way .. You have to pin the crank , pull out the x2 green bungs ( they will need replacing ) and lock the cams with the tool . If i was replacing an IMS bearing then i would be doing this for certain . I can't remember if you have to drain the oil out first .. sorry but it might be better to do this .. we tend to do this job as part of a service so the oil is already out . Once again .. my disclaimer .. do it with a cam tool

Chain tensioner oil leak Thanks demort for the info re removal of chain tensioner. You say that there is a 50/50 chance of which cam is in the balanced position when at tdc. I understand that to be because the ims is rotating at half the crank rpm? ...but looking at pictures posted on earlier postings on this sort of subject (ims etc) I notice that that the slot in the camshaft end is not on a diameter but offset, so that one edge, only, of the slot is on the true diameter and the other is offset to the right, say. Another 360 degrees on the crank and then it would be offset to the left. Would this not give a certain indication of whether that particular cam was on the lift or not? The 64000 dollar question then being .... if the slot is on, say, the crankshaft side of the true camshaft end diameter ... is it on the lift? Can anyone confirm this? With that knowledge the cam in question could then be arranged to be 'not on lift' ..... which, if I understand your post correctly, is the safer of the two positions when removing the tensioner. (.... still fully appreciate your cam locking advice, which makes this question unnecessary, but it is still interesting!)

Chain tensioner oil leak double post

You are correct .. there will be a relationship to which bank cams are on the lift and so .. balanced shall we say which a slight pull could cause the cams to slip . Without being locked then without a tensioner in place the chain timing would slip . Im afraid ive never bothered to look and take note ... i've never needed to . There is a big difference from what i do at work and what i can tell you to do here .. i have no problem locking the crank then pulling a tensioner .. BUT .. i can't tell you to do that .. i do this for a living ( i can also fix something that goes wrong ) so in a sense ( loosely ) i'm a professional giving advice .. if i give the wrong advice then i could be held liable for any damages . Considering i'm poor .. all mechanics are then i can't afford to make a mistake .. hence .. you lock the cam .. simples I will , when i get the chance , try and work out which side is on the rock so i can advise better .. for now though i have to say lock the cams . i simply have no choice .