This message is a summary of my findings while performing my first amateur head gasket change on a 1996 Renault Megane Coupe 1.6, 8 valve using a K7M engine. Hopefully useful to someone in a similar situation but probably a lot of waffle; most people will find useless.
Firstly I thought I needed a gasket change as I had a little oil getting in to the coolant system. This has been building up over a period of about 3 to 4 years.
When is a head gasket change not required:
-------------------------------------------------------------- It appears that a head gasket was NOT required. Strangely Renault has decided to pass an oil circuit out of the head and routed through the thermostat and then back in to the head (maybe to open the thermostat when there is no coolant in the engine?) The gasket between this oil circuit and the coolant is a very thin 'squeeze on' type. In my case this had eroded over the years allowing a small amount of oil to leak. Only learnt this while stripping the head to get skimmed!!!
Changing the gasket:
------------------------------ Really this is quite straight forward. Just follow the Haynes manual. I was a bit paranoid about cleaning up the old gasket residue and used a scouring (scotch bright) pad and very very gentle scraping with a blade.
Rebuild - Cam belt:
---------------------------- I had my belt changed by a 'cheap' garage a few years ago. They used a different belt and the timing marks on the belt DID NOT match that on the cam/crank. My advice would be to mark the belt and the pulleys with tipex before you remove the belt. Do not mark the outer surface of the belt (the bit that is pushed on to by the tensioner) this will make all sorts of odd noises and cause plenty of rapid wear.
There is a mark on the crank pulley surround. It's a very small black/ grey dot and is really hard to spot - very easy to confuse with a grease spot. It is located about 10mm away from the pulley when the pulley timing mark is direct on 6-oclock.
Note cam pulley is not aligned directly at 12-oclock but is a few degrees off.
When putting the belt on feed it tight from the crank past the water pump and on to the cam pulley, that way the slack is taken up by the tensioner and does not rotate the pulleys when tensioning the belt.
Rebuild - Missed bolts
--------------------------------- I had a nasty problem (outlines in another thread) but it turned out I had not torqued up a bolt holding on a couple of bolts. Nest time I`ll keep a written record of the bolts taken out and cross them off when I have torqued them on the rebuild.
Rebuild - Refitting the cam
--------------------------------------- I needed to take off the cam when getting it ready to be skimmed (=A330). When I put it back on ALL the clearances were far far off, which was a surprise. They all were very tight, I suggest slacking all the clearances off prior to setting them up. I didn't do this and suspect it caused inaccurate adjustment - so I had to come back and do it all over again.
Summary:
-------------- I`m inexperienced with engines and this was the most extreme thing I had done. Previously done valve clearances but I have a well equipped garage as I do up motorbikes. You'll be surprised how many tools are required!
I think most of all; allow lots and lots of time if it's your first time out. I messed things up a lot and it took about 30 hours in total (youch!). If I had not to do things twice (or 3 times in some cases) it should have taken me about 18hours. Reckon it'd take me about 10 hours if I was to do it again.
Well, hope that helps someone! Good luck!