It's been a while since I've done oil seals in situ. I never used
theair method, just used a spring compressor. Get the engine timed,
depending on the year. Up to 1992ish, cambelt has 113 teeth, and two
lines which you use when you put it back on. Get the cam pulley hole
lined up with the hole in the head (around 7 o'clock) and insert a
suitable sized bolt. Look at the mark on the crank pulley which should
be at 3 o'clock. Tipex a mark adjacent to the crank mark on the block.
Remove the belt, camshaft and shim buckets with the shims (keep in
order). Remove the plugs. Using a long screwdriver in plug hole 1
ensure the piston is at the top. Turn the crank if necessary. Remove
the valve spring and collets and allow the valve to drop onto the
piston. Hold a finger on top of the valve stem and push down. At the
same time turn the crank so that the valve drops down level with the
seal. Remember which way you turned the crank! Remove the seal and fit
a new one. Then turn the crank the opposite way until it gets to the
top. Then refit the spring and collets. Do the same with all the other
valves. Keep thinking all the time about the position of the pistons
and which way to go. Then refit the camshaft and belt. Best to fit a
new belt unless you have done it recently. If the two lines aren't
visible then renew with a Peugeot belt. Fit the bolt into the hole of
the cam pulley and into the head and make sure the crank mark is lined
up with the tipex mark. Line the two marks up with the marks on the
crank and cam pulleys (it'll only line up in one way--you'll see what
I mean).
After 1992ish the belt has 114 teeth and there are no marks on the
belt. So time it up as above and tipex on the belt a dot in line with
the crank and cam pulley marks. Remove the belt and carry on as above.
When refitting the belt count the teeth between the cam and crank
clockwise. (Should be 49 and a half). Then on the new belt put two
marks 49 1/2 teeth apart. Make sure they are in exactly the same place
as the old belt. (Of course if you are refitting the old belt then you
won't need to do that!!) Then refit the belt lining up the marks.
I hope that is clear and I haven't missed anything important out.
Good luck.