Where is engine thermostat situated on 1993 l reg1.4 vauxhall astra?

the thermostat can be in one of 2 places (possibly depending on the cars age), either at the end of the thermostat housing, where the pipe from the radiator goes to the left side of the engine, this one is relatively easy to replace, to check if its this type you have just undo the jubilee clip holding the pipe onto the end of the thermostat housing, you should see it in the end if it is..

The other place, which is more likely, is behind the cam (timing) belt cover actually on the side of the block, meaning the cam (timing) belt and cover will all have to come off, and the bolts that hold the thermostat housing on are covered by the back piece of the cam cover.

when removing the cam (timing) belt, place marks at certain places before taking it off, tippex is good for this, then when rebuilding be sure to line up all of your marks otherwise the timing will be out and can damage your engine

9 times out of 10 on the later "phase 2" models (95-) it will be the 2nd type of thermostat and you will have to remove the timing (cam) belt and pulleys.

so when changing a thermostat it is usually good practise to also renew the timing belt and have a good check around the water pump to make sure the gasket isn't leaking