Hi..Sorry for the delay..
Going by your description of an canister object that would be the coolant regulator/thermostat housing like pictured below..
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This is an all plastic housing bolted to the engine - there is ring seal inbetween that and the engine to inspect for leaks - aswell as that any small fracture wouldn't be easily seen especially if this is under pressure..the only way to fully verify that would to artificially pressurize the system "cold engine" via the expansion tank..its a special tool that fits in place of the expansion tank cap builds up pressure in the system and thus forces the leak to appear to investigate there is also another way of using a uv dye and pour some into the coolant run the engine and then by using uv light/special glasses go around that area to see where the dye leaks out from..I do hope this helps..If you need to ask anything else or include anything further then just continue before you rate
Thanks for that, it is as I suspected. The leak seems to disappear as quick as it comes because when I open the bonnet it's all but dried up sometimes but I need to refill expansion tank with approx 2 pints of water! How easy / difficult a job is it to change? I was a qualified mechanic, in my youth, and still have all my tools etc If it is reasonable to change, what would I need to be aware of and would I need any special tools? Approx how much would they cost, if you know please?
Again many thanks,
Hi..there thanks for your reply..
Its more room to get at it thats the problem there is only generally two bolts holding that housing on anyway - the main item to remove will be your alternator to get a better view the housing sits quite near the timing side of the/water pump - ive got some details below for the BWA engine - no special specific tools for this job - cost wise usually around £40 mark however that dpends where you aquire it from dealer will obviously be the most expensive route it will come as complete housing and should inc the the o ring seal..