[AlTheJazzman]

First off, my van is well looked after. I service it regularly and repair anything as soon as I can. The engine is the Isuzu 1.7 D n/a

Problem 1: It has always slowly lost water from the cooling system. Neither the oil or coolant are contaminated with each other. The water level in the bottle just slowly goes down all the time. Over the last few years I have replaced with new: radiator, water pump, thermostat, header tank cap. It doesn't leak out of the engine or pipe work, it just slowly disappears! I gather that the head gaskets on these engines are bulletproof. The engine doesn't smoke ever, or overheat.

Problem 2: the rocker cover leaks oil. I replaced the rocker cover gasket last year, but it still does it. Checked bolts tightened up properly to the correct torque. My local mechanic has suggested putting in some small brass washers under the bolt heads to stop the oil leaking through the bolt thread, but this still hasn't helped.

So hopefully someone here has had these problems and can recommend some solutions. Looking forward to reading them!

 

[Walksall]

(1) The problem here is that, with a VERY small coolant leak, what has leaked out can evaporate without being able to see it.
Is there any signs of a 'powdery' deposit, being of similar colour to the coolant ANYWHERE on the engine? If so there may be a leak in that area.
Another possibility, there could be a slight leak on the heater matrix - Have a look for damp carpets and/or the smell of coolant in the car.

(2) I would suggest that you remove the rocker cover, separate it from the gasket and place the flange face (the area that bolts to the cylinder head) on a FLAT surface (a sheet of glass will do), keep a gentle pressure on it and attempt to get a thin feeler gauge under it at all points around the flange face.
This will show up any distortion on the flange face.
Also, make sure that there are NO traces of old gasket stuck to the rocker cover, or the cylinder head.

Regards