I thought I had a problem with the head gasket on my 1988 740.
There was a strong smell in the water header reservoir which I now think may be from changing the water pump, plenty of sealant was used on the water pump so its possibly the sealant I can smell in the water.
Have just taken the car for a run of 50 miles and have lost no water from the radiator, if the head gasket was gone should I not be losing water.
There is at time what appears to be quite a high pressure in the water hoses but this I assume could be caused by the cap on the water res playing up.
If I leave the car overnight when I take the header cap of the reservoir when the car is cold there is still pressure in the system so this would again I hope indicate that the head gasket is not gone or there would be no pressure.