Help needed, peculiar water leakage

[aabdelhamid]

I have a 1990 520i M20. I changed the radiator, internal thermostat, water hoses and water pump as well. Now I have a leakage causing me to top-up the water by almosrt 1.5 litres every three-four days. There is no apparent leak and when doing the pressure test, there is not leak as well (warm and cold). My mechanic dismantled the cyliner head and told me there is a lower area (corroded from the engine block) between two of the water channels inside the block thus leading to leading inside the cylinder, this is why we are not seeing any leak outside the engine. I am not convinced as a leak inside the blosk would lead to bad running of the idling engine which is not the case and would cause some residues to build up inside one of the compartments and on the spark plugs. Please inlighten me and help me decide, do I need a new block or not ?????

[DaveVoorhis]

A leak into a cylinder will steam-clean that cylinder. If you've got one plug that looks unusually clean, then it may well be leaking.

However, mysteriously vanishing water can also be due to a leaking heater matrix. My '90 525i did that for a long time before the leak became so bad that it started drizzling coolant down the carpet.

[aabdelhamid]

ilku;lu

[Ferret]

Shouldnt show up if your heater valves are shut pretty snugly - though it'd have to have valves on both sides. I'd expect BMW to do something that quirky.

ilku;lu

Nice random letters there btw.

[DaveVoorhis]

The matrix leak can be too slow to show up on the pressure test, and too slow to soak the carpet (yet), but still fast enough to drain coolant over time. Does your windows tend to develop a greasy film on the inside? If so, that's a classic symptom of a leaky heater.

The valves operate on only one side of the matrix.

[aabdelhamid]

I will isolate the matrix and by-pass it to make sure the leak is coming from there. I will then change it if it needs to