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E30 M52B28 overheating and cooling issues

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    E30 M52B28 overheating and cooling issues

    Hi guys,

    Unfortunately I guess I am not the first one , but I am having overheating issues with my E30 M52B28 swap.

    My engine becomes too hot when idling, coolant starts leaking after some time out of the radiator expansion tank cap and the electrical fan doesn't kick in... I am distraught at the moment and hope someone can help me. Below my setup and things I already tested to solve the problem.

    - Stock E36 328i coolant hoses
    - Donor car E36 328i radiator with expansiont tank included
    - Donor car E36 328i pusher fan
    - New waterpump
    - New thermostat
    - New double temperature sensor switch 81/89 degrees
    - Mechanical driven fan delete

    In short, I used most parts from the car the engine came from and replaced the waterpump and thermostat for new ones. I wired the E36 electric fan through the E30 power distribution box which works fine. Next things I already tested to be sure there are no big other issues.

    1) Carried out head gasket leaking test with fluid (no carbondioxide in coolant system, only O2) -> so no head gasket leakage
    2) Tested the electrical fan circuit with the temperature switch in external boiling water, switches on and off at right temperatures

    For me it is strange how it is possible that after some time the engine became hot and started leaking coolant out of the radiator cap. I replaced it for my old E30 one which was always fine and it still starts leaking after some time. The system is not pressurized so how could it start leaking here?

    Also after removing the double temperature switch in the upper right corner of the radiator, it doesn't start leaking coolant here which means there is no coolant water in that place. This could be the reason the electrical fan doesn't kick in as well while idling. Is my radiator clogged or is there still too much air in the system?

    The last thing that could be occuring problems I think, is the mechanical driven fan delete. I thought that an engine normally does have an electrical fan or a mechanical one. However, I was suprised by realoem the donor E36 328i does have both and the reseller of the swap also confirmed this. Unfortuntately this will be a really hard fit and maybe only a 2-3 mm clearance between radiator and fan will be possible.

    Hope anyone takes the time to ready my above story and could help me where to start. Thanks in advance guys!

    If the system is not pressurized replace cap rings with new ones and test, also check expansion tank neck seat for cracks.
    i believe the problem is with the expansion tank.