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Heater not working and can't get air out of the coolant system on an e46?

  • The heater hasn't been working for over a year now and the coolant light keeps coming on fairly quickly after being topped up, it seems to be leaking out of somewhere but we can't tell where. The water pump has been replaced and the thermostat has been replaced. The coolant system has been bled properly several times but there's still lots of steam coming out of the bleed cap when the car is restarted and the heater inside the car just will not get warm. The hoses we can easily get to in the engine bay get hot when the engine is revved but we haven't yet investigated into the pipes behind the heater. Any ideas?

  • Answer:

    you need to pressure test the cooling system and check for any visual leaks also you need to flow test the heater matrix to make sure its not blocked. if no visual leaks found and matrix ok then possible head gasket failure or air lock. to remove any trapped air put a large funnel in the top of the radiator and fill it right upuntil level is stable and run the engine till warm, if problems still persist then suspect head or head gasket failure.. hth

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On my 540i for some reason known only to BMW you cant bleed the radiator in the same way as a normal car, you have to pressurize the cooling system. I would fill it up run the engine and the coolant level would be the same ,but as soon as you took it on a run and the stats opened the level would drop. it would take weeks of topping up to get the level right. If your not careful you could warp your heads, take it to a BMW specialist (they should be cheaper). If yours is the same you have to get the engine hot then crack the radiator cap (not the exspantion tank cap, but the cap on the rad itself, be VERY careful as it is pressurized and hot, then let the steam out then close immediately , then when the water cools it will draw water from the exspantion tank in to the radiator, as I said you may have to repeat the operation several times.

matrix

The problem your decribing is a little more complicated than it sounds. Since the E46 BMW has 2 water pumps, a primary and seconary, has the auxillary water pump been checked and verified for correct operation? Has the A/C heater acutator been checked? this will prevent warm fluid from entering the heater core. If it is working right then ruling out an external leak that would leave an internal one somewhere. A compression check on the cylinders would be the next action to take. This would rule out and identify and internal cylinder problems. Leaking head gasket, bad worn or damaged valves and seals, piston ring sealing etc. If this test dosn't identify a internal leak then have a flow test done on the cooling system. There might be a passage inside the head that is blocked and isn't allowing coolant to flow.Unfortunatly there is no easy fix for it.

icecube508

you may have an internal leak in the head gasket and so the missing water is vapourising in the combustion chamber(s) and coming from the exhaust as steam.

maclaren

I HAD THIS EXACT SAME PROBLEM ON AN E46 AS WELL. you need a new radiator. it is leaking.

deautophile

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