I'm going to change a thermostat on my BMW E90 (N46). In the bleeding step, Can I leave the coolant expansion tank cap opened (since there is no radiator cap) and start the engine to bleed the system? Is there any difference between do it via the bleeder screw?
I don't even want to touch the bleeder screw since they made of PLASTIC and got LOOSED or STRIPPED or SNAPPED or whatever all the time 🙄 .
Well you can try but sometimes you have to use the bleeder screw on a BMW. I do it from there but I have a vacuum system and I hooked the vacuum system up to the expansion tank and it sucks all the air out creating a vacuum. Then when I turn it off and hook the system up to a jug of antifreeze. When I open the valve the vacuum sucks it all in and there's no air. That's how we mechanics do it. But if you want to try you would want to jack the car up in the air for the front so it's higher and that would let the expansion tank burp air out better
I guess I have to try my luck with the bleeder screw then. When unscrewing the bleeder screw should I leave the expansion tank cap opened or close it? Does it make any difference?
unless the expansion tank is pressurized, no it won't make a difference