BMW Repair: Please Help, head gasket sealant, coolant temperature

Question
I have a 1989 BMW 535i I believe 6 cyl and my car won't idle. In the beginning when I stopped it would shut off now it does it at anytime, Driving/ Parked and any other way. I tried a head gasket sealant thinking I could of blown one but that didn't work and there is no gunk nor do I see water in the oil. It all started when the radiator busted and I fixed the radiator but it kept over heating so I took the thermostat out and it doesn't do it anymore. Now it just keeps idling and will not stay on???(scratch head) I was wondering if it could be. Could it be the sealant was bs or something else? Or could it be the throttle pressure thingy? Haha sorry I don't know the correct name for it.

Thx very much!

Answer
Not knowing how many cylinders your car has tells me you shouldn't be under the hood.By adding the sealant you just probably made a mess inside of the engine.Taking the thermostat out isn't a good idea as well.The vehicle needs it to control the coolant temperature so it knows where the idle should be.My advice would be to take it to a shop that has some experience in automotive repair,preferably BMW.There are way too many things that could cause the idle issue.The overheating issue is a concern as well,damage could have or has occured.