My bmw 316i coupe 1998 is overheating

sounds like the radiator is blocked either coolant flow or ext air flow through the matrix the thermostat can get ruined when the system overheats so allways change the stat after a overheat problem GET THE RAD CHECKED FIRST if ok check the coolant pump

Have you checked your coolant levels as well as thermostat and waterpump functions? These can all atribute to engine overheating.

yes, if the water pump is bad, input hose will be hot output hose will be cool, but that also could mean a bad thermostat.

a way to see if the water pump is pumping coolant is to remove the bleed screw on the thermostat housing and see if coolant spews out.

But it overheats. may as well change out the water pump and get rid of the original plastic impellers. While you're there, replace the thermostat with a 12 degree cooler one and drill 2 3/16" holes 180 degrees from each other in the thermostat.

2.8L motors are sensitive to overheating. you can bust a head gasket this way in no time. Also warp that long cylinder head.

well this depends on what engine you have, i have a 316i e46 and has a 1.9ltr engine, if that is the same it might be the engine thermostat has stuck and need replacing, thats the good news, the bad news is it could be your head gasket, 1.8ltr engines were prone to blowing the head gasket, look in the rad water bottle to see if there is any oil residue in there, and also take off the oil filler cap to see if its a creamy colour thats your worse senario, but its proberbly just the engine thermostat

Are you sure the Fan is turning to cool the Engine? If it is not coming on to cool Engine Check the Rad. cooling fan relay.

You should take it to a rad shop and get the whole cooling system cleaned and flushed,then pressure tested to eliminate it before goig any furter because an y other cause of overheating is going to cost you a bundle.

check if the water is circulating as you might have a blockage in the header tank. this can be checked by opening the radiator cap and check if the water is circulating on top.

you can check if the water pump is working by feeling the top rad hose , if it is hot it should circulate into the rad and the rad should be hot at the top and cool at the bottom if the pump is faulty there will be no circulation of hot coolant into the rad. I suspect your head gasket might be blown if you are getting pressure built up in the rad. in that case you will need a new gasket and have your head skimmed

Also check the radiator cap. If the spring in the radiator cap is worn, it is not pressurizing the cooling system properly and therefore it will cause the vehicle to overheat. This is often overlooked and is a cheap repair. Every additional pound above atmospheric pressure that the cooling system is under causes the boiling point of the coolant in the system to raise 3 degrees F if memory serves me correctly. So, if the cap is old it will boil at 212 instead of 230 (for example)-and cause the system to overheat--even though everything else in the system is new/operating perfectly. If this is not your problem you may want to check to see if the cooling system itself is, indeed, holding pressure. You can get a gadget that fits on your radiator from any auto parts store to pressurize the system--after you pressurize it...leave it alone for about 20 minutes and see if it maintains pressure. If it doesnt, you have a leak somewhere. Hooah.

You actually need the thermostat in to pressurize your cooling system or the coolant won't cyle through the radiator, it'll just cycle around the engine. Most people think without the thermostat in the coolant will just pump freely through the engine and radiator, but it doesn't.

Chuck in a new thermostat, purge the air out of the system and see if it overheats then. I gaurentee it won't, if it does then you've got head problems (but they should already be obvious by now).