Hello, i need to remove thermostat, but i even don't know where is it. Perhaps its on the front side of engine, under escape water from block of engine. Tommorow must go over 200km, themperatures now in Poland are so low, and themperature of engine is scared in speed over 100km/h. That is cause that i don't have enough time to remove it, and to look service too. Help me!
Bad news, Jan. Thermostat on M43 is inside the tube of the coolant thermostat housing on the front of the engine, near the top, that connects the hose to the radiator. When I say inside, I mean it is part of the housing, not a separate unit like on just about every other car on the planet. I suppose that you might be able to ream it out of the housing, but try the procedure for bleeding air from the cooling system first.
I believe that I understand you to be in cold weather, and the engine is overheating (scared), too hot. Most likely cause would be a broken water pump. Removing the thermostat might assist you to try to drive 200 km without the water pump, but shouldn't allow you to drive at normal speeds. Drive very slowly, with frequent stops to allow the engine to cool down.
DO NOT put cold water in an overheated engine to cool it down quicker. I can't say how prone an M43 is to warping the cylinder head, but I've done it to my M20 recently by adding water on a hot day, and the temp gauge wasn't even above normal. I noticed that the coolant level was a little low when I stopped for fuel on a hot day. I added water from the garage hose while the engine was running, and that's all it took to bend the head enough to allow coolant past the head gasket into the cylinders. Went home on the back of a tow truck...
The reason that I have suggested trying to clear the cooling system of trapped air (bleeding air from the system) is that extra air can form a pocket in the engine, blocking the water flow as the air is heated as the engine warms up, and causes the water temperature gauge to indicate that the engine is too hot. Properly purging the air from the system is simple, but is often overlooked by garage mechanics who don't work on BMW engines all the time. This isn't important in many cars that have an overflow tube from the radiator, but some cars (such as the BMW) have sealed, pressurized cooling systems and air in the systems upsets this.
Before opening the air bleed screw in the thermostat housing (probably with the 10mm wrench in your BMW tools kit), be sure to move the heater control to the hottest position and turn the heater fan on. This allows any air trapped in the heater core to be purged, too.
There are two air bleed screws. One is on the radiator expansion tank, a plastic screw close to the radiator filling cap. Use a screw driver to loosen this a little, don't remove it completely. The other bleed vent is a small metal screw with a 10mm square or hex head on the metal housing near where the radiator hoses connect to the engine block. Again, loosen but don't remove this screw. Before starting the engine, add coolant to the radiator until it begins to flow from the two screws that you have loosened. Then replace the radiator cap tightly, and start the engine.
Allow the engine to idle and watch the coolant bubble from the screws as the engine warms. Eventually, if the water pump isn't the real cause of your problem, the air bubbles will stop and the water will trickle smoothly, without splattering, from the screw on the engine. At this point you should tighten the metal screw. Then tighten the plastic screw carefully, don't tighten too much, it can break off and leave you with another problem.
Check that the heater in the car is blowing warm air, this is generally a good sign that you have purged the air from the entire system. If the engine temperature gauge is scared (too hot, in the red) then you are no better off than when you began - it is something worse. However, if the engine overheating was caused by air trapped in the cooling system, then you are on your way home, at a normal speed.
Judging from the number of overheating posts on this and other BMW newsgroups and forums, bleeding air from the cooling system is too often overlooked after we've replaced the coolant every year as recommended by BMW. The BMW service department won't forget, but not all of us go to the BMW dealer for this annual ritual.
Good luck, hope it's the air and not the pump.
Bill K. in Sydney Australia E34 525i M20 (and a new head) E36 316i M43 Compact
Bill, thanks for this useful & informative post. A coolant hose popped off = my M43 in my newly acquired 318i convertible leaving myself and some friend= s stranded by the side of the motorway; I got it back on, topped up the coo= lant again (luckily after it had cooled down although had I read this soone= r I'd have left it longer), this appeared to cure the problem and it was on= ly after a few miles the engine temperature suddenly shot up again. This ti= me we thought we'd leave it to the pros and called breakdown recovery, the = recovery man followed exactly the procedure you outlined above, most import= antly he bled it. Lucky I've owned E36s for several years and am aware of t= he various problems that affect the M54 so I knew to get off the road ASAP.= Subsequently the car's done about a hundred miles and is running OK so I'm= hoping that the HG is fine. Any tell-tale signs of light HG damage I shoul= d be looking out for over the next few hundred, or would you think I got aw= ay with it? =20
Signs of head gasket damage: -
Steam in the engine bay!
Oil leaks from around the head gasket.
Misfiring sound
Low power
Oil in the water.
Water in the oil (appears as "mayonnaise" around the filler cap).
White smoke from the exhaust.
Blue smoke from the exhaust
Poor starting
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.