Tip & How-To about BMW 318

Cabin heater not working or not working good enough in BMW 3 series.

A common problem in the BMW 3 series of the 99 - 2002 year is that when there is a leak in the cooling system for what ever reason ( perished hoses leak in the 3 series a lot along with expansions bottles, radiators ) air leaks in as tiny amounts of water leave through the leak.
This air rises to the highest point in the cooling system which is the internal cabin heater matrix radiator in the 3 series models of the pre-said years.
As it fills with air over time the water pump can no longer circulate the coolant ( A pump designed for liquid will not move air only liquid ) leaving the internal cabin heater matrix radiator empty ,the coolant now takes the alternative route hence no heat.
A temporary solution is to put in more water or coolant remembering to ;

1 Loosen the air bleed screw or remove it when doing so.
2 Do it while the engine is running and cold and the pump is rotating.
3 Make sure the heating in the car is on full tempeture so as to allow the water to flow up and into the internal radiator.
4 Leave the bleed screw open for five minutes so to be sure all the air has purged.

After that tighten it and replace the filler cap and you should be good to go. if it does not fix the problem bring it to a garage to have the system pressure checked for leaks. they may also do a sniffer test to see if there is any combustion gases in there that should not be, this may indicate major machanical failure of the engine block head gasket or more common in the 2000 318 's is a cracked engine block head which needs total replacement.

So remember! practice and enjoy :)

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1 Answer

My BMW 5 series 1989 model vehicle is overheating.


If your car is overheating it means that there is a leak in the coolant system somewhere. A common problem with a car this age is the in car heater core. Also the auxillary cooling fan may not be working. The first thing to do is a pressure test on the cooling system to determine where the leak is, and proceed from there.

Jan 18, 2011 | 1989 BMW 5 Series

1 Answer

the car is overheating i do not know where the thermostat is


I assume you have checked the cooling system to ensure that first that it is full of coolant and second that there are no leaks and the radiator cap is in good condition. The heater hoses and those pesky little bypass hoses in the cooling system tend to go hard and split if they are over 10 years old, allowing coolant loss. If there are no leaks or air locks, the over heating could also be caused by a clogged radiator (more than 15% restriction in the radiator flow capacity will cause overheating problems), a faulty water pump or as you suspect, a faulty thermostat.
If there are no leaks but undetected loss of coolant, then it could indicate a problem with the head gasket (Usually caused by allowing engine to become excessively overheated when cooling system has run dry) allowing high pressure combustion gases into the engine water jacket, which super heats the coolant which then boils off, and is released via the cap.
If unsure take vehicle to cooling system specialist and have them do a pressure test and more thorough diagnosis.

Aug 28, 2010 | 2000 BMW 3 Series

1 Answer

Saturn has been going through coolant very fast. Leak? radiator?


1. Obviously there is major leak in the cooling system and you will need to rectify this before you cook your engine.

2. The radiator, all coolant hoses and hose connections need to be checked including the heater hoses. If you cannot locate the source of the leak yourself you will need to take it to a mechanic to check. He will pressure test the system.
Hopefully it is just a perished hose that is letting coolant escape and if so this will not be expensive to fix.

If the radiator has a leak, which is common in older vehicles, you will have to invest in a replacement unit.
If all flexible hoses on the cooling system are old you should, in any event, replace all of them as preventative maintenance.

3. The worst problem you could have is a faulty head gasket which is allowing coolant to escape under pressure into the engine cavities including the cylinders. Check your oil on the dip stick and if you can see a whitish substance in the oil you have coolant leakage. This will be expensive to fix as the head on the engine will need to be removed.

4. You should not be driving the car whilst it is losing coolant so quickly as you are risking very expensive engine damage from overheating.


Dec 04, 2009 | 1999 Saturn SL

1 Answer

antifreeze leaks out


this can be a defective water pump, a leaking radiator, a leaking cooling system hose or hoses, the heater core and other engine problems like core plugs, have the cooling system pressure tested, this will allow the technician to pinpoint the leak.

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1 Answer

I have a coolant leak on my 2000 BMW 528i and now it overheating.


Pressure test cooling system to determine origin of leak. Radiator and coolant reservoirs are common problems. Vehicle is very difficult to purge air from cooling system and may take multiple times of idling until thermostat opens. Sometimes help to rev engine to about 2500 rpm 5-8 times to help build heat and move coolant through system. Must have heater on while performing this task.

Mar 29, 2009 | 2000 BMW 5 Series

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