I have a 94 bmw 318i the car overheat i change fanclutch,termastat,waterpump,radaitor,the radiator hose build a lot of pressure that when i change the water pump because i believe the water pump is not working the car still overheat
I HAVE A 2000 323I AND HAD THE SAME PROBLEM BUT MY PROBLEM WAS THERE WAS AIR IN THE SYSTEM,THAT'S WHAT HAD MY CAR OVERHEATING,ONCE IT WAS POWER FLUSHED IT RAN LIKE A TOP,YES I KNOW I HAD REPLACED THE RADIATOR , RESERVOIR, THE THERMOSTAT,HOSES EVERYTHING AND THAT WAS THE PROBLEM AIR IN THE SYSTEM,THIS IS A FOREIGN AUTOMOBILE
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It's possible that you have a bad head gasket. Have your cooling system pressure tested, see if it holds roughly 18lbs of pressure. Could also be air in system, did you bleed system when waterpump and thermostat were installed?
A lot of the time the core in the radiator are partly pluged. The radiator needs boiled out or replace the radiator. One other item that can cause problems is old hoses. The bottom hose could be collapasing under pressure and the radiator cap could be at the wrong pressure setting.
Ok, I know you said that you replaced the t-stat, however they do have a 20-30% fail rate.
Lets assume that your t-stat is functioning properly (if it is you should see the temp gauge fluxuate when the engine reaches its hottest operating temp, the t-stat will open and the needle will drop, Also your car will overheat or blow luke warm air if your tstat is bad.)
If you have blockage in your coolant lines your system will build excessive back pressure depending on the line (coolant system flush fixes this issue)
and the final thing to factor in is that the coolant system on any vehicle is always under extreem pressure when the coolant is hot and the engine is running, your return hose from the radiator will have massive pressure in it if the thermostat is closed, and it should relieve itself some when the t-stat opens. Your low end hose (engine to radiator return) will have low to mid pressure at all times because the only thing building pressure on this hose is the pump trying to cycle the water, heat is not a big factor with this hose compaired to the top end hose. Thanks for using fixya.com
I assume you mean the radiator fan. This might be indicative of a different problem. The main issue is, does the car overheat? If not, then it's probably a thermostat that's stuck open. A lot of things can fail in the fan system...the fan motor itself, a fuse, a relay, or the temperature sensor that tells the fan to turn on.
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).