I have a bmw 318i auto 1998 model, ive changed the water pump, the radiator, took the themerstate out, put the fan on direct, & had the head gaskit checked & still it overheats when driving after 10 minutes. the temputure shoots up suddenly. please help me cure this problem. thanks.
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).
The reason I know of the head problems is because my partner's 97 BMW (4 cylinder 318i) actually overheated after I had done the water-pump, radiator, all hoses, thermostat, coolant and purged the air properly. It was driving me nuts!!! What was happening is that the head gasket itself had developed a small leak near the fire wall. I initially suspected a water hose near where the leak was between the head and the firewall, so I carefully replaced that and sealed it a number of times too. That wasn't it! Running the car would heat and pressurize the water in the cooling system and once hot, it would escape through the gasket leak. Only after 15mins, once the engine had reached running temperature, would it be pressurized enough to blow out the gasket leak. I drove it for nearly 40kms before enough water had escaped, and only then did the water temperature gauge rise beyond halfway - so keep your eye on the temp gauge. Nearly cooked the engine twice!
Anyway, I shut it down and got a tow truck home that night. Inspecting the car in the morning, I discovered the water leaking from the rear of the block between the head, near the firewall.
When I pulled the head off, everything looked okay, but the end section of the head gasket near the firewall had corroded and looked like Swiss cheese. On a 318i engine, that at the time was just over 10 years old with only 120,000kms on the clock, you wouldn't expect to see corrosion like that on a head gasket, but there it was. It had a number of water galleries with thin passages to seal in the area, which is probably why it lost seal quicker than your average gasket.
In the end I changed the head gasket, put it all back together an the engine ran cool for the rest of its life before I sold it in 2013.
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We removed thermostat completely? thinking it may have a hairline crack in head
i have 95 mw it ha been sitting on the drive for two years when i got round to driving it the rad blew put i knew one in a week later same thing hapened car over heted could this be the water pump or head gasket
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