1997 318iS Overheating - cooling fan not working

[Drouo]

Hey guys, brand new, but did search before posting. I think I have an idea for next steps, but was looking for validation or suggestions.

Problem:
Overheated idling in driveway, it's only been driven a couple times since then, got very hot, had to stop a couple times to let it cool down. I don't believe I was getting any heat out of the vents either when attempting to cool the engine by turning on the heater. Added coolant, bled it, continued to overheat. Not seeing any milky oil, or white smoke from the exhaust.

Steps taken so far:
Added coolant, then we bled the system for a long, long time. It kept blowing out steam. I told him it was a pressurized system so it would keep blowing steam if you let it run with the bleeder screw loose... but he said he thought air was getting in some where.

Replaced thermostat, then removed it entirely to see if coolant was flowing. Noticed that both sides (before the block and after the block) are getting quite hot when the car has been running, so we assumed the water pump was working. It continued to overheat.

Replaced radiator and radiator cap. It continued to overheat.

Then we realized that the cooling fan was never turning on (not the aux fan that sits in front of the radiator, but the bigger fan that sits between the radiator and the block). I don't even have an aux fan.. We pulled the fan, jumpered it and realized it was blown. A capacitor looked burnt, so we soldered a new capacitor onto the fan and it started working right away when jumpered! Worked very well, figured we had fixed the issue. Plugged it back in, started her up and idles for 20 minutes or so and starts creeping above the middle line. The fan still never turns on!

Next I was thinking maybe the fan's thermostat (the cylinder looking thing attached to the electric fan (forgot to mention this is an electric fan, not clutch)), or maybe the engine coolant sensor was not sending a signal to the ECM to tell it to turn on the fan? Either that or the fuse (fuse 48, I think) was blown. Pulled the fuse from under the knee bolster (below steering wheel) and the fuse looked fine. Next we were wondering if maybe it was a bad relay, but we weren't sure which relay to replace..

So next we were thinking either say forget it, and take it in to a shop to determine why the fan never turns on... or run a switch inside the cabin so that I can turn the fan on whenever I want, or replace the water pump. This doesn't explain why we weren't getting heat. Blockage? Another concern is that it appears someone did some custom electrical (oh crap... I know) because it looks like there is electrical tape around some of the wires from the fan towards the fuse box. I don't see an external relay or anything though. I'm not sure if it was FDM type work, or if it was some hack job. I did see one pair of wires loose near the front headlight. Also this 318iS has the "M3 Package" the dash says M3, and apparently it has the 'level 2' suspension.

Just because we were getting hot hoses on each side of the block doesn't make absolutely sure that the water pump is doing a good enough job, but I don't want to spend the cash/labor replacing it if its working fine only to find myself still with an overheating BMW.

I'd love to hear suggestions. Oh, another thing, I bought a Coolant Temp Sensor from Pelican Parts, and after we pulled the existing sensor, we found that the plug requires a 4 pin sensor, and the sensor I got from Pelican was only a 2 pin. Not sure what that means... as I said, I don't know the history of the vehicle, so does anyone know why that might be? I searched for another style coolant temp sensor, but couldn't even find a 4 prong part. Argg...wondering if this has had a new engine put in it.. but no other evidence that I know of.

Here's the part I bought:

13-62-1-709-966-M323 $8.25 1 $8.25
Temperature Sensor (20 Degrees Cel/2500 OHM/12 x 1.5mm/Blue Top),
318i/is/iC (1992-98), 325i/is/iC (1992-95) Brand: FAE

[url]http://www.pelicanparts.com/cgi-bin/smart/more_info.cgi?pn=13-62-1-709-966-M323&catalog_description=Temperature%20Sensor%2C%2020%20Degrees%20Cel%20-%202500%20OHM%2C%20318i%2Fis%2FiC%201992-98%2C%20325i%2Fis%2FiC%201992-95%2C%20M3%20with%203.0%20engine%20[/url]

Thanks all, and sorry for the long post. I am so eager to get this car road ready again, but trying to CYA before dropping cash at a shop. I got it for 3400$ with about 115k miles on it. Looks really nice, but with the tires (700) and the radiator and other work I've put into it, I'm really not looking forward to selling it for super cheap because of the overheating problem. Thanks again. I will monitor this post and provide more details as necessary.

[Drouo]

Did more reading, I realize now FDM stands for (Fan Delete Mod), I was thinking it stood for 'from dealership mod' or something like that (especially because I know my 318iS has the 'M3 Package' (supposedly from the dealership?)

It seems obvious that someone intentionally removed the fan that pushes air into the radiator, but the cooling fan between the radiator and the engine is still there, and I want it to turn on!

[Drouo]

I called a local BMW mechanic and he said "If it ever geysered, it's a blown head gasket". He said to start it up with the rad cap off, and once it heats up, if it starts pushing coolant out onto the ground, its a bad HG.

Then I told him about the cooling fan, and how I replaced the radiator.. etc.. he said that I probably have multiple issues.

[BIGlil]

Definitely its your head gasket. it's blown from having no cooling fan. Hopefully you've installed one by now. Best advice is to isolate the problem by running the car with one plug out at a time. You should be able to determine which cyl is causing the overheating. The straight six is an ingenious design and can take a lot of abuse but no fan will cause thermal breakdown. You won't have interior heat because the air in the cooling system is causing no circulation of coolant.

[Drouo]

Thanks much for your response. I did install cooling fan, but it never turns on. I was thinking of running it with a switch instead of relying on the computer to turn it on, because apparently its not doing so!

I am going to sell the car, as I need a 4 door anyways. Not sure how much I'll get for it, but we'll see.

[olzhas]

i have the same issue with 318i, 1996. So, what did you do? What was the issue? I am trying to fix my friends car.