Engine Overheat Indication?

[jrobie79]

kind of related but not really...what would cause the temperature to stay "too" cold? From what I remember of my first m42, the temp needle would stay a touch below the half line. On my current m42, it barely gets over the 1/4 mark, regardless of condition. I have an electric m44 mounted in front of the radiator, with a different temp switch (not stock, forget what degrees it is), cleaned out the entire system, and refilled with BMW coolant.

Before I put the m44 fan on, the mechanical fan wasn't working, and the temp needle would creep up to 3/4 if I was stuck in traffic, dropping back down to just over the 1/4 mark once I started driving.

Any ideas?

[bmwman91]

There are a couple of possibilities. One is that the thermostat is worn out since it typically fails in an open state. The other is that someone installed an 80 degree thermostat instead of the standard 88 degree one.

[jrobie79]

There are a couple of possibilities. One is that the thermostat is worn out since it typically fails in an open state. The other is that someone installed an 80 degree thermostat instead of the standard 88 degree one.

I recently replaced the thermostat with an Autorad 88 degree one, that I verified was operating correctly via a temp gun with water on the stove. I'm pretty sure it opened at 190° (88°C) vs 176° (80°C). I'm not 100% sure on that, and there is a hairline crack in my t-stat housing, which I will be replacing, I purchased one new, so I can double check the t-stat, but I wanted to rule out if it could be anything else while I dig into it and replace it.

Could the heater core valve cause that? My heat works fine, it's properly bled, the channel on the housing is clear of gunk/gasket material.

Also, I'm going to be replacing the radiator as there is a slight leak somewhere in the fins, are there any recommended products to use to flush the system? I was planning on just filling it up with distilled, after draining, and running it for a bit, then draining, and refilling with distilled, repeating until its clear then filling it up with 50/50 BMW blue coolant.

[bmwman91]

I don't think that the heater core would be bypassing that much coolant, especially if the blower is not set to hot. The only other possibility is that maybe the thermostat is in backwards or somehow not seated fully.

I wouldn't worry about flushing. If you use the block train behind cylinder #4 before the thermostat and radiator replacement, you will get like >90% of it out.

[downforce22]

I ran my 318is on the track at a lapping day once. I was riding passenger as my brother drove for a few laps. At some point the temp gauge was wonky so an aftermarket gauge was added at the top radiator hose from the engine by the PO.

Well as my brother drove, the old alternator/water pump belt came off the pulley at some point. He didn't notice the temp gauge and took a couple laps to see the voltage was down to 11 volts. We drove about 2-3 laps all out without a waterpump circulating, then one last lap once we noticed to get back to the pits. Coolant boiled out of the system and the temp was off the aftermaket gauge (260 F).

I got a new belt on, new fluid and bled it and drove it home and it has been fine ever since. These m42s as tough, here is video proof. The aftermarket gauge where the obc goes is at 220 F in the 12 o clock position, 260 on the far right. It starts heating up after like the 4 minute mark and we notice at 8.5 minutes. After the track day I also added a voltmeter so I knew if something was up with the battery or the belt coming off.

https://www.youtube.com/watch?v=z0Mgvu-aQCo&lc=