Why would my car overheat?

[E30_Narek]

My car overheated today. I turned the car off for an hour to go eat something, came back and as soon as I turned the car on the temperature gauged jumped to the middle and slowly started exceeding it. My car has an electric fan and I only turn it on when I'm stuck in traffic. When the fan is off, the car cruises with the temperature gauge on the first line. My car has all new radiator hoses, new heater hoses, a new radiator, a new thermostat, and a new waterpump and the fan was on, there's no reason it should overheat. My coolant level was alright too. I pulled over once I saw the temperature hit the red and popped the hood. The engine felt cold (I could leave my hand on the valve cover for a while before it hurt), the radiator was pretty cold and so was the coolant. What could be wrong here? Is it a faulty gauge?

EDIT: I was driving it 20 miles before this happened and the temp gauge was either on or below the first line. Only went above first line when driving slowly.

[efficient]

Maybe thermostat is faulty and is stuck in the closed position. not sure if you replaced that.
Or maybe you didn't bleed it properly

[E30_Narek]

Maybe thermostat is faulty and is stuck in the closed position. not sure if you replaced that.
Or maybe you didn't bleed it properly

Yes, the thermostat has been replaced. It's been working fine for the past 2k miles, it's just now this happened.

[efficient]

I'm not so sure what it could be but Next time it starts reaching the red you should turn the heater on full blast to bring the temp back down.

[E30_Narek]

I'm not so sure what it could be but Next time it starts reaching the red you should turn the heater on full blast to bring the temp back down.

I did that it wasn't going down....

[digger]

sounds like gauge is stuffed, check the connections at the back of the cluster. there is a nut that comes loose and clean the contacts of the gauge as well

[dnguyen1963]

When was thew last time you looked at the SI board/batteries?

[E30_Narek]

Update: So I went to go turn my car on this morning after it being off for 10 hours or so and as soon as I put the car in the 'on' position, the temperature gauge hit the first line. I turned the car on, and sure enough, it was a very cold start. It was idling at 1,000 RPM or so (what it usually idles at when cold) and it was running normally. After 10-15 seconds, the temperature shot up to the middle. I turned the car off shortly after this and popped my hood. Everything was still cold, the hoses, thermostat housing, the coolant, and the engine. I have a feeling only my gauge is broken.

[dnguyen1963]

It's most likely not your gauge. You have described classic problems related to loose ground nuts or bad SI board/batteries.

[E30_Narek]

It's most likely not your gauge. You have described classic problems related to loose ground nuts or bad SI board/batteries.

When I said gauge, unwashed referring to the ground nut as it is part of the gauge.

[digger]

When I said gauge, unwashed referring to the ground nut as it is part of the gauge.

yeah gauge issue means the gauge is not showing correctly which could be the sensor, wiring, gauge itself, nut, contacts, stuff mentioned above etc etc

[95BMWIC]

Hey Narek - I thought this was taken care of back in September.

I thought you had already done this? - A discussion (similiar to this) was posted once before..

http://www.bimmerforums.com/forum/showthread.php?2130026-E30-temperature-goes-up-and-down&p=27944574#post27944574

I suggested the nut but you doubted it because of "the pattern" of pulsing..

Later you stated you would "try fixing that" and then stated the "the gauge isn't faulty... "

Did you tighten the nut in September? - because if you did - it is not the nut - it would be the gauge - the nut completes the ground - it is not a measurement tool like the gauge.

I may have another E30 temp gauge in my garage - if you want to double check..

[E30_Narek]

Hey Narek - I thought this was taken care of back in September.

I thought you had already done this? - A discussion (similiar to this) was posted once before..

http://www.bimmerforums.com/forum/showthread.php?2130026-E30-temperature-goes-up-and-down&p=27944574#post27944574

I suggested the nut but you doubted it because of "the pattern" of pulsing..

Later you stated you would "try fixing that" and then stated the "the gauge isn't faulty... "

Did you tighten the nut in September? - because if you did - it is not the nut - it would be the gauge - the nut completes the ground - it is not a measurement tool like the gauge.

I may have another E30 temp gauge in my garage - if you want to double check..

I didn't fix it back in september. It wasn't really a big deal for me back then.

[95BMWIC]

Well then..

Now that it is a bigger deal - I suggest the same thing (as others, as before) - check the nut first.

Let us know if that fixes it.

If it doesn't - Id then try to switch out the gauge- since your previous posting stated you put in a new cooling system (water pump, thermostat, radiator, hoses) - you could probably get a another gauge real cheap (or free) from another forum member..

Next step - would be the sender (see my answer to your posting from September)

[E30_Narek]

Well then..

Now that it is a bigger deal - I suggest the same thing (as others, as before) - check the nut first.

Let us know if that fixes it.

If it doesn't - Id then try to switch out the gauge- since your previous posting stated you put in a new cooling system (water pump, thermostat, radiator, hoses) - you could probably get a another gauge real cheap (or free) from another forum member..

Next step - would be the sender (see my answer to your posting from September)

I tightened the nut but that didn't seem to work. I'm going to change the coolant temp sensor tomorrow. That broke off a while ago for me and I glued it back (haha) but I guess it's not working as it should. If that doesn't work, I'll replace the SI board batteries and re-add the solder if it's needed.