Coolant Temp fluctuation?

[bimmerR75]

Tale the steering wheel off, the cluster is much easier to take out with breaking anything.

Airbag steering wheel unfortunately. Not sure how to take it off.

[efficient]

Tale the steering wheel off, the cluster is much easier to take out with breaking anything.

[bimmerR75]

Warm the car up on full heat to purge the heater core and open the tstat then bleed as usual (with the reservoir cap on).

As for the IR gun go buy one

Thanks and will do on the IR gun!

With a good stock temp thermostat, the temp will hover very close to 1/2 most of the time. This is because the the thermostat opens (to start allowing cooling) just below the 1/2 mark and the fan clutch engages shortly after, about at the 1/2 mark. If a lower temp or faulty thermostat is installed, the needle will fluctuate more because the thermostat opens further (temp) away from the fan clutch. At highway speeds you have tons of cooling air regardless of the fan so the temp sits at the thermostat opening number which is probably close to the 1/4 mark shown in the picture.

Good to know about the hovering. As of now it hovers close to 1/2 when idling on a hotter day, but goes back and fourth between 1/4 and 1/2 (sorry for the confusion on the 3/4 aspect). Going to bleed the heater core as suggested and sounds like its fine overall.

Tried to take the cluster out last night but it seems that whomever had the car before broke off both of the "A" clips that are connected to the cluster to get it out. That being said I tried pulling it out but couldn't get it forward past the steering column. Decided to put it back in and leave it for another time as I dont feel like purchasing a new cluster if I accidently damage this one haha.

[LJ851]

This isn't a photo of my car, but this is exactly where the needle lies when I'm on the highway. It previously used to stay at this level, but not it slightly moves between that mark and almost the middle, then back.

That needle position would be considered 1/4, not 3/4.

With a good stock temp thermostat, the temp will hover very close to 1/2 most of the time. This is because the the thermostat opens (to start allowing cooling) just below the 1/2 mark and the fan clutch engages shortly after, about at the 1/2 mark. If a lower temp or faulty thermostat is installed, the needle will fluctuate more because the thermostat opens further (temp) away from the fan clutch. At highway speeds you have tons of cooling air regardless of the fan so the temp sits at the thermostat opening number which is probably close to the 1/4 mark shown in the picture.

This could be what is happening to your car.

[jeffnhiscars]

Thanks, no loss of coolant since I replaced the rad temp switch. So turn it to full heat, should I do that with the bleeder screw out and reservoir cap off?

Unfortunately dont have an IR gun :/

Warm the car up on full heat to purge the heater core and open the tstat then bleed as usual (with the reservoir cap on).

As for the IR gun go buy one :)

[bimmerR75]

That's close enough to where your needle should be to not be concerned. Mine is rock steady a little above that and will rise closer the the halfway mark when sitting at idle for any length of time. If you only lost a little coolant you may not have a major bleed issue but being in LA chances are your temp dial is set to max cool. Turn it to full heat to make sure no air is trapped in your heater core, def check actual temps with an IR gun and do a newspaper test on your fan clutch.

Thanks, no loss of coolant since I replaced the rad temp switch. So turn it to full heat, should I do that with the bleeder screw out and reservoir cap off?

Unfortunately dont have an IR gun :/

[berndt]

Mine used to move around. In my case the thermostat was completely busted (in two pieces). Replaced that, and all is well.


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[jeffnhiscars]

That's close enough to where your needle should be to not be concerned. Mine is rock steady a little above that and will rise closer the the halfway mark when sitting at idle for any length of time. If you only lost a little coolant you may not have a major bleed issue but being in LA chances are your temp dial is set to max cool. Turn it to full heat to make sure no air is trapped in your heater core, def check actual temps with an IR gun and do a newspaper test on your fan clutch.

[MrBurgundy]

I agree with the IR temp reading to make sure that the car is not actually getting hot. This way you'll know if its an electrical or mechanical problem.

[bimmerR75]

it shouldn't be at 3/4. Your temp needle should be between 1/4 and 1/2. The original fan switch is designed to switch on the low speed at 3/4 and the high speed at full hot.

If it stays at 3/4 while driving on the highway it would suggest a coolant mix with too much antifreze (never go more than 50/50) or an air bubble in the system.

This isn't a photo of my car, but this is exactly where the needle lies when I'm on the highway. It previously used to stay at this level, but not it slightly moves between that mark and almost the middle, then back.

[Das Delfin]

it shouldn't be at 3/4. Your temp needle should be between 1/4 and 1/2. The original fan switch is designed to switch on the low speed at 3/4 and the high speed at full hot.

If it stays at 3/4 while driving on the highway it would suggest a coolant mix with too much antifreze (never go more than 50/50) or an air bubble in the system.

[bimmerR75]

When I changed the radiator temperature switch I lost some coolant, refilled it. Once refilled I unscrewed the "bleeder screw" on the top of the thermostat housing and turned on the engine and waited for there not to be air coming out, but coolant, soon as coolant came out, closed the screw back up, is this the proper way to bleed the air out? Sorry for the questions haha, every month I am learning something new on this car by doing the work myself. Appreciate all the advice.

Finally getting a chance to address the cluster today. Would anyone be able to verify the bleed procedure. I see things all over the net about bleeding with the car jacked up. Coolant is flowing from the bleed screw when the car is sitting level, and engine is on. So not sure if that means there are no air bubbles, or that you have to have the car on ramps/jacked to really see if theres air stuck.

[bimmerR75]

This screams a small bubble of air in the coolant to me. If nothing else pans out I'd bleed the coolant system.

Id start with bleeding the air as suggested, as the air would be around the thermostat which may give similar symptoms to a stuck thermostat. A properly working cooling system, once up to temperature the temperature should be pretty much solid. That is the thermostat's job after all.

When I changed the radiator temperature switch I lost some coolant, refilled it. Once refilled I unscrewed the "bleeder screw" on the top of the thermostat housing and turned on the engine and waited for there not to be air coming out, but coolant, soon as coolant came out, closed the screw back up, is this the proper way to bleed the air out? Sorry for the questions haha, every month I am learning something new on this car by doing the work myself. Appreciate all the advice.

Going to try out cleaning the backside of the gauge points via the instructions in this video and tightening the nut. Hopefully that will work, but if someone could confirm whether or not my bleeding process was correct, that would be a huge help. As if its not, I am sure it may just be air as you suggested as it seemed to be working fine until my old switch went dead and I replaced it.

[e30davie]

I wonder if a stuck thermostat could cause this? If its stuck say half closed, it would cause the coolant to heat up at lower revs but cool down at higher revs?

Id start with bleeding the air as suggested, as the air would be around the thermostat which may give similar symptoms to a stuck thermostat.

A properly working cooling system, once up to temperature the temperature should be pretty much solid. That is the thermostat's job after all.

[Gregs///M]

Unless you have had your SI board refurbished by us, don't trust your temp gauge. Even SI boards from E30_dad and Programa only change the batteries and capacitors but the transistors that help power and control the temp gauge are not replaced by anyone except us. We replace all transistors, voltage regulators, capacitors and batteries.

Additionally, you will need to inspect your temp gauge for copper oxidation as well as the condition of the landing pads on the main board.

When the SI boardand/or temp gauge is failing, it will error on the high side. You can try tightening the 7mm nut behind the gauge but if your SI board is not refurbished, it will still be inaccurate.

In the end, be sure there are no air bubbles. Bleed, bleed, and bleed to make sure there are none. Your temp gauge sending unit should read around 1000 ohms at room temp. Good luck!