Water Temp Fluctuation - Rising while driving. Normal when idling

[Anri]

Do you recommend doing a full system flush and seeing how system performs thereafter? Thinking about flushing the system and maybe installing a new radiator - my current radiator appears to be the original one and may be gummed up.

Hi,

Seems like you are still with the same issue.

If you want to resolve your over heating, reach out to me, bring me the
car and I will fix it. You are not the first one I have fixed the same
issue you have..

I am in Los Angeles area


Regards
Anri

[sapote]

[I had my alternator replaced before all of this started happening (also OEM BMW). The alternator is showing 13.3-13.7v when operating (reading this from my Avin head unit). I've never hit 14v when cruising. I am wondering if the alternator is not providing enough power to the aux fan. See Post 55 from this thread - member installed a 140A X5 alternator and it fixed his cooling issues when his AC was on...

1. Did the e-fan run when the gauge needle passed the center?
2. Use a genuine voltmeter and measure the battery voltage at various engine RPM. 13.3 to 13.7v variation is not normal.
3. Can you check the engine temperature using INPA or any OBD reader to verify the dash gauge when it passed the middle center?

[sapote]

"There’s a check valve in the pump"
I think you meant the Tstat.

[bigjae46]

I’ll verify that. The condenser was cleaned before the new radiator went on. No major damage or notable issues other than typical patina due to age.

If the process you’re suggesting was not completed, the system self-bleeds, doesn’t it? Any manual bleeding just expedites that process - is that correct?

There’s a check valve in the pump but it’s probably doesn’t fully seal. So you get some drainage from the heater core loop which introduces air. So unless you get flow through that loop you’ll probably have air. It might eventually bleed itself but it usually results in a slightly higher reading especially if it causes the coolant level to drop enough.

[nextelbuddy]

can you post a pic of your cluster temp needle when ignition is off?. it would be interesting to see your needle placement when at rest. if anyone has ever touched the cluster for work involving needles, ten they could be off after being reinstalled or bumped by accident from other work when cluster was open.

[AWE46M3]

Also, did you turn the heater to the highest temp and fan on low when refilling the coolant? This circulates coolant through the heater core loop and gets any air out.

and check the bottom front of the condensor…that is usually beat up. Might be so beat up it’s reducing air flow through the radiator.

I’ll verify that. The condenser was cleaned before the new radiator went on. No major damage or notable issues other than typical patina due to age.

If the process you’re suggesting was not completed, the system self-bleeds, doesn’t it? Any manual bleeding just expedites that process - is that correct?

[AWE46M3]

Did you replace both coolant temps sensors, one under the manifold and the lower radiator hose one?

I’ve replaced oil/coolant sensor 13621433076 last summer.

13621433077 was replaced yesterday. Both have been replaced. Thank you for calling that out

[bigjae46]

Also, did you turn the heater to the highest temp and fan on low when refilling the coolant? This circulates coolant through the heater core loop and gets any air out.

and check the bottom front of the condensor…that is usually beat up. Might be so beat up it’s reducing air flow through the radiator.

[Slideways]

Did you replace both coolant temps sensors, one under the manifold and the lower radiator hose one?

[AWE46M3]

sapote , Obioban , Casa de Mesa , bigjae46

8/2 Update: 80 degrees and sunny weather in So Cal.

Replaced the radiator, water pump, aux fan switch, radiator hoses, and installed high temp o-rings on all connecting points. Besides the O-Rings (bought from WOLFN8TR ) all parts are OEM BMW.

My water temps are still off center. Not as bad as they were before (nearing the middle dot), but off center. Temps return to center when I turn the heater on and allow the heater core to evacuate some hot air. The temps are normal until I turn the AC on, and then they begin to creep off the center line.

Car running, AC on - apologies for the glare, taken while driving.


Car running, AC off, Heater On:





I installed a new temperature sensor and thermostat last September and have about 3K miles on the car since those were replaced (OEM BMW).

Clutch fan was obstruction tested and appears to be running full power (could not be stopped by rolled up newspaper test). I am not sure where to go from here.

I had my alternator replaced before all of this started happening (also OEM BMW). The alternator is showing 13.3-13.7v when operating (reading this from my Avin head unit). I've never hit 14v when cruising. I am wondering if the alternator is not providing enough power to the aux fan. See Post 55 from this thread - member installed a 140A X5 alternator and it fixed his cooling issues when his AC was on.

Could this be my alternator not powering the aux fan sufficiently since all other major components and points of failure have been replaced?

Open to any and all suggestions for next steps to take. Car is driven modestly around town and it is ~80 degrees out. I expect more from this cooling system...

[sapote]

Do you recommend doing a full system flush and seeing how system performs thereafter? Thinking about flushing the system and maybe installing a new radiator - my current radiator appears to be the original one and may be gummed up.

On radiator gummed up, if the thermostat housing inner surface looks clean with minimal mineral scale built up, then I would expect the same for the radiator. If the overheat issue happened only recently then I don't think the the rad could change this suddenly. I'm thinking Tstat or e-fan failed (low chance on water pump).
Try to clean the debris on the rad and condenser fins.

[AWE46M3]

"Considering an electric fan conversion at this juncture if the cooling system is verified with no issues tomorrow."
I would stick with the clutch fan instead of the conversion. Even with a bad clutch fan, no overheat should happen if the elec fan in front is working properly.

At operating temp, grasp the rad lower hose and see how long you can hold it without crying. If not hot then you have coolant flow issue.

Do you recommend doing a full system flush and seeing how system performs thereafter? Thinking about flushing the system and maybe installing a new radiator - my current radiator appears to be the original one and may be gummed up.

[sapote]

"Considering an electric fan conversion at this juncture if the cooling system is verified with no issues tomorrow."
I would stick with the clutch fan instead of the conversion. Even with a bad clutch fan, no overheat should happen if the elec fan in front is working properly.

At operating temp, grasp the rad lower hose and see how long you can hold it without crying. If not hot then you have coolant flow issue.

[AWE46M3]

Quick Update from my Shop:

They inspected all my connections, tested both of my fans, and ensured the thermostat and other sensors were operational. No faults or errors logged. I am going to pick the car up this afternoon and will likely spring for a new OEM Radiator, Water Pump, and hoses. I'll bump this thread after that work is completed and let everyone know the culprit. It's still a mystery at this juncture.

Car did not heat past the center line at idle during all of their testing. Car only starts overheats when it's brought up to 40+ mph's so I need to document my replication steps a little better and start throwing parts at this thing.

Drove the car home with the AC on and the car did not overheat (some help to the cooling system from the electric fan). Water temps started to climb as soon as I turned the AC off and reached 40-50 MPH

[bigjae46]

Yes, fans degrade cooling at higher speeds.

My bet is it’s a water pump. Check for play in the shaft or pull the thermostat and check.

Here’s what mine looked like when - with no fans - performed normally at idle but ran hotter at speed.