e46 cooling system issues dash light intermittently on

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rc944
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e46 cooling system issues dash light intermittently on

Post by rc944 » Sat Nov 05, 2022 3:22 pm

So the dash light pops up when the engine is up to temp and then goes off sometimes. The level is fine. The coolant was changed 2 months ago. It has never happened before and first happened a week ago.

Just now the needle moved briefly into the red quadrant but not onto the red zone before moving back to normal middle position

I've not yet tried to top up the level with the bleed screw removed until it pours out of the bleed screw hole. That won't purge air unless in the top hose so I'm not hopeful that will work

It's done 115k miles and my touring with similar miles had most of its cooling system replaced.

I know that there is a prescribed process to flush and refill the system and I know it has been observed

If it was a duff sensor I don't think the needle would move the way it did. I also don't see obvious signs of a leak but I've not removed the undertray nor have I yet checked hoses for obvious signs of a leak.

Anyone had similar symptoms and if so what was the cause and remedy?
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Re: e46 cooling system issues dash light intermittently on

Post by hap » Sat Nov 05, 2022 3:28 pm

Sticky thermostat not opening fully possibly ?air lock so needs bleeding

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Re: e46 cooling system issues dash light intermittently on

Post by ScooBeeFive » Sat Nov 05, 2022 3:43 pm

rc944 wrote:
Sat Nov 05, 2022 3:22 pm
Just now the needle moved briefly into the red quadrant but not onto the red zone before moving back to normal middle position
I had some cooling issues on a Subaru I once owned and the needle would move around randomly like this. Turned out to be airlocks caused by the heater matrix. That needle behaviour could well be due to air in the system.
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Charles
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Re: e46 cooling system issues dash light intermittently on

Post by Charles » Sat Nov 05, 2022 7:44 pm

Some thoughts ...

If the coolant was changed two months ago then it is unlikely to be due to airlocks if you've been using the car regularly. If there is air in the heater matrix then you will struggle to get hot air blowing so this is easy to check, as well as checking coolant level (which you have already done).

If you want to try and bleed the system then park on a slope with the front of the car higher than the rear before running the car with the coolant cap off as this helps force any air towards the front high point.

A faulty thermostat fails open so the gauge struggles to reach normal, so probably not that.

A faulty sensor might be the issue causing the electric fan from not being triggered but the overheating may also be due to the electric fan failing, which happened on mine recently. Is this happening only when stuck in traffic? If so, then this is likely.

Finally, you can easily check if the viscous fan mounted on the front of the engine is moving freely, as it should, by spinning it (when the engine is off, of course) and observing it when running.
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Re: e46 cooling system issues dash light intermittently on

Post by rc944 » Mon Nov 07, 2022 2:23 am

thanks for the input gents

so it transpires when i checked the level all was not what it appeared to be

i re-checked and it needed topping up by about 1 litre. its now fine but theres clearly coolant loss somewhere. im wondering if there is a loose fixing/hose clip from when the coolant change was done

ill get it booked into the garage and update when i have news
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Re: e46 cooling system issues dash light intermittently on

Post by rc944 » Thu Nov 17, 2022 3:02 am

expansion tank split

new tank and thermostat to be fitted - glad nothing more sinister
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Re: e46 cooling system issues dash light intermittently on

Post by Charles » Thu Nov 17, 2022 9:31 am

rc944 wrote:
Thu Nov 17, 2022 3:02 am
expansion tank split

new tank and thermostat to be fitted - glad nothing more sinister
Glad that you've found the problem and it isn't too major - this is a predictable failure for the E46.

You might consider replacing the hoses at the same time - whilst the system is drained down and access is easy - as, from my experience, the E46 cooling system has a habit of having cascading problems until everything has been replaced.
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Re: e46 cooling system issues dash light intermittently on

Post by Henry » Fri Dec 16, 2022 8:06 pm

Could the coolant loss not be the fact that there was trapped air in the system and when expelled the air pocket was then filled with coolant. To leak 1 ltr is a lot of coolant that would surely leave a trace on the engine or at least in the compartment. Perhaps the problem is now fixed
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Re: e46 cooling system issues dash light intermittently on

Post by hap » Fri Dec 16, 2022 9:33 pm

Yep common issue mine did same split could only see it in right light

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