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Coolant Bleeding

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Hi Guys

My low level coolant light comes on after approximate 10 miles. There is no coolant loss and temp is normal (does not overheat even after 2-300 miles)

I presume its an air lock . So decided to check the radiator after running and its warm at the top but cold at the bottom.

Therefore seems its air lock in the rad.

Whats the best way to bleed air out of the radiator without draining the system ?

Thanks in advance

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the level sensor is dry it fits into a recess on the outside of the bottle and reads a magnetic signal from the float in the bottle. They are a bit fragile and people seem to have problems when mixing aftermarket parts. I don’t know of a way to specifically bleed the radiator but I’d be checking the sensor first and then go from there if there is no loss of coolant. 

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Hi Incredirog

Thanks for your reply. I've fitted a new sensor and checked and it works ok.

My question is how do I bleed the system without draining it again.

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Hi Ian1001

Thanks for the post. Unfortunately the link is for a E36. Have tried finding E46 316i 2004 without success.

Have already Googled bleeding E46's but they all show how to bleed after draining and refilling.

I really cannot face draining out the system again, so was asking if anyone knows how to extract air pocket without draining.

 

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Have you tried running the engine with coolant reservoir cap off until the engine come up to temperature? Then squeeze the lower radiator hose (and any other coolant hoses that are easily accessible) multiple times. Make sure you keep your hands away from the radiator fan and keep an eye on the coolant level. That should get rid of an air locks.

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Hi 2clubsp

Thanks for the post. I've not tried that so will give it a go later today -- thanks.

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When I came to replace the thermostat I researched coolant system bleeding, did as per 2clubsp's advice and also had the car parked on a steepish upward incline. With the cap off and engine running you should be able to see coolant squirting back into the reservoir.

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10 minutes ago, B.Merr said:

When I came to replace the thermostat I researched coolant system bleeding, did as per 2clubsp's advice and also had the car parked on a steepish upward incline. With the cap off and engine running you should be able to see coolant squirting back into the reservoir.

Hi B.Merr. Thanks for your reply. I already have coolant squirting back into the reservoir.

From what I can gather it seems I have an air lock in the radiator ( warm at top but cold at the bottom even after 20 miles ) So its another drain out and refill. Will take your advice and make sure the front is raised high this time.

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I'm guessing you have opened the bleed screw on the top of the expansion tank?

I'm also guessing you'v bled it with the ignition on and the heater on the hottest setting?

Squeeze the upper and lower radiator hoses when cold and the engine off with the radiator cap off too. The movement of coolant as you displace it ought to help.

Did this come when you drained the system in the first place or out of no-where?

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1 hour ago, kirkynut said:

I'm guessing you have opened the bleed screw on the top of the expansion tank?

I'm also guessing you'v bled it with the ignition on and the heater on the hottest setting?

Squeeze the upper and lower radiator hoses when cold and the engine off with the radiator cap off too. The movement of coolant as you displace it ought to help.

Did this come when you drained the system in the first place or out of no-where?

Thanks for your post Kirkynut.

I originally had a leak on the expansion tank so had it replaced plus top hose. Since then I've had the problem. Have tried squeezing top and bottom hoses without success. Top of radiator is hot but bottom is cold so looks like a air lock. Therefore I've got no choice but to drain the system again and raise front of car, bleed with ignition on and heater on max setting.

 

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I don't think you'll need to raise the car but the heater needs to be on full with the ignition on or you'll get an airlock in the heater matrix.

Did you not have the heater on when you refilled it last time?

Kirkynut 

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28 minutes ago, kirkynut said:

I don't think you'll need to raise the car but the heater needs to be on full with the ignition on or you'll get an airlock in the heater matrix.

Did you not have the heater on when you refilled it last time?

Kirkynut 

Yes -- heater and ignition was on when last filled and I have heat coming through the car.

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Should be bleeding the system with the car running and the bleed screw cracked open.

I use a funnel that seals into the expansion tank and fill it up into the funnel to make the water level higher so you can physically see the bubbles and the final burb. While the car is running open the bleed screw every now and then so to not make such a mess. Once the fan has come on twice i switch it off and leave it to cool down and it sucks the remaining coolant from the funnel if any air remains.

Had my coolant system apart many times and never had a problem this way.

Edited by R11CH

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On 16/04/2018 at 21:45, R11CH said:

Should be bleeding the system with the car running and the bleed screw cracked open.

I use a funnel that seals into the expansion tank and fill it up into the funnel to make the water level higher so you can physically see the bubbles and the final burb. While the car is running open the bleed screw every now and then so to not make such a mess. Once the fan has come on twice i switch it off and leave it to cool down and it sucks the remaining coolant from the funnel if any air remains.

Had my coolant system apart many times and never had a problem this way.

Yes, it needs to be running but after you've got as much coolant in without it running with the ignition on and the heater on full.

I'v done it about 6 times across our 2 E46's with no issues.

Kirkynut 

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