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Steve van hool

96,528i overheating when turning heaters on

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My 528i, 1996 year, I altered the heater/demister settings from 16 degrees to 26, and temp gauge went into the red, its as though the coolent isn't circulating when the temperature setting is altered upwards, radiator top hose, red hot, bottom hose cool. Any ideas folks? Hopefully not a blocked heater matrix, as that is a dashboard out, I believe.

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Or could be an air lock in the cooling system

 

I'd give it a good bleed first and see what goes on from there

 

Could be a dodgy stat or failed/failing water pump too maybe?

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1 hour ago, d_a_n1979 said:

Or could be an air lock in the cooling system

 

I'd give it a good bleed first and see what goes on from there

 

Could be a dodgy stat or failed/failing water pump too maybe?

 

Dan, When I took it for an mot it was playing up the same way, my friendly tech bled it, and took about a kettle full of water, and been alright since, till I  altered the heater temp, so an airlock which only occurs when the heater is activated? Water pump, and stat replaced a good while ago.

 

 

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5 minutes ago, Steve van hool said:

 

Dan, When I took it for an mot it was playing up the same way, my friendly tech bled it, and took about a kettle full of water, and been alright since, till I  altered the heater temp, so an airlock which only occurs when the heater is activated? Water pump, and stat replaced a good while ago.

 

 

 

I'd still check pal; pumps can fail unfortunately; whether new or old.

 

Are the pipes to and from the heater valve hot too (on the nearside suspension turret)?

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Had a proper look at it, would seem to be an air lock, as when driving it it will briefly go into or very near the red band on the temp gauge, before dropping back to the middle of the temp gauge, happening once every 5 minutes when driving it, so air getting in when the heaters are activated, question is where, hardened radiator cap seal?

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4 minutes ago, Ray112 said:

Fingers crossed it's not head gasket, because that's most common reason for never ending airlocks. Is system heavy pressurised when running?

 

No it's not, and will happily run all day long without playing up, if I don't activate the temp setting on the heaters. Dealer fitted a new engine block at 38,000, now on 147,000 miles, so not been to the moon, and back.

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FWIW, just a bit of feedback folks, a new thermostat and housing have solved the overheating problem, the old one wasn't opening, so preventing the coolent circulating. Also the new stat came with a small bleed toggle valve on it, it was a Myle thermostat.

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10 hours ago, Steve van hool said:

FWIW, just a bit of feedback folks, a new thermostat and housing have solved the overheating problem, the old one wasn't opening, so preventing the coolent circulating. Also the new stat came with a small bleed toggle valve on it, it was a Myle thermostat.


Good news :) 

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11 hours ago, Steve van hool said:

FWIW, just a bit of feedback folks, a new thermostat and housing have solved the overheating problem, the old one wasn't opening, so preventing the coolent circulating. Also the new stat came with a small bleed toggle valve on it, it was a Myle thermostat.

Good news, but little weird actually. With heater to coldest setting you can run it all day long, but actually then thermostat need to open/stay open more often than when using heater, because great amount of heat is given away through heater matrix, and less hot coolant getting passed into radiator. That's a bit of theory about heating and cooling, and how it works. 

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4 hours ago, Steve van hool said:

I don't know Ray, just glad it's been resolved, when the heater is turned on, normally you are effectively increasing the capacity of the coolent, but if it isn't circulating anyway!!!

Thermostat only stops coolant from circulating through front radiator, it doesn't have ability to stop coolant flow to heater matrix. And like you said, turning heater on increases coolant capacity, so logically engine temperature will even drop at beginning, when increasing cabin temperature. That's actually what I can see on my e39, when hidden temperature screen is selected and I turn up heat from let's say 20° to 26°. 

Definitely a little strange issue, but good it's sorted.

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