[Kearnski]

TLDR - Flushed coolant, car now blows hot and cold air intermittently in the cabin when set to hot, flushed with electric pump countless times.

Hi guys,

New here. I've owned lexuses in the past and recently decided to switch it up and picked up a late 2006 e92 325i with less than 100k miles. Bought in Manchester and drove it 500 kilometers home, it didn't skip a beat and was a joy on the Welsh roads.

I serviced the car with fresh shell helix 5w30, genuine filters etc. I then flushed the cooling system, filled it up with fresh coolant and bled the system.

Ever since, the car over heats, I've bled the system countless times, seeing airbubbles each time. I se the cabin air temp and blow hot air for about 10mins max then it decides to blow cold air and then she overheats.

I can't figure out what's causing this, I've bled the system atleast a dozen times at this point, not sure if stubborn airlock or something worse.

Hoping someone can shed some light!

Ps. Did a sniff test on the coolant, head gasket is still good.

[Brian86]

Are the heater valves open when you run the self-burp routine?

[cyow5]

Or rather, are you doing the self-burp routine or manual? A dozen rounds of the automatic coolant bleed would take a few hours; mine only took two rounds for the coolant level to stabilize.

[Kearnski]

Originally Posted by Brian86

Are the heater valves open when you run the self-burp routine?

Afaik yes, temp set to hot, fans set to low, blowing all directions.

[Kearnski]

Originally Posted by cyow5

Or rather, are you doing the self-burp routine or manual? A dozen rounds of the automatic coolant bleed would take a few hours; mine only took two rounds for the coolant level to stabilize.

Utilizing the self burp method. When I lost patience and it was still overheating I did the manual process, some air came out after squeezing all the coolant hoses I could see! Lifted the reservoir higher to try forcing the air to rise. Few bubbles here and there.

[cyow5]

You must be getting air in somewhere. Or can you confirm the water pump did run when doing the automatic burp? That process worked very well for me, so something seems off.

[Brian86]

I also found the self-burp routine to be very effective. Just ran it once and the car was fine after that each time I've emptied the water.

Is it possible the thermostat is acting funny? IIRC these cars have a 'heated' thermostat, the purpose of which is to electrically open the thermostat at a lower temperature than the normal set point.

I imagine that during the self-burp routine it utilizes the heater force the thermostat open in order to clear air bubbles

Grain of salt of course... I don't have that level of detailed knowledge. Just throwing spaghetti at the wall.

--------- Ninja Edit:

Is the car throwing any codes? If the electric water pump is malfunctioning the DME should know about it and be throwing a malfunction.

[Kearnski]

Originally Posted by cyow5

You must be getting air in somewhere. Or can you confirm the water pump did run when doing the automatic burp? That process worked very well for me, so something seems off.

Seemed to have run! started squirting coolant from the upper hose back into the expansion tank, that being said it did not run for the 10-12 mins, maybe 3-5 mins and that was it.

[Kearnski]

Originally Posted by Brian86

I also found the self-burp routine to be very effective. Just ran it once and the car was fine after that each time I've emptied the water.

Is it possible the thermostat is acting funny? IIRC these cars have a 'heated' thermostat, the purpose of which is to electrically open the thermostat at a lower temperature than the normal set point.

I imagine that during the self-burp routine it utilizes the heater force the thermostat open in order to clear air bubbles

Grain of salt of course... I don't have that level of detailed knowledge. Just throwing spaghetti at the wall.

--------- Ninja Edit:

Is the car throwing any codes? If the electric water pump is malfunctioning the DME should know about it and be throwing a malfunction.

I can see your point! No codes, although i only had a cheap code reader to hand at the time

Figured i'd bite the bullet and get a new pump and thermostat, along with a few new hoses, bolts and coolant temp sensor. I have no service history on the car and with it hitting it's 100k anniversay i figured it's the best thing to do. atleast i wont have to go out of my way for another long while to do these, and if the pump/ stat was dying (i feel like it might be, the 'self-bleed' only ran for 3-5 mins max), kills 2 birds with one stone (or 2?)! will update once parts installed!


---EDIT
i tried the self burp again over the last few days, waterpump doesnt kick in, nothing happens, maybe she was just on her last legs?

[Kearnski]

Originally Posted by Kearnski

TLDR - Flushed coolant, car now blows hot and cold air intermittently in the cabin when set to hot, flushed with electric pump countless times.

Hi guys,

New here. I've owned lexuses in the past and recently decided to switch it up and picked up a late 2006 e92 325i with less than 100k miles. Bought in Manchester and drove it 500 kilometers home, it didn't skip a beat and was a joy on the Welsh roads.

I serviced the car with fresh shell helix 5w30, genuine filters etc. I then flushed the cooling system, filled it up with fresh coolant and bled the system.

Ever since, the car over heats, I've bled the system countless times, seeing airbubbles each time. I se the cabin air temp and blow hot air for about 10mins max then it decides to blow cold air and then she overheats.

I can't figure out what's causing this, I've bled the system atleast a dozen times at this point, not sure if stubborn airlock or something worse.

Hoping someone can shed some light!

Ps. Did a sniff test on the coolant, head gasket is still good.

Update:
Changed the waterpump and stat and let the burp run again and I knew immediately that it was fixed, previously when the self burp was running there was a stream of coolant coming from the upper hose but had very little pressure behind it(I thought this was normal). Once I ran the bleed after changing the bits I could hear the coolant gushing about. Took it for an hour long test drive and no more overheating!