overheating confusion need help.

[fpmbw325]

So, 325 vert 91, I am having overheating problems. I start the car and when I drive for like 20 minutes or less the temperature gauge starts to go up and keeps going towards the red area :( If I stop and turn off the car and then turn the ignition switch on/open, the gauge is at the center,normal temperature. I boiled the thermostat and it opened/good, I bled the car the correct way, lift the front, etc... Fan clutch is good, I don’t know where to go from here, faulty cluster maybe?

[Paukert11]

wrong place for this man.....

[ANDRÜ]

You are lost. Since youre here though, I would just replace the thermostat instead of boiling yours. They're cheap.

[davericher20]

that sounds like air or a thermostat, maybe even a waterpump? did you bleed it till all the bubbles came out?

[downernsp]

Did you turn on heater to full blast when bleeding? One would be surprised how much air is the system. If it was youre thermostat the lower hose would be cold. Are you certain its even getting hot or is gauge receiving bad info do to temp sensor?

[Morfhieus]

agreed with all above. Also unless you monitored the opening point of the T-stat with a thermometer to verify it opened at the right temp, it could still be bad but opening too late if at all. Their cheap and easy to change. My suggestion is to replace, bleed with the heater on full blast defrost (the vent position really doesn't matter, but makes it easy to reach in an open window and feel if heat and coolant are circulating thru the heater core while you are outside the car adding coolant etc) If the defroster never gets hot and the gauge still goes more than half way to the overheat direction, its one of two things. 1. no waterpump flow, or 2. air trapped in the system. Shut the car down, let it cool completely without opening the system and it will normally burp while it cools, then top off the coolant cold the next morning and check it again. As a BMW tech in the field on these cars it was common to have this happen after replacing any drained coolant for repairs and the overnight cooldown seemed to do the trick everytime for me. Hope it works for you.

[fpmbw325]

Thank you so much for the input. Boiling was a thing people would do to check it. I did replaced the thermo like 2 years ago but maybe is time for a new one. I will try the suggestions. Yes when bleeding the car i turned heater to full blast. @ downernsp, thats a great question how do i go about checking the temp sensor. Could it be the cluster as i said, the car overheats, i shut it off and immediately turn on the ignition only, gauge is at the center turn car on after 5-15 seconds gauge is not at center. Thank you guys