Hey guys, so as the title states, I just did a cylinder head job on my ‘87 325i m20b25 and I’m slightly overheating in a very odd way. Can someone help me pin point what it could be? I’ll attach a video of what it does, but basically filled the coolant and though I didn’t properly fill it with the front raised and bleed screw open, i tried to bleed air from the system afterwards. Some symptoms of the car.. Car blows hot air once it gets up to temp. When driving temp gauge goes one needle width’s from center to the cool side. After coming to an idle from driving the needle goes to 2-3 needle widths from the center to the hot side. It takes a long time for it to”creep” up to this point but doesn’t seem to “get hotter” than that. If I rev the motor the needle goes back to dead center but then creeps up again. If I drive it goes away but the other day it actually stayed hot even on the highway cruising in 5th gear. I have replaced the cylinder head with all new gaskets. Tested head with new internals. New fan clutch, new water pump, 80° thermostat, coolant flush and refill with BMW coolant, new coolant cap, all new ignition parts, new vacuum lines, new fuel injectors, and new V belts. Fan clutch is a Mahle-Behr, water pump and thermostat are OEM. Coolant level has not gone down in the past 12 hours and no visible leaks present. Any clues as to what this may be? [Here’s a short video of what it’s doing.](https://youtu.be/-D4tE0wtf30) Mind you the temp goes up as high as the first line to the right of the 12 o’clock position but doesn’t quite ever touch it. And of course while all this is happening my [vanity plate](https://m.imgur.com/a/8dYSRLI) comes in the mail...
Hmm - a better one for our resident tech, Charlson, than me - sounds, I think, like the termostat's working as expected. I had a mechanic tell me once a test for a working fan clutch is take a rolled up newspaper and put it into the fan blades when the engine's hot, if the fan clutch hydraulics are doing the coupling as they should, that shouldn't be enough to stop the fan from turning and would instead shred the end of the newspaper, but a bad fan clutch, the newspaper would stop the fan from turning. Just mentioning that since it's possible for parts to be bad outta the box (have seen it with thermostats). I'm not sure if it's particularly possible, but it might be, any chance you mounted the fan blades back on backwards? Did you spray the radiator and condenser out to clear any dirt/debris in the fins? Is the aux fan working as it should? Doublecheck the radiator temp sensor & plug, mine was so cooked from time and heat it was nearly crumbling, I _think_ (can't remember for sure without checking) the aux fan is triggered from the radiator coolant temp sensor, which I think tend to be pretty long-lived, but that doesn't get you anywhere if the wiring's out from bad plug or broken wires.
First recommend making sure the system is fully bleed properly. What is your average temp outside? Do you have the a/c on when the overheating concern is happening?
