Should I disconnect the battery when doing thermostat???
 

I read a DIY on the thermostat/Water pump procedure. I figured I should disconnect the negative terminal because I will be removing the aux fan, but the article after they drained the coolant he turned the power on to run the heater to flush through the heater core???

What do you guys recommend?

I didn't disconnect the battery for the thermo or to remove the aux fan. Change it out, torque to spec, reconnect hoses, fill'er up and burp the coolant reservoir... All done!

Good luck!

Burp??? Is that really a process?

Im also doing the Water Pump to... Any info will help

Sure is. Its like a "last removal" of air from the cooling system after the t-stat opens.

I dont think I've ever disconnected a battery while working on the car that didnt actually require, you know, disconnecting the battery (airbags).

Bleeding e3/4/5's is kind of a trip. The e46 guys have some writeups on this down to a science, but basically, turn the key to on, heat to 90, three dots to red, and fill until its full. BUT, by full, I mean when its actually full per the mark, not until the reservoir is full. Thats why people keep blowing up ET's.

You don't need to disconnect the battery.

Three dots to red????

And ET???

I dont get it

Listen Padawan... The secret of the three dots is something that mere mortals are not capable of handling. Its like a password into the secret ubergermanclubthingus (real german word actually) of BMW's.

If youre ready....

on your dash board, above the center vent is a wheel with red and blue dots. 1,2,3 red and 1,2,3 blue. On some models it has a white line in the center, for, you know, the center.

I'm only a level 7 BMW jedi having owned 3 of them, so I only loosely get the concept of the three dots, but dont pretend to UNDERSTAND the three dots.

Basically, if its in the red, hot air will come out of the vents. How is this different than mission control below (HVAC)? I have no idea. Thats the mystery. You will never get that to the right temp. Its either too hot or too cold.

So, long story short, to bleed the coolant, turn it all the way to the 3 red dots (make sure it goes all the way, it kind of 'pauses' at the top).

the ET is expansion tank and you will hear it spoken about in angered tones the longer you stay around BMW's. BMW's dont pressurize directly through the actual radiator, thats why the cap is on the ET. The ET is both a overflow tank, pressure regulator and reservoir. They are notorious for bursting at the least opportune time (shortcut through the ghetto?). Its been suggested that this is in part due to the fact that the design of the tank encourages you to considerably overfill the max level. At that point its pretty simple. Too much pressure, no place to go, Pop!

So, when filling the ET, pay attention to the float, and never fill past that line.

Just did my water pump and thermostat + hoses and left the battery connected without any issues.

Hey guys so I just did my T Stat, When refilled it i didnt know about this special burping sequence... Today (2 days later) I burst my ET.

My Indy says its easier if he uses some "Vacuum" tool to suck the air out. I would prefer not to pay him right now.

I am getting another tank but I want to make sure I do not do this again. So when i replace the tank All i need to do is turn the heater on 90 (three red dots up top)

Start the engine (Do i run it like this while off at all??). And then slowly fill until the floating dipstick thing is in the full position?

Is that IT??

I do not want to pay for this air vacuum service but I really do not want to pay for another expansion tank either.

thanks!!