Coolant level sensor etc etc.

[rob101]

hello everyone,

when i first bought my car this coolant level warning was coming on all the time when the engine was off so i got the coolant bleed and changed, It went a while without now i get it on hot days if i switch off the car and restart it after a short time ie 5 minutes on hot days (lets face it everyday atm in brisbane is a hot day 32+ Celsius or 90+ Fahrenheit). doesn't seem to happen if i leave it for 15+ minutes. seems to be a heatsoak thing. does anyone know why it might do this?

on a side note would it be possible to retrofit a seperate expansion tank so the system was self bleeding and not dicky like this?

[632 Regal]

Hi Rob,
standard expansion tank is adequite for almost all bimmers. I think you might still have a residual air pocket that is messing with the level. Remeber to bleed with the heat fully set to hot and high, you may have air in this section.

[Kalevera]

The system is already self bleeding.

Any chance the current level sensor was manufactured by Ronak? Been hearing about those being notoriously shitty as of recent...

best, whit

[632 Regal]

whats self bleeding? still run the heater on full for a few minutes

[rob101]

why would a self bleeding system have a bleed screw?
I am talking about the version that has the filler on the radiator.
the radiator system is usually self bleeding if you have an seperate expansion tank because the air travels to the highest part of the system that being the expansion tank. Since the top of the radiator seems to be at roughly the same level as cylinder head, i believe that having the expansion tank on the radiator means that it is not self bleeding.

I will try running the heater... but i don't really want to bleed the system sounds like a bastard of a job.

[Kalevera]

You're absolutely correct, the system isn't self bleeding in the sense that the air hangs around in the radiator until the bleed screw or expansion tank cap is opened, versus possibly being vented out of a theoretical vent tube, if there were one. I think I was mixing up terminology. But a vent tube doesn't replace the necessity of a bleed screw. The purpose of a bleed screw is to remove the massive amount of air volume that is displaced when the system is filled with liquid; any system should have one, or multiple ones, regardless of whether there's a vent hose associated with the expansion tank. It doesn't need to be located at the highest point in the system. They all seem to serve a different purpose in the process of removing air.

A vented expansion tank could be installed by replacing the radiator, or finding a way to bypass the existing expansion tank. But I'm not sure why anyone would want to do this, and I can't think of any bimmer after the E34/E32 that used a vented expansion tank. The car will still need a bleed point that should be opened when being filled with coolant or to remove residual air shortly after a coolant fill.

Edit: I can't seem to get anything correct tonight. Sorry. According to webTIS, the N62 has no bleed screw and no other type of vent beyond an expansion tank hose; the procedure indicates the importance of running the aux water pump when filling the system in order to properly vent it. So you might want to try an N62 tank :D

best, whit

[rob101]

true,
but i just don't understand why these systems seem to be bled not just during changing coolant but when they randomly decide to get a bubble somewhere...... i mean last time i checked the top of the radiator should be the highest point of the system thus if you get boiling coolant or an air bubble it will flow to the radiator and condense again or reside in the expansion tank. Am I correct in assuming that the radiator is not the highest point in the system on a m50 e34?

M62 you mean, that is the v8 right, i have heard the V8s don't have the same degree of issues with the cooling system.
Sorry about the rant,
rant level error check owner's handbook.

[632 Regal]

dont confuse it with the problematic V8s, we add rad fluid and drive.

[Kalevera]

Nope, I'm talking about the N62, the valvetronic version of the earlier M62. The M62 uses a separate expansion tank, mounted to the radiator, with an integrated vent screw, but no vent line. Basically the same setup as your M50, only the tank isn't physically part of the radiator, just mounted on the fan shroud. So there's a pisser line that runs back to the expansion tank, versus a port between the radiator and the side expansion tank on the M50. I haven't yet worked on one, but the N62, according to TIS, has a vented expansion tank, so it meets the requirement.



best, whit

[rob101]

oh Right interesting, that leads me to another question, what do the letters mean for the Engine designations. I guessed M's are the "normal" engines, S engines are most of the ///M engines (i think one of the euro M5's has an M88) so what does the N Prefix mean?


dont confuse it with the problematic V8s, we add rad fluid and drive.
Forgive my ignorance, but what do you mean by problematic v8s? you mean the m62's have bad cooling systems?

[632 Regal]

just kidding with you, I have the V8 M-60 3.0 litre, they self bleed.

Forgive my ignorance, but what do you mean by problematic v8s? you mean the m62's have bad cooling systems?

[Kalevera]

Alright, let me kick my own ass for a second here and apologize for the ridiculous misinformation I was giving out last night. Moments of retarsion? Too many to drink? It's anyone's guess, but it's still probably a wise idea to disregard what I wrote. Anyway. Maybe the third time's the charm :) Let me try again.

I spent a few hours this morning working on a '91 525/m50. It is self bleeding, the requirement for which is having the expansion tank is at the highest point in the system; air collects there, as you described, and is subsequently removed when the cap or vent screw is opened. I was confusing the purpose of the vent line, which will bleed fluid pressure when the system overheats/as directed by the radiator cap, versus blowing the cap off of the tank or blowing a hose or heat exchanger.

best, whit