Bleeding the 02 cooling system.

[Guest Anonymous]

I have driven 02's for many years and never once have I bled the cooling system. Fortunately, I dont think I ever had to. I dont recall the manual mentioning that the 02 system required bleeding the system and have always assumed that after a few on/off cycles, any residual air would be purged automatically. Am I just stupid, uninformed, lucky or all three?

Yes, I know the 6cy models have a "bleed screw" on the thermostat housing. And yes, I have been known to drill a small hold in the 02 thermostat plate. However, I am currently running a 320 behr radiator, an unmolested 75 degree Whaler thermostat, the "gold" Mercedes coolant and a short 12" fiberglass aftermarket fan. Gauge holds steady at 3:30 with or without the air conditioning on in traffic. Now, why am I supposed to bleed the system of air again? What am I doing right?

Thank you in advance

[MatthewCervi]

I think you've been lucky and I've been unlucky. I've never once *not* had a problem with getting air out of the system and invariably spend the first week after changing coolant lifting the front end, adding coolant, watching the temperature guage jump all over the place and worrying about damaging the head. This is all after doing it "right"...nose up, heater valve open, add slowly, tiny hole in thermostat...

So whatever you're doing, don't change.

[Mars]

You only need to bleed a system if you get air 'trapped' in your cooling system. Based on what you are saying you have no need to bleed your car.

I've only ever had to do it twice in 10 years honestly. And one of those two was for my E30 which had a bleeder valve.

You can flush/fill a system, drain it and even fill it with no issues but sometime some folks pour coolant in to quickly and develop air in there.

Old rule of thumb - if it ain't broke, don't fix it. If your cooling system is fine, thermostat is working properly and your gauge holds a steady 3:30 leave it well enough alone and just enjoy drivin' it!

[Guest Anonymous]

I wonder if you dont have something else going on there. My friend told me that he needed to burp his 02 regularly if he opened up his cooling system. I used to tell him I always smelled coolant when I poked my nose in his car. He was so used to it he never noticed or was in denial. After five years of this cat and mouse game, he plugged off the hoses to his heater core and that fixed his need to burp the system and ended the constant ethylene glycol perfume.

If I were to remove my radiator for other than cooling system reasons, I typically go the messy route of flushing the radiator and engine in every direction with a garden hose. Its messy, but has a cathartic effect on me. I do not necessarily loosen the block plug under the exhaust manifold. I also flush the system so often that I rarely go the distilled water route. Although to avoid feeling guilty I once hung a sacrificial zinc anode in the neck of the radiator. WHile I understand using distilled water makes perfect sense, I hasten to note that the BMW dealerships I used to visit used the same city water. I mention this because I wonder if you couldnt reduce your air intake problem by first flushing and later adding water via the garden hose under slight pressure to the hose that goes between the thermostat and the upperhead (where the temperature sender is). By doing that you might purge the system of air there. Then, fill the radiator with undiluted coolant and add water or coolant as necessary.

Just a thought.

[BillWilliams]

Radiator, start the car and slowly fill it. So far so good.

One time, older son had his fancy tool here and we did it that way

[c.d.iesel]

...NO- it's not in the Owners handbook because It's not a Repair

Manual - and It's not stated because It's assumed your a Trained

BMW Technician.

A TIP FOR ALL :

WHEN YOU REFILL A.N.Y. COOLING SYSTEM;

mix your antifreeze with H.O.T!. water and fill SLOWLY!

FEEL your hoses and 'milk' them to circulate the hot re-fill mix - and you will virtually eliminate air pockets BEFORE you start the motor.

ALWAYS have the heater set to HOT, and then start the motor.

Keep adding HOT coolent mix SLOWLY and keep an eye on the temp gauge.

Avoid running if the gauge begins to soar to the RED zone. If it does,

switch off, let the car sit for 15 - 30 min to cool. Restart and continue to add coolent mix till you feel heat from your ducts.

Shut off , let cool completly (over night) and add coolent to the lower mark in the radiator - your COLD fill line.

good luck

wear safety goggles.

p.s. If all is 'correct' with your cooling system, head gasket, ignition timing - you don't need to drill a stinking-hole in the thermostat.

Leave that for your John Deere "B" or yer MGB-GT.