engine and drivetrain Bleeding coolant system - sound reasonable?

[worzella]

Does this procedure, found in the BMW service manual, sound like the best and easiest way to complete the job when draining radiator and replacing hoses? It raises some questions in my mind...

"Before refilling the coolant system, set heater level to "warm". Fill in water and screw on cap until the second stop is reached. Run engine so coolant is heated to 80 degrees C (176 degress F). After the thermostat has opened, bleed system by turning radiator cap to first stop. In this process, press the upper and lower hose manifolds together by hand a few times, as this generates a pumping affect and ensures that any air still in the system can escape through the radiator. Check coolant level and turn radiator cap to second stop."

? How does one tell when the thermostat has opened? Is there an approximate idle time to shoot for.

? Is seems to imply that you use water for this operation since it says "before refilling the coolant system... fill in water", but .... ughhhh... when do you replace the water with antifreeze.

? If the system is heated up, is turning the radiator cap to the first stop tricky or is there no danger of hot liquids shooting out of the cap.

Sorry for the newbie questions.... but gotta start somewhere!

[wagnerf15]

Before you dick with a radiator cap on a hot/pressurized system, I recommend you put a heavy towel over it, because hot antifreeze WILL shoot outta there. Guess how I know this tidbit? And I reckon you can tell if the thermostat has opened by feeling the lower radiator hose...when it's warm/hot, the thermostat has prolly opened and pulled the hot water through the radiator.

I've always bled by filling the radiator, starting engine (with cap off radiator) and allowing it to idle until warm while topping off the radiator. When it's pretty warm and won't take any more, put on the cap, go for a short drive (with your bottle of antifreeze) and assuming you haven't had to stop to add fluid, top it off when you get home. Then check it cold next time and top off. That usually gets all but the most stubborn air bubbles out. HTH

[worzella]

Great... thanks for the more practical approach!

[John_in_VA]

as mentioned in the initial instructions. That will get new coolant-water combo circulating throughout the entire system.

[yeewiz]

and point the car uphill too while doing all of the above

[jgerock]

I just did this on my car. The "burp" method of squeezing the hoses seemed to work for me.

BTW - I'm trying out the Prestone pre-mixed coolant.

[yeewiz]

aren't you supposed to use the BMW brand coolant because it's got some gizmo chemistry that's low oxidation or whatever that other brands don't have?

[Jeff]

I think everybody here has a good recommendation.

I would spend the extra $10 on the BMW antifreeze, it's really good quality. I would also spend a extra $1.50 on some distilled water at Safeway to help keep the electrolysis in check.

Read this Pelican Tech artical on BMW Cooling Systems.

http://www.pelicanparts.com/bmw/techarticles/E36-Coolant_Flush/E36-Coolant-Flush.htm

[golf73]

I just did this on my car. The "burp" method of squeezing the hoses seemed to work for me.

BTW - I'm trying out the Prestone pre-mixed coolant.

i use prestone, about 60-40 coolant to D.I. water. it's good to squeeze the hoses, but i go the extra mile and actually get the car up on ramps in the front to get the radiator cap to be the highest point in the cooling system to let all the gases escape.

[robspeed]

by "water" im sure they mean coolant/water mix. The expensive mysterious BMW blue coolant is actually BAD for any plastic cooling system parts, so if you have an e21 plastic-tank radiator (or any newer BMW you intend to keep past warranty) I personally would FLUSH IT OUT and get some prestone or other universal coolant which does not contain the evil 2-EHA plasticizer that BMW uses, and paradoxically eats their plastic cooling system parts from the inside out.

[jimk]

On final level, there should be a small air space in the top tank for expansion or it will push out later what coolant it doesn't want anyway. This design is "pre-expansion tank" or "pre-small radiator" and needs the expansion room.

[robspeed]

I just did this on my car. The "burp" method of squeezing the hoses seemed to work for me.

BTW - I'm trying out the Prestone pre-mixed coolant.

i use prestone, about 60-40 coolant to D.I. water. it's good to squeeze the hoses, but i go the extra mile and actually get the car up on ramps in the front to get the radiator cap to be the highest point in the cooling system to let all the gases escape.

in SF's climate there is no reason to use so much coolant to water. In fact you can use less. Water is what provides the thermal transfer from hot engine to radiator/air. If you lived in an area where the temps dropped past -34degrees, then a 60/40 mix might make sense. Otherwise you are just wasting coolant and/or limiting your thermal transfer capacity. Racers will often just run pure distilled water or maybe 15/85 coolant to di water for this very reason...

[BillWilliams]

but bike racers use pure water because the tracks require them too for safety reasons, nothing to do with cooling capabilities.

Water evaporates when on the track, anti-freeze stays slickery for a long time on the track, even hard to clean up.

[Green2k2]

...and the water pump on our car needs some "slickery" to stay functioning longer.

we don't need a lot of coolant in warmer climates...but we need some.

[golf73]

I just did this on my car. The "burp" method of squeezing the hoses seemed to work for me.

BTW - I'm trying out the Prestone pre-mixed coolant.

i use prestone, about 60-40 coolant to D.I. water. it's good to squeeze the hoses, but i go the extra mile and actually get the car up on ramps in the front to get the radiator cap to be the highest point in the cooling system to let all the gases escape.

in SF's climate there is no reason to use so much coolant to water. In fact you can use less. Water is what provides the thermal transfer from hot engine to radiator/air. If you lived in an area where the temps dropped past -34degrees, then a 60/40 mix might make sense. Otherwise you are just wasting coolant and/or limiting your thermal transfer capacity. Racers will often just run pure distilled water or maybe 15/85 coolant to di water for this very reason...

i drive out of the city every day for work, there are a lot of microclimates around here. it was 32F the other night in Walnut Creek - 15 miles east of Berkeley