New to Z3's- Basic question on cooling bleed screw

[David9999999]

I recently picked up a '97 2.8 roadster that I'm refreshing. I'm new to the M52 engine (previously worked with older cars). I've read about coolant bleed screws breaking often. I am not sure if the screw on my car is broken- it came out but the end does not have a nice taper.

What I'm wondering is, how deep is the hole for the bleed screw? I'm not sure if what I'm seeing is the end of the bleed screw or the bottom of the hole. If I squeeze the upper hose, I see coolant enter the hole. Will upload some pics later today.

[MIKYZZ4]

This is it, tiny taper:

[bluptgm3]

This is it, no taper:

Yes, bleed screw has a square end and an o-ring under the head accomplishes the ‘seal’.
Don’t over tighten the screw, as all that is required is ‘just seated’ pressure.
You can buy a brass replacement that will polish up and look cool but breakage of the bleed screw - fractures just under the head - isn’t really an issue as long as you use a light touch.

Only a partial turn is required to open the port and bleed excess air.


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[BimmerBreaker]

If it isn't leaking when the engine is running, it's fine

[Tallyho322]

Watch out for the radiator drain plug (also plastic). Mine broke while wife was driving the car.

Could have been catastrophic, but luckily she noticed the puddle of antifreeze and parked the ca4.

$7 part, but required to keep the antifreeze in.

I bought a brass bleed screw (not sure it is better than the plastic ones, but it won’t get brittle I guess).

Greg

[Vintage42]

... I bought a brass bleed screw (not sure it is better than the plastic ones, but it won’t get brittle I guess).

I bought a brass bleed screw, but have not used it since I heard the plastic screw is designed to break before it strips the plastic radiator threads.

[zellamay]

I bought a brass bleed screw, but have not used it since I heard the plastic screw is designed to break before it strips the plastic radiator threads.

I wouldn't tighten it enough to find out. One might be able to damage the radiator with the brass one, but neither one should be tightened enough to threaten. A screwdriver with no real muscle behind it is enough.

[David9999999]

Thanks for the helpful responses. The screw is sealing fine and is working, even though the end does not have a nice flat surface like some photos I have seen. Still, I will replace the plastic screws (including radiator) due to age- cheap insurance.