To Bleed Or Not To Bleed

[JMI]

I have a 1989 535iA, North America (an E34) with the coolant expansion tank up against the fire wall, not attached to the radiator. According to the following:

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

that type system is self bleeding. Is this been the experience with others who have flushed and refilled their own coolant? Thinking I should bleed it no matter what it says.

TIA

[joshua43214]

if its not broken or about to be brake, don't fix it.

[JMI]

if its not broken or about to be brake, don't fix it.

Well, the unstated question was is it true about the self bleeding? Going to change the coolant tomorrow to get the "green goo" out and replace with BMW coolant.

TIA

[Kristuphir]

You definitely, most certainly want to bleed it. It might go really quickly or it might take quite a few tries. But by all means, bleed it. When you replace the coolant you're going to get bubbles and air pockets that are above and beyond what the "self bleeding" system can handle, and those will make your temp needle and engine do scary, expensive things if you don't get rid of 'em...

[dternst]

No need to bleed. I just completed the same messy task last weekend. You should worry more about how to get to and loosen the driver's side engine plug.

[joshua43214]

Well, the unstated question was is it true about the self bleeding? Going to change the coolant tomorrow to get the "green goo" go out and replace with BMW coolant.

TIA

Sorry missed the unspoken question, sounded kinda like you had a bug from something you read and wanted to bleed as "preventaive maintainance". If you flush it, you have to bleed it. Your system is "self bleeding"(in theory anyway) once the T-stat opens, but if not prebled, the T-stat may not open before the car overheats.

[JMI]

No need to bleed. I just completed the same messy task last weekend. You should worry more about how to get to and loosen the driver's side engine plug.

Thanks for the replies.
Been thinking about the block drain plug. If I understand correctly it is suppose to be under the exhaust line(s) which in my case is the passenger side. Was wondering if you used a combination wrench or a socket and ratchet or breaker bar and how long was it. Also was told the hex size on the drain plug was 19 mm. Does that sound right?

TIA

Jim

[Kalevera]

Well, for the record, a coolant change on an M30 is a completely different animal from one on an M60 V8.

There's a lot of confusion in what "bleeding" means. On engines that have a bleed screw at a cooling system high point (M30/M20/M52/M40 variants), it's important that it remain open while initially filling the system. It is the first, and most critical, bleed of air. In fact, it's practically impossible to fill such systems without cracking open the screw -- a bit hard to know what's normal and what's not when you've never done it before, though.

It should take less than a minute to do the secondary bleed on a carefully filled M30 system. Once coolant runs out of the bleed screw, close it and fill the reservoir to the top, even above the return inlet (and overflow outlet, in the case of the firewall tanks and others so equipped). Close the system, start the car. Heat on full. Give it a few revs, nothing too sincere -- it's cold. Open the expansion tank, watch the return stream. Bring revs up a bit. If the return line is clear (and they often clog), the stream will get consistent with revs, meaning little to no visible air, within about 30 seconds. Crack the bleed screw again just to verify that no air comes out with the coolant. Drive and watch the temp gauge. The system will dump any excess coolant out of the overflow. It may sometimes be necessary to correct the fluid level once the car is cold again. Occasionally, it's necessary to crack the bleed screw again and let more air out.

I've used a socket + wrench, socket + universal + extension + wrench, and plain old spanner on those plugs. It's an M14 bolt, 19mm head. Watch your eyes if doing this on jackstands or ramps. You'll probably get bathed in coolant the first go around.

Good luck!

best, whit

[JMI]

Thanks for the detailed instructions. I'll let you know how it turns out.

Jim

[JMI]

It went very easy. Was worried about the block drain plug but once under the car the plug was fairly accessible.

Thanks to everyone.