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Old 09-13-2018, 08:10 PM
jpilk99 jpilk99 is offline
Join Date: Aug 2018
Location: Bolton, MA
Posts: 70
jpilk99 is on a distinguished road
Originally Posted by oldskewel View Post
Yes, this is the main improvement you need.

BTW, on the mechanic rev'ing, I think that's typical of how they have to operate differently than an owner does. He has to basically get it all done at once, so he can give you the keys and the bill, and you'll be on your way and done. As owners, we can do it more easily and probably better, taking advantage of the fact that we can fill it, bleed it, run it, and then do the final fill adjustment more accurately the next day when it has cooled down.

In my cooling system and cylinder head problems this summer, I did a few cooling system fills/bleeds on my 3.0i. Here are my notes from the procedure I used:

Bleeding cooling system:
  • This may work best with the engine heading up on a sloping driveway like mine.
  • Install drain plugs on engine block (right side, towards front, can be reached from above and front, with left hand. 13 mm hex head) and radiator (bottom left end)
  • Bleed screw loosened to free the o-ring, but not fully removed
  • Expansion tank cap removed and set aside. Yellow funnel in top of expansion tank.
  • Fill through expansion tank until full
  • Key to ON (not START), heat set to max heat. Fan speed to low. Doing this activates the electric coolant pump. Filling before doing this step prevents damage from that pump running dry. Should now see a stream of coolant flowing diagonally when looking down into the expansion tank.
  • Keep filling the expansion tank until bubbles stop and some fluid comes out of the bleed plug opening. Can squeeze the upper radiator hose to free bubbles if that helps.
  • Close bleed plug, fill expansion tank. In theory, the tank needs to be siphoned out down to red rod max level. But there is usually enough air still in there to accommodate that, and then require a little addition on the final check.
  • Drive it around normally (the above steps should get most of the air out, even without driving, running the engine)
  • When done, let it cool down, then fill expansion tank so the floating stick is at spec, but not overfilled

Regarding the leaking you notice at the expansion tank cap ... look out. That's what I had. Turned out there was no problem with the cooling system at that point, but the head had warped, and combustion gases in the coolant (confirmed with my tester) were pressurizing the cooling system, and being released by the 2-bar cap.

If you can confirm coolant leaking out of the cap, there is a chance the cap is bad, but if not, the next step is to check for combustion gases in the coolant.

Here's my thread on my warped head problem this summer:

Hopefully yours does not require the work mine did.
Thanks Oldskewel. I guess my big question, about the "geyser" of coolant coming up/out of the bleed screw: IF I had a warped head or headgasket issue, HOW would that come into effect with the engine not running? There would be no combustion going on?

Thank you.
03 X5 3.0
01 740iL
01 325Ci

00 750iL sold
95 740i sold
99 328i convert
95 325i convert
95 325iS
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