Weird coolant leak...

[ecrabb]

I already posted about this in the "random questions" thread, but I thought I'd start a thread so it's easier to find in case this happens to somebody else.

Basically, I found a small puddle in front of the car, figured out it was coolant, but couldn't any obvious leak under the car. I posted in the random questions thread, and confirmed I should drop the plastic belly cover, and that I should check the radiator, water pump, expansion tank, and the aux fan temp sensor o-ring.

I jacked the car up, put it on stands, dropped the belly pan, and couldn't see much other than dried crusty drips in a few places, including all over the bottom of the sway bar. It looks like it's all coming from above. Looks like it's the expansion tank. I'll post pics from Tapatalk in the next post so you can see what I'm looking at.

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[ecrabb]

That's neat. Tapatalk won't let me post a photo. It appears to be totally broken.

[ecrabb]

Just a few drips here and there...

http://uploads.tapatalk-cdn.com/20160624/dd5438d4eeb0b81b9e6ec309189eaee4.jpg


http://uploads.tapatalk-cdn.com/20160624/2b872b04d8e47385b5b0804bc18f81a6.jpg


Ah-ha... I saw a few drops here when I glanced, but didn't see the crusty coolant pooled on top of the expansion tank...

http://uploads.tapatalk-cdn.com/20160624/6938f4488e9a927b83f8fa46f67ce1d9.jpg



I still wasn't clear where the actual leak was from though so I fired it up for five minutes and brought it up to operating temp. Temp held steady. Looked at the tank again and saw this...

http://uploads.tapatalk-cdn.com/20160624/67521914d60a9d3ad33818aea09776ab.jpg

Looks like a pressure relief or something.

So, new expansion tank? Should I just do a cooling system refresh at the same time? The serpentine belt is original so I assume the other one is, too. The lower radiator hose is a Napa, but the upper looks original.

Thoughts?

Thanks!

SC

[09mageec]

Looks very familiar to one I used to have. With the car fully warmed up after driving a bit, turn it off and take a good look around the filler neck of the expansion tank, you may see some slight bubbling, and hear a fizzing noise like air escaping. Right where the neck creases to form the tank... I developed a hairline crack on mine.

[Sockethead]

That's the air bleeder. when you do cooling system maintenance and refill the system, use open that bleeder to bleed off the air as you fill it with coolant. It's easy to over tighten that bleeder and it develops a crack.
If you don't know the age of the expansion tank, it may be a good time to swap it out for peace of mind. Otherwise just replace the bleeder screw and see what happens...

[johnrando]

You could also borrow/buy a pressure test kit to pump some air into the system and see where the leak actually is, but I agree with Rob.

[ecrabb]

I have no doubt the expansion tank is the original, so it's 45k miles and 12 years old. Like I said earlier, I definitely want to do a complete cooling refresh at some point. The kit with tank, hoses, pump, and belts at ECS is only $300-some dollars, so it's a no-brainer.

That said, I'd like to wait and do that this winter if possible so I can use the car now. So, would you guess the vent screw is what's developed a leak? Looking at Real OEM, that's a separate part...

http://www.realoem.com/bmw/enUS/part?id=BW53-USA-06-2004-E46-BMW-330Ci&mg=17&sg=30&diagId=17_0215&q=11537793373

Should I just pick one up at the dealer if they have one and try it?

Just hoping to drive the car this weekend instead of spending the whole weekend working on it or leaving it parked until I can order all the parts for a whole refresh. ;)

As always, thanks guys!!!

SC

[BMWCurves]

I did my cooling system at 49k miles due to age rather than mileage. The components were about 10 years old at that time. If the leaking's not significant beyond the bleeder screw, which you can replace as you stated above, then I would think you could hold off until the winter or at least the fall.

As for replacement kits, I recall Vas not having a great experience with ECS' kit. I went with Turner Motorsport's kit and haven't had any issues. If I were to do it again, I would look up all the individual part numbers through RealOEM and then price it out as cheap as possible through FCP and ECS.

[ecrabb]

I did my cooling system at 49k miles due to age rather than mileage. The components were about 10 years old at that time. If the leaking's not significant beyond the bleeder screw, which you can replace as you stated above, then I would think you could hold off until the winter or at least the fall.

As for replacement kits, I recall Vas not having a great experience with ECS' kit. I went with Turner Motorsport's kit and haven't had any issues. If I were to do it again, I would look up all the individual part numbers through RealOEM and then price it out as cheap as possible through FCP and ECS.

Sweet! Good to hear! Thanks for the help!

Definitely want to do the cooling system refresh. It's a 12-year old car, and there's just so much plastic in these cars now. It just makes sense. But, it's supposed to be sunny and in the mid-80's here tomorrow, so I just want to drive the car. :) Plus C&C on Sunday morning!

SC

[ecrabb]

The dealer has the screw for $5 or whatever. I was just there yesterday buying coolant. Here's a trip that requires $5 in gas to buy a $5 part. Doh.

That said, googling "bmw vent screw leak" yielded 163,000 results, so apparently this isn't very weird. Hindsight.

SC

[Sockethead]

Nope, not at all. Usually it's over tightened so bear that in mind when you replace it. It has an O-ring so it doesn't need to be super tight.

[danewilson77]

Have we discussed the brass replacement option yet?

S7 Edge, out

[Sockethead]

Negative...

[ZacharyMikel]

Oooh! I had a coolant leak that looked exactly like yours. Crusty around the top of the expansion tank, and lots of drips all over the place. I replaced everything in the cooling system except my upper radiator hose. Guess what? The plastic fitting on my upper rad hose was a piece of crap, and was letting coolant slowly drip out over the top of the expansion tank.

I remember worrying about it daily, every time I drove it. Constantly turning my center display to show temperature, etc. while I was trying to eliminate the issue. While it would be SWEET if your problem was just the bleeder screw, I would assume that with that much around the ET, it's gonna be either the tank or the upper radiator hose.

[ecrabb]

Have we discussed the brass replacement option yet?

We didn't, but I saw the discussion on E46F. I kind of had to agree with the poster who said the risk of the brass plug is that it's much harder than the plastic it goes into, and that the plastic plug is safer by design.

SC

[ecrabb]

So, follow up... It's fixed. I think it was indeed the bleeder screw.

I took it out and cleaned it up, and couldn't see anything wrong with it. I screwed it back in and it broke off in the receptacle. Arggghhhh...

http://uploads.tapatalk-cdn.com/20160626/6b2be007d6437db7c745eb336a8787de.jpg

So I used a technique I saw on E46F, heated a regular screwdriver with flame, and melted a slot to screw it out...

http://uploads.tapatalk-cdn.com/20160626/d4d37a7b4ef6c0956488b127216d7195.jpg

Picked up a new one at the dealer, put it in, bled the system, and I think I'm all squared away.

Cars and coffee in the morning!

Thanks, guys!!!

SC

[ecrabb]

Btw, after comparing new and old, I think it was a combination of a deformed (flat) o-ring, and then the screw itself was failing structurally and developed a pinhole from the top of the threads to the big recess in the center.

SC