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coolant leak under expansion tank

 
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MJ



Joined: 21 Oct 2001
Posts: 211
Location: CT

PostPosted: Sun Sep 15, 2013 8:59 am    Post subject: coolant leak under expansion tank Reply with quote

Car seems to loose coolant when its cool. Expansion tank is fairly new seems like its leaking underneath the holding tank somewhere. When I ran the car after adding more coolant. It seemed okay but needle started to go up. I opened hood and noticed the holding tank still had coolant in it?? Upper hoses seemed warm but lower hose near coolant tank seemed cold. Is the holding tank supposed to go down when car is started or does it remain level. Radiator fairly new. If it over filled can it leak??? It has been leaking though as I noticed the tank went down bit by bit, but never really saw leaks till today after I added a bit to the tank? and it sat overnight?
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walshja



Joined: 03 Apr 2001
Posts: 1139
Location: guilford, ct, usa

PostPosted: Tue Nov 05, 2013 11:28 am    Post subject: Reply with quote

MJ, you can't overfill the cooling system. The idea is to fill it and remove as much air from the system as possible.

From your description, it sounds like you need to bleed your cooling system. The expansion tanks have been know to crack. But before replacing anything tighten the clamps on all the hoses, and make sure you expansion tank cap is on TIGHT. I was leaking at the cap for a while, because I wasn't really, REALLY tightening the cap. But be careful you don't twist the break the expansion tank when tightening it
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1994 325iC, 195k miles
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MJ



Joined: 21 Oct 2001
Posts: 211
Location: CT

PostPosted: Thu Nov 07, 2013 6:52 am    Post subject: Reply with quote

whats happening now when car sits overnight coolant comes up through the cap and settles above and around the black area on top. Its a new tank with a new cap.????
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85-325e



Joined: 30 Jun 2002
Posts: 4710
Location: Southampton, NY

PostPosted: Thu Nov 07, 2013 9:23 am    Post subject: Reply with quote

When the coolant cools, it contracts. The expansion tank is there to capture the coolant as it expands when it gets hot.

If it's coming out when cool, you have to bleed the air out of the system, as that's what rises when the engine sits.

Make sure the car is sitting with the engine higher than the trunk, and bleed the air out of the system.
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MJ



Joined: 21 Oct 2001
Posts: 211
Location: CT

PostPosted: Thu Nov 07, 2013 9:49 am    Post subject: Reply with quote

But why should it happen at all?? Is air getting in somewhere? There was a leak which they tightened on the passenger side of the radiator weeks back?
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85-325e



Joined: 30 Jun 2002
Posts: 4710
Location: Southampton, NY

PostPosted: Sun Nov 10, 2013 5:51 pm    Post subject: Reply with quote

My guess is that it leaked quite a bit before it was fixed, and then the coolant was topped off, but not bled. It's a pretty closed system, and the air forms pockets. Your cooling won't work properly until all that air is bled out anyway. The cooling system doesn't suck air in. In fact, if it's working properly and there's fluid in the expansion tank, when it cools, it pulls that coolant from the tank back in, and when it expands, it fills the tank up.

Just bleed the thing, but make sure the engine is higher up than the trunk... do it on a little hill or on stands so that the car is angled up. Loosen the bleed screw and air will come out. it's only when ONLY coolant is coming out that it's bled.
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MJ



Joined: 21 Oct 2001
Posts: 211
Location: CT

PostPosted: Mon Nov 11, 2013 8:47 am    Post subject: Reply with quote

Turns out I think there is a coolant line that goes from one side of the radiator On top but runs underneath then hooks(clamped) somewhere under/near the bleeder screw. We feel thats is what is leaking as the slight pool of coolant settles on top of the coolant reservoir in the indentations around it, There looks like no drippings coming down from cap, So that what we think.. Will find out later this week
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85-325e



Joined: 30 Jun 2002
Posts: 4710
Location: Southampton, NY

PostPosted: Mon Nov 11, 2013 11:40 am    Post subject: Reply with quote

Well, if that little hose is kinked, perhaps the engine isn't drawing the coolant back in the way it's supposed to do when it cools.

If it's a new reservoir and a new cap, there'd be no reason for them to leak unless the cap wasn't screwed on correctly.
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