I've been losing coolant for a little while now, very slowly. Every month or two I'll catch a low coolant warning on the OBC. I had yet to see a leak until yesterday when I was changing the oil.

The car ran for maybe 5 minutes when I brought it around back to the garage. As I was just getting started on the drain plug, I noticed a drip by my left shoulder, well I found the SOB. I thought I had anyways...

The drip was coming from the blue drain cap area. The whole bottom side of the reservoir side of the radiator was kind of covered, so I couldn't pin-point it.

I know it's NOT the upper radiator hose, but I've never heard of any other weaknesses with the radiator.

You guys got any ideas about where this might be coming out? I can't get my head in there to see what's going on. I think I'll see what I can see in the Bentley...

Just figured I'd ask around and check if anyone else has had a similar issue-- I couldn't get it to leak again for the rest of the day, even after it was pressurized.

TIA

Hrm...looks like I'm flying solo with this problem...

I had a small hole partially under the clamp on my upper hose.

A small leak in the heater core can also go unnoticed, sometime it evaporates before hitting the ground.

The upper hose is dry, and I saw the leak at the lower driver side of the radiator. The problem is that the anti-freeze was running from wherever it was leaking from to the lowest point, so I don't know where it was originating from.

Quite frustrating...

i have a very small leak some where on mine. i've been too lazy to go look for it. i'll notice a drop maybe once a week for the past year. two weeks ago i got a low coolant message, so i filled it back up. kinda annoying, i got a coolant leak fixed once and now it's doing it again. i'm thinking about trying some of the that stop leak stuff, that supposedly seals up small leaks.

From my AutoZone days in college, I remember that they sold a small vile/tube of radiator sealant. It was just really fine bits of aluminum (I think), but you could just add a little and hope it worked without having to totally contaminate the cooling system with metal flakes.

I have some doubts about how well a plastic water pump would react to said circumstances. I'm not sure which water pump is in mine...but I do have a spare at home. It's still plastic, but it's black, not the orange one that was/is problematic. A BFC'er sold it to me claiming it was metal...now I'm screwed with it. Another story there though...

I don't think any of the leakstop solutions will work in this case though, just because they rely on some moderate flow to suck them into the opening and plug the hole. If there's not enough draw to let them plug up the leak, you're still at square one, just with a bunch of shit in your coolant.

I'll figure it out...eventually. If and when I do figure it out, I'll make sure I have my camera handy :)

I've just purchased a 91 525i and I've heard that the coolant reservior tank can become brittle and develope a leak. Also my local BMW dealer said that the valve in the heater core line near the firewall on the drivers side is another very common leak spot. Just a word of caution. I'd have to advise against using stop-leak. It has a nasty habit of clogging the cores of the radiator and heator core.

Thanks for the input- I currently suspect the reservoir, but I need to inspect where the coolant level sensor is as well.

I haven't had any trouble with the valve on top of the aux. coolant pump (yet)...(knock on wood).

I'm not a fan of stop leak, it's the kiss of death. I've always advised people to use it in very small amounts and hope it works.

Oh BTW-- Welcome to the forum!!