Well this one makes no sense to me. Put on new a clutch fan and belts. Removed the connection at top of the radiator of the small hose that runs along the top of the shroud and flipped the tank/shroud over to the passenger side as I have done many times before. Put everything back car drives great...or so I think.
Now when I drive the car I have a puddle of coolant the next morning. First two times I lost 1/3 of the tank. Drove it 20 miles yesterday...this morning the tank is down to nearly empty. Could not find any active leaks while the car was running or within an hour of shutting it off. Just changed the reservoir a couple months ago.
Could the new clutch fan have taken out an old water pump? It's maybe three years old. Maybe the connection at the bottom of the expansion tank is loose (where I can't see it)? Radiator neck looks solid.
I figure I'll grab some UV dye before replacing everything (radiator is almost due anyway). Guess this more a vent about fixing one issue and having another pop up thing. Sigh.
You should be able to see whereabouts the coolant is coming from by getting underneath and following the wetness upwards, unless it's just everywhere. My guess is the hose at the bottom of the expansion tank since you can't see anything from above. Nothing should've happened to the water pump if you didn't remove it during your work.
1999 M3/2/5 - Titanium Silver - Track/Weekend Toy
You cannot find any green "crust" (assuming you're running OEM blue coolant) to indicate where it's leaking? I've had a really hard time getting that tiny hose you mention to seal to the nipple on the radiator and lost a fair amount of coolant right there. I ended up using a screw-type clamp from the FLAPS and cranking down on it pretty hard. A spring clamp didn't do it.
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I had the same exact issue after doing a cooling system overhaul (minus swapping out the hoses). In my case it happened to be the small hose going from the top of the expansion tank to the radiator. I needed to really tighten the expansion tank side clamp down because the hose had gotten hard after however long it's been used for. This took me 2 weeks to diagnose because it would only dump coolant after everything cooled down, and it was still leaking after the first time I tightened it.
pressure test it and you will see where the leak is coming from. The water pump will leak from the shaft and from the area where the small circlip is.
Update: I ended up cutting off the end of the other side of that hose that goes to the top of the radiator (the one that I disconnected) and reclamping it down on fresher tubing. Seems to have solved the puddle issue although I haven't had time to go in there and make sure it isn't leaking anything. Very odd as a I just disconnected the hose in July and had no leaking issues after reattaching it then. Hose at the bottom of the expansion tank is not leaking. Luckily my door panel broke off today so on to the next project!
Last edited by realjones; 10-06-2017 at 01:40 PM.
If this comes back and you still can't find where the coolant is coming from, you can try some UV coolant dye that they sell at most general car shops. Under black light it's super easy to follow the traces up to the leak. And you can easily tell the difference between old dried coolant and the newly leaked coolant that glows.
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