Massive Coolant Loss
 

I apologize in advance for the length of this... :thumbup:

I have an 02 4.4 that has needed a coolant system refresh for a while. I replaced the radiator ~10 months ago.

Around 2 months ago, the water pump gave out and left me stranded. The belt was shredded with pieces everywhere, but that was the only damage I could see.

I finally got around to replacing the water pump and pulley, thermostat, overflow tank, upper/lower radiator hoses, and belts yesterday. The valley pan was already replaced ~2 years <15,000 mile ago.

After getting everything replaced, I followed the recommended procedure to fill the cooling system and thought all of the bubbles were out of the system. Started the car up and everything seemed fine other than a slight tick tick noise. Took it for a quick drive around the block checking the temp with my phone and Torque and everything seemed good.

The next morning I adjusted the belt tension trying to get rid of the ticking noise which worked. Checked the fluid level again and took it for another drive. This time it was a bit longer at ~2 miles, and I got onto it some. Max temp I saw was ~215 toward the end of the drive.

Pull into the driveway, stop the car, and immediately all of the coolant is flowing out of the engine. I checked under the hood and couldn't see a source. Checking under the car, all of the fluid was coming out around the middle of the re-enforcement plate. There was a small trail of fluid coming up the driveway from before I stopped.

I've refilled and bled the cooling system with just water. The only leak I could see was around the overflow cap. It definitely needs to be replaced and a new one is on the way. I also checked the oil. No foam or milky color under the cap and the dipstick looks and smells good. So I hope it isn't a head gasket.

At this point, I'm at a loss. What else would cause all of the anti-freeze to drain, at once, when the car is turned off? I've checked every hose I can get to. I haven't pulled the re-enforcement plate off yet, but that's my next step. My intuition is one of the parts I replaced is the cause of the leak, but I just don't see any coolant on any of those parts.

did you check the hoses going to heater core near fire wall?

Hoses 5, 6, and 7 from here?

http://www.realoem.com/bmw/diagrams/e/l/85.png

I looked from up top and didn't see any visible coolant leaks from there while the engine was at idle. I did see what may have been evidence of coolant splash on the cowl, but I would think with such a massive dump of coolant any leaks from there would be really evident.

what type of coolant did You have in You x5?yellow [non bmw].You have to use blue bmw coolant it protects the water pump and the whole system.

Zerex G-05 which I realize is not BMW approved but have run it in other M62 engines with no problem.

yep those ones can get missed easily swince there hard to see.

When you say you looked but couldn't see any visible leaks, was the engine running when you checked? There was nothing evident for me either when my No. 6 hose gave out on my way to work one day a couple of years ago. Lucky I wasn't far from work so I limped in, but needed a tow truck to take me home later that morning. When I got home I topped the fluid up, removed all cowling around the bulkhead and started the engnine. It was only after seeing a geyser of coolant coming from the back of the engine (still couldn't see where the leak was coming from), then climbing on top of the engine to feel around the hose area could I establish it was one of the hoses split at the jubilee clip. Replaced the hose. Job done.

What's strange is I have been able to refill it and it has held coolant while running at idle. I checked those hoses while running at idle and didn't see anything.

That's one reason this is so strange to me. It didn't dump the coolant until running pretty hard and then turning the car off. It's not gushing out while sitting at idle.

Did you double (or triple check) to make sure the hoses with the o-rings and spring clips are on properly? Sometimes the new hoses will fit really snug eluding the the feeling that they're on, and the spring clip will "lock" when in fact the hose is not on far enough.. and the clips isn't actually locking anything in place.

It may be enough to hold it together at idle, but as soon as you bring up the revs and start pushing water through it'll leak.

To help make you feel better, a head gasket typically won't catastrophically fail to dump all your coolant out. You'd notice a little (a lot) of smoke first, along with overheating and poor running before that happened. You'd also see the coolant in your oil or vice-versa. What X5SND says, check all your hoses to make sure they are pushed on all the way.

I also recommend getting your vehicle up in the air high enough that you can remove that front plastic splash shield and look around for leaks from underneath. Don't mess with the metal reinforcement plate as it isn't hiding any cooling system parts. Use a good bright flashlight and look at all the hoses and parts of the radiator and waterpump and alternator.
From your description it doesn't sound like the heater hoses, and usually the valley pan doesn't spring major gushing leaks. Still a good idea to look back there anyway. I'll wager the VPG is seeping. You didn't happen to replace this while you did your waterpump did you?

You seem to already know, but at the age of your car, its better to replace ALL the cooling system components at the same time, now. Else you are risking more strandings and tow trucks in the future.