Coolant overhaul failure
 

2003 BMW X5 3.0, this past Saturday I replaced the waterpump, thermostat, upper radiator hose and lower radiator hose with new coolant sensor and o-ring, ac and waterpump belts. Parts cost, $308.00. Flushed and bled system with BMW coolant. Ran vehicle for 1/2 hr. Checked for leaks, none. Let cool down. Checked level, ok. Let vehicle run at idle for 20 minutes, no leaks. Drove home, 40 miles, no problems. Next day, Sunday morning, before I got ready for church, went out and checked level again. Ok. Let vehicle run for 1/2 hr. No leaks. Went back inside to get dressed for church, come out 2hrs later, moved wife's car to other side of the driveway, backed the X out and let it run to heat up the interior. Nice and toasty for the wife. Come back out and I see a stream of coolant from underneath. :dunno: popped the hood, it's coming from the darn expansion tank. Pinhole on the side. :rant::rant::wtf: parked the X back in her spot and we took the 2012 Mazda 6 to church. I was furious. Just spent another $200.00 for parts. Tank, cap, clip, tank thermostat, level sensor and water connecting assembly from tank to trans cooler. Paid $45.00 for 1 day shipping, from Pelican Parts in CA. Guess I should have done tank along with everything else the first time. So I will be taking my wife's car to work tomorrow, (she's off), drop her off to work Tuesday, (I will be late for work), and take off Wednesday to do the repair in 30 degree weather. Gotta love the X. Can't complain. 182,000 miles
Any info on expansion tank replacement.

Parts replaced since bought in 2007 with 42,000 miles
Dealer installed thermostat. (Warranty did not cover)
Heater control head (warranty covered)
Front door handle carriers
Front axles
2 sets of tires. (1st set, 18's yokohamas with Beyern wheels, now riding back on original 17's with Bf Goodrich.
Ac and water pump belts (2nd set)
2 sets of brake pads (front and rear). My second set are evolution racing pads with cross drilled rotors
Valve cover gasket. ( about 2 years old. Still have an oil leak. Oil splatter right front part of engine. Washed down when I did waterpump. Will keep an eye on where it is exactly coming from.
Bilstein touring struts and shocks.
Disa valve
CCV valve and tubing ( cold weather)
Alternator and battery (left stranded after install, $212.00 to tow to my house, had to reinstall with a Bosch unit. So far so good....
Updated to projector headlights with hids and halos and led tails.
Change the engine oil every 15-17,000 miles with Mobil 1 0w40, previously using Castrol Syntec 5w30.
Like I said previously, not a bad X with 182,000 miles. All highway driven.

And that is why BMW vets recommend overhauling the entire cooling system all at once as much as possible. I recommend that myself after going through similar as you.

Expansion tank replacement is pretty straightforward, just disconnect upper radiator hose from radiator and expansion tank, disconnect lines below expansion tank (one at the bottom and one at the lower side) and pull upward. It will take some effort as the AT thermostat extends into the tank from the lower tank line. Do be careful as the thermostat can (and often does) break when you pull the tank.

Install is simply reverse. Good luck!

Just wondering -- is it really necessary to replace the reservoir tank? I mean, I understand about Europeanlover's reservoir. But, was that just a fluke? Or do the tanks have the same sort of fixed life as the hoses? Just wondering what most of you out there who have any knowledge or experience on this think. How far do I go with all these new parts when I work over my cooling system?

I'm looking to overhaul my cooling system. There are a large number of coolant hoses on this vehicle. I have already replaced the radiator and upper & lower radiator hoses (upper included the two smaller hoses attached to it), and I want to replace all the rest. I'm wondering if anyone out there who has done this has a "shopping list" of them all. I'm not so concerned about any of them which are essentially "straight" hoses, with plain ends instead of the fancy plastic flanges -- I can replace those with generic hose stock. But, I'd like to find a list of all the ones that need to come with the plastic flange connectors on one or both ends, or which need to come pre-shaped. I can't readily tell by just looking at a parts diagram. Or, do I just need to order them all vehicle-specific? (Also see my last post on the reservoir.)

I'm not sure you have many hoses that are just straight. The heater hoses are the 'plain' ends, but they are all pre-curved. Using a straight hose and bending it usually causes the hose to kink and lose flow rate. Or maybe there is a way to shape generic hoses that I'm not aware of?
Ordering the hoses online doesn't seem very expensive considering you'll get around 10 years of life or more, and getting the specific hoses means they'll fit and have the correct shape.

The expansion tanks in the BMW are under pressure rather then the typical, atmosphere vented siphon expansion tank seen in most cars. From what I have gathered the typical failure on the tank is at the seam weld that puts the top and bottom of the tank together. I had the same issue. Replaced hoses, tank sprung a leak. Makes sense if you think about it. Old hoses had more give which reduced system pressure and pressure trainsients. New hose, no give there for higher pressure spikes which cause additional stress on the tank seams. Would have been better if they had designed a better tank, but that may have lead to a catastrophic failure rather than the typical pin hole leak.

if you also want to lower the pressure in the system a bit, consider installing one of these on your next overhaul:

Buy G.A.S. BMW 1.2 Bar Coolant Cap

BMW recommends a coolant flush every 2 years - the inhibitors wear out, and it seems they affect the plastic life as well (and aluminum)
The plastic components of the cooling system get brittle, this is why you have to change all of them when you do the cooling overhaul. Some components might "look" good, but when you remove the hoses (sometimes they come off with a little of persuasion), you induce more stress, or even a crack without realizing it, and next you know is a leaking component.

Also, for these plastic parts, it's best to get the OEM from dealer. Not the "equivalent" that have the "correct" brand, but are made in PRC or God knows where, and will fail rather quickly.

0.02

For the oil leak on the right front of the engine, I'm assuming you mean the driver's side. Check for leaks around the oil filter housing, those gaskets tend to go bad. It's a time consuming job, but not difficult by any means.

Nope. My leak is on the passenger side. Right side if sitting in vehicle.