blackfalcon

At 110,000 miles, coolant expansion tank blew a pinhole leak last week. I epoxied it when I got back to my house which was a temporary fix in order to be able to keep driving the car, when the tank blew, the steam in the tank caused the coolant level indicator to fry as well. I picked up the new tank today at BMW for $127.?? with tax. The tank includes the level indicator (which is the same part as what is used in washer fluid resevior, ie if you change out the tank, keep this part for a spare).

This process only took me about 15 minutes from start to finish.

1. Allow car to fully cool.
2. Open resevior cap and insert small tube to bottom of resevior, and syphion fluid into empty gallon jug or container.
3. Remove two torx screws holding resevior to car body/frame.
4. Remove two radiotor hoses at top of resevior and pull them back out of the way and keep them higher then radiator so no fluid pours out.
5. Pull up on resvior itself (there is male end on bottom or resevior that snaps into rubber grommet that you can't see until you lift). You want to lift it high enough so any remaining fluid in the resevior drains out of the lower coolant hose and into the radiator. While keeping this hose higher then the radiator, disconnect hose.
5. Connect same hose to new resevior and reverse installation process.
6. Take fluid from container you had syphioned into and fill resevior.
7. If you did these steps correctly you will only have lost/spilled several tablespoons of fluid and shouldn't need to add any fluid. Start your car and take it for a quick spin and then pop your hood and check for any leaking fluids etc.

luigi524td

You lucked out @ 100K + miles for this cooling system component. Good that you were in a position to prevent major coolant loss and overheating.

The first time it happened to me I was several hundred miles from home and over a weekend! From that time on I replaced these parts at 50-60K miles because I knew they were prone to sudden death.

VERY DISAPPOINTED to learn that some things haven't changed after more than 15 years of engineering know-how!

blackfalcon

The coolant system on this car seems to be one of its weekest links. I've only replaced parts as they failed, but so far its been water pump, thermostat, leaking seal from lower inline thermostate/sensor, broken hose, and finally leak in Coolant Expansion tank. All these problems starting happening randomly after I've crossed 75,000 miles. If you ever smell coolant, or see it on your garage floor have it checked out.

ASpec818

thanks for the DIY. will attempt to replace the tank myself as my local bmw mechanics want $400 to do it.

slicknick

URO makes an aftermarket expansion tank for these models. I was reluctant but I decided to go ahead and try it out. So far so good. I have put about 8K miles on it. It looks exactly like the original and I was able to use the original cap. Just do a Google search and they are pretty cheap.

7_rocket

I was replacing the coolant tank which was fine until I started to pour coolant in and this was what greeted me after I replaced the tank.



Damn. huge pic sorry.

Now I have to get a coolant hose on Monday from the stealership that. It's so brittle

ColonelLonewolf

Why are we replacing these parts with the same flawed parts? Is there not an aftermarket part that is more durrable? Maybe something in aluminum?

2007525i

Mechanic at local dealership says after repeated failures of the OEM tank in his E46 (he thinks its the heat), he finally put heat shielding fabric/mat around it between it and the engine, and that seemed to have solved the issue.