Would silicon seal work while the coolant expansion tank is installed with liquid and has hair line crack?

 

it should work as long as the coolant level is below the hair line crack upon application and then keep it there until the silicon cures.

 

Probably, but not for very long - I've tried it but the silicone doesn't adhere well to the plastics used to make these tanks. So, at best you'll buy some time. Good thing the expansion tank isn't that expensive - I recommend you replace it.

 

Yep. Same with me.

 

Forget long, I tried silicon and let it dry for 2 days, and started the car on the 3rd and it leaked just as normal. Not sure if I did not get the right or whole area, but definitely silicon did not help me. I have ordered OEM tank ...........

 

Most silicone adhesives - sealants will not adhere to automotive plastics ... especially the coolant tanks. However, one item I've carried in my car toolkit for years is a "superglue" type product called "Future Glue". Quite by accident I discovered it would adhere to the plastic coolant tanks and connecting pieces when on an overnight trip I had to reattach a part of the overflow tank on one of our Audis. It held for 2 days - long enough to get a replacement tank at an Audi dealer. Since that time I keep some in the trunk of my car - along with zip ties, duct tape, and a few other quick fix items.

Another must have - especially for road warriors - is a gallon of distilled water - Just remember to remove it when winter weather approaches!! And, since BMW had thoughtfully engineered placement of important electronics in the worst of places under the trunk floor ... my gallon is double-bagged in zip-close plastic bags.

 

Having a slow leak as well. It looks like a small amount of coolant under what I would think is the water pump. The pump was replaced 20k miles ago at the dealer, so I am doubting that. Any ideas of what I should look at in that general area? 105k miles total.

I just replaced the whole system on my x5 (tank, pump, thermodynamic, hoses, belts), so I was hoping to not have to do all of that again, especially with a pump only 20k miles old.

Does the whole system on the e60 need replacing at 100k like the x5?

 

I have a crack\leak on my expansion tank vent pipe around where it goes to the radiator. Any tips on replacing it? Do I have to drain the radiator? I would think since it's at the top, I would just remove the pipe and just catch whatever coolant that runs out and replace the coolant?


Thanks!

 

You can most likely just replace the tank and catch the coolant at the hose.

However, if the coolant has never been changed then now is the time to do it. It is a pretty simple process, especially with an electric water pump.

 

It is easy to drain the radiator, especially if you have an older car with an actual drain plug. My 2006 has a drain plug. Wife's X5 you need to remove the lower radiator hose and that is a bit messier.

If you have the electric water pump, follow the bleeding procedure - you can hear it working, so you'll know if you got it started.