E46Fanatics - View Single Post - DIY Complete Cooling System Overhaul (Pump, Hoses, & Tank)
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Old 12-15-2009, 02:50 PM   #16
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Join Date: Jul 2006
Location: Atlanta, GA
Posts: 610
My Ride: 2000 323i
Originally Posted by frogg320 View Post
I, for one, would like to say that even if you have a high mileage car, if things don't need replacing, I don't think they need to be replaced. Sure, things like the water pump which have a bad reputation and are hard to inspect might be a very good idea--I upgraded to a Stewart pump myself based on just that concern. But hoses, for example, you should be able to manually inspect for wear and age. If they're fine, there really isn't any point in replacing them. When the thermostat goes bad, you'll know about it, just stay on top of inspecting your car and reading codes regularly and I think you can save a lot of money by not replacing perfectly good parts. Just my two cents!

That said, good writeup, thanks! I'm a big fan of your site.
So, my expansion tank just popped, luckily I was only a couple miles away from home and some duct tape and cold weather managed to get me home safely! I took out the old one to inspect damage and found I also had a bad radiator cap (the bottom O-ring section broke off) and I have a hose going bad connecting to the expansion tank...also a bad idler pulley.

Anyway, in light of this, I think it may make sense to preemptively replace the expansion tank. It fails because it gets brittle over time and heat cycles (NOT because of overfilling, as lots of people will say...you basically can't overfill this system if the cap is functioning properly, it will just overflow to the right level).

It's a $40 part online (autohausaz is my shop of choice), and it is kind of a PITA but it's probably worthwhile. Now, I have 152k on the clock, so I think replacing it every 60k might be excessive...that said, some will break earlier, and perhaps it's hard to prevent that. Maybe replacing it every 100k is a good policy--hoses I still believe you can inspect/feel and watch for signs of failure, but brittle plastic is hard to tell from new plastic, and that's why I'd replace it early. I'm driving from GA to NJ next week, and I'm lucky this didn't happen then.

This has got me thinking, though...there are plastic end tanks on that radiator, which is probably the same age. Is this a good time to replace that as well? Hmmm. It costs more like $140, so I'm a little less eager to do so, but perhaps I should learn my lesson. On the other hand, expansion tanks have a much worse reputation, and the end tanks look a little better-designed (reinforcing ribs and such)...

...shall we find out?

Last edited by frogg320; 12-15-2009 at 02:52 PM.
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