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Old 01-09-2013, 08:34 AM   #60
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Join Date: Nov 2009
Location: Fairfax, VA USA
Posts: 22,857
My Ride: 330CiC, M5, X5, E93
Originally Posted by MJLavelle View Post
I'm curious about exactly what particular driving habits would be contributing to the failure of DISA's for some people, and what habits are allowing others to keep theirs for 10+ years?
There are people on here who still insist that all ET failures are due to overfilling, even though that is clearly not the case. If I have learned anything on here, it's that a large percentage of people neglect their cars, rather than constantly topping off fluids such as the coolant. The fact that there are many posts about ET failures written by people who have obviously never even bothered to flush their coolant makes that assumption ridiculous.
Assume DISA lifespan can be impacted by driving style? Stop and go/city driving likely works the DISA far more than someone that drives primarily highway miles? Also be interested to see if there is a different on manual vs automatic transmission cars? The last one I changed was on an automatic.

As for the expansion tank failures, there are many failure modes of the tank, most split a seam or on the side. Plastic does temper and become brittle with many temp cycles. But there are many documented failures where the ET blew the day or 2 after cooling system work was performed on the car and/or the coolant level was topped off. Overfilling is not the only failure, but it is a common failure that does impact older/neglected cooling systems as well. If I had an unlimited amount of money and time, I would get the air compressor and video camera out and have fun blowing up ET in my off hours!

Not sure why BMW put a 2 Bar cap on these system. There is entire thread here where all the Jr. Scientists claim the E46 cooling system will function up to 3-4 bar??? These guys are out of their minds, there is no reason the cap would even hold that level of pressure, much less the coolant system need or operate at this pressure/temp.

2 Bar is 29 PSI!!! I have never seen any cooling system run a pressure cap this high! Most run about 15 PSI tops. I am guessing BMW put this arbitrary number on the ET cap expecting the ET to function as it is designed and likely the pressures never exceed 10-14 or about 1 Bar?? But over fill the ET, then the 2 Bar pressure limit quickly becomes a possibility. If I was so inclined I would put a fitting in a spare cap or the bleeder screw port and monitor the cooling system pressure on a properly filled ET under typical driving conditions. The Jr. Scientist spent all their time and effort running calculations for thermal expansion and volume, but what these guys fail to understand, run all the calcs you want, you need to prove either with a real model or live device that your calcs were both correct and you did not forget to include assumptions and other real world exterior factors. You could only imagine what the classroom group never learns by never spending 1 day in the field!!
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Last edited by jfoj; 01-09-2013 at 08:36 AM.
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