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Old 10-05-2012, 11:54 AM   #85
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Join Date: Sep 2012
Location: Old Greg's Cavern
Posts: 12,560
My Ride: '13 128i, '04 330Ci
Originally Posted by joegr View Post
No, the hose itself is not stiffer. It is the same resistance to squeezing when the engine is cold, as the hoses on my other cars when they are cold.
No, it is not due to the flow from the water pump, because I am squeezing after shutting the engine down, not while it is running.

I don't present this test as proof of pressure, just as reasonable doubt to it not being higher pressure. If you want proof, install a pressure gauge. If this discussion is not about actually finding out what is going on, then carry on as is.
Interesting. Thanks for the insight. Your methods are pretty much valid, you just can't put a number on it. Do keep in mind though, that the change in pressure we calculated (about 0.3 bar) is probably enough to feel, as it is a 30% increase. Imagine feeling a bike tire at 30 psi then you bump it up to 40 psi. You can easily tell the difference. This may account enough for the difference you feel in the hose, but I can't be sure. Honestly, given the operating temperature, there is no way for the system to be over 1.3 atm when static, unless it is solid (which it is not).

Also, i need another piece of information. Where is the car's coolant temperature sensor located? Is it on the outflow from the block or is it after going through the radiator? This is a pretty big thing to know.

Great forum members -

We have:
WDE46 = Automotive Engineer
SeanC = Ph.D Theoretical Physics

Now if we can find a Materials Engineer to chime in... we'll be rockin'.
I'm actually a mechanical engineer who happened to learn a lot about engines and vehicle dynamics and I work in the automotive industry. I also know a good bit about material properties, though mostly metals. We need a Polymer/Fiber engineer or a Materials Scientist for the ET material. I can apply my knowledge of fatigue and failure theories, but I can't break it down to plastic thermal wear and thingso n the molecular level.

As far as installing a pressure gauge, I want 2 on there. I want one in the top of the ET and one on the output side of the water pump at least. A dial gauge would work well enough. We don't need one of those $500 high temp pressure transducers haha (they are incredibly accurate and log great data though).

I think we need a couple liquid filled gauges. I'm not sure if the non filled ones will read well with the engine vibration or not.

Only $20 plus an NPT tap and new parts for the ones we **** up haha. The 0-30 psi gauge should do it. I would do this myself if I had a second car, but I don't so I can't really spare it to do this.

Last edited by WDE46; 10-05-2012 at 12:31 PM. Reason: gauge picked
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