Mystery metallic sound at very low temperature
 

Does anyone ever had pronounced metallic sounds coming from the suspension at very low temperature on a Gen2 or any MINI models?

Every winter we get some knocking sound when it gets very cold. Two days ago the temperature were in the low teens. I though there was a serious problem somewhere with the car. It sounded like something was very loose every time we would go over any sort of rough pavement or bump in the road. Smooth road, no issue.

Today I'm driving the car. It's back up to 45°F and the sound has gone completely. I thought it was extremely strange considering how it felt two days ago. I was about to say, we need to take it in...


And then I though, hmmm I wonder if the bushings are contracting so much around the lower control arms, or else where on the suspension or mounts, at very low temperature, that metal it touching somewhere? Is this a known issue I am not aware of with MINIs?

It sounded pretty bad but if I take it in now they will say that they checked everything and all looks fine. I had mentioned that same concern a year ago, and they didn't find anything...

I know that rubber is one of the few materials that expands when it is cold, the opposite of any metal. Rubber also becomes more pliable when cold. I am wondering if neoprene has similar qualities and with colder temps metal is able to hit/rub against something it normally does not do.

I'm not certain this is very accurate...

Pretty much any materials contracts and hardens at cold temperature. That goes for tires for example. Summer tires are slightly harder than all winter tires which allow them to be grippy during hot days. But will become harder and slippery during cold temperature, partially an effect of contracting. Winter tires are the opposite. They are made of a soft rubber which works great at cold temperature to get that nice balance, but will soften too much during the summer and would wear too fast. Just to use an example.

I guess it's possible in some instances it may absorb more moisture but usually most materials contracts at colder temperature. At least that is what I've always believed...

EDIT: oh, ice does expend :) but that's because it is trapping air bubbles when freezing...

Below are links that discusses the properties of rubber, it does expand and become softer when cooled. I did some checking on neoprene and it has different properties relative to softness when cooled. I am still checking on the temperature affect. I do know that neoprene is made by passing chlorine gas through a solution. Stay tuned.

I also have an answer to the Chicken and Egg question.


http://www.physlink.com/education/askexperts/ae573.cfm

https://www.scientificamerican.com/a...a-rubber-band/

Not to make a big deal about all this because really it doesn't really help me out with the mini :lol:

But both articles talk about elasticity. I think that's a little bit of a different property to the material (its ability to come back to its resting state). The use of the word softer is a little bit miss leading...
The fact that it looses it's elasticity doesn't say anything about its dimensional state. I still believe that dimensionally a chunk of rubber contracts on itself has it gets cold, regardless of its elasticity. But I'm open to be proven otherwise :)

Yet until then my mini is still making worrying sound at low temp :cry:

I spent 7 years managing pharmaceutical construction projects. Learned allot on expansion coefficients of materials. Allot of automobile "techs" only know how to fix something that is obviously broken. If they cannot see it or hear it, there is no issue.

Rear or front suspension? Makes the sound while in gear or not? Driver side, passenger or both? Stock suspension or aftermarket? Was there any snow buildup in the wheel well?

That sounds just like most of the dealerships I've been to :lol:

- Most likely from the front suspension.
- Makes the sound at any point in time over rough pavement, be it a small bump, or long stretch of winter patches. The only variable is cold vs warmer temp.
- Can't tell what side it's from.
- Stock suspension
- No snow build-up. Sleeps in the garage every night
- Car about 3.5 yrs old, about 36k miles ish.

Have you posted in your individual gen? I don't always view the general thread.

I'm thinking the strut. Assume when you pull out the garage no issues but as the metal cools or the oil viscosity within the shock thickens you get the clunk. Maybe stupid but have you thought about discharging a CO2 fire extinguisher on it while at the dealer and then driving it? Dry ice is about -78 C so if you do, wear some hand protection for frost bite.