My MINI has a problem the dealership can't fix. Well two to be exact but I'll only go into detail about one.

This problem occurs only when it rains. I'll be driving and if I hit any water, no matter the speeds or depth of water, I get a resonance from the exhaust. When I say hit water, it can be as little as 1/2 inch and speeds of 30mph, or basically your normal rain with water on the road. It seems to occur only when there is enough water and speed to get something on the bottom of the car wet. It doesn't have to be deep enough or fast enough to splash water several feet from the tires like occurs with deep water at faster speeds.

The resonance is a deep sound and enough that I can feel the vibration of it coming through the seats or whatever I am touching at the time. Similiar to a small subwoofer vibrating at one frequency at low volume. Performance isn't effected that I can tell. Normal wet weather performance is there but without being dry I don't know if full performance is there. Idle also seems to be fine but once I did hit some water at faster speeds, enough to splash the water beyond the sidewalk, and I did get a rough idle at the next stop light and diminished power on take off.

This resonance stays, what it seems to me, until something dries out. It can happen for five minutes then go away, possibly and has comeback, or it can stay up to 20 minutes. It depends on how much water remains on the road during my drive.

Now to give some details of what I have done to the car or what has happened previously.

I do have a Pilo intake and that is the only mod. This resonance does occurs with both the Pilo and the stock intake. I haven't noticed a difference in the resonance between either and I have checked the Pilo for dampness. There is no water getting in the intake, even from the inlet by the grill. I understand water dries very quickly on a hot motor but I have not seen any signs of water on or near a component on the motor that I would think would cause a problem.

The first time I noticed diminished power was during a downpour while at Mardi Gras in 2004. I was driving across a bridge, no standing water, and my wife asked if I smelled something burning. About 3 minutes later at a red light several lights came on then very little power on take off. What it turned out to be was a broken harmonic balancer. I'm not sure of the details to what broken meant but it was replaced and off I went.

Because of old age I don't recall if I had this resonance problem before the harmonic balancer broke. I've taken it to the dealer but obviously this is a problem that happens only when it rains so it's not even worth taking in anymore. It's a 100 mile drive and it may not happen so you get the picture.

I was thinking water in the exhaust but I don't know much about cars. BTW, my exhaust is what I consider gassy while sitting in the garage after a drive. Even several hours later. When I say gassy, I mean it sounds like it is releasing air on occasion. Anyone else's MINI have the need for Beano?

Sorry for the long post but it has become a little irritating.

:smile:

 

The only things I can think of are the O2 sensor (maybe check to see if the wiring insulation has any issues, or if the connectors are good). or that when the exhaust gets wet, differential cooling causes it to flex, and touch something.

If it's in the electronics, then a data logger may help. Then you can see what changes (at least according the what data you can get access to) in the motor. for the O2 sensor, the fuel trims may change....

Anyway, sorry to hear of your predicament. Its the first Ive herd of such a case....

Matt

 

The same thing happened to me for the first time this afternoon. I was driving home from work through a pretty good thunderstorm. I ran through several puddles. Then I heard this rather pronounced resonance that I'd never heard before. I checked all the indicator lights and everything was fine. There was no sensation that anything was wrong, just the sound. By the time I got home, the sound was gone.

My '05MCS is completely stock (except for the rear fog light, two cup holders, an "ACTUAL SIZE" sticker, and a South Carolina emblem. :smile:

 

Gotta be the sticker. . .

 

I have a really wierd resonance...and the MINI dealer i worked for also heard the noise but cudnt pin point what it was....mine comes and goes when ever really....yet im now thinking if its the road surface making the runflats make wierd noises ??? only certain road surfaces mind

 

Could be. I also have the sticker.

I'll look into that, Dr Obnxs. A freind has the MINI shop manual so if it helps it will give me a reason to buy one.

 

The runflats are definitely noisy ...
SB,
The tires could well be the issue for you too - any way you could switch tires / wheels for a while to compare? 16 to 17 or 17 to 16, or even non-runflats?

 

My problem can't be the tires as it varies with the throttle. Also it will do this while stopped at a light. My runflats were replaced last year.

Elmer, does your resonance seem to come from the rear of the car? Another thing, do you happen to have a cold start or hot start problem? The hot start is just like the cold start but happens only above 60 degrees when the car has be driven for 30 minutes then try to restart after a few minutes.

 

pardon my ignorance...what is a harmonic balancer, and where is it located? perhaps this does have something to do with it.

This sounds a little like my old car, a Chevy Cavalier....when raining and especially making left turns, I would pick up a vibration or rumble under the car....my assumption is that it had to do with "aging" of the exhaust or suspension as it never did it when new.

 

I noticed a boomy resonance from about 2000 - 3000 rpm with heavy rain.
If I stopped, it would go away, then return on continued cruising in the
rain. I then changed to the MiniMania intake (this is a MC), and the
MM intake has a similar but different boominess all the time between
2200 and 3300 rpm. The MM intake is similar to the stock one, but a
little larger intake into the stock box and does away with the stock
resonator/snorkel.

I believe the bottom of the snorkel can fill with water in heavy rain, and
the slight vacuum while motoring can keep it from draining to gravity.
This keeps the snorkel from doing its job of reducing intake noise at low
to mid revs.

The one thing that doesn't make sense is that you get the resonance
with the Pilo intake as well.

 

Have you tried spraying water on the electric power steering fan? I suspect a bad / noisy bearing on it that is causing the noise.:smile:

 

Tremec may be on to something. What if you were spraying water into a fan (power steering fan), couldn't it cause the resonance your talking about regardless of a bad bearing etc.?

 

I'd like to say that when the exhaust gets drowned in water, it cools down and contracts, and may cause odd vibrations from all the contracting/expanding. But since you say it happens regardless of depth or anything and simply getting its feet wet causes the vibration, this is beyond me.

 

gone_motoring, the harmonic balancer fits on the end of the crankshaft. In my limited knowledge of engines, the best way I can describe it as a part that reduces or minimizes vibration caused by the spinning crank shaft in the engine. I may be way off with that.

Tremec, that's it. When I can get a chance and my wife knows when it occurs, I'll see if she will sit in the car while I spray water under the car. I'll slowly water down small areas until hopefully it will start.

I'll start at the fan but I believe there are wires and sensors, like Dr Obnxs mentioned, under the car near the rear of the engine. When the harmonic balancer was replaced, a cv boot had to be as well since the belt came off and ripped it. Maybe the belt skinned some wires while it was flopping around.

I'll be sure to post if and when the problem is found. Thanks for all the help and advice.

 

I had an old camaro that had this problem. It started out just making strange noises and lost of power when it it hit puddle or rained. AFter a few weeks, the power went away and the car could barely accelerate and sounded like a cow. It ended up being the catalytic converter. Luckily the repair shop replaced it for free. All cars in the US have a 7 plus year 100 percent warranty on all emission problems. Perhaps that is your problem. The converter got wet and the beads inside are coming apart.

 

I also have experienced this "resonance" in the rain. I have an '04 MCS, and this year in CA we experienced record breaking rainfall (>54 inches in Pasadena)...I noticed that the Mini would seem to "load up" and lose power in heavy rain accompanied by a pronounced low frequency vibration / sound. I was able to correct the problem by grabbing a lower gear and bringing up the RPMs. I would be curious to know if this is a harmonic balancer issue as I have another bone to pick with that particular part: the dreaded "knocking at or around 3000 RPM problem" that the dealer claims ALL MCS's have (and therefore it must be normal ). Some Mini owners on NAM believe that this condition is related to the Harmonic Balancer. I offered a compromise with the Mini Service manager on this issue: I would pay to have the balancer replaced...if it fixed the knocking, then Mini would pick up the expense under warranty, if not I pay...they turned me down . What a shock...

 

I was under my car this past weekend and also noticed that the fuel lines supply/return are plastic and the spacers mounting them to the underbody are relitively far apart thes lines could also "flutter" in the rain causing a vibrating sound :smile:

 

I took my Mini into Mini of Universal City and low and behold they told me that I have a bad harmonic balancer (no kidding!). The issue is that this part seems to be on back order from the factory...like maybe there's a run on them as of late . The good news is that they will replace it when the part comes in. In the meantime, I've got a bad wheel bearing (or something worse) going on that needs more immediate attention. I hoping that the problem will limp along until I get the call to replace the harmonic balancer so I can knock out both problems at the same time...I hate not having the Mini for a couple of days!

 

Some cars (not necessarily MINIs) will have exhaust sound issues in wet weather. Most of the time it's caused by the pipes becoming unevenly wet and cooled by rainwater splashed onto them. Such localized cooling causes the pipes to contract. If the bottom of the pipe were to get wet and the upper part remain dry, this would cause the pipe to arch upwards, sometimes touching the body or heatshield.

As for the booming sound in the back while driving in heavy rains, I've come to the conclusion that it's caused by the rooster tail of water tossed by the rear tires reflecting the sound back towards the rear of the car. After seeing the shape of the spray coming off the back of MINIs I followed in the rain, it makes sense to me.