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I have an 09 Passion, I have owned the car for 3 years and know all the usual noises and rattles. The issue is that it has developed an intermittent knock at certain RPMs and at idle once the engine has come up to operating temperature. The knock can be heard inside the car and outside, with timing of the knock changing with RPM. Odd thing with this noise is that it does not do it all the time, seems to be most prevalent with light throttle and on cooler days. Any ideas?
 

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the cooler days is inconsistent with my suggestion that you bleed the head for air in the coolant, but I would do that anyway just to eliminate that as a possibility. My knock went away when I eliminated an air pocket in the engine. Two different smart centers could not figure that out. The first one said I had a tank of bad gas. The second one said We don't know. You need to drive eight hours to another dealer with more technology to figure it out.
I used Water Wetter in the engine and had to top off the reservoir two more times and been okay ever since. It apparently absorbed the air and got it to the reservoir.
This may not be your issue, but if you have a hot spot, the water wetter may solve that for you, also.
A third alternative is to replace your coolant with a much higher boiling point waterless coolant. Evans makes such a thing.
Here is a very informative list of FAQ's on their site that addresses hot spots, water pump cavitation, and micro nucleation. Very informative reading: http://www.evanscoolants.com/evans_waterless_engine_coolants_faqs.html
 

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Thanks for the information. Is a post available here describing the steps to bleed air from the head? I searched and found a few post referencing this process but have yet to find a step by step procedure to do it.

I just checked my coolant reservoir and it is low. Would adding water wetter and additional coolant correct this issue or will the head bleeding still be required?
 

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All I did was top off the reservoir with water wetter. I drove the car, let it cool over night, and the next morning, the reservoir was back to min. topped up with water wetter like this two more times and perfect ever since.
I am about to eliminate the water/steam issue with Evans waterless coolant. Chieftmc has already done it and is happy. I made the mistake of not buying enough to properly fill the system, so I need to buy another bottle, and then I will be ready to convert mine. It is a lifetime fill. The "Tonight Show" host uses it in his Dusenbergs to stop oxidation of the aluminum parts. Yes. Sorry, I can't remember his name, not Carson, butttttt.... Jay Leno. (CRS! and I am only 62.)

When I picked my car up NEW, the coolant was at Min. from the factory. I thought that was normal for a smart, having never seen a reservoir like this before. Drove it this way right up to the end of the warranty when it started knocking when hot with the a.c. on under acceleration, and later going up hills it would knock. I would ease up to get it to stop. Very stressful for me AND the engine I'm sure. At the first year's service, no coolant was added at the dealer. None at the 24K check either.
There is a sticky for bleeding the coolant on here somewhere. See my next post below.
 

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Thanks again for all the info BB Benz. I am going to try the water wetter method as you described and see if that corrects the issue.
 

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Maybe it's not, I hope it is not....I am just guessing but usually hard knocks like that are internal faults. Some can be lived with for years, depending upon what it is.
 

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the cooler days is inconsistent with my suggestion that you bleed the head for air in the coolant, but I would do that anyway just to eliminate that as a possibility. My knock went away when I eliminated an air pocket in the engine. Two different smart centers could not figure that out. The first one said I had a tank of bad gas. The second one said We don't know. You need to drive eight hours to another dealer with more technology to figure it out.
I used Water Wetter in the engine and had to top off the reservoir two more times and been okay ever since. It apparently absorbed the air and got it to the reservoir.
This may not be your issue, but if you have a hot spot, the water wetter may solve that for you, also.
A third alternative is to replace your coolant with a much higher boiling point waterless coolant. Evans makes such a thing.
Here is a very informative list of FAQ's on their site that addresses hot spots, water pump cavitation, and micro nucleation. Very informative reading: http://www.evanscoolants.com/evans_waterless_engine_coolants_faqs.html

Just keep in mind that, that FAQ page has not been updated in a while :rolleyes:

I also used Water Wetter before my conversion :)
 

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Mike T that is not the answer I was hoping for.
A Shade Tree Check...With the car in N, If the knock goes up and down in time with the RPM, and is heard best at the point the power is increased then let off, chances are it's a rod knock.

If it only knocks under load it may be a main.

No expert here but had a few worn out cars as a kid. Even had a $75 Lincoln V-12 with a rod knock :D A2Jack
 

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How many miles on the car? Some owners have had success in reporting these issues to smart USA and getting some help with repairs on lower mileage cars, even out of warranty. Worth a shot. :)
 

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Clintsiler. Oh man I'm sorry to hear that. Your options are limited and you are looking at 3k+ and much hassle.

You can sell as is, there is a market at around 2.5 k selling price.

If you have time to spare... you .can part it out right here on our market place. But buyers expect instant response. One seller was overwhelmed and just sent his to a bone yard.

There is a third option of finding an Independent mechanic willing to take on such a job, and remember all parts will have to come from MB.

The last option, taking it in to the MB dealer for a check out and quote will probably cost $150. At 90k miles, a dealer repair is out of the question.

Above all do get a second opinion. Good luck A2Jack
 

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I would just use thicker, higher quality oil, maybe 5W50, and drive it until it dies. Meanwhile, if you want to keep the car a long time, keep an eye open for used engines.
 
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