Fan noise loud? Engine ticking sound normal?And I have mice/rat poop & pee under hood
 

A really loud fan noise just started happening twice today on two different startups and now it is making the noise I am not sure if it's the same loudness as earlier today but yes the AC is on and when the car turns off a weird sound is made in the front when the fan goes off too. It's around 85 and the temperature has been higher today than most. Also a loud ticking, not a quiet ticking, but very loud ticking sound in engine wondering if this is normal?

Also both GL450 4Matic and E350 4Matic have a lot of rat and or mice poop and pee on the engine cover and saw one poop also towards the end of the engine as well. Cars turn on and run okay, but could the rat/mice cause fan problem or engine ticking problem??

What kind of problems can mice/rat cause? What are areas or places they may damage? In other words how do I know if they damaged something? How do I know if they are still in some where? Don't hear or see any mice or and rat

Hi,
My 2014 E350 has the same engine ticking noise and loud fan as well. I attributed it to the a/c running full blast during the hot texas summer. I'm interested in knowing if others have the same as well.
Thanks.

G

Generally, rats and mice eat wire harnesses which can cause all sorts of problems. Had to replace the wiring harness on my tractor because of the rodent lunch club in my shed. Never had that problem with my Benz though.

Sounds normal to me. You'll definitely want to solve that mouse problem though. My dad's friend's car had the mice tear through the wires on a BMW, they had to basically disassemble the car and replace all the wires, took over a month.

Ticking sounds normal, it's the fuel injector, a byproduct of direct injection into the cylinder instead of injection over the valve into the cylinder. About the only German manufacturer that I've seen that's been able to make the design not tick is VW on the 2.0t 4-banger engine, but they've been working on it for the past dozen or so years. Listen to a BMW 328, and you'll be surprised by how loud it is.

I'm about ½ through a second tank of 93 octane that has a second can of Gumout fuel cleaner added (ultimate with PEA) and starting to notice a reduction in the severity of the ticking noise in mine, plus a bit more responsiveness in the acceleration with a very smooth idle. Might be worth the $20 to pick up a couple of bottles and use one each for the next two tank fills...

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my quick post apparently went to wrong thread

You need to verify If mice are getting in and out of the cars - fast. They will chew on everything short of steel parts. If it's fairly fresh poop then they are showing up after you've left the cars , probably liking the warm engine area.
An MB harness repair can be very expensive. You need to get under the hood and probably under the car (pull the belly pans) and inspect as much harness as you can get to. Plus lay out deterrent and/or poison but be aware of access to it from kids or pets.
I'm saying this with some urgency - the destructive nature of these rodents can be amazing.