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Eric, Automotive Repair Shop Manager
Category: Mercury
Satisfied Customers: 31659
Experience:  20+ yrs. experience as repair shop manager and technician.
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2007 mercury mariner: knocking..engine while idling..rev..oil change

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i have a 2007 mercury mariner and yesterday i noticed a slight knocking coming from engine while idling. when i rev it up its gone, up to now the truck has been running great. it had a recent oil change and i checked the level and it was good, i checked the water and it was good..any suggestion before i drop in at the shop

Is it a high pitched metallic sound, or lower deep sounding knock?

Does it matter whether the engine is cold or hot?

Can you tell by listening to it if it is coming from the front of the engine, or more towards center of engine?
Customer: replied 6 years ago.
sound is a faint tapping sound

engine was hot at time, i will go start it up right now its cold,i just started up car and you can here it still but engine don't sound bad, i also have been running the air more this week its been hot here in florida

sounds like its coming from the front of the engine

Ok, lets first eliminate the valves. you just need a long screwdriver for this.

with engine idling and making the tapping noise, place the metal end of the screwdriver against the valve covers one cover at a time. Now place your ear to the handle end of the screwdriver. Is the noise amplified? If it is, then its valve lifters causing the noise. If not, then no problem there.

If not the lifters, then the noise could be from either one of the pulleys(I have heard pulleys make a light tapping sound before), or could be a timing chain guide that is worn enough to allow the chain to tap against cover at idle. when rpms put to it, the chain tightens enough to not hit the inside of timing cover.

For these, you need a mechanic's stethoscope to listen to and find which is the cause and use extreme caution as you are working around a moving belt. I dont recommend people doing this unless they are experienced around engines as the belt will take off skin and muscle. If you feel comfortable doing this, you can get the stethoscope for about $10 at a parts store. place the long end against the timing cover to listen to for amplification of the noise and if none heard, then place by each pulley until noise amplification is heard
Customer: replied 6 years ago.
i was also reading the the wrong oil filter will cause the oil not to flow right which will cause tapping also. i believe a fram was put on but of course the manual recommed using the motorcraft oil filter and since the oil change was done 2 days ago

that is correct, but I have never ran into a problem with Frams. I have with store brands such as Autozone and Advanced Auto Part's house brands, but never with a Fram in over 25 yrs.

it wouldnt hurt to run by the dealer and pick up a Motorcraft and replace the Fram filter, but unless the Fram is simply defective, I dont see this a problem.
Eric and 6 other Mercury Specialists are ready to help you
Customer: replied 6 years ago.
ok thanks for the response