2015 Mustang GT Piston Slap? Maybe??

[Jrobinson]

So, recently on cold starts my engine makes a loud noise that I could only guess is piston slap. Correct me if I am wrong, but it is a constant almost slapping or knocking sound for the first 20 seconds and then goes away until I let my car sit for 4 or 5 hours and start it again. I have attached a short video of the sound. Now in this case my engine had only sat for 3 or 4 hours so the sound does not last long at all. However it usually lasts around 20 seconds. What is the sound and is it harmful to my engine? I am running a full synthetic oil approved for this engine, not the motocraft synthetic blend suggested in the manual. No other mods have been done. It has 75000kms on it and is my daily driver. Please help!

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[TruBlu16GT]

Definitely not piston slap. Piston slap is an indication of wear to the piston and/or cylinder wall and actually sounds like a gentle tapping or knocking due to the piston having excessive clearance on either side. What you'd hear in that case is the piston rocking side to side.

This sounds more like it's taking a few seconds to build oil pressure. What you're hearing is rod knock because the main bearings are starved for oil. Are you using a quality filter? Generally speaking, the Coyote seems to be perfectly capable of building adequate oil pressure simply in the time it takes to spin up the engine - even before the engine actually starts.

To diagnose this properly, one may have to attach a mechanical oil pressure gauge and see what's actually going on.

 

[Jrobinson]

Thanks, I will do that as soon as possible. I am using the Motocraft OEM Filter and have changed the filter and oil every 5000km.

 

[Nerass]

resonator delete and muffler delete? mine sounded the same

 

[Jrobinson]

Working on the rez delete. How does the muffler rez delete sound?

 

[Nerass]

identical to that haha

the noise you're hearing is going to get louder - mine did the same

 

[Jrobinson]

well I did the rez delete and muffler delete. It is extremely loud now.

 

[Jrobinson]

The scary sounds are gone though

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