10 RPM clicking mystery

[TerryP]

OK,First time on the forum here. Appreciate someone putting my mind to rest on this mystery. Vehicle: 2018 Yukon, 95,000 miles, 5.3 and 6 speed tranny (build date October 2017) Purchased pre owned two years ago, clean Carfax.

CONCERN: Engine idling at 650 rpm. No tapped noise but there is a tap or click. Not loud can only be heard standing next to vehicle or with hood open. Today I counted the clicks with a stopwatch running and i get 65 clicks a minute. So idling at 650 rpm means every 10 revolutions there is THAT sound. Ruled out anything camshaft driven, (tappets and high pressure fuel pump). About to do a 2,000 mile road trip and don't need any surprises. Any Ideas?

Thanks! Terry from Texas

 

[Rygrego]

Sounds like a belt or pulley issue.

 

[Joseph Garcia]

^^^^^x2^^^^^

Look closely at the belts, and you may find a nick or tear on one of them that would cause a repetitious noise at a frequency lower than the motor's rpm's.

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please. If we can't see it, it does not exist.

 

[Fless]

Try using a stethoscope around the engine compartment, bell housing, etc. to see if you can narrow it down.

 

[TerryP]

At a mere 95,000 miles now, hope for many more. Done Range, trans cooler bypass and K&N catch can. This was my neighbor's car and always admired it. I saw a new Tahoe in their driveway and assumed it was a service loaner. Then while passing the local Chevy Cadillac dealer it was on the lot Mine! I am a lifelong FORD guy. So how did I get into a Yukon? A story for another time.

 

[Doubeleive]

OK,First time on the forum here. Appreciate someone putting my mind to rest on this mystery. Vehicle: 2018 Yukon, 95,000 miles, 5.3 and 6 speed tranny (build date October 2017) Purchased pre owned two years ago, clean Carfax.

CONCERN: Engine idling at 650 rpm. No tapped noise but there is a tap or click. Not loud can only be heard standing next to vehicle or with hood open. Today I counted the clicks with a stopwatch running and i get 65 clicks a minute. So idling at 650 rpm means every 10 revolutions there is THAT sound. Ruled out anything camshaft driven, (tappets and high pressure fuel pump). About to do a 2,000 mile road trip and don't need any surprises. Any Ideas?

Thanks! Terry from Texas

100% normal.
if in doubt go listen to ANY other k2xx anywhere. any mileage
other things to note:
the fuel pump primes when the drivers door is opened, the mileage shows on the cluster (for a few seconds) when the drivers door is opened
the radio (most-bus) is also activated.
when these vehicles go to sleep mode, not even the brake lights will come on when the brake pedal is pressed. they are ZZZZzzzzzzz

 

[TerryP]

From what I can see from above the serpentine belt looks OK but also appears like it has some miles on it. Taking a road trip next week so heading to NAPA tomorrow for a new belt.
Just a note here: I normally do not buy extended warranties but this thing is a rolling appliance so I bit. Had to replace the stat and temp sending unit out of pocked last year. Then the rear air shocks started leaking after towing a car trailer so the dealer covered it, front sway bar bushings and all four TPS sensors for my $300 deductible. I'm still in the hole on the warranty cost but bought it in case the engine or tranny blew up. I may not renew that warranty when it expires.
You did not ask me why a Ford guy bought GM. One big reason is the Ford Expedition is only available with the EcoBoost 3.5. The only way to get a naturally aspirated V8 in a Ford is a pickup truck or Mustang GT. Well the Mustang would sure be fun but will not tow my trailer. And I already own a 1978 F150 so don't need another PU. So Tahoe, Yukon and Escalade all have naturally aspirated PUSH ROD V8's. I am old school all the way so that tripped my trigger.

 

[Joseph Garcia]

While you are changing the serpentine belt, consider changing the tensioner assembly as well, as the spring tension degrades with time and heat.

 

[TerryP]

OK, new serpentine belt installed, the belt I removed had a gm part number so I am assuming it was original. HOWEVER the tapping every 10 revolutions continues. Got out the stethoscope and located the source at some pressure hose at engine driver's side rear . Looks like it goes to the intake or VLOM and disappears between the engine and firewall. Visible in the photo above the valve cover almost straight up from the yellow dipstick handle. I hate little strange noises. Guess I could live with it if I knew what it was and it's not terminal.