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Ask Gm Tech (Cam) Your Own Question
Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 29457
Experience:  GM Grand Master Technician 2007. 14 year experience.
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Have a 2011 Yukon Denali with 200K on it, that just started

Customer Question

Have a 2011 Yukon Denali with 200K on it, that just started making a loud tapping sound coming from inside engine. Still running fine and no codes have been set. oil pressure is fine. and looks good. as do all fluids. Had to drive it home about 20 miles after it began but is now parked and trying to figure out where to take it and what I am probably looking at for repair.
Submitted: 1 year ago.
Category: GMC
Expert:  joeplow replied 1 year ago.

Ok , If its a Tap on the upper most part of the engine.....its a lifter or rocker arm......if it sounds like a deep knock ...its the Piston hitting the cylinder head cause by the rod or its bearing that's went out......Thanks Joey : Please rate my answer if we are as I will get paid or ask more

Customer: replied 1 year ago.
if it were a Bearing oil pressuree would be affected if it were a lifter check engine light or message would be displayed.
Customer: replied 1 year ago.
PS I am a Auto mechanic also; However I have not seen many of these newer engines with this type of problem. I believe it may be tied to the sensor that converts it from eight to four cylinder operation.
Expert:  joeplow replied 1 year ago.

Hello , Oh the oil pump would compensate for that small oil pressure loss.....which I think its the lifter......because of the tap noise

Expert:  joeplow replied 1 year ago.

Sensor will not cause a noise

Customer: replied 1 year ago.
Saw this in a Ford Coyote engine with dual overheads. causing the valves to float stuck in between cycles
Expert:  joeplow replied 1 year ago.

ok , ill opt-out....let someone else help you...take care

Customer: replied 1 year ago.
Do not even know how this 6.2 converts back and forth though. I am a ford man
Expert:  Gm Tech (Cam) replied 1 year ago.

Hi there, I am Cam, can I get your first name please?

Can you describe the noise more? Light tapping? Does it change with any cylinders disabled?
What scan abilities do you have?

Customer: replied 1 year ago.
Sorry I have left for today for an appointment Loud tapping like a lifter but seems to be coming from lower in engine toward rear middle. have not put a stethoscope on it yet just took a brief look this morning saw it was not anything minor and went to another project.
unfortunately it is at my home and not my shop which is 40 miles away.
Customer: replied 1 year ago.
Greg is first Name Cam.
Customer: replied 1 year ago.
How do disable cylinders?
Customer: replied 1 year ago.
I am more of a diesel mech. and have done nothing on GM The Coyote was my first experience with engines that drop from 4-8 when cruising and I had a skilled Ford guy with me when we found it.
Expert:  Gm Tech (Cam) replied 1 year ago.

Greg, do you have a scanner? WE disable with the injector balance test, but I suppose you can disable by unplugging each coil control wires one at a time.

Expert:  Gm Tech (Cam) replied 1 year ago.

Knowing what cylinder will help. Its 1 4 6 and 7 that cut off by the lifters and this can be seen if one failed by removing the valve cover, hooking the coil pack back up and running it. Now on these I have see the odd one with a build up of carbon that when warm would make the pistons carbon hit the head and make a knocking noise.

Customer: replied 1 year ago.
will try the disconnect tonight And get back with you tomorrow thanks for your patience. have and older snap on scanner
Expert:  Gm Tech (Cam) replied 1 year ago.

Ok, sounds good.