Q: 2004 gmc envoy

asked by on

I have a 2004 GMC Envoy XL. Recently there was a knocking coming from what we think is the top of the engine. We ended up replacing some spark plugs replacing the oil and replacing the valve cover gasket as well as the timing chain .. gears .. sprockets .. Etc. after doing this it was still knocking. Still think it could be a lifter but completely unsure when you start it up it starts knocking immediately I drove it down the road last night and immediately turned around because it sounded almost like my husband left Tools under the hood were falling out along with that I also noticed what sounded like almost a fan blade hitting the edge of something as well... my husband did check the fan nothing's wrong. Does anyone have a clue as to what this could be because we are now dumbfounded. Also we replaced the water pump as well since it was easy to get to while replacing timing chain. Any ideas would be greatly appreciated!

My car has 100000 miles.
My car has an automatic transmission.

The origin of the noise can be pinpointed if you request an engine noise diagnostic. The mechanic will consider the knock intensity which will vary depending on source or type. Light knocking or tapping noise is caused by the valve train and camshafts not getting enough lubrication. This area is the first to experience problems from lubrication issues. Indeed, overall, most engine knocking is ultimately attributable to loss of oil pressure from a clogged filter and oil pickup screen causing oil pump failure or just running the engine low on oil from oil loss through oil burning, oil leaks, and lack of maintenance oil and filter changes. Therefore, measuring engine oil pressure helps to understand the cause.


Knocking of medium intensity is often due to wear in the piston wrist pin or piston rod bearing. This noise may worsen as you accelerate due to the increased pressure on the bearings. The bearings may even spin, causing louder knocking that increases with higher engine speed. This area of the engine will be the next area to start getting damage from lack of lubrication after the valve train and camshafts. Often the loudest knocking noises will be heard in the lower part of the motor and may even sound like thumping. The noise will mostly stay the same with a little increase in volume as engine speed increases. Knocking here is caused by failed crankshaft bearings and is mostly caused from loss of oil pressure or running the engine without enough oil.


There are a few knocking noises that may not originate from worn engine internal parts and low oil pressure. For example, the front crankshaft damper can come apart and can cause a crankshaft imbalance and create a knocking noise that is sometimes mistaken for a crankshaft bearing problem. The damper can be examined externally for damage but the crankshaft cannot be so inspected. Other causes of knocking are a cracked flywheel flexplate. The plate may get cracks where it is bolted to the back of the crankshaft. This noise is sometimes mistakenly attributable to the piston wrist pins or rod knocking. The noise changes when you put the transmission in drive or park. A piston knock will be more consistent than the noise from a knocking flexplate. Timing chain slap from a slack chain or guide and tensioner issues will cause knocking noises similar to a piston noise or slapping but will stay constant, while pistons change with rpm and load. Your best option to get the origin of the noise pinpointed is to request the engine noise diagnostic. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. 2004 gmc envoy

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Which GM pick up rear end has posi, disc brakes and will match my 67 measurements?

Hi there. The axle from a 2001 Chevrolet Camaro should fit your 67 GMC. The axle is about the width of your original axle and it has disc brakes with the posi loc traction control in the differential. If you...

Q: My key is stuck in the ignition // GMC Envoy

The ignition key release is electronically actuated in your car, via a switch. If the battery is missing or discharged, the switch will stay in the closed position which is interpreted as "not in Park". Consequently, you cannot remove the...

Q: Car won't start after flooring accelerator while going 75 MPH.

Your Dodge Stratus sounds as if it may be experiencing a serious problem. The initial symptom of the RPMs jumping from maximum to 2000 RPMS, appears to reveal that your transmission has slipped out of gear. The maxing out of...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...