Skip the auto shop - Our mechanics make house calls

Q: Knocking from engine.

asked by on

My jeep's engine is knocking.

A: Unfortunately without more information it w...

Unfortunately without more information it will be difficult to narrow down why you are experiencing a knocking sound in your vehicle. In my experience Envoys have had many different reasons that could duplicate an engine knock. The most common is oil starvation. If engine oil is unable to travel through the oil passages to lubricate (this may be due to lack of oil or oil pump failure), metal to metal contact will occur on moving parts. At any time you hear an engine knock coming from your car, turn the vehicle off immediately and check the engine oil. Engine oil is probably the most common reason for the engine knock, especially in higher mileage engines.

Older engines with higher mileage tend to burn and/or leak oil between oil changes. When this happens the crankshaft bearings are usually the first to make noise. When you reach this point, it may be time to rebuild the engine. Rebuilding an engine would be a worst case scenario. If you have sufficient oil on the dipstick and the condition of the oil is good (not black, or contaminated with debris) the problem may lie in the oil pump or elsewhere.

Other possibilities include having bad or noisy bearings on one of the pulleys that drive the accessories. These include the alternator and the A/C compressor. To verify exactly why you are hearing a knocking noise in your GMC, it is best to enlist the assistance of a certified mechanic to inspect and properly diagnose your vehicle so you can get back on the road safely.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Vehicle stalls when I drive over bumps

When an engine stalls, it is usually due to lack of one or two things: Either the ignition system temporarily quit working properly, or the fuel system temporarily quit working properly. It is also possible that you may have an...

Q: Why won't it start with a low battery and a good jump start connection?

Hi, thanks for writing in. Your battery may not have had enough cold cranking amps (CCA). The volts may be correct but if it doesn't have enough CCA, it will not start for you. Batteries that specify cold cranking...

Q: AC actuator making popping noises

Hi, there are blender doors that control where hot and cold air go inside the cabin. The motors that control the doors eventually go bad and can start making some clicking or popping noises. Does the sound occur when turning...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.