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: What type of carb to replace with?

Picking out the appropriate size carburetor is a factor of how much air your specific engine build will pump. This is measured in CFM's (cubic feet per minute). You are most likely correct in needing a smaller CFM carburetor. Your...

Q: Will a 19 gallon tank fit on a 2003 Chevy trailblazer ltz currently has a 22 gallon tank

You can try looking on www.car-part.com as there are plenty of listings for the 22 gallon tank. The 22 gallon tank was an option (substituting for the 19 gallon tank of course) in that year and so would probably require...

Q: Driveline clunk and greasing the slip yoke

You can try using transfer case fluid as a lubricant. The transfer case fluid is just automatic transmission fluid. Using the lastest version of Dexron transmission fluid should work out fine. The service bulletin for drive line clunk instructs mechanics...

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...
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...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...