Q: My son bought an S10. It drove for a week. It was good until I changed oil and heard a knock!

asked by on

Truck ran fine for week.changed oil started knocking.i went to listen pulled plug wires one at time,no difference.still good oil psi. doesnt sound like anything(knock) ive heard son revs truck knock seems to come and go almost go away!i research 4.3 found several issues with balance shaft.found TSB gm repair bulletin tensioner kit to install on 96-03 4.3.i cross ref every gm pt number found aftermarket kit available.jump gun didnt further diagnose engine my bad as im fairly good wrench.tore front of engine down,t-chain very worn.could cause balance shaft noise/knock?pull engine up to get oil pan off btw the oil was black sludge(fresh oil only a day ran)and oil filter was seized?took 3 hours to get off.no rods loose on crank little side to side.i installed tensioner kit the chain was single roller per gm cross ref 12458911. but looked chincy. any ideas on the knock in case we start up and its still there?we put in hv oil pump in case guage was wrong and check rockers too. Checked flex plated and torqued conv bolts, h balancer everything external i could think of.pushed down on rocker for collapsed lifters,no bent p rods,took long pry bar couldn't find play in pistons.all be it they were hard to get to the engine was still in truck.

My car has 190000 miles.
My car has an automatic transmission.

Hi there. I hate to be the bearer of bad news, I but I think you will need to pull the engine out, disassemble it, and check clearances precisely to determine the source. Given your mileage, and the "sludge" condition you found, worn timing gear set, etc., there are multiple wear conditions that likely exist, and a rebuild or engine replacement is the solution. Most often, when an engine "knocks when you rev it" as you describe, the connecting rod bearings have excessive clearance between the crankshaft bearing journal and the connecting rod bearing (not side-to-side as you mention). If you would like to have a professional inspect the engine knock in person for a second opinion, a certified technician from YourMechanic can come to your location to do so.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 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!
  1. Home
  2. Questions
  3. My son bought an S10. It drove for a week. It was good until I changed oil and heard a knock!

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: Just bought car, sputtering and loss of power going up hills 1991 Dodge B250

Hey there, thanks for writing in about your Dodge B250. If the vehicle runs better when above half a tank, the pick up tube in the fuel tank may be broken or disconnected. Replacement does involve replacing the fuel pump....

Q: Car began knocking after an oil change, then exploded blowing 2 holes in the side and the oil pan off

It may be hard to figure out why the engine failed without knowing if the oil leaked out or was not filled up. I have seen situations where after performing an oil change the oil leaked out from an oil...

Q: My 2002 sliverrodo won't start turns over could the cold have gotten it

The fuel pump may not be turning over and providing pressure or enough pressure to the engine to get it started. The cold if extreme may be causing the pump to seize or freeze any water moisture that may be...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
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...