Skip the auto shop - Our mechanics make house calls

Q: Knocking noise from under the hood

asked by on

Noticed a knocking noise from under the hood I checked my oil and there was smome coming from where I add oil but it's reading normal not low it does have a oil leak

My car has 180000 miles.
My car has a manual transmission.

Hi, thanks for writing in. There are many possible sources of the knocking noise you hear, especially with the advanced mileage on your vehicle. Most likely are worn connecting rod and crankshaft main bearings (will knock worse if you rev the engine in neutral), piston slap due to worn pistons and cylinders, even noisy valves lifters and timing gears.

With your mileage, there could easily be some crankcase "fumes" which can be very much like smoke coming out of the dipstick. As long as your crankcase ventilation system is properly maintained, the engine will burn these fumes - up to the point where you have blue smoke exiting your tailpipe.

I would recommend having a noise inspection completed by a mobile, professional mechanic, such as one from YourMechanic, to diagnose this problem, get an accurate assessment of damage and cost estimate for repairs.

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

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: help to fix ac

This is most likely an AC compressor issue as they will often times make a rattling sound when they are going out. This is typically not an easy fix depending on your mechanical abilities and access to the proper tools....

Q: Ignition problems with car.

Your issue might be low battery voltage. When your crank your car, the starter draws amperage from your battery. Once the car is running, the alternator recharges the battery and gets it ready for the next start up. Things like...

Q: Brown sludge and losing coolant constantly - 1995 Toyota Celica

Brown sludge in your radiator is most likely an indication of a blown had gasket since this is the only way oil would be able to make its way into the coolant. The fans not working suggests that the cooing...

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 Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...