Skip the auto shop - Our mechanics make house calls

Q: It knocks once after i start it up only one time and when i'm drivin a charm is played kind of like an alarm what should i do?

asked by on

it knocks only when i turn it on, one time and the knock is sometimes soft or hard and other times it doesn't even do it at all weird

My car has 160000 miles.
My car has an automatic transmission.

A: Hello there, a knocking sound can cause pro...

Hello there, a knocking sound can cause problems if left unresolved in your 2008 BMW 535xi. A knocking noise can be caused by a few different faults such as an engine mount, engine knock, failing alternator, or AC compressor. If you have an engine knock this needs addressed immediately. If you need assistance, a qualified technician such as one from YourMechanic will be able to diagnose your knocking noise and determine what the cause is.

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: Plastic intake manifold on the North Star engine.

Hi there. The 1993 Northstar intake is made of magnesium, and has a different system for "blowout" or backfiring protection. It has been used by some folks who have had bad experiences with the "plastic" intake manifolds. There will be...

Q: The ABS is faulty and the wipers, speedometer, and rev count are acting erratically

Hi and thanks for contacting YourMechanic. First, check the battery for any corrosion or loose cables. Then, check the fuses in the fuse box for any burned fuses. Check under the dash for any loose wires or loose grounds that...

Q: My car idles very roughly on first start up of the day

The lean fuel mixture codes may explain everything. They frequently occur when there is an air leak in the intake system somewhere. Your engine has an Air Flow Meter (MAF) that measures the air going into the engine. The ECU...

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...
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 P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
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.