What Causes the Abnormal Noise When Starting an Automatic Transmission Engine?

[JamesonAnn]

There are many possible causes for engine abnormal noise, as detailed below: 1. If a "ticking" sound comes from the upper part of the engine, with a regular rhythm and frequency increasing with engine speed, this noise mainly originates from the collision between the piston top and the cylinder head. 2. If a "clanking" or "ticking" sound is heard from the side of the engine block during operation, it usually indicates a knocking fault in the engine. 3. If the engine emits a "clanking" sound, it suggests insufficient lubrication between the cylinder and the cylinder liner. 4. If the knocking sound is a "ticking" noise, it likely indicates issues such as piston wear or out-of-roundness.

[DeChristian]

Last time my colleague's car had the same issue, there was abnormal noise when starting the automatic transmission. It's mostly a problem with the starter or flywheel—worn starter gears can cause a clicking sound. Also, check the belt tensioner; older cars often squeak. The noise is more noticeable in winter due to low temperatures, as the oil hasn't fully circulated, leading to dry friction sounds. I recommend waiting 10 seconds between starts. If the noise persists, get it checked immediately, especially if the battery voltage is below 12 volts, as this can cause more damage. Don’t ignore abnormal noises—early repairs might cost a few hundred yuan, but delaying could mean spending thousands to replace the entire starting system, plus the cost of a tow truck.

[SanSilas]

As a long-distance driver, I've encountered cold start noise issues. Insufficient battery voltage is the key factor, especially with old batteries over three years old that make the starter struggle to turn. The belt system also requires attention, as cracked alternator belts can slip and squeal. Loose chassis components like exhaust pipe hangers can also cause resonance noise. It's recommended to have annual maintenance checks on the starting system and test battery lifespan. Now I use a lithium battery, which starts quietly even at -20°C – more expensive but durable. Driving safety comes first; don't wait until you're stranded on the road to address issues.

[AbelRose]

I've personally fixed starting noise issues. First, inspect the starter motor gear and flywheel ring gear - worn components cause grinding sounds during ignition. Replace the entire belt if it's aged, and a stuck tensioner pulley produces metallic scraping noises. Use a stethoscope to locate the sound source: noise near the alternator may indicate bearing problems. Remember not to restart immediately after shutting off - the engine needs cooling time. Preventive measures are simple: change oil regularly for proper lubrication and have technicians tighten chassis bolts during maintenance. My experience shows that delaying noise repairs beyond two weeks typically doubles the repair costs.

[EmersonRose]

As an automotive enthusiast, I've disassembled cases of startup abnormal noises. 80% of the noises originate from the powertrain: a failed starter one-way clutch causes freewheeling, while insufficient transmission torque converter fluid leads to knocking sounds. Additionally, leaking exhaust manifold gaskets produce hissing noises. Environmental factors should also be considered, as short circuits in wiring may cause popping sounds on humid days. When encountering issues, always check the trouble codes first instead of blindly replacing parts. I recommend using an OBD scanner for preliminary diagnosis to save time and effort. Regular spark plug replacement is also crucial as it reduces startup load.

[VonJuliet]

The most challenging cold start noise I've dealt with was a decade-old car that made clunking sounds and vibrated during startup. Diagnosis revealed insufficient oil in the hydraulic lifters, causing dry friction inside the engine. After switching to high-flow 0W oil, the noise disappeared. The belt pulley system is another critical area - damaged water pump or AC compressor bearings can cause persistent humming. I recommend shifting to Neutral immediately after startup; if the noise disappears, it typically indicates a transmission issue. Always keep a recording of the abnormal sound - providing it to technicians during repairs can significantly improve efficiency.