SLCPUNK

2012 TSX 43k miles

Today I started the car up on a cold engine. Immediately there was an extremely loud thunk under the hood (like somebody hit the hood with a hammer.) I turned off the car, checked the oil, and everything looked fine. I inspected the engine bay and nothing looked odd.

I had the Missus recrank while looking at the engine, and everything was normal. No noise, and the car ran fine. I tried to replicate the sound, while restarting several times, but it didn't do it again.

The only thing I can think is that something was engaged improperly on start up. The AC was on, so maybe that was it? It wasn't a starter noise, and I don't think it was a mount (I've never heard a lose mount sound like that.)

I was really bummed to hear something like this under the hood with such low miles.

Any thoughts/ideas are appreciated. Thanks.

thoiboi

Engine mount is my guess

briq456

My guess would be the AC Compressor engaging. Sometimes when it's been rainy/humid the surface can become like brake rotors with small amounts of rust, so when it engages instead of being smoother is grabs suddenly and can sound like a THUNK. just my .02. Nothing to worry about, I've got 88K on the odometer and have heard this on occasion.

RTM

Seen the neighbors cat lately?

ceb

That would be a "thunk" instead of a "clunk" as the cat gets tossed about the engine compartment.

atsx1313

I had this happen to me as well... still didn't know what was that about..

SLCPUNK

So I'm not alone, lol. It freaked me out when I heard it, I thought the engine blew.

I haven't had it happen again. Although I've kept the AC turned off on start up since.

I could take it to the dealer I guess, but I'd imagine they wouldn't do anything about it.

JDMaccord3.5

Just wondering.... does this only happens when the car is cold? parked overnight or for over a 8+ hr period? since you can't replicate the sound

wrayman

I've had the ACT ( Air Conditioning Thunk ) twice. First time scared the shit outta me as I was merging onto the highway and hit the AC.
I had repaired the condenser the day before.... thought it blew up ! All was well with the AC though, worked great.


Second time gave me a lift too, but figured out what it must / might be.


Hasn't happened since....but summer's coming, LOL

SLCPUNK

Yes. It only happened one time. It had been turned off over night. The AC was "on" when I cranked the car. I have not yet cranked the car again with the AC in the on position to start.

I had been running the AC the previous days while on a long trip with no issues.

devinv1994

happened to me a couple times in the 2 years I've had my 2011, super rare to happen and I may be crazy but I think its happened when it's hot and my car was sitting for awhile like 5+ hours.

atsx1313

mine happened when it was cold (60s)... first start up in the morning...

I thought I ran into deep pot hole or something... scared the crap out of me... then I restarted, and nothing really happened... even still to this day... i have 13 tsx