I've noticed in the past couple of weeks a nasty, sudden graunching/thump kind of sound a second or so after the engine kicks over. It seems to be coming from the engine bay area. The car is still stationary when it occurs.

The weird thing is, it's not every time I start the car. My car is usually garaged but on Mondays and Wednesdays it's out in the sun all day. It's happened when starting the car up in the late afternoon on a couple of those days. The interior of the car is quite warm.

It's quite noticeable, to the point of exclaiming 'WTF was that?!' and getting out of my car and checking under the bonnet when it first occurred.

First thoughts are that it is the A/C compressor turning over. Should I get it checked and are there any other suggestions?

The car is otherwise running fine and I have no warning lights or other signs of a problem. The A/C appears to be running fine too. It is an '04 manual.

 

I wonder if the timing belt and other thing hitting a loose object. But then you have a loose object, you could hear it while driving.

Unlikely the engine itself, there are not many loose engine parts in there? At least you cannot blame the valve like in the piston engine.

I would say get a good torch and look around, get someone to start the engine for you while you are looking.

 

Each time it's happened, it's only made the sound once and at about the same time after startup. Sounds perfectly normal after that and while driving. I did have a good look around under the bonnet but couldn't see anything amiss.

 

is your aircon on when you start the car up?

Before I shutdown the car out of force of habit i turn off the aircon and radio.

 

Well it's not the timing belt, of that I am 1000% certain. The Rotary engine does without such trivia......

This sound occurs during start..........or just after the engine starts? A metallic sound? No stray tools under the hood? (other than the quizzical one looking for a strange sound )

 

whats the ABS test?

 

Dave, I've been getting something like this too (occasionally on starting from cold) and I reckon azza's got the answer. See if it happens when a/c is left on, or off?
Will

 

you may notice when you start your car and first take off, there is small clunk sound when you reach approx 6km/hr, or if you have your foot on the brake (steep driveway) then the brakes shudder slightly. only happens once on startup.

 

Whatever it is, it doesn't seem serious. If you want to track it down, you'll need to be under the bonnet while someone else starts it.

Good thing is, you're still under warranty. If it's a heat related issue it'll surface this summer. Now.......where's the champers? Oh, here it is......cheers!!

 

It will happen in reverse too, if that's the way you first travel after starting the car. About 6mph (10kph), according to the manual..... .

 

I can't remember if it's been on each time or not (it's happened about 3 times now).

I know the aircon is on atm and the car is outside in the sun all day today, so I'll see what happens when I start it up after sailing this evening.

Mind you, I've started the car plenty of times with aircon switched on previously and it's never made this sound before. As previously stated, it's not a minor mechanical sound. It's a quite audible thump and I've never heard it before, so I'm concerned something might be struggling and want to identify it before warranty expires (I've got a year to go though).

 

It's not during start. It's a second or so after the engine starts, which is usually when the A/C jumps into life (hence my suspicion as to an A/C related cause).

Doesn't sound metallic as such. More a graunching/thumping kind of sound.

No stray tools that I'm aware of. Mine's married.

I changed my oil cap after the Nationals (to a shiny Mazfix one ) but I can't see how that could be causing a noise. If it was, surely I'd be hearing it either once only or each time I start up.

 

Will do Will.

 

Check for Possums....

 

LOL

 

I expect more constructive advice from my Melbourne co-driver .

 

I'd like to add my vote to an A/C-related noise. It could be a vapour lock in the system. I've heard that sound on some fridges we've had too.

The advice to turn off your A/C before switching off the ignition has merit. It does help to decrease the load on the battery when you start the car as well.

 

Dave

Misfiring starter motor not cranking up properly due to weak battery .

At least its not ticking ............ (disgruntled client )

 

MACCAA said he might join me for the Victorian sojourn. Reckons driving for 10 hours each way to go on a one day cruise also suits his mentality .

Would that be okay with the Vics?

 

Yes, that's sound advice but I don't always remember to do so.

And as posted previously, my concern is that this is a new phenomenon, and perhaps a harbinger of failure somewhere.

 

No Michael, the car is starting without a problem. I've had the starter motor, battery and plugs upgrade too.

As for disgruntled clients, never had one.

 

I'm hoping it's something like this and is merely an isolated, occasional problem.

Guess I'll find out this evening.