I’m hoping someone can tell me what’s causing this rattle. Today after a service, my local Mitsubishi dealer tried to tell me there’s nothing wrong - but I’m not so sure.

When the air-conditioning is turned on, I get quite a noticeable rattle from the engine. When the A/C is off, the noise is gone. Still, it sometimes comes back (though not as loud) even with the A/C off.

The A/C itself is working beautifully, but the rattle makes my car sound like a heap. Also, you can only hear the rattle below about 1500 RPM. Once you rev the engine, it goes away.

Any idea’s what might be causing this and how much it might cost to put right?

Thanks for your help.


http://www.youtube.com/watch?v=GkupLOq2Zwc&feature=youtu.be

can not diagnose a rattle like that on the internet but can diagnose one thing, your dealer is a dick

First unplug your fans, is poss they have dropped something down there and that would account for the rattle when the air con is off occasionaly

Does sound plasticish if that makes sense.

If not I would be looking at the compressor

First unplug your fans, is poss they have dropped something down there and that would account for the rattle when the air con is off occasionaly


does sound a bit like a leaf or twig or piece of plastic in a fan.. Don't go poking around fans while they are on though.

Agreed the dealer is a dick. He also tried to tell me my car has “significant underside damage”. Why? Because there’s a couple of cable ties holding up the thin plastic guard thing at the front of the engine. Unreal.

Anyway – I tried unplugging the fans, but the noise is still there. Nowhere near as bad tonight but still noticeable when revved slightly.

I’ve got no mechanical knowledge but the clutch bit on the A/C compressor moves freely and didn't make any noise with the engine off when I spun it with my hand . Could the ancillary belt just need replacing?

Try removing all belts - spin all components alt/aircon/powersteering and idlers by hand to check for roughness. Start car with all belts off to see if noise disappears. If noise is gone then connect one belt, then the other....note when noise re-appears and check component that is on that belt drive.

Try removing all belts. Start car with all belts off to see if noise disappears.

Except perhaps the timing belt? :-)

I’m pretty sure it’s the air conditioning compressor. Both with the A/C on and with it off (but engine under slight load) I get that clattering noise.

I’m going to ring around to a few places tomorrow, but what are my options?

Difficult over a forum I know, but will the compressor need replacing? If so, how much would this be?
Is it possible to replace the bearings or the clutch bit or something?

It’s just annoying more than anything, the A/C still works fine :doubt:

If is both ac on and off is not ac comperssor. Compressor is doing nothing with ac off, when it is on, the ac pulley is directly connected to the ac pump and the bearing in the pulley is inactve

Groan can be belts not tight enough or engine pipe

A/C rattle is very intermittent and the A/C itself still works great - so I’ll leave that for now.

At least part of the noise is coming from the belts, so I’m having them changed on Monday.
Alternator/A/C belt seems to be a bit loose and worn, so hopefully a new one will help. It's definitely deflecting more than 9mm even with just a little pressure.

Thanks again.

Good news – changing the A/C belt has all but silenced the groaning and ticking engine noise.

My car no longer sounds like an old tractor :)