Engine Noise on cold starts.

[Reedy]

Yo,

Got a bit of a noise that occurs on cold starts with my 2010 Gen II.

Its a sharp, brief grinding sound that happens a few seconds after the car has started. Sounds like a squeal in a shutter slowly opening or maybe a fan belt spinning up. I know it has something to do with the airconditioning system because it doesn't do it when I have that turned off.

Anyone know what shutters/fan belts I should direct my can of WD40 at on my next cold start? The car is in for a service today but the issue is this noise only happens in the morning, when the car is dead cold. If it's been driven any time in the 2 hours prior, it doesn't happen. So the mechanic servicing it wont be able to replicate the noise so I don't think they will be able to diagnose it.

Has anyone else noticed this noise? Ill look up diagrams for the aircon system and see what belts drive what, my inkling is that its the compressor belt or bearing so I will take a close look/listen at that.

[Scaredycrow]

Yo,

Got a bit of a noise that occurs on cold starts with my 2010 Gen II.

Its a sharp, brief grinding sound that happens a few seconds after the car has started. Sounds like a squeal in a shutter slowly opening or maybe a fan belt spinning up. I know it has something to do with the airconditioning system because it doesn't do it when I have that turned off.

Anyone know what shutters/fan belts I should direct my can of WD40 at on my next cold start? The car is in for a service today but the issue is this noise only happens in the morning, when the car is dead cold. If it's been driven any time in the 2 hours prior, it doesn't happen. So the mechanic servicing it wont be able to replicate the noise so I don't think they will be able to diagnose it.

Has anyone else noticed this noise? Ill look up diagrams for the aircon system and see what belts drive what, my inkling is that its the compressor belt or bearing so I will take a close look/listen at that.

Still under warranty? Take it to Mazda.

otherwise... up to you.

I would never put WD40 on a belt of any kind.... That will help it slip and make noise surely?

[Reedy]

Depends on the type of belt, but it usually works a treat for squeaky ones, just use a tiny amount, enough to stop it squeaking but it doesnt make them slip.

[Doug_MPS6]

I wouldn't go near any belts with WD40 if that is what you think your problem is. It contains petroleum products that will degrade your rubber AND cause slippage. There is a readily available spray on belt-grip that works well. Are you sure it's not your starter motor Bendix gear being a bit sticky to retract from the flywheel ring-gear in cold conditions?? That will whirrr and grind immediately after a start. By the time you get the car to Mazda it will be hard to reproduce the noise when it is warm. Just a thought.....

[Reedy]

Nah its definitely aircon related.

After the car starts, it idles for about 4 seconds, then the noise sharply occurs. It doesnt do it if I turn the aircon off, and then when I do turn it on it does it shortly after.

Will check with the fan turned on but aircon off next time, see if its the fan belt or compressor.

[Doug_MPS6]

I see - My air-con idler/tensioner pulley died a while back with a bearing collapse. It made quite a racket when the air-con clutch was engaged. Run the engine and shine a torch down there and see if you can detect any pulley precession and related noise.

[Reedy]

Ok having the fan but not A/C turned on during startup doesn't make the noise. Then once I hit the A/C button, it happens. It's gotta be the A/C compressor in that case. Let's see if the service manual can help me out here......

[shakespeare]

Have a look at this link, doesn't sound like your problem is the VVT but worth having a mazda look at it in case it is, also as Doug mentioned the belt tensioner pulleys had problems, mine was replaced due to strange whirring noises

Noisey valves at startup - MPS 6, MPS 3 Gen I, CX7 2.3T

Also I've attached a noise diagnostic checklist for the DISI engine from Alldatadiy this covers all models, worth having a look at

Good luck with this (moved to Tech Talk too)

[Reedy]

Update!

A bit of silicon spray on the belts seems to have finally solved the noise issue!