Bad Sound from Engine Bay

[MattJackson86]

So on a cold start up in the morning yesterday I heard what sounded like really bad knock as the car was warming up (after running for 2-3 mins). Happened probably 6 times about 1/2 second apart and then stopped. Nothing to really hear afterwards. No CEL of any kind, no KR readings, nothing. Drove to work no issues and honestly is driving like nothing is wrong.

Today I heard another bang 1-2x when coming out of driveway at work, also when stopping in the garage at home. Now there is a pretty consistent rotational scratching/whine is present in engine bay. It may stop and then come back worse for a second, it may just get fainter. It may get worse and turn into that knock sound for a couple times. But its there and noticeable. Spent some time trying to pin point it and its somewhere around intake manifold -> exhaust manifold -> turbo area. It is definitely rotational and sounds like metal scratching/whining.

Car has 90,500 miles, driven hard. On the second K04 turbo for last 50,000 as first one had leaky seals. Hoping its just the turbo that has finally crapped out, out of balance, etc. Dont think its the engine itself only cos it drives great, no CEL, etc.

Thoughts? I am probably going to drop it off at Mazda tomorrow for a look over, it just came out of there 4,000 ago for a timing chain, VVT, replacement.

[jfspeed6]

I would say your VVT needs to be looked at. The sound you are hearing is most likely the timing chain hitting the valve cover. a dealership around my way was putting the VVT on th wrong way. One of my friends cars sounded like that after he got his swapped out by them.


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[Captain KR]

Check your tensioner pulleys for loose/wobbly pulleys when they go bad it sounds like vvt issues.

[MattJackson86]

I looked at my pulleys as they seem fine, but I will take a closer look. As for the vvt, I did check the chain and its tight. The sound is quite different than when I had the vvt issues before. Again I will take a closer look.

I'm going to also try taking the inlet off and see if the turbo shaft is wobbly. That's what I suspect so far.

Thanks.

[MattJackson86]

Just got back from Mazda. Its a bad AC compressor. The pulley is wobbling around. They quoted $1400 + tax. Going to call around some other places.

[Shadow]

Ac compressor can be done anywhere, including home if you hate the environment. I would def take it to a local shop should be like 800 bucks installed.

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[rfinkle2]

Good to hear (although expensive).

Good luck Matt.

[Speeden6]

subbing here as i have a "chirping" noise or squeeking upon cold starts that goes away when the engine warms on my MS6. is this VVT? or something else.

[Jfishe]

Sucks it was the AC compressor. Had what seems to be the same problem recently...thought it was VVT and had it replaced under the extended warranty but didn't fix the problem. Turns out it was the pulley tensioner and my friend and I replaced it. Cost $65 from advanced auto.

Hope you get it fixed up.

[mtnrunner]

i got an ac compressor for like 150 bucks off Car-Part.com--Used Auto Parts Market, swapped it out myself and took it to a shop to recharge. total cost was under 250 bucks for everything.

[speedms6]

Originally Posted by Speeden6 subbing here as i have a "chirping" noise or squeeking upon cold starts that goes away when the engine warms on my MS6. is this VVT? or something else.

high pressure relief valve(hprv) at the end of your fuel rail, search on here there is a thread about it, had the same problem, got a new one, went away

[MattJackson86]

Going to TriPoint today to have them give it a once over to confirm if its the compressor or not. Parts alone seem to be about $850 (compressor, clutch, "receiver dry can", etc), then $300 for labor from them. Trying to see if I can get the parts cheaper or not. For $300 labor its not worth me doing it personally, even if I get someone to do the evac and refill.

[Shadow]

If you lived closer I'd do it at work and cut you a deal. :/

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[06Speed6]

$850 is about right, if its the bolt that holds the clutch on, you can get a new one at lowes for $2... my a/c clutch completely fell out and got pinned between the compressor and frame and I drove that bitch 300 miles home like that and I just bought a new bolt and its been fine for the last 40k miles and that clutch material was all fubared.

[MattJackson86]

Got it on jack stands and under tray removed. Going to see if I can see the issue as is happens tomorrow morning. Tripoint also mentioned my idler pulley was iffy as it too was wobbling slightly. I did confirm that myself.

[MattJackson86]

So got under the car today and started it up. AC off, and the noise started.

YouTube - Broadcast Yourself.

YouTube - Broadcast Yourself.

Let me know your thoughts. I dont see the AC pulley wobble much before, maybe a bit more during the noise. Its got a slight wobble and so does my idler. I dont know if thats normal but TriPoint said idler for sure not.

[Uberfly]

holy shit! that sounds horrible. I hope you're able to figure it out.

[mikeblackspeed3]

I recently had this noise and was able to fix it by replacing just the pulley on the compressor; the bearing was bad. Does your noise only occur with the a/c off? If so, scour the internet for a used compressor with the pulley and clutch attached and swap that pulley! Easy job, no need to evacuate and recharge the system, and you'll have a spare compressor if you need it. Only cost me $150, and a set of snap ring pliers. Good luck to you!

In other words, if the noise goes away when the compressor clutch engages, you only need the pulley. Unfortunately, they aren't sold as a separate unit, hence the need to find a used compressor.

[MattJackson86]

Yes it is a pretty horid sound :-(

I have only found the noise with ac off yes.

[MattJackson86]

So got a whole new ac compressor, pulley, clutch, receiver can installed yesterday. Started up the car this morning and same exact noise

Took it back to Tripoint and they heard it and diagnosed the issue with a stethoscope. They said its the AC compressor again and must have received a bad unit. They are overnighting a new one and should be installed tomorrow. Hopefully this time it works.

[btstarcher]

I had this noise and let it go; a few months later I was replacing my compressor.

[MattJackson86]

So maybe it was just a faulty compressor, just seems odd to have same issue 2x.

Any thoughts on if it could be a water pump issue? Trying to think why it mainly occurs early morning when warming up and only when the AC is off.

[btstarcher]

Might not line up properly; mine went bad because when my engine was replaced they mounted the compressor slightly crooked. Over time the bearings wore out. Lots of shaft play, you could reach down and move the pully.