Loud Rattling Noise at Start Up
 

Hello everyone!

Does anybody know what is making this noise whenever I start the car? The rattling goes on for a couple of seconds after starting. If I turn the car off and quickly start it up again, the noise doesn't happen. However, if I wait even 5 minutes after turning it off, the noise comes back when I go to start it again.

Someone told me its pre-detonation (knock) because of poor fuel. Not sure if that is the case.

Thank you!

[ame]http://www.youtube.com/watch?v=Dffoe78k14Q[/ame]

Holy shit that sounds terrible.

If it was bad fuel why would the sound go away like that?

Because the computer senses the knock and adjusts the engine parameters for the lower octane fuel.

I'm not an expert so hopefully someone can chime in. I would think the knock wouldn't disappear shortly after start (since the fuel quality isn't changing).

Would it have something to do with injectors? Doesn't the fa20 start on direct then switch to the port? Again I might be mistaken (more than likely I am) so hopefully someone more knowledgeable will have an answer.

I agree with you. I also thought knocking had a different sound than this. Not sure about the injectors but this happens when the engine is cold and when it is warmed up as well.

That sounds ugly. Definitely something I would want a dealer to look at. The sound seems to go away as the engine builds some oil pressure...cant really tell from the video, but it is likely either valvetrain related, or (gulp) the bottom end. Get it to a dealer. Just an opinion...others may vary.

Go to the dealership. There is nothing normal about those sounds. It sounds like the Pistons are rubbing on the cylinder walls. Terrible sounds are coming from your engine.

Good luck the dealership should make it right.

Damn that doesn't sound good. That is definitely not from bad gas. Have you checked your oil level lately?

Sounds like shit, when's the last time you changed your oil?

I'm gonna go out on a limb. A/C compressor? Disengages after fault detect? No CELs?

No CELs. AC works fine.

About 4 months ago (I go by months since I don't drive enough for the mileage count). I was actually planning on changing it today since I do it about every 4 months so I'll see if this somehow fixes the problem. Oil level has been good.

Yes, I regularly check it and it has been good throughout the 4 months since I last changed my oil. I'm planning on changing it today though.

You seem to be right about the built up oil pressure because if I turn the car off and immediately turn it on, the sound doesn't happen. But if I wait a minute and then turn it on, the sound happens. I do plan on taking to the dealer now, it sounds like a serious problem.

Please share findings. Best wishes on a solid fix.

mine developed a slight sound at start up but not that loud. arter i changed the oil it was ok but after 5000km's its starting to come back. Courious to hear that it goes when the oil light goes out. my old car used to do that but the big ends were shot and that had done 300,000 km's. Get it to the dealler and dont let them tell you its a characteristic like they do with me, good luck and please keep us posted

Do yourself a HUGE favor and have the oil analyzed. Even if it turns out to be nothing, you need to make sure there's no excessive wear.

-alex

@tomaszjanczak, have you taken it to the shop yet?

No I have not had time but since I had changed the oil on Saturday, the noise occurs only once in a while and when it does, it's very quiet, no where near as loud as before. Most of the time now, the car starts without any noises. I'm using Mobil 1 0w-20 advanced fuel economy. Maybe the oil sucks?

If you take it to the dealer let me know, I have a similar sound on startup (although less pronounced) and it reminds me of the sound back when I blew my engine on my Mazda 3 ... Scares the fuck out of me every time ..

No, that was a really really ugly metal-on-metal sound. I've heard that sound on a loose old engine where the oil would drain out of the galleys leaving air gaps. The loose rod bearings would knock like hell until oil started circulating and the system regained pressure.

I want very much to be wrong but I'm afraid you may have spun a bearing.

Someone else chime in.

^^this

I'm sorry I missed your post. Yes, this exactly - especially the correlation between oil pressure light and sound.

Is there any way that a spun bearing can be proven if the dealer tells me that's normal and such ? Oil analysis ? Independent garage inspection ? Like that's exactly the sound my Mazda was making at first when I didn't realize it was burning oil like crazy and I ended up starving it ...

[ame="http://www.youtube.com/watch?v=m_dNxOt612I#t=80"]Blown Mazda Engine - YouTube[/ame]

Damn. Is it strange that the noise is now gone or very silent after I changed the oil? The oil level has never been low since I got the car. In fact, the oil level practically doesn't change in between oil changes. Could it be something I did that made this happen, like my driving?

Used oil analysis. Before the journals shit the bed, they will start fretting and contaminating the oil. Also, oil pressure drops because it flows more freely through the wider gaps in the worn journals.

Do you know if a dealer would recognize a oil analysis ?

I'm a noob with this engine - another reason I hope I'm wrong. Maybe someone dumped water into your crankcase accidentally? Did you see the used oil?

Be very concerned if you hear it at all the first time you start it in the morning. That deep knock is an expensive sound.

I change the oil myself and still have the old oil in a container. I saw it lol, but I don't know what to look for. I can take a picture of it tomorrow since you know a ton more than I do. Sunday, Monday and today, the noise didn't happen on the first start up in the morning, it might have happened once each day (very quietly) but later in the day.

Awww, man. I've been looking around for some of the "real" experts in between posts.

Stir it up before you take the pic. If there's water in there it would sink. Otherwise, doubtful we'd see anything.

I just went out and compared with mine. If you look again at your vid, notice how long it took for the oil pressure light to go out and how it corresponds to the disappearance of the knock.

Also, that knock is not general clatter. It sounds like only one rod.

Oil pressure is directly related to engine speed. You can use this principle to listen for a bad bearing.

Find yourself a long uphill climb. One where you can run in 5th slowly enough the engine lugs around 1500 RPM. Set yourself up so you can do this test and get it over with quickly. It's terrible even for a healthy engine. Low RPM is not bad by itself (engine idle - duh) but it's not cool to ask the engine for any real work down that low.

Shift up into 5th or 6th (whatever, you get the picture) and smoothly but quickly floor it. Listen for any knocks. You might even feel it in the gearshift. After no more than a second or two, pick the correct gear and get the revs back up.

The only real way you can do it your self is to cut the filter open and look for metal in the filter paper but BE CAREFUL you don't cut the sh1t out of your hands doing this, I DID, its a slippery little sucker. Magnets in oil will only pick up rings cam or cranks etc, bearings are a non metallic alloy. I had them check my oil pressure and it was fine. At this stage I have put it down to oil viscosity break down ?? it hasnt com back for 5000Km's fingers crossed.

Hey, so this morning at first start up, it made the noise but very quietly and for a very short time (3 knocks maybe). Now I can't even replicate it consistently because sometimes when the car has been sitting for a while, the noise won't happen but if it's off for 15 seconds, it might happen. It's very random now.

Later, I did the test going uphill exactly as you said but I did not hear anything. Did it a second time, and still nothing.

I took some pictures of the oil and you can see them by going to this link: http://imgur.com/a/YcKxJ

Thank you for all of your help! :thanks:

I think that's just bubbles from the stir. I don't see any white or beige globs so, no water.

@73TORANA! has great advice. I've never tried that but it makes sense.

Just wanted to add my two cents

Looks to me like there is a LOT of tiny silver particles that the bubbles are attached to hard to tell from the photos.

But what I can see is for this oil only being four months old and you saying you don't drive enough to reach the oil change mile interval this oil looks thoroughly used.
Color isn't a tell all but 4 month old oil would still look pretty damn clean in fact mine is over 5 months old and about 3k miles and it still gold as the day I poured it in there.

Do yourself a favor and do as others have already said get it to a dealer ASAP make sure you save your oil and filter receipts I see that becoming an issue when they ultimately diagnosis you with severe engine damage....

Good luck dude, thanks for sharing, and keep the updates coming

Going to the dealer tomorrow! I have all receipts and I don't think warranty can be voided if the owner does his/her own maintenance but I will just have to wait and see what happens and update here.

Good luck, its a shame anyone should go thru this

Sux but, statistically, some of us are gonna end up with that one bum part. That's just plain mass production.

OP, chin up. Especially if you have your receipts, you are in great shape. Just be cool no matter what. I bet it'll go well from the first visit.

Hey litemup thats a perfect way to listen for bearing knocks, we used to do that years ago, i forgot all about it nice one. Yep cutting open oil filters is pretty standard in the aircraft industry .

tomaszjanczak : get the dealer to check the oil pressure when the engine is hot I.E after at least 15mins running as it will take that long for the oil temp to stabilize. If you got the old oil keep it as they may want to look at it.
The knock sound will go away if you stop the engine and start it again in a few mins as there will be still a lot of residual oil in the lines and around all the bearings etc. I had to leave my car for 4 hours before it would do it again.
Out of interest what grade oil did you put in.
Good luck mate and keep us posted.

Thanks for your advice! I used Mobil 1 0w-20 advanced fuel economy.

Well, the visit at the dealer was uneventful. They said they started it multiple times waiting in between and got absolutely no noises. They went for a test drive as well. When they gave me back the keys and sent me on my way, no noise. Oh well.

I've also realized the same knocking noise when I'm slowing down, don't know if it's the same noise but it sounds like it. I guess I'll have to go back another day.