Weird rattle until oil pressure builds?

[Zdos123]

I have a 2009 Mazda MX5 1.8L which after changing the oil recently started to rattle for 1-2 seconds on certain cold starts, seemingly relating to angle and duration length but also sometimes when I've only had turned off for 2-3 minutes after driving hard it'll rattle slightly.

If I crank the engine by holding the throttle and turning the key it doesn't do it after that, I've tried 2 new oil filters, they seemed to make it slightly better and I'm now on the original Mazda OEM filter.

I replaced the oil with 5w-30 as specified in the owners manual. I also know these engines are very prone to oil starvation so I'm curious if the previous owner let it run slightly low and wore the rod bearings our and put something in the oil to quiten the sound to fob it off.



It's still under warranty for the next 3 months from the garage so I want to figure it out before then so I'm not suddenly left without a car.

 

[flash7210]

Idk all the specifics of your motor but I suspect valve train rattle.
It just takes time for the oil to get pumped up to the lash adjusters and cam phasers.
If it were an issue with the rod bearings you'd see glitter in the oil when you drain it into a pan.
It wouldn't hurt to try a 10w-30 to see if that helps.

 

[Danno]

I would take it in right away for warranty repair. Oil spec changes or different oil filters won't fix it.

 

[Zdos123]

I would take it in right away for warranty repair. Oil spec changes or different oil filters won't fix it.

I tried they claimed they couldn't hear it and that it was running perfectly, I'm trying to get some solid ideas of what it is before I go back again

 

[flash7210]

Also, try recording the sound from over the engine with the hood up.

 

[Danno]

Seems to me like you have a warranty but you don't where the place you deal with plays "stupid".
There are ways to escalate this, but it would be good if the seller would step up here.

 

[Zdos123]

Seems to me like you have a warranty but you don't where the place you deal with plays "stupid".
There are ways to escalate this, but it would be good if the seller would step up here.

It's a legal protection in the UK so I'm going to email them

 

[Danno]

You may need a written diagnosis from an independent garage, otherwise this may come down to a matter of differing opinions.

 

[bullwinkle]

That’s not a valvetrain noise-that’s a bottom end noise, likely rod or main bearings. Something bad has happened down there!

 

[doublebase]

Valve train actuators when they start to wear will rattle upon startup as the oil pressure equalizes in the phasers. But valvetrain itself is more of a light ticking sound. Piston slap can sound like a rattle, and it's usually upon startup, then it tends to go away upon warmup. Thumping noises are lower end bearing stuff (and big problems). Rattle at idle can also be a cracked flywheel. Louder ticking noises can be an exhaust manifold leak.

 

[Greasymechtech]

Miles or kilometers on engine? maintenance history? any oil consumption?
2009 with warranty? Seems to old to have warranty

Change the oil/filter now with a 0w40 or 5w40 oil.

 

[Zdos123]

Miles or kilometers on engine? maintenance history? any oil consumption?
2009 with warranty? Seems to old to have warranty

Change the oil/filter now with a 0w40 or 5w40 oil.

It's miles so almost 90k miles, no oil consumption that I can tell, had oil changes as specified by Mazda until I bought it where it missed an oil change for a year.

In the UK all cars have a 6 months warranty if bought from a dealer.