Re: Engine Rattle on Cold Startup

[Black miata]

Hey all,

The last few days when I start up my NB8A MX5 there has been an engine rattle on cold start up. It only occurs for a few seconds then goes away not to be herd again but still i am concerned as to what might be causing this to happen. I have check the oil and the levels are high etc.

Does anyone know any idea what could be causing this at all?

Thanks heaps

[aviper4u]

sounds like cam train noise that every mx5 nb engine has that i have heard starting cold has.
unless it is belt noise etc...... but if it's a gentle tapping in unison with engine speed i'd say its just the tappets

dont worry about it OR do what i do and wait till the engine quietens down abit then pull out

hope this helps

[Black miata]

Thanks for that Aviper. little bit of peace of mind but with the noise it is only for literally 2 seconds then stops so idk seems weird to me.

Probs go get it check out anyway just wanted to know if it was something of a sign that could lead to a bigger issue/ costly issue in the near future.

[94 clubman perth]

I was a mechanic in a past life and come winter people would often comment as you have- as the weather gets colder you may notice it takes a little longer for the (thicker and colder) oil to circulate around the engine, therefore those startup rattles take a little longer to go away.
As a rule of thumb if the sound is a light rattle at a fast speed its in the vavetrain (cams/valves going at twice the speed of the bottom end), a slower deeper knock is bottom end (pistons/big ends). Some engines are very prone to piston knock/slap when cold, I dont believe MX5's are one of them.
Could be as simple as the drain back valve in the oil filter playing up , or you may be due an oil change. For peace of mind you can always get an oil pressure check (mechanic will screw in a gauge, normally by removing oil pressure sensor, then check pressures at dufferent temps/engine speeds).
I know my NA8 rattles every startup, love those HLA's!

[Black miata]

Thanks for that Clubman, ill probs get it checked out by a mechanic for the pressure check just to be safe.

[NitroDann]

Probably just valvetrain noise. The lifters specifically.

Dann

[94 clubman perth]

let me just edit my last response (before someone else does). Its the bottom end turning more than the top end (small cog driving big one- der).

[NitroDann]

to help clarify, although the bottom end turnd twice as fast as the top it is only likely to make one clunk per cycle, as opposed to hlas which can make 16 taps.

Dann

[Sailor]

Replace the oil filter.
Sounds like the drainback valve is a dud.

About the cheapest beginning to tracking the noise that you'll encounter.
Oh and buy a decent replacement. I still use Ryco and have never had a problem yet.

[manga_blue]

Oh and buy a decent replacement. I still use Ryco and have never had a problem yet.

or a Mazda one which are pretty cheap and work well.

What grade of oil are you using?

[93_Clubman]

my NB8A

NB8A=solid lifters

[NitroDann]

Doesnt change anything, solids still make more noise when the heads dry due to thick oil on a cold startup.

But thanks for clarifying that.

Dann

[93_Clubman]

Doesnt change anything

It does - rules out HLA being the problem.

[NitroDann]

Doesnt rule out lifters generally though.

Dann

[93_Clubman]

But does rule out HLA, which the OP probably knows, but as you say:

...necessary for the new people to know...