RATTLING NOISE ON COLD STARTUP

2001 Mazda Miata

Tiny

kingbryant

March, 23, 2010 AT 12:20 PM

Noises problem
2001 Mazda Miata 4 cyl Two Wheel Drive Manual 26000 miles

When the Miata is cold or semi-cold there is a very loud rattling noise coming from the engine area. We call it " the diesel" because the noise resembles a semi-trailer diesel engine noise. Otherwise the Miata runs fine performance-wise.

One dealer said it was something like a backpressure oil valve that they see in their CX-7s, the timing cover would have to be removed/might as well replace the timing belt while at it. And $1500 later it is fixed. I believe they are trying to generate revenue for unnecessary repairs.

Could something be loose in the engine or catalytic converter/exhaust system?

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5 Answers

Tiny

Jack42

March, 23, 2010 AT 12:59 PM

That could very well be the oil pressure by-pass in the pump. It may have a weak spring or be sticky. If it is that they are correct that the timing belt and the front needs to come apart to access it.I would have something done about it, low/no oil pressure damages the engine internally and drastically shortens its life

Tiny

kingbryant

March, 23, 2010 AT 1:14 PM

The oil pressure gauge on the dashboard does not indicate no or low pressure, is the same as always. Is this a good indicator or could the oil pressure be low despite the gauge?

Tiny

Jack42

March, 23, 2010 AT 5:10 PM

Not necessarily low, just taking a second to build up in the engine. The incorrect oil filter can cause this problem as well.

Tiny

kingbryant

July, 26, 2010 AT 1:59 PM

It was the oil back pressure valve. Mazda had a TSB on this part in 2005. Valve replaced, engine runs much better with 2x acceleration, and no rattling/diesel noise on startup.

Tiny

Jack42

July, 27, 2010 AT 8:24 AM

Glad to hear it is fixed

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