1995 Mitsubishi Diamante Engine rattles at low RPM

MANFRED08

MEMBER
1995 MITSUBISHI DIAMANTE
6 CYL
2WD
AUTOMATIC
130,000 MILES

I searched your archive but couldn't find an answer, so here's my question: A rattling noise comes from the engine when I turn the car on in Park. The noise increases when I shift to Drive, even when coasting without the accelerator down. With the accelerator gently pushed down in Drive-- between about 1,800rpm to about 2,600rmp--the noise gets very loud, but at any higher rpms the noise goes away. The noise is the worst first thing in the morning when I start it, and even though it gets less through out the day, it never goes away completely. I'd appreciate any ideas before I take it in to the mechanic. Thanks!

4 Replies

SERVICE WRITER

MECHANIC
9,123 POSTS

Is this a heavy metallic noise or a light tinny kind of rattle. Sounds like a heat sheild that loosened up by your description, which would be the latter symptom.

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Sunday, March 2nd, 2008 AT 6:59 AM

MANFRED08

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4 POSTS

Hi Paul, thanks for the response.

It's definitely more heavy and metalic, almost gutteral. And I looked at the rpms more closely, and I have a correction to what I said in the original post: I hear the noise starting out in Park, just after I turn the car on; when I shift from Park to Neutral, the noise goes completely away; when I shift from Neutral to Drive, the noise comes back, and louder; when coasting in Drive, the noise is loud, as well as when the gas is down, BUT the noise goes completely away in Drive past exactly 1,100 rpm. (Not 1,800-2,600rpm I originally said).

I tried keeping the car in 1st gear to see if it was a gear problem (as opposed to when the rpms reached a certain point) and the noise still went away when I passed 1,100rpm in 1st gear.

Any thoughts? Thanks again for the advice.
Brian

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Monday, March 3rd, 2008 AT 6:56 PM

SERVICE WRITER

MECHANIC
9,123 POSTS

Cracked flywheel maybe?

I think I would try to get it up in the air and rev it up to about 20-30 mph and poke around from the bottom.

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Monday, March 3rd, 2008 AT 7:54 PM

MANFRED08

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4 POSTS

Hi,

Just took the car in for a regular service check and had them listen to the noise. They said it was a loose belt in the air conditioning system and that it was something they'd seen before in the model. I never had the air conditioning running when I heard the noise, but they said even when the AC isn't turned on, the belt still spins and that was causing the rattling. They tightened the belt.

Anyway, I've only just driven it home but the noise is gone. I'll update if the noise comes back, but hopefully it's gone for good!

Brian

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Tuesday, March 4th, 2008 AT 10:45 PM