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dan93st
11-02-2006, 08:53 AM
I've recently discovered that the natural frequency of the celica is the noise the engine makes at about 3400 rpm. Everything in the car seems to rattle right around there.

Now, I have a relatively new rattle, which started when I replaced the exhaust manifold. I'm pretty sure it's the heat shield, but I've taken it off and put it back on many time to no avail. So, maybe it's the lower heat shield. But tightening that requires pulling the manifold off the car again. Before I do all that, I want to really make sure it's the lower heat shield.

To do that, my idea was to remove the upper manifold heat shield temporarily, drive car around a bit, see if it still makes noise. If the noise is gone, I know it's the upper shield and I can't tighten bolts. If its still there, it could possibly be the lower heat shield. My question is - is it safe to run the car with no upper heat shield on the manifold? It would only be for maybe 10-15 mins to see if the rattle is still there or not. I just don't want to damage anything in the process.

If anybody knows, please share! Thanks.

david in germany
11-02-2006, 12:18 PM
yes, it is safe :)

dan93st
11-25-2006, 04:33 AM
Update. I took off the manifold, and replaced it with new gaskets making sure all of the heat shield bolts were tight. The result...Same annoyingly loud rattle. So, I'm going to guess it's not the heat shield.

It's a ringing metallic-sounding rattle/buzzing sort of sound. Occurs around 3400rpms. Anybody have any other ideas what in the engine bay can cause such a rattle? What else should I be checking?

Hookecho
11-25-2006, 02:18 PM
engine mounts

CelicaZ-R
11-25-2006, 02:39 PM
Just a thought, do you A/C, if so, is it running, if "yes" then possibly the a/c bearing is damaged.

Does it only occur when the car is in motion, or anytime the car reaches 3400rpm?

elektrateq
11-25-2006, 04:42 PM
what about the connection between the exhaust manifold and the downpipe? That's what rattling on mine right now. I'd do an inspection all the way down the exhaust line.

Benny_gustavson
11-25-2006, 06:42 PM
i had a rattle a while on my carina e gti, wich use the 3sge engine, drove with that rattle for a month or so, finally one day the rattle got more frequent(spelling) for abouth 15min or so, then i did a hard acceleration and i heard a bounce inte floor and the exhuast note became a bit loud, stoppde the car and took a look under it, then i saw that my oxygen sensor was hanging in free air hehe, the bolts to the oygen sensor had rusted away

hobbie2k
11-25-2006, 07:55 PM
My Jetta was rattling only at idle for quite a while. It turned out to be a broken fuel line bracket.

dan93st
11-25-2006, 10:27 PM
Well I found it...I think. The heat shield for the catalytic converter appears to be somewhat loose. And now it's too dark to see what I'm doing. So I guess it turns into another project for another day.