Engine rattle when hot

moab911 · 12-07-2009, 02:13 PM

I have a slight engine rattle after my engine warms up. Starts and runs well. No smoke. Do not have the noise until engine heats up. I have two front coolers that are functioning well and the engine does not get over heated. All of the posts that I have read pertain to noise going away at higher Revs. I don't think the noise goes away at high RPMs. Ideas before I take it to the mechanic ?

ossiblue · 12-07-2009, 04:44 PM

You really will have to stick your head back into the engine compartment (figuratively, of course) to give us some more information like, where is the rattle coming from--in the engine, on the engine, around the engine? Is it a light metallic rattle like loose sheet metal? Is it coming from the top, bottom, rear? Does it come from around the exhaust? What year is your car? What model? Does it have a catalytic converter?

Any little bits will help before you take it to a mechanic. Even posting a sound clip/video would be helpful if the sound is distinct enough to be heard over general engine noise. Keep us posted.

moab911 · 12-07-2009, 06:32 PM

The sound does not seem to be an engine knock. It sounds more like the sound is coming from the back of the engine. Certainly not loose sheet metal. Definitely not around the exhaust. The car is an 86 Carrera Targa with 104,000 miles. Everything is stock with the exception of the added front valance oil cooler.

cygtoad · cygtoad's Garage

Bearing on the fan or AC unit maybe?

Is your AC still working and if so have you removed the belt going to the compressor yet?

Aurel · Aurel's Garage

Is the rattle occuring under load, or even if you rev it in neutral? Just curious because I have a rattle too...

dtw · 12-07-2009, 07:11 PM

Bad alternator bearing?

moab911 · 12-07-2009, 07:34 PM

cygtoad-The air conditioning works and I have not removed the belt. Will try that.

Aurel- The noise happens even when not under load. You can hear it more at idle.

dtw- I thought about the alternator bearing initially. If I remove the belt this should tell the tale if indeed it is a bearing.Correct?

tobluforu · tobluforu's Garage

It could also be the the starter not releasing from the ring gear?

GaryR · GaryR's Garage

If it's consistent try the AC belt but if not while it's still it hot and you hear the rattle, then pop off the alt belt and listen. Only run it for a 30 seconds or so and shut down and put it back on. Not that or a loose fan housing maybe the cam chains? Do you have the hyd tensioners?

86 911 Targa · 04:40 AM

Quote:

Originally Posted by moab911

I have a slight engine rattle after my engine warms up. Starts and runs well. No smoke. Do not have the noise until engine heats up. I have two front coolers that are functioning well and the engine does not get over heated. All of the posts that I have read pertain to noise going away at higher Revs. I don't think the noise goes away at high RPMs. Ideas before I take it to the mechanic ?

We had the very same problem on our '86, and it was frustrating!

Removing the A/C belt did not resolve the issue.

And here is what we found.

A loose bolt.......

There is a bolt (the lower one) which appends the compressor mounting bracket to the engine.

The bolt has a reduced size head to accomodate a 1/4" drive socket and extension.

A very busy place and hard to get to.

You will need to, remove the compressor belt, tighten all of the bolts which append the compressor to the engine, and the four which append the compressor to the bracket.

Also check the heater blower motor ducting in the engine compartment.

There are several small screws and bolts that hold the ducting to the engine and the blower motor.

Page 801-6 of your Bentley bible..........

Sorry, no pics.

You may pm me.

Good luck,

Gerry

moab911 · 12-09-2009, 05:19 PM

Thank you all for the suggestions. Will pursue all of them and get back to you. Thanks. Bruce