87 Carerra Engine bay rattle/vibration

[olly22n]

Hello! My name is Olly and this is my first post on Pelican!

I own an 87 Carrera and have an issue that I hope you guys can help with;


First things first, I don’t believe my engine is broken. It feels as strong as an Ox and makes no nasty noises. Minimal oil consumption and my garage floor is clean as a whistle.

However, when hot (and I mean, been driven for over 30 mins hot) I get a rattle, from 2000 to 5800 rpm, most noticeable on the overrun.

I think it comes from the rear n/s side of the engine bay and can only be heard clearly with the radio off. With the radio on, the noise is not loud enough to be heard.

Imagine a heat shield come loose, but less tinny, and more a playing card in bicycle spokes, but more hardcore!

I don't believe this to be drivetrain linked, but something attached to the engine, as the noise can be heard when sat still and in neutral (again, only between 1000-5800rpm).



Since first hearing the noise I have covered 150 miles of long and short journeys and the sound is yet to re-appear.

This is leading me to think it is something working itself loose/vibrating when hot/worn rubber bushings or mounts.

The nice chaps on impactbumpers.com suggested the following;

*Camchain tensioner
*Headstud

Would these occur under my conditions? I would expect these to be present all the time if they were broken?



To summarise;
Rattle between 1000-5800rpm
Only when hot/30 mins + of driving
Car can be stationary or moving
Happens under acceleration and deceleration
Does not occur on every journey
No oil leaks/ no oil usage
Any ideas chaps?
Appears to come from the LHS of the engine bay
New clutch, release bearing and clutch fork bushes

Over to you!

Olly

[DRACO A5OG]

Olly,

Where are you located?

Check the Pulley to see if it has severe wobble, Mine recently had a loose pulley bolt. I had a rattle and thought the vibration was normal, NOT


Results of a Loose Pulley Bolt, make sure AC belt is not too tight either.

How are your engine mounts?

[steely]

I'd look at the cat converter shield. You mentioned it didn't sound like a shield, but who knows. I would think that'd be more likely than a head stud. Although I have never heard the sound, I've read where the cam chain sound can be likened to a chain rubbing over/inside a garbage can. I hope this helps.

oh yeah, WELCOME! Please post a pic of your car (rite of passage).

[Chuck.H]

How many miles are on your car? My rear engine mount failed at about 150k miles, it cracked right where the threaded post connects to the flat part.

BTW, what is the n/s in: "the rear n/s side of the engine bay"?

Hope this helps,
Chuck.H
'89 TurboLookTarga, 332k miles

[CCM911]

+1

I had a heat shield rattle from the Cat and it drove me to install a Test Pipe. It is now ten years later, and I think I still need to test a bit more.

Welcome to Pelican.

Originally Posted by steely

I'd look at the cat converter shield. You mentioned it didn't sound like a shield, but who knows. I would think that'd be more likely than a head stud. Although I have never heard the sound, I've read where the cam chain sound can be likened to a chain rubbing over/inside a garbage can. I hope this helps.

oh yeah, WELCOME! Please post a pic of your car (rite of passage).

[NoLift911]

Recirculating Air Valve -

Try this - open up your engine compartment (I know you said sounds like left side) this is on the right) by the oil fill behind the cap....small flying saucer looking disk with hoses going in and out.

Put your hand on it and rev the engine a bit - you should be able to feel it if it is making the same noise...as what you are feeling.

If it is replace it - cheap



#31 in the pic...

Long shot but when mine went bad it was a similiar "faint" noise....

[olly22n]

Mines the one on the left.

It is intermittent, most recent guess by a mechanics was the fan/alternator bearing was on its way out. so I am going to wait until the noise re-appears and then whip the belt off.

It won't be the cat, as its an '87 and I live in England!


Thanks for the help so far!

[DRACO A5OG]

I am sorry to say, I thought the same as your wrench. A fellow pelican and I were driving in my car with the top down and we both noticed a rattling sound, we promptly opened the lid and heard what we thought was a alternator bearing.

Well, while I was in there, I took the alternator out for service and found the bearings to be fine, I re-packed the bearings for extra measure.

That is when I discovered my pulley belt was loose, rattle and vibration was coming from it. Think of it as a severely un-balanced wheel loose on a hub. I HOPE IT IS NOT THIS! but to verify, remove the belts, see if the pulley has any sort of play side rotation or anything at all it is supposed to tight as a bug.

Cheers,

Jim

BTW, Welcome and she is a Beauty

[olly22n]

99.9% sure it is the fan/alternator. The noise retunred today so quickly whipped off the belt, noise disapeered. Put it back on, noise returned and took it off again and has gone away.

So next question. Is this a job i can do, a job my uncle can do (he is a mechanic, but not a porsche specilist), or a job for my indy?

And how much!

Olly

[pete3799]

Yes you can do it.
Had mine out in about 1/2 an hour. Not a lot of room to work with behind the alt. but not a difficult job. Take pictures or make a drawing of where the wires go and take note of the position of the air diffuser that is bolted to the back of the alt.
I'm currently waiting for the FedEx truck to roll up the driveway with my new Pelican alt.
Good luck.

[86 911 Targa]

Originally Posted by olly22n

99.9% sure it is the fan/alternator. The noise retunred today so quickly whipped off the belt, noise disapeered. Put it back on, noise returned and took it off again and has gone away.

So next question. Is this a job i can do, a job my uncle can do (he is a mechanic, but not a porsche specilist), or a job for my indy?

And how much!

Olly

Olly,

I went through this a few years ago on our '86.

Same identical symptoms.

It turned out to be a loose A/C compressor bracket to engine mounting bolt causing a vibration,
and, loose screws on the heater blower motor ducting were the source of the vibration/noise.

Just a thought.

Hope this helps.

Good luck,

Gerry

pm me as needed.