964 odd engine noise

Deanh · 07-08-2014, 02:34 PM

Hello all. I've been lurking here for awhile, and was finally able to get my hands on a p car. Its a 90 c4 black on black. I got it for a steal, and im waiting on it to be transported home. in the meantime Id like to get some opinions on a funny noise the car has developed. The current owner says the noise started about a week ago, after a recent oil change. It sounds like taking a quarter and tapping it on a counter top, pretty quickly. If your looking at the engine its coming from the right side, at the corner of the fan and airbox. It does get somewhat louder with incresasing rpm, but not by much. The noise comes and goes, but it doesnt fade in it just clicks on and clicks off. oil pressure looks fine. Car drives fine with no hesitation or misfire.

She has 183k on the obo and no recent maint as far as valve adjustments or the like has been mentioned being done. Im a mechanic and dont mind doing the work, just racking my brain trying to figure out what it could be. I have a good video on my phone that I will post tonight, along with pics of the car. Thanks for any help in advance.

RedCoupe · 07-09-2014, 05:24 AM

My first thought is a timing chain tensioner, particularly if the car hasn't been driven regularly or if oil changes have been infrequent. One time my 964 had the dreaded timing chain noise when starting it after a long period of storage. I ran the engine for a few minutes and the noise disappeared, never to return. But, I definitely wouldn't just jump in and go, hoping that the noise will disappear.

porterdog · 07-09-2014, 05:55 PM

Check for broken head studs.

efhughes3 · efhughes3's Garage

I'd say you have a leak, as noted above-perhaps a stud broke. Or intake gasket leak, although I don't think it would tick. Is it a mechanical noise, like a fan blade dragging at a given point in its rotation?

So, how does the car develop a noise when you haven't even got it yet, yet seemingly AFTER you bought it? Was the PO taking a romp in it AFTER you bought it? Or, did you know about it prior?

Doesn't sound like anything to do with a tensioner.

Deanh · 07-10-2014, 01:16 PM

No no, the noise was present before I bought the car. I sounds as if you took a bolt and touched it to the fan while it was running. Sounds like the fan is catching something. It comes and disappears.

porterdog · 07-10-2014, 02:30 PM

Fan hub bearing. Easy fix, about $100 and a couple hours. It's good practice to have your alternator rebuilt at the same time if you have someone local who is qualified.

Deanh · 07-10-2014, 02:48 PM

Porterdog, Thanks! I know its not a sure thing but it does give me hope. Headed to Boston tomorrow to pick up the car. When it gets back to Atlanta and I tear into it I will post my findings.

efhughes3 · efhughes3's Garage

Has the owner painted or powder coated the fan recently?

Deanh · 07-10-2014, 04:41 PM

No, but he did mention drive belts were done recently.

efhughes3 · efhughes3's Garage

Then, the first thing I'd do is check belt tension and possibly adjust the shims. As noted above, the bearing could be on its way out. But, it also could be way overloaded, and making noise. Or, too much tension has the fan a bit off kilter and interfering with the lower part of the shroud-in the vicinity of where you noted the noise.

Justin@Athens · Justin@Athens's Garage

Dean,

There are lots of atl. pelicans who'd be willing to lend a hand if needed, myself included. Pictures required when you get the car!

porsche964guy · porsche964guy's Garage

I would find out when it had the last Major service. Sounds like needs valve adjustments Also check to see if both distributors are working. Some times the belt between them fails.

Deanh · 07-13-2014, 06:10 AM

Got the car up on the trailer and the noise is coming from right at the corner of the timing cover and valve cover on the passanger side. I'm now thinking chain tensioner maybe. Based on records I have, a valve adjustment hasn't been done in 60k! What's the best way to upload pics and vid here? Photobucket?

efhughes3 · efhughes3's Garage

The thing is, it's impossible to discern where a noise is specifally located, or often what it is from a video. You should get a stethoscope to pinpoint.

efhughes3 · efhughes3's Garage

What you need to do is get the valve covers off, adjust valves and inspect head studs to start with. If it has been 60k since, that time is not wasted. See what you get at that point, and move forward as needed.

bazar01 · bazar01's Garage

An exhaust leak will sound the same.
If not, remove the lower valve covers and inspect for broken studs. Loose cylinder to head or case will also sound like exhaust but is actually compression leak.
Engine fan bearing will not make a sound like that.

I hope you find the problem.

RedCoupe · 07-13-2014, 06:51 PM

I have to agree with efhughes3. A valve adjustment and close examination of the rockers, elephant feet and cams is definitely in order, particularly after a 60k interval since the last adjustment. The comment about a stethoscope is good, but I have also used the old "rubber hose" technique where I put a piece of clean hose about fuel line size up to my ear and move the other end around the engine until I find my noise. Perhaps not as good as a stethoscope, but it definitely helps you isolate noises better than you can do with an unaided ear.

Deanh · 07-18-2014, 12:46 PM

Finally had the time to do some investigating. pulled the exhaust valve cover off and had a bit of play, seems excessive, but not too crazy. Pulled the intake side off and every single one of them has at least an 1/8th inches of play in them and all make a decent "clack" when you agitate them. Needless to say first thing is a full valve adjustment.

RedCoupe · 07-18-2014, 01:38 PM

Congratulations! Not only have you solved the noise problem, but after your valve adjustment, you will have given your C4 a nice increase in power! An 1/8" is a big difference in valve lift so it should be noticeable.

Deanh · 07-22-2014, 02:08 PM

Thanks! A few more questions. I noticed one of the rocker tips on the intake side looked really dry, like it hasn't seen oil in a very long time. it also looks like the oil tube that sprays the rockers with oil is clogged up. Should I replace the tubes or clean them? Also the car needs a clutch badly, and being a c4, the trans removal is not as straight foward as a c2. Is it possible to just pull the engine and leave the trans in? Can the engine come back far enough with all the accessories in place?