About 2 months ago I noticed a slight ticking from the engine when driving and applying a little gas. At first I thought it was "pinging" and was going to fill up with premium gas next time, but then changed my mind. This sound was regular and not quite as high pitched and "scratchy" as pinging, and it happened at only light loads. My next guess was tappets, but this was no different hot or cold and was not there at idle. From inside the car, in neutral, I didn't hear it, but in Drive, with the brake applied, I started to hear it past about 1200 rpm. Originally I tried to identify it by opening the hood and revving the motor by turning the throttle, but the general engine noises were a lot louder and, obviously, since it wasn't under any load, I wouldn't have heard the sound I was looking for anyway. I can't check it that way under load by myself, because the hand brake doesn't work.

I've searched here and couldn't find anything that exactly matched what I'm hearing. What I want to know is; what is it, should I be worried and how do I fix it?

The car is a 1992 745 NA wagon, with 478,000 klicks on it. Timing belt and water pump replaced a year ago.

Happy New Year!

If you haven't found the problem yet, start the car and run your hand down behind the manifold to drop pipe flange and see if there is a leak there. You can also use a piece of paper if the manifold is hot.

Regards,
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Will Dallas, www.willdallas.us, www.willdallas.org, www.willdallas.com, www.dallasprecision.com 86 245 DL 222K miles, 93 940 260K miles, 88 765 GLE 152K miles, 88 780 246K miles, 93 Buick LaSabre 119,000 miles

Hello John,

This came directly from the FAQ's. There's loads of great info there. Just so happens I diagnosed my exhaust man gasket leak with this method. It was pretty obvious that I had a leak, but with this method, you can verify.

Detecting Manifold Gasket Leaks. [Tip from Mike McBane] To locate an exhaust manifold or gasket leak, duct tape a shop vac hose onto the exhaust pipe outlet, set it on blower, apply soapy water to the manifold gasket and turn it on. Bubbles or air leaks will show the location of the cracks or failing gasket

Marty Wolfson

Thanks for the tip, Marty.

I would never have found that unless I'd known to look for the cause, not the symptoms. As I mentioned elsewhere in this thread, I've actually experienced this kind of "ticking" on another one of my cars (a Camaro) and found it was a loose exhaust manifold nut. I think I even recall suggesting to someone else here on this board that a sound like this can be an exhaust gasket leak; yet I completely overlooked that when I had the same symptom. Maybe it's just that I was paranoid a noise like that from a 479,000 klick engine engine could be some serious mechanical problem.

Come to think of it, an exhaust leak could also explain why this winter I'm getting a slight smoky smell in the car and the other day a passenger getting out wondered if I was burning oil, which I'm not.

Why rear out a tree? Why not simply have a (reliable and trusted) helper assist you. You should be able to easily isolate the noise. Sometimes a small exhaust manifold gasket leak can sound like a tick.
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David Hunter

You're probably right it could be an exhaust manifold leak because I've seen that before on other cars and it did sound like a ticking. The fact that it's there under a bit of load and not when idling also points to a difference in cylinder pressure. I just hate tackling those rusty manifold studs and nuts in case one snaps. I'll have to give them an good overnight soaking with PB Blaster.

Don't touch the manifold till you correctly diagnose the problem. Listen all around with a plastic tubing (3/8" works well). Forget the tree stuff, use an assistant.
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David Hunter

Take a long piece of hose of any species, tape it to the car from where you think the noise is to inside the cabin (window down an inch, hood on the safety latch). Back the car up to or drive it forward to a large tree or some other largely un-movable object. Keep the wheels from spinning and put a load on it after you've made contact. You should be able to hone that hose until you get it right where it needs to be, guess and check. You could start with a short hose with the motor idling and put one end to your ear, the other towards possible sources for the noise (valve cover, lower block, etc).
It's probably piston slap. Although, that would diminish when the engine became warmer.
B

Good idea. I could probably hook the trailer hitch up to a tree and do that without hurting the bumper. What I was really looking for was someone who has experienced the same symptoms and pick their brain.