My 1990 4afe Sounds Like A Saxaphone - Pre-1997 Toyota Corolla and Geo Prizm

For the past few months, I have noticed a strange noise coming from the 4AFE engine of my 1990 Corolla. This car has 75k on it. When the car is cold, the engine seems to run fine. Once driven for a few miles, it decides to play a song for me under the hood (when I stop) ... sounds like a saxaphone. My first guess, is that there is a vacuum line off or something controlled by the vac line, acting up. I've looked around and can't find any vac lines off or cracked. The engine runs pretty good, but this noise is driving me nuts. It's an automatic shift, if that helps any. Any ideas as to what is causing this noise?

Having an engine that sounds like a saxophone isn't necessarily a bad thing. It just depends on who's playing it!

Max

Yeah- Clarence Clemons can play in my engine bay anytime he wants. Seriously, a vacuum hose would be a likely culprit.

Yeah- Clarence Clemons can play in my engine bay anytime he wants. Seriously, a vacuum hose would be a likely culprit.

When I come to a stop sign, it sounds like a note (maybe key of C) from a sax. If I put the car in neutral (a/t) the sound will almost stop. Once in gear again, the sound will start back up until I take off down the road. When cruising across a parking lot around 5 to 10 mph, it is loud enough to cause people to look at the car like something is funny. It really is aggravating. I guess I need to get a service manual and try to trace every vac line to see what's wrong. I thought maybe someone else on this forum may have had a similar problem.

Don't forget the vacuum hose running to the brake booster - has a one way check valve that can get gummed up or leak. You should have a vaccum diagram under the hood of the car - if all of those are OK, then you need to look at possible culprits with the EVAP system, bad bearings in your accessories (alternator, PS, water pump), pulleys, cooling system, and belts.

Since the noise almost goes away when you put it in neutral and when you drive at speed - only really shows up at low speeds points to a belt/pulley issue or accessory problem (noise under heavier load). Noise that is loud enough to be heard from outside the car is probably not a pulled vacuum hose, but you really won't know unless you can duplicate the noise with you standing infront of the offending component. You can try having someone rev the engine (or you can open the throttle yourself under the hood and see if you can reproduce the sound). You may have to try and rev the car in gear (a dangerous prospect) but can be done if you take precautions and a good partner in the car.