jackelliott

2000 Jeep Cherokee Sport - I6

There has been a whistling sound coming from the front of the jeep ever since I bought it. It is loudest at startup and when I accelerate or when I am going slow. After some research, I am pretty sure that there is a crack in the exhaust manifold, I just can't figure out where.

I want to replace the header myself, but I don't want to spend money on a new one without knowing for sure that there is a leak.

How can I locate a leak that isn't visible from above the engine?

jordan96xj

If it is loudest when going slow or at lower RPMs, or when under heavy load, it could just as likely be on the intake side. Like the intake manifold gasket (which acts like a reed and whistles when air finds a way past it).

You should also check all vacuum lines, and especially the line that goes to the brake booster.

fb97xj1

Since we cant hear it, remove the belt and start the engine. If the whistle is gone, one of the accessories or a pulley was whistling. If the whistle is still there, its something with the engine or exhaust.

A used belt takes 140-160 foot pounds of tension. New belts take 180-200 foot pounds. I use a Gates 91132 Krikit II tension gauge. There are other brands, just make sure it can read up to 200 foot pounds.

extrashaky

I agree with Jordan. It's actually a pretty common problem for the intake manifold to develop a leak toward the rear of the motor and make an irritating whistle. Sometimes all you have to do is torque down the rear manifold bolts. Other times you have to take the manifold loose, reseat it and torque it down. It whistles because it's air moving through a slit, like air over the reed of a penny whistle.

If it makes the sound at idle, you can find it pretty easily. Get a length of hose (garden hose, vacuum hose, whatever). Stick one end up to your ear. Move the other end around the engine bay until you find the source of the sound.

Also, if it's an intake manifold leak, it will likely respond to carb cleaner or starting fluid. If you spray a little carb cleaner on the joint between the intake manifold and the idle jumps, you've found a leak.

It's enough of a common problem that I'd rule it out before assuming you have an exhaust leak.