I think your refering to the water flow regulator, not the exhaust pipe.Here is some information on it's use:
This Regulator valve plays an important part in cooling the engine. Each fitting is a special size and controls the flow of water to the different part of the engine depending on the rpm. Never mix up the fittings or you'll have problems with over heating and maybe seizure.
Is it leaking? It could if it has a little bit of carbon in it...here is some info on that too.
The water flow regulator has been calibrated at the factory and should not be tampered with or modified in any way.
CAUTION: Strictly adhere to the calibration procedure or otherwise serious engine damage will occur.
If engine does not maintain RPM or the engine is experiencing poor performance, the water flow regulator valve might be out of adjustment. The normal adjustment as done at the factory is as follows: On the top of the water flow regulator valve locate the red plastic adjustment screw. Mark the location of the screw with a dab of paint for reference. Turn the screw clockwise (tighten) until the top edge of the screw is flush with the top of the black cap. Turn the screw 2 clicks counterclockwise (loosen). This is the factory spring setting. The bottom tapered screw should be screwed in just snug.
This Regulator valve plays an important part in cooling the engine. Each fitting is a special size and controls the flow of water to the different part of the engine depending on the rpm. Never mix up the fittings or you'll have problems with over heating and maybe seizure.
I hope this helps.
Karl