I just bought a 1991 Z28 with a little over 149K miles on it. Today I went and started her up and was just messing around with things and I noticed that there's a clattering coming from the passanger's side of the engine in the front. It is either coming from the AC compressor of the A.I.R injection compressor. The ac blows fine and is ice cold and there are no leaks at all from it, so is it safe to say that the noise is simply coming from the air injection compressor (which I plan on removing when I install my LT's)? The sound does get louder and faster when the RPM goes up so it has to be either accessory. Would the ac compressor make this kind of noise?

Also, when I initially bought the car, the lady told me of it habitually overheating. IT was true, and after about only 20 mins of driving it from her house to mine, it was at about 260* and when I turned it off it was boiling. Today when I was checking it out, I started it up and took off the radiator cap and inside the rad it looked like everything was already boiling....it had foamed up after about 1 min. of idling. Would this foaming cause it to over heat? And what would be the cause of this...air in the system?bad coolant? bad fan sensor not turning on the fans? The coolant doesn't look crap brown but it isn't anywhere near new either....so should I just flush the system, add all new coolant and see where that gets me? Any info or help would be greatly appreciated.

 

Get a piece of heater hose, stick it in your ear (!!!!), probe around with the other end to find the noise.

Yes it sounds like a coolant change is in order. If the various parts are actually working (fan, WP, thermostat, etc.) then cleaning it up and putting in 70/30 water to AF should fix it up. PUT A NEW RADIATOR CAP ON IT. Make sure the lower air dam is in good shape.

 

Possible worn timing chain, pooched water pump, leaking headgasket or cracked head.
Does the water appear to move (circulate)in the rad when the thermostat opens? is it loosing water?
Pressure test the rad. do a compression test on the cylinders.

 

Yeah the water was swirling around in the rad. when I took the cap off to look inside. It does not appear to be losing coolant anywhere, but I haven't checked it out completely yet. I plan on doing a compression test of all cylinders soon though... thanks for the advice.