I know there have been a few threads lately for A/C trouble. My issue is a little different.
Starting off, i have a 1968 J code running the original smog/thermactor equipment, and the original Tecumseh compressor.
Problem 1:
After recharging and running the compressor, i noticed a loud noise coupled with a vibration at certain RPM’s, mainly low rpm. I initially thought it was my compressor, but i quickly realized it was coming from the smog pump. The pump does not make any noise with the compressor off, and seems to be working normally. The pump does get pretty hot, but i dont know if that is normal or not.
What could be causing the pump to make noise when the AC is turned on and none when its off??? Its on the same belt, which is tight and not slipping.
Second issue is that while driving around with the AC on, i made a right turn and water gushed out of the evaporator box and onto my passenger floorboard. I looked under the car and water was draining out of the drain tube in what i think is a normal amount. The drain tube is brand new, although the repro is not exactly the same as the original. I squeezed the drain hose and didnt feel any blockages. I tried to replicate the problem and could not. What could be the problem?
I am no expert on this topic but would surmise that when the AC compressor is engaged, it is creating more drag on all the pulleys, hence the vibration. And I think you are on the right track – the smog pump shouldn’t get hot.
Secondly…I would wonder if the nipple/drain hole on the bottom of the AC/heater box is partially clogged, preventing full flow into the drain hose. I might suggest pulling the hose off and carefully probing to see if you can drag some detritus (leaves, dust/mud, etc.) from it to clear it up. I have had had to do this once. At the very least, it sounds like you also might need to remove and reseal the AC/heat box. There is a seal kit out there readily available.
It doesnt seem like the pump is vibrating. The noise it makes almost sounds like a fast rod knock. Any idea of why it might be getting hot? Anyone know the inner workings of the smog pump. I read about possibly de-veining the inside to keep it looking original, but effectively eliminating the function.
Well I removed the thermactor and disassembled it. Everything looked fine inside. Lubed up the bearings and reinstalled. While reinstalling, I noticed the bolts holding the mounting bracket were loose. That eliminated 90 percent of the vibrations and noise.
Glad to hear that solved the issue.