Join Date: Feb 2017
Location: Springfield, MO
Re: AC drive belt "slap"--Help!
Again, thanks to everyone for the responses thus far.
The bearings are all less than one year old. I reinstalled the AC system last summer and had new bearings pressed in the AC clutch pulley, idler pulley, and tensioner pulley. They all now turn smoothly and silently with no wobble. Around two weeks ago I replaced the bearing in the tensioner pulley so it is less than two weeks old. I replaced it because in an attempt to make the belt tighter (hoping then to avoid the "flop") I overtightened and burned out the bearing. Lesson learned.
The integrated clutch design lasted into the 68 model year and spanned two idler/tensioner pulley designs. Anything built before March 1 1968 used the older pulley setup (the lower idler pulley made two points of contact with the engine block, the tensioner pulley looked like the attached photo). After March 1 1968 the tensioner and idler pulley design changed (the lower idler made three points of contact with the engine block, the tensioner bracket connected at two points on TOP of the compressor and one one the side as well as the engine block). The integrated compressor pulley spanned both idler/tensioner designs only later to be replaced with the magnet separate from the pulley. My Galaxie came off the line "06C" which I assume is March 6 1968.
When I purchased the car a little over three years ago it came with a trunk (and back seat) full of parts. Included in this collection were the elements for the factory AC system attached to the engine block (idler pulley and bracket, two tensioner pulley brackets--one old, one new, compressor with integrated pulley attached, hoses, fittings, etc). They had all been removed at some point (there had at least been a bad engine block repaint at some point) so I assume they were removed at that time but, of course, have no way of knowing. The mounting bracket for the AC compressor was still on the engine (the power steering pump hangs partially from it). But it is interesting to note that there were two tensioner pulley brackets (one old design but missing the tensioner pulley and one new design) but only one idler pulley bracket of the new design. It took me a while to figure out that I had two different tensioner pulleys. As I said the old design tensioner pulley was missing the pulley--I just had the bracket. I was also missing the actual pulley from the idler (the newer design with three legs). So I had parts of things but nothing complete. I found a donor car at a small salvage yard nearby. The yard owner was very helpful. He had two 68 Galaxies (in various condition of partial dismantlement). One of them had a 302 auto factory AC and had a date code for 1968--I don't remember the month. It had all the original AC system intact. He gave me a cost for all the mounting pieces which was extremely reasonable so I got from him the tensioner pulley and bracket and idler pulley and bracket and used them on my Galaxie. Put new bearings in them, got a new compressor, took it to a shop in town to evacuate the system and charge it and, presto, ice cold AC. Except that the belt wobbled.
The first part I replaced in an attempt to fix the problem was the AC compressor pulley. I went back to the same salvage yard from which I got the brackets/pulleys and took the compressor and pulley. Again, very, very reasonable price. I took the pulley off the compressor, replaced the bearing, put it on my Galaxie. Problem still there. It was at this point that I reached out to the community here for help and got the helpful advice to replace the belt.
Several assumptions made here any one of which could be the source of my problem. It is my understanding that the date code stamped on the ID tag wasn't always 100% accurate so my Galaxie might have been earlier or later than "06C". And I assume also that it could be that if the factory still had the old AC parts lying around they could have continued to use them past the March 1 1968 date until they depleted their stock of the old design. I guessed that since I had two pieces of the new design that I was probably looking at a vehicle that had the new design (and mind you, I had to first learn that there were two designs in the first place) and the older tensioner bracket was just a fluke. This was somewhat confirmed when I found another 68 Galaxie with similar specs (power steering, auto, factory AC, 302) manufactured around the same time and saw that it had the newer design pulleys. And, most important perhaps, I assume that the trunk full of parts was from my particular Galaxie and not just random parts that a previous owner had collected. A lot to assume.
So then back to the matter at hand. Is it possible that I actually have a vehicle designed only to work with the older design? Were the design changes from the old bracket/pulley system to the new so radically different that it would cause my problem (that I actually should have the old design parts on the vehicle and not the new)? Since the older integrated AC compressor pulley was used in both old and new bracket/pulley setups I assume that they were interchangeable. And if I've got all the parts from one vehicle that should work together does that mean that the crankshaft pulley is the only possible culprit (that is the only part I didn't install myself or change out)?