Repair Information On Your Imperial's Air Conditioning Belts

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Question from Rex (1959):

I would like a little help with a very annoying problem on my 1959 Crown. Whenever I turn on the air conditioner, which works great by the way, there is a very annoying flopping of the a/c drive belts. I have tightened the belts as much as I dare to, and this seems to help for a couple of days and then they start flopping again. The noise is so loud that I have to turn the a/c off at red lights out of embarrassment! Someone told me that new auto belts are designed with greater elasticity than older belts, and this was the source of my trouble combined with the great span of the belts from generator to compressor.

Has anyone encountered and solved this problem before? I would surely like to hear from you if you have.


From Chris:

I have chased this problem with a number of RB engines.

Here are sources of A/C belt vibration that I have discovered through trial & error.

1. Use the shortest belts that will can fit. If you do NOT have the original '59 compressor clutch (about 6") across, you might have a later, smaller replacement version that is about 4" across. This would require you to use shorter belts than those listed for a '59. Is there room to adjust the generator to use 1" shorter belts? If so, try it. (Note: Imperials through '66 - using the smaller 4" diameter clutch - use the same belts as used on a 66 Dodge/Plymouth w/ 361 engine. Oddly enough, Chryslers used a different, longer belt. So tell your parts guy to look up belts for a 66 Plymouth Fury instead.)

2. Speaking of generators (and later, alternators) this is the biggest source of wobbly belts. It must be cinched down as tight as possible to then engine at all points, including its lower mounting points. Alternators often have sleeves in their lower mounts that protrude beyond the mount. Cinching up to the protruding sleeve rather than to the alternator mount itself is a source of vibration. I file these sleeves off until flush with the alternator mounting arm and use washers for a tight fit to the engine brackets.

3. Compressor brackets. Are they as tight as they can be to the compressor and to the engine?

4. Compressor clutch. Is it tightly cinched down? A new compressor I installed on my '66 was silent when I first fired it up. Later, the belts started dancing and there was an audible growl during its operation. I cinched down the central clutch bolt tighter and it was once again smooth, silent, and vibration-free. And no dancing belts. (To do this, engine off, turn the ignition to "ON", turn A/C on engage the clutch. Cinch down bolt in middle of clutch.)

If all the above do nothing to help, you may have a compressor that is on the way out.

From Kerry:

I had the same problem on my '73 and just lived with it. The problem is that incredibly long span from the alternator to the compressor. In '74, they put an idler pulley in that span and the flopping went away. I don't know of another cure. If you can find a set of "matched" belts, it might help. Usually one belt is looser than the shorter and flops more.

From Paul:

Flopping belts! Oh my! Several of my Imperial's with and without air conditioning have done this to some degree. The worst one was the '65 and it has air conditioning. The problem also can be related to a wiggling power steering pump.

The things that I have done to lessen the problem have been to order "matched sets" of belts for the systems where dual belts are required. Believe it or not, two belts of the same number are not necessarily the exact same size.

The other thing I have found that helps is to check the power steering pump bracket for proper adjustment and/or damage. This adjustment can be tricky, and if not done right, or if the bracket is broken it will cause the symptoms that you describe on the rest of the belts as well.

Finally, I regularly use a good quality belt lube on all belts. This will keep them quiet and functioning properly even if they do vibrate a little bit.

Do not overtighten the belts as this will damage many different things including the power steering bracket mentioned above, water pump, and even in some cases engine bearings.

Question from Joe (1967):

I need you help regarding replacing or repairing a part on my other car. Along with our '67 Imperial 4Dr HT we also have a 70 Ford Country Squire. I need to replace and or repair the A/C Idler Pulley on the 390 V8. The part# is D0AA8A617. Does anyone know who rebuilds these idler pulley assemblies.


From Dick:

This is a common problem in older cars with idler pulleys, including Imperials.

There is no need to spend money and time trying to find an exact replacement for the whole assembly. Unless the pulley itself is damaged in some way, the only likely problem is the bearing inside it.

Any machine shop can remove the old bearing - it is probably a 203SS or 205SS, either one is available over the counter at any bearing house, which the machine shop can buy for you, or you can pick one up and take it to them
to be replaced. You can do this yourself if you have tools to handle the retainers for the bearing - which are probably large snap rings or "C" rings. The bearing number is on the bearing itself - just take it to your bearing house and have them match it. NAPA stores also stock these. If they have more than one grade, take the best - it will last another 30 years.

From Mikey:

Fwiw, any other big block mopar ( and in the case of the fords, if it fit a 390 find a 429 or 460 as I belive the blocks are basically the same for external things like this ) such as a later 400 or 440 car of any body style with air conditioning . They all had some version of the idler pulley for the water pump. The worst case here is having to get a different belt in case the geometry makes the belt length longer or shorter than the adjustment will allow.

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