AC Compressor Knock
Thread Starter
Drifting
Joined: Dec 2005
Posts: 1,309
Likes: 20
From: Woodstock Georgia
AC Compressor Knock
Alright...this question seems just really stupid to me, but I know zilch about AC systems. The AC compressor on my new 86 makes the loveliest knocking sound. I don't hear it when I'm driving, but at idle when I'm out of the vehicle....I thought at first that I had a rod going!
Just curious if this may be a low oil condition in the compressor. It seems to work fine outside of the knock, and I don't remember my 85 exhibiting this same issue.
Just curious if this may be a low oil condition in the compressor. It seems to work fine outside of the knock, and I don't remember my 85 exhibiting this same issue.
Racer
Joined: Nov 2005
Posts: 456
Likes: 3
From: Sumner Texas
First of all you need to determine if the knock is the clutch or the compressor. To do this, with engine off, turn the forward most portion of the compressor with your hands. If it turns smoothly then the compressor is probably okay so you need to remove the belt and turn the pulley by hand to see if it is smooth.
If turning the forward most portion of the compressor feels like the compressor is full of rocks, then the compressor is shot and you have a huge job on your hands to fix it. It isn't too much trouble to change the compressor itself, but when a compressor fails internally, it scatters debris throughout the system and the ENTIRE system must be broken at every connection and flushed repeatedly and thoroughly. If it is not flushed when replacing a compressor the new compressor will be quickly destroyed by the debris.
There is no such thing as just adding oil to the compressor. The oil circulates with the refrigerant, and it is difficult to know how much to put in. If there is too much you can lock up the compressor and not enough will wear it out.
One other thing, check the mounting of the compressor for broken castings or loose bolts. In fact I remember having to replace an aluminum webbing on mine some years ago because it broke. If the compressor is not mounted solidly it will make lots of racket.
Good luck,
If turning the forward most portion of the compressor feels like the compressor is full of rocks, then the compressor is shot and you have a huge job on your hands to fix it. It isn't too much trouble to change the compressor itself, but when a compressor fails internally, it scatters debris throughout the system and the ENTIRE system must be broken at every connection and flushed repeatedly and thoroughly. If it is not flushed when replacing a compressor the new compressor will be quickly destroyed by the debris.
There is no such thing as just adding oil to the compressor. The oil circulates with the refrigerant, and it is difficult to know how much to put in. If there is too much you can lock up the compressor and not enough will wear it out.
One other thing, check the mounting of the compressor for broken castings or loose bolts. In fact I remember having to replace an aluminum webbing on mine some years ago because it broke. If the compressor is not mounted solidly it will make lots of racket.
Good luck,
Last edited by MBDiagMan; Dec 28, 2005 at 09:49 AM.
Race Director
Joined: Sep 2005
Posts: 13,269
Likes: 0
From: Sharpsburg Georgia
GA Events Coordinator
Originally Posted by MBDiagMan
First of all you need to determine if the knock is the clutch or the compressor. To do this, with engine off, turn the forward most portion of the compressor with your hands. If it turns smoothly then the compressor is probably okay so you need to remove the belt and turn the pulley by hand to see if it is smooth.
If turning the forward most portion of the compressor feels like the compressor is full of rocks, then the compressor is shot and you have a huge job on your hands to fix it. It isn't too much trouble to change the compressor itself, but when a compressor fails internally, it scatters debris throughout the system and the ENTIRE system must be broken at every connection and flushed repeatedly and thoroughly. If it is not flushed when replacing a compressor the new compressor will be quickly destroyed by the debris.
There is no such thing as just adding oil to the compressor. The oil circulates with the refrigerant, and it is difficult to know how much to put in. If there is too much you can lock up the compressor and not enough will wear it out.
One other thing, check the mounting of the compressor for broken castings or loose bolts. In fact I remember having to replace an aluminum webbing on mine some years ago because it broke. If the compressor is not mounted solidly it will make lots of racket.
Good luck,
If turning the forward most portion of the compressor feels like the compressor is full of rocks, then the compressor is shot and you have a huge job on your hands to fix it. It isn't too much trouble to change the compressor itself, but when a compressor fails internally, it scatters debris throughout the system and the ENTIRE system must be broken at every connection and flushed repeatedly and thoroughly. If it is not flushed when replacing a compressor the new compressor will be quickly destroyed by the debris.
There is no such thing as just adding oil to the compressor. The oil circulates with the refrigerant, and it is difficult to know how much to put in. If there is too much you can lock up the compressor and not enough will wear it out.
One other thing, check the mounting of the compressor for broken castings or loose bolts. In fact I remember having to replace an aluminum webbing on mine some years ago because it broke. If the compressor is not mounted solidly it will make lots of racket.
Good luck,
with everything he said
