Replacement sight glass parts

Anonymous on Mon September 22, 2003 10:59 AM

Year: 1966
Make: Cadillac
Model: Deville

I've been through two "rebuilt" original GM driers for my '66 Cadillac now at about $90.00 a crack...both leak oil around the sight glass. Mitch tells me that they are replaceable. About all I can do now is attempt to replace the sight glass seals myself. Can anyone tell me where to find the parts? I assume there is a sealing ring below the glass, and one above? I assume they are a special "flat" seal of some type? What should the retaining ring be torqued to? Any advice would be appreciated.

Mitch on Mon September 22, 2003 7:53 PM

This is the 100% deal on the sight glass O-ring for a VIR. I am 99.5% certain that it also applies to the receiver/dryer O-rings. I looked at an original 1968 dryer and the size appears the same as the VIR.

The GM VIR parts kit lists 2 IDs for the sight glass O-ring; 15-580 and 6556527.

I measured one in the kit and it is 0.468 ID x 5/8 OD x 0.078 W. Fractional dimensions are 15/32 ID x 5/8 OD x 5/64 W. That corresponds to industry size ARP-906. Now most folks don't even know that the 900 series O-rings exist and most would go to a standard O-ring kit and match up industry size ARP-014.

The dimensions for the -014 O-ring are 1/2 ID x 5/8 OD x 1/16 W. Close to the -906 but no cigar.

The tightening spec for the sight glass retainer in a 1969 factory service manual is to turn the retainer down until it is flush with the body - do not overtighten. If that instruction is followed when using the 1/16 Width O-ring, it will not generate enough squeeze on the O-ring and therefore, will not seal properly.

This appears to be the same situation as the POA 901 O-rings and the cycling switch 904 O-rings; most folks just don't know they exist, or that a separate 900 series O-ring kit is available with all the 900 sizes.

Anonymous on Tue September 23, 2003 12:51 AM

Wow! Thanks for going to all that work, Mitch!

To throw a few more confusing things into the equation, I'm looking at an old Cadillac Master Parts Catalog right now. It lists the following:

59-73 - 3144749 - sight glass o-ring, exc. VIR system.
73 - 6599462 - sight glass o-ring, VIR system.

Interestingly, they are different part numbers yet - neither of which correspond to the 6556527 one listed in the parts kit you describe. This is taken from a '74 parts catalog though...the number may have changed or cross referenced somewhere over the past 30 years.

However, since we're looking at a 1966 application, that point is null. If you're looking at a 1968 drier of similar vintage, I would agree that the ARP-906 should be the one. clarify for me what kit I need to buy to obtain the ring. Also, forgive my ignorance, but is there a special tool that I need to remove the slotted ring and where to I get one? It looks like one could work it out with a flat blade screwdriver, but I'm sure that would nick it up in the process.

Also, as a matter of personal opinion, do you think I should try just tightening the current one down a bit and see if it stops leaking? I'm a little hesitant to try it with the system charged, but I think that glass is pretty thick and probably nearly impossible to break. What do you think? Thanks again for your help.

Mitch on Tue September 23, 2003 7:43 AM

The factory service manual says to use a screwdriver to remove and install the retainer. It would have to be a big one and in good shape. I don't think it could hurt to try to tighten it.

I didn't pull the O-ring from the 68 dryer because it was not leaking and I didn't want to disturb it, but it looks to be the same size sight glass as the VIR. Your catalog info adds a little more uncertainty that the VIR and R/Ds are the same.

GM may still have the O-ring, or you can get one at a hydraulic shop.

Edited: Tue September 23, 2003 at 7:55 AM by Mitch

Anonymous on Tue September 23, 2003 2:11 PM

Hi Mitch. Thought I'd follow up and let you know what I found out. I went to a GM dealer this morning. They looked up the old part number that I had from my manaul - 3144749. Interestingly, it now cross references to part number 6556527, which is the 906 series one listed for the VIR kit. They even had one in stock. So, you are correct on all accounts!! Thanks again.

Mitch on Wed September 24, 2003 11:51 AM