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HD6 compressor seized. PAG oil type?

Marshall on Tue October 23, 2012 4:02 AM User is offline

Year: 1998
Make: Oldsmobile
Model: Aurora
Engine Size: 4.0
Refrigerant Type: 134a

I'm replacing compressor, condenser, accumulator, orifice valve, and the suction/discharge/muffler hose asy. The solid lines I can easily clean out. My system has been inop for about a year. Drive-able because I bypassed the compressor pulley with a shorter drive belt. All of the old parts have been removed and I'll install the new parts when I determine if the evap core must be flushed.

The system contained only a small amount of refrigerant when evacuated to begin the overhaul. Does PAG oil evaporate? There isn't a drop of the oil in any of the components I've taken off the car. The belly of the compressor does have a crust of dried black oil all over it.

First: The new compressor came with a notice to use only PAG 150 lubricant and gave a specific GM number for the oil to use. Today I checked this oil part number with a Delco part supplier and their system gave an alternate that has superseded it and that oil is viscosity 46. Are either of these types safe for this model compressor?

Next question. The orifice valve screen trapped only a few tiny metal particles. I'm talking a very small amount. I've seen pics of others that have had comp failures and their OV's were completely clogged. My screens appear intact. No PAG oil on my OV either. Where did it go? I vacuumed the OV tube after I pulled out the valve just in case some little metal flakes were in there. Get the evap coil flushed out anyways? I have read that flushing evap cores isn't recommended unless there's good reason for it. Could the evap core be compromised and leaking?

HECAT on Tue October 23, 2012 9:01 AM User is offline

There are so many different failure scenarios, that the failure evidence is often very different.

From your description there is evidence of a low charge, "belly leaker", and little debris found in the OT. The compressor probably failed from the refrigerant charge getting too low to provide adequate lubrication flow. The compressor may have died quickly and may not have "chewed" itself up and burnt a lot of oil to produce the junk in the OT. The condenser acts as primary filter and may contain any shards of debris; that is if the compressor even kicked any out.

Although some oils are lost with a "belly leaker", it is a very minimal amount. As the oil migration slows the oils begin to pool in the evap and this is evident with the lack of oils being found in removed components. If the evap has been sitting open and unused for a year these oils will have absorbed moisture from the ambient air and may have even begun to "goo". Yes, the evap should be flushed and blown completely dry; and given the potential volume of "goo", this is not going to get done correctly without a high volume solvent blast system.

Use the oil recommended by the compressor manufacturer. Vacuuming lines will not remove any debris. Yes, the evap could be a leaker. Have it professionally flushed and vacuum checked, or just replace it. You are risking all the time invested and the expense of all the other new pieces, if you do nothing with it.


HECAT: You support the Forum when you consider for your a/c parts.


Marshall on Tue October 23, 2012 12:11 PM User is offline

The compressor did seize instantly and in doing so, the main drive belt began smoking from friction over the frozen pulley. I parked immediately thinking "engine fire". I turned off the A/C before re-starting. The comp clutch was destroyed and rattled the 10 block drive back home. This was 1 year ago.

The system has not been opened until yesterday. After removing the OV, I tightly capped and wrapped the ends of the tubing leading to the evap with layers of plastic cling wrap as a preventative to dirt and moisture. Since the system hasn't been "gaping" open for an extended time, maybe the oil hasn't emulsified too badly.

Ideally I would replace the evap, after going through all of the labor and expense so far and may still do that. The deterrent is the anticipated amount of labor as it resides in the module box behind the console and dash. As you imagine, numerous fasteners and risk of breakage to trim pieces that have been discontinued long ago.

Flush and leak check is first. Do you have a resource list of repair facilities that utilize your HECAT equipment in my region, Burbank, Van Nuys, Glendale- north of Los Angeles?

Thank you for your explanation of where the oil went. It makes sense.

HECAT on Tue October 23, 2012 5:03 PM User is offline

I have 2 answers for your question regarding shops that use HECAT equipment.

1. As a manufacturer that sells through distribution, I do not have such end user data to share. (Thanks for the call, I will keep looking)

2. Many professional shops that have invested in such equipment will be more interested in doing the entire job and less interested in doing a partial service for a DIY tech. Unfortunate, but true.

This tool available from this sites sponsor is an option.


HECAT: You support the Forum when you consider for your a/c parts.


doctorbee on Thu October 25, 2012 10:38 PM User is offline

stagnant pag oil exposed to air needs to get flushed out because it absorbs moisture from the air. call some shops in the area if they can flush your evaporator and condensor.

after getting the flush i'd recommend installing an in-line AC Delco AC Filter. reinstall with the OEM spec'd oil and find out what viscosity is needed. if i had to guess i'd rather go with 150 than 46 for this model year,

iceman2555 on Fri October 26, 2012 8:59 AM User is offlineView users profile

The failure of your unit can be traced to the lack of refrigerant in your system. All lubricant is migratory in this system and is controlled by the amount of refrigerant and flow of refrigerant. A undercharge (leak or lack of proper charge ) will cause this or will result in a replacement compressor failure.
Your plan for repair seems to be on track. A strong suggestion would be to have the system serviced by someone with a very good working knowledge of automotive ac repair and who has the correct equipment and knows how to utilize this to insure a proper repair. If you accomplish the installation of all means have the system evac'd and charged by a competent technician.
Lubricant for this compressor should be PAG 150 if this is a Delco unit, also if this unit was made by someone other than 4Seasons. 4Seasons spec's PAG46 for their units. This is because the 4S unit is built on a Denso design instead of the standard GM platform.
This is an 8 oz system. Place three oz of lube in the suction side of the compressor (larger of the two orifices) and the remainder into the inlet side of the new accumulator. Lubricant ALL hose connections with MINERAL oil. Have the system charged by weight and not by cans and using pressures to determine charge rate.
Insure that all parts are clean...clean...clean.
Evaluate the system after repair for leaks and proper engine cooling and system performance.
Good questions post back...some one will respond.....and glad to see that you are approaching this repair in a straight forward manner and not attempting to simply 'fix' the problem.

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