Background: 1995 Chevy Suburban K1500 5.7L w/ rear A/C. 142K miles. System has never been open and since I've had it, bought new in '95, and I've had it serviced once. The shop did a recovery, recycle, vacuum, and recharge along with fresh oil. The guy said as long as nothing major was wrong, it didn't make sense to open a system. He said he'd liked to change the OT, but the fitting was rusted and without heating it up to break it loose, that it might cause further damage, thus he opted not to do it. OK, he's the expert and I let go at that. That was in 2000. He did mention to run the A/C at least 30 minutes all year round each month, at a minimum, to keep the seals from drying out and compressor lubricated.
It seems that when it's really humid, it doesn't cool as well, the front circuit anyway. In fact, it feels like it's more so warm. The rear circuit is blowing cool air. If the humidity is low, it seems to do alight.
Current weather conditions: Hot & humid. At test time: 90F shade, 50%RH. (Been worse, heat wave here in Northern Virginia area this week). Hooked up the gage set and got a static reading of 95 psi on low side, 100 psi on hi side. OK, says there is a charge.
I opened all windows and doors, started truck, set front AC to max and fan on high, set rear fan to high, held idle at 1500 RPM and run 5 minutes. Gage readings at 1500 RPM as follows: clutch cycled on at 35 psi and off at 20 psi at low side, hi side peaked at 200 psi.
I then checked the vent temp. 80F degrees, Not good. I have a chart that indicated at the current temp and RH, the vent temp is acceptable at 63F degrees. It also indicated gage pressure readings for a CCOT system should indicate between between 22 psi and 45 psi for clutch on-off cycling, respectively, and hi side pressure of 2-2.5 times the ambient temp. OK, so I figure I'm good in that respect.
After I shut everything down and about 5 minutes had passed, the static reading on the gage was 50-50 for hi and lo (If that means anything). When I disconnected the couplers from the service ports, I noted the refrigerant was foamy. Perhaps it means something?
A visual inspection of system doesn't indicate any noticeable leaks, like oil residue. Of course I can't access the evaporators to check them. I don't have a sniffer either.
So I'm wondering how to proceed. Check for leaks with a sniffer, UV dye? Evac system, replace drier and OT, and recharge (which I think I'll do regardless)? The compressor is dry, no oily residue visible, but it a noisy SOB, chatters like crazy. but it's always done that. In fact, the tech that serviced it in 2K said R4 Delco units are extremely noisy.
Thanks in advance.
You can bet you have lost more than half of your refrigerant- due to a shaft seal leak-- If you were to pull off clutch driver off front of compressor- you'd see the oil deposits--I see them all the time-- The noise is from the R-4 which has worn yokes internally- causes rotational lash--hold the clutch like you were opening a jar- now rotate to and fro- (back and forth) rotational lash is indicated by amount of free movement rotationally- 1/4 inch on the circumference is a lot! keep running it like this and you will soon lock up the compressor- just did one last week that I saw 6 weeks ago knocking badly-- came in last week locked up.
The worn yokes happen due to liquid flood back from the rear system when the rear system IS NOT in use. The rear txv temp tube is not mounted to the evap oulet tube properly. see the TSB for this situation- I am intimently familiar with this one- since I did all the testing for it back in '94-- So to fix your system right- get the TSB -see cut and paste below, then replace that machine gun compressorand evac and recharge to spec and your cooling will be 100% better.
LOUD KNOCK FROM A/C COMPRESSOR #56-12-01
SUBJECT: LOUD KNOCK FROM A/C COMPRESSOR (REPLACE COMPRESSOR AND THERMAL EXPANSION VALVE)
MODELS: 1994-95 CHEVROLET AND GMC C/K MODELS WITH REAR A/C (RPO C69) OR REAR HEATER AND A/C (RPOS C36,C69) BUILT BEFORE THE FOLLOWING VIN BREAKPOINTS:
DIVISION VIN CHEVROLET SJ300349 GMC TRUCK SJ701253
SOME OWNER'S OF THE ABOVE LISTED VEHICLES MAY COMMENT THAT THE A/C COMPRESSOR HAS DEVELOPED A LOUD KNOCKING NOISE. THE A/C SYSTEM WILL CONTINUE TO COOL.
WHEN THE REAR A/C SYSTEM IS SHUT OFF, A REFRIGERANT FLOOD BACK CONDITION MAY OCCUR THROUGH THE REAR A/C SYSTEM. THIS FLOODING DEGREASES THE INTERNAL PARTS OF THE COMPRESSOR RESULTING IN RAPID SLIDER BLOCK WEAR AND THE RESULTING LOUD KNOCKING NOISE. A POOR CONTACT BETWEEN THE TXV CAPILLARY TUBE AND THE REAR EVAPORATOR OUTLET TUBE CAN ALLOW THE TXV TO REMAIN OPEN WHEN THE REAR SYSTEM IS NOT IN USE. THE OPEN TXV MAY ALLOW LIQUID REFRIGERANT TO FLOOD BACK THROUGH THE REAR SYSTEM (LIQUID LINE, TXV, EVAPORATOR, REAR SUCTION LINE) AND SUBSEQUENTLY FLOOD THE COMPRESSOR.
REPLACE THE A/C COMPRESSOR, THE THERMAL EXPANSION VALVE (TXV), AND ADD AN IN-LINE FILTER.
1. RECOVER THE R-134A REFRIGERANT CHARGE (SECTION 1-B OF SERVICE MANUAL). 2. REPLACE THE COMPRESSOR AND BALANCE THE PAG LUBRICANT IN THE SYSTEM FOLLOWING THE PROCEDURES IN THE VEHICLE SERVICE MANUAL. 3. INSTALL AN IN-LINE FILTER IN THE LIQUID LINE AFTER THE CONDENSER AND BEFORE THE "Y" IN THE LINE SEPARATING THE FRONT AND REAR SYSTEMS. 4. REMOVE, INSPECT AND CLEAN THE ORIFICE TUBE FOR THE FRONT SYSTEM. IT IS LOCATED IN THE LIQUID LINE AFTER THE "Y" JOINT. 5. REPLACE THE ORIFICE TUBE. 6. DISCONNECT SEAT BELT AND REMOVE REAR BENCH SEAT. 7. REMOVE THE RIGHT SECOND PASSENGER SEAT SHOULDER BELT RETAINER FROM THE RIGHT SIDE C-PILLAR. 8. REMOVE THE (5) SCREWS FROM THE RIGHT SIDE C-PILLAR TRIM. 9. REMOVE THE (2) SCREWS SECURING THE RIGHT SIDE LOWER TRIM PANEL TO THE C-PILLAR. 10. REMOVE THE (5) SCREWS SECURING THE D-PILLAR COVERS. 11. LIFT THE RIGHT SIDE LOWER TRIM PANEL AND ROLL FORWARD TO REMOVE, THIS EXPOSES THE REAR HVAC EVAPORATOR CASE MODULE. 12. USING TEMPLATE (FIG. 4), MARK CUTTING LINES ON THE UPPER EVAPORATOR CASE USING A CHINA MARKER OR EQUIVALENT. DO NOT REMOVE THE LOCATING TABS FROM THE TEMPLATES, THEY ARE NEEDED TO POSITION THE CUT AREA FOR THE ACCESS DOORS. (FIG. 1). 13. USING TEMPLATE (FIG. 5), MARK CUTTING LINES ON THE LOWER EVAPORATOR CASE USING A CHINA MARKER OR EQUIVALENT. (FIG. 1). 14. CUT THROUGH THE PLASTIC UPPER EVAPORATOR CASE AND THE LOWER EVAPORATOR CASE FOLLOWING THE MARKED OUTLINES OF THE TEMPLATES TO CREATE TWO ACCESS DOORS (FIG. 1). DO NOT CUT REAR EDGE OF EITHER ACCESS DOOR (FIG. 4 AND 5). USE A HOT KNIFE OR A SMALL (1/2" DIA.) ROTARY ABRASIVE CUTTING WHEEL.
NOTICE: CUT THROUGH PLASTIC CASE MATERIAL ONLY. ALUMINUM TUBES ARE LOCATED APPROXIMATELY 1/8" BEHIND THE CASE WALL (FIG. 2, VIEW 1). DO NOT USE A LARGER DIAMETER CUTTING WHEEL.
15. USING A HEAT GUN TO SOFTEN THE PLASTIC CASE, PULL BACK THE ACCESS DOOR ON THE UPPER EVAPORATOR CASE CAREFULLY TO PREVENT BREAKING THE CASE. REACH IN CAREFULLY AND REMOVE THE HOLDING CLAMP SECURING THE CAPILLARY TUBE TO THE EVAPORATOR OUTLET TUBE. BE CAREFUL NOT TO DAMAGE THE CAPILLARY TUBE. DISCARD CLAMP. 16. USING A HEAT GUN TO SOFTEN THE PLASTIC CASE, PULL BACK THE ACCESS DOOR ON THE LOWER EVAPORATOR CASE CAREFULLY TO PREVENT BREAKING THE CASE (FIG. 2). REACH IN CAREFULLY WITH TWO SMALL ADJUSTABLE WRENCHES AND LOOSEN THE FITTING ATTACHING THE TXV TO THE EVAPORATOR INLET TUBE. IT WILL REQUIRE A 7/8" CROWS FOOT EXTENSION TO LOOSEN THE TXV OUTLET JOINT FITTING HIDDEN BEHIND THE TXV ITSELF. REMOVE AND DISCARD THE TXV. 17. REMOVE ORIGINAL O-RINGS FROM THE EVAPORATOR TUBES AND REPLACE WITH NEW O-RINGS THAT HAVE BEEN OILED WITH 525 VISCOSITY REFRIGERANT MINERAL OIL. DO NOT USE PAG LUBRICANT. 18. INSTALL THE NEW TXV TO THE EVAPORATOR TUBES BEING CAREFUL NOT TO DAMAGE THE O-RINGS. FINGER TIGHTEN THE JOINTS AND THEN TORQUE THE JOINTS, USING A BACKUP WRENCH TO HOLD THE TXV IN POSITION TO: INLET 20-35 N.M 14-25 LB.FT. OUTLET 15-22 N.M 11-16 LB.FT. 19. PULL BACK ACCESS DOOR ON THE UPPER EVAPORATOR CASE CAREFULLY TO PREVENT BREAKING THE CASE (FIG. 1). ALIGN THE TXV CAPILLARY AGAINST THE EVAPORATOR OUTLET TUBE BEING SURE NOT TO DAMAGE THE CAPILLARY LINE. PLACE THE FIRST HOLDING CLAMP SO IT IS LOCATED 1/4" OR LESS BELOW THE CRIMP IN THE CAPILLARY TUBE (FIGURE 3). INSTALL THE SECOND CLAMP 1/4" OR LESS BELOW THE FIRST CLAMP. BE SURE THE CLAMPS ARE FULLY SEATED ON THE TUBE AND THAT THE CAPILLARY IS RETAINED IN THE FORMED SEAT OF EACH CLAMP (FIG. 3, SECTION 1-1).
NOTICE: AFTER ALL COMPONENTS ARE INSTALLED, EVACUATE AND CHARGE THE A/C SYSTEM. LEAK TEST ALL JOINTS THAT WERE OPENED.
20. USING A HEAT GUN TO SOFTEN THE PLASTIC CASE, CLOSE BOTH ACCESS DOORS AND ALIGN THE EDGES OF THE PLASTIC. USING A SOLDERING GUN, MELT BOTH EDGES OF THE CASE TOGETHER ALONG THE FULL LENGTH OF THE CUTS, AS SMOOTHLY AS POSSIBLE. 21. COVER THE SOLDERED CLOSURES WITH DUCT TAPE TO PREVENT AIR LEAKAGE. 22. REINSTALL THE RIGHT SIDE TRIM PANEL, THE D-PILLAR TRIM, THE C- PILLAR TRIM, THE C-PILLAR SEAT BELT RETAINER AND THE REAR BENCH SEAT.
P/N DESCRIPTION QTY 52450767 OR 52470592 FILTER 1 1134328 COMPRESSOR 1 52469382 THERMAL EXPANSION VALVE 1 3096068 ORIFICE TUBE 1
PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.
FOR VEHICLES REPAIRED UNDER WARRANTY, USE:
LABOR OP DESCRIPTION LABOR TIME USE PUBLISHED D4440 COMPRESSOR ASSEMBLY-REPLACE LABOR OPERATION TIME
D3220 VALVE, EXPANSION-REPLACE 1.7 HRS.
CAPTIONS: FIGURE 1 - EVAPORATOR CASE MODULE, TEMPLATE PLACEMENT 1. UPPER EVAPORATOR CASE 3. UPPER TEMPLATE PLACEMENT 2. LOWER EVAPORATOR CASE 4. LOWER TEMPLATE PLACEMENT
FIGURE 2 - ACCESS TO TXV AND CAPILLARY HOLDING CLAMP 1. TXV 3. HOLDING CLAMP 2. A/C TUBE 4. CASE WALL
FIGURE 3 - PLACEMENT OF HOLDING CLAMPS 1. A/C TUBE 4. SECONDARY HOLDING CLAMP 2. CAPILLARY CRIMP 5. CAPILLARY TUBE 3. PRIMARY HOLDING CLAMP 6. TXV
FIGURE 4 - UPPER EVAPORATOR CASE TEMPLATE
FIGURE 5 - LOWER EVAPORATOR CASE TEMPLATE
GENERAL MOTORS BULLETINS ARE INTENDED FOR USE BY PROFESSIONAL TECHNICIANS, NOT A "DO-IT-YOURSELFER". THEY ARE WRITTEN TO INFORM THOSE TECHNICIANS OF CONDITIONS THAT MAY OCCUR ON SOME VEHICLES, OR TO PROVIDE INFORMATION THAT COULD ASSIST IN THE PROPER SERVICE OF A VEHICLE. PROPERLY TRAINED TECHNICIANS HAVE THE EQUIPMENT, TOOLS, SAFETY INSTRUCTIONS AND KNOW-HOW TO DO A JOB PROPERLY AND SAFELY. IF A CONDITION IS DESCRIBED, DO NOT ASSUME THAT THE BULLETIN APPLIES TO YOUR VEHICLE, OR THAT YOUR VEHICLE WILL HAVE THAT CONDITION. SEE A GENERAL MOTORS DEALER SERVICING YOUR BRAND OF GENERAL MOTORS VEHICLE FOR INFORMATION ON WHETHER YOUR VEHICLE MAY BENEFIT FROM THE INFORMATION.
COPYRIGHT 1995 GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.
ÃÂ© Copyright General Motors Corporation
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......
I've got a '94 Sub with R134a factory, and dual air. I got mine in 2000, and it's been through several R4 compressors. These are known to leak from the compressor body, especially when used in dual-air set ups, like GM Tech stated above. Earlier this year I replaced mine for similar, after it had leaked out over the past 6 months. So I replaced the compressor with NEW (don't go rebuilt route with R4), and also replaced the accumulator since it was out of refrigerant for 6 months.
Your system is not out of refrigerant, just low, so I might just do the compressor only, as sometimes the accumulator to evaporator threads can get bad. I've replaced orifice tubes on it in the past, all were clean, so didn't do this at this time. It was 115 a week ago here, and 112 yesterday, AC works great (Arizona).
Continued tear down yesterday. I believe the evap tube assy will have to be replaced since the orifice flare nut and fitting were galled, but managed to get them separated. The threads are buggered up some, but I don't trust reusing the assy. Besides, I had to remove the tube in an attempt to install an inline filter. The only way to install that filter between the condenser and Y block is to remove the line.. (Take note '95 Suburban owners)
I posted earlier about switching the OE R134a serpentine condenser to a parallel flow and had no comments. I guess I answered my question because I probably should've left well enough alone. I wanted to check out the inlet tube for any accumulation of junk. Removed the front grille and proceeded to disconnect the fitting. I had to use brute force to get the nut loose. After it came loose, it was stripped out. My guess is not from galling, but during assembly at factory when truck was built. Stripping like that had to have been caused by cross threading and then tightening it down anyway. So comes a new condenser. Gets better, the flare nut on the compressor/condenser hose is stripped as well. So comes a new hose assembly.
Per the TSB instructions above, I prepared the rear AC casing to access the TXV. I was surprised it went without a hitch. However, I would caution a DYI'er doing it to be extremely careful when loosening the nuts. Despite doing my best to hold the valve, the evap tube it's connected to will give at the slightest bit of movement. It must be super thin aluminum and could split or break very easily I suspect. Anyway, I got the old valve off and the new one installed per the TSB.
Today, going after the Receiver/Drier.
Edited: Sat July 31, 2010 at 2:04 PM by SeppW
The saga continues. Well, managed to get the accumulator off. The flare nut on the eavp outlet line is rusty, but threads are in tact. The suction line had no galling. However, as I stated earlier, the entire compressor hose assembly will have to be replaced since the line to condenser inlet was crossthreaded and stripped out upon removal. Maybe it was galling, but it sure looks like a cross thread situation.
As it stands now, the entire front circuit will be all new parts.
So now all that's left, at this point, to is flush rear circuit and front evap. I'm hesitant to break the lines under the rear evap since they are exposed to everything kicked up by the tire. I don't think I can get a good flush by leaving them connected and use a drilled-out TXV.
May as well go whole hog because when I had system evacuated, only .59 lbs of refrigerant was pulled out along with an oz of oil. So. yeah, major leak. The accumulator had almost 2 oz of oil. The ol' Harrison R4 had no oil. I'm surprised it held together without seizing.
Any suggestions? No telling how much oil is sitting in the evaps. So far, everything looks clean except for the small amount of debris on the orifice. The old TXV had some debris in the screen as well.
BTW, I could turn the Harrison R4 clutch by had. I understood one shouldn't be able to that with a compressor.
I guess the consolation is that 15 years of service was pretty good in my book.
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