Automotive Air Conditioning Information Forum (Archives)

70monte on Tue August 09, 2011 9:31 PM

Year: 1999
Make: Chevrolet
Model: Suburban
Engine Size: 5.7L
Refrigerant Type: R134a
Country of Origin: United States

I replaced a leaky compressor on my fiancee's ex-inlaw's 99 Suburban about 14 months ago. The owner just called and said that the air doesn't work anymore. I'm going to look at it Friday. The system worked fine last year after the repair. I did not replace the condensor, front evaporator, or any lines on the front part of the system. This vehicle doesn't get driven much and sat quite a bit in the last year.

When I did the repair last year, I replaced the compressor with a Sanden unit from ACKITS. I also bought the accumulator, OT, O-rings, and nylog from here. I also installed a HD fan clutch.

I did not mess with any of the rear part of this system. I did look under the vehicle to see if any of the connections looked like they were leaking but they weren't. The system vacuumed down fine last year and held vacuum with no loss for 30 minutes or more.

I'm very familar with the front portion of the system on this vehicle but not the rear. Is the rear evaporator or expansion valve known for leaking? Thanks.

Wayne

GM Tech on Tue August 09, 2011 10:39 PM

Look for corrosion and dye around the grommets that hold the lines to the frame--are you in a road salt state? I take it this is a factory rear air and not a conversion company-- actually conversions are less prone to leak since they use all rubber hoses insted of aluminum lines....rear txv and evaps don't leak in general terms...You may have a rub through somewhere under or behind the engine-- look for aluminum up against steel-- steel always wins!!

-------------------------
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......

Cussboy on Wed August 10, 2011 4:09 AM

I had an R-12 1988 Sub with dual-air (apparently rear unit was spliced-in using rubber lines to the rear after coming from Ohio to Arizona) from 1994 to 2000, and an R134a 1994 sub with factory dual-air from 2000 to 2010, and never had a leak in the rear system of either. I had a leak in the high pressure manifold crimp on the 1994, and of course, several R4 compressor leaks. Once I caught a stone that punctured the 1998 condenser.

I did have the rear unit of the 1988 fall down from the roof as GM apparently didn't provide threaded bosses for a rear unit unless it was factory (similar to no slots/brackets for 3rd seat unless it was ordered that way). I simply drilled THROUCH the entire roof andused through-bolts to hold it up, but that fall did not cause a leak (drove it home with a 2x4 holding it somewhat in place).

70monte on Wed August 10, 2011 6:23 AM

I do live in a state that uses salt on the roads but I don't think the lines looked very rusty or anything. I will check out the rear lines that I can see very closely. This is factory rear air.

I'm going to be looking at the high pressure port on the manifold lines as I had problems with that on one of my 98 trucks. I will also check out the condensor really well.

Thanks for the ideas.

Wayne

70monte on Fri August 12, 2011 3:09 PM

Well, I just finished working on the Suburban but I'm not sure it's fixed.

I initially looked over all of the line connections and compressor and did not see any dye. I also crawled under the truck and looked at the rear lines but did not see anything. I installed dye with the oil last year.

I hooked up the gauges and the static pressure with the vehicle off was only about 25psi so I knew it was low on charge. I evacuated what was left and checked all of the line connections. I found one at the condensor that was slightly loose but it showed no signs of dye.

I hooked up the vacuum pump and vacuumed the system down for about 35 minutes and then let it set for about 15 minutes when I noticed that the vacuum had dropped down to about 25. I rechecked all connections but did not see anything. I turned the vacuum pump on again for about 15 minutes and then let it sit for about 35 minutes. This time it did not leak down.

I recently bought a refrigerant scale and 30lb bottle of R134a so this was going to be my first time using both. I hooked up the charging hose to the bottle, removed the air from charging hose and started charging.

The original sticker on this truck speced 56 ounces of refrigeant but all of the charts I had seen said 64 ounces so I decided to charge to that amount this time. This sub has rear air.

When I first opened up the valve on the bottle, the low side went up to about 75psi and pretty much stayed there. After the vacuum sucked in as much as it was going to, I started the vehicle and finished charging.

My final pressures were about 48psi on the low side and about 220 on the high side. The ambiant temp was 88 F and humid. I was not happy with the low side pressure. I did not retake the pressure readings after taking a drive so they might have come down. When I reved the engine to 1500 rpms, you could watch the vent temps come down. I have read that the duel air pressures are sometimes higher than single ones but I don't know if that is true or not. A new HD fan clutch was installed last year when I fixed the system then.

My final vent temps on the drive were 48.6 F and at idle when we returned they went up to about 58 F. This was on max cooling with blower speed on high. The vent temps this time around were much better than I got last year. I only had about 59 F vents while driving that went up in the 60's at idle.

I did install a shot of dye through the low side port after I got done charging to see if I could see any leaks but did not see anything after we got back from the drive. I don't know if the loose connection at the condensor was my leaking point or not. I told the owner to drive it awhile to see if anything visable starts leaking. I also tested the evap drain water with my fluorescent dye light but didn't see anything. For some reason this time, the rear evap drain was not draining anything. I stuck some wire up the drain to see if it was stopped up but it didn't appear to be.

I will say that I like using a scale and 30lb bottle much better than cans. Charging is much faster and more accurate.

So, what do you say about my low side pressure and can a line fitting leak but not show any dye? Thanks and sorry for such a long post.

Wayne

Airstream on Fri August 12, 2011 4:38 PM

That's a short post compared to mine.

I new at all this, but I'm wondering if the compressor can really be ruled out. The way I see it, anything escaping the shaft seal will get slung away by the rotating parts. The glycol-based lubricants R134a systems appear to be both water soluble, and do not hang around long after leaking out (especially when slung out).

The compressor in my '99 Silverado is pretty much hidden from view. Could you really see much of your Suburban's with your dye light?

Tom

70monte on Fri August 12, 2011 4:57 PM

The compressor was replaced about 14 months ago with a new Sanden clone from AMA and the owner told me he only drove it about three or four times since the repair so the truck sat most of the year.

This is an old body style Sub so the compressor is on top of the engine where it can be seen pretty easily. I looked the compressor over pretty good, even around the front seal area and did not see any dye at all.

All of the connections and components that I could see did not have any dye showing. I looked at all of the common leak points on this vehicle under the hood and saw nothing. I'm not going to rule out either evaporators or the rear expansion valve since I cannot see any of these things.

I'm hoping that it was the loose line connection at the condensor but with no dye showing, I don't know. I'm keeping my fingers crossed.

The owner is happy with the vent temps so hopefully this thing will stay charged.

Wayne

Airstream on Fri August 12, 2011 5:15 PM

Quote
Originally posted by: 70monte
The compressor was replaced about 14 months ago with a new Sanden clone ...
Mine was replaced less months ago with a no-name refurb, and the truck needed to be recharged this year.

I suspect my compressor more than I suspect yours because you bought a new unit from a reputable source.

But leaks can happen in spite of best efforts by everyone involved.

Tom

Stresst on Fri August 12, 2011 8:09 PM

I know what you mean about the 56/64 ozs, I have a 2000 Escalade with rear air and same thing I was trying to find out how much it held. Every place I check says something differant. Alldata, chilton say 44ozs, while tech choice, autozone, Napa say 64ozs then another site stated 56ozs. Really unbelievable IMO!

I wish I knew a GM tech that actually does a/c's day in and out so he would know off the top of his head without looking in a book. Someone told me that GM made an error when releasing the capacity for the C69 when they say 2.75lbs. IDK

-------------------------
2000 Cadillac Escalade w/rear air

70monte on Fri August 12, 2011 8:40 PM

Well, I know that the vent temps are colder with the 64oz vs the 56 that the original sticker said. I don't know why there would be a disparity in the information.

Maybe when these systems were first designed they got decent results with the 56oz but then had a lot of customer complaints that the air wasn't cold enough so that they did some additional testing and found out that 64oz got better results. There has to be some reason that there is conflicting information.

I was happy with the vent temps but was wondering if I had a condensor issue since the idle vent temps were around 10 degrees higher than going down the road.

Wayne

pinch on Sat August 13, 2011 12:23 AM

I have a 99 Tahoe old style with rear air and the sticker and manual states 44oz.

GM Tech on Sat August 13, 2011 7:33 AM

Always use underhood info as your basis- it is more accurate- gets changed with part numbers, service manual lag behind a year or two...

-------------------------
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......