Blocking Rear A/C on GM Burbs and Yukons

[mwilson]

Had to stop messing with the boat for one evening at least...

Any of you that own GMC Yukons, Yukon XLs, Chevy Tahoes and Suburbans that are in states with winter weather and road treatment chemicals be aware....

At some point you will have trouble with the rear A/C aluminum pressure and suction lines.

I knew that mine were blocked off when I bought it and put it on the list of things to repair this summer. Ordered the new line assembly along with an expansion valve in case that was rotten as well. Ready to do it up right...

Lines arrived from GM and guess what??? They are shipped cut in half!!!! I went "What the Hell is this???" and called my dealer. Well apparently between the flat rate repairs and extra shipping due to length GM decided that they could cut all four aluminum lines right in the middle. And then don't add splices (not that I would have used them) which cost about $50.00 each so there is another $200.00 added to the $300.00 cost of the line package.....needless to say the lines went back...

I have set to install in the Town and Country laying on the garage floor right now that came as one piece. They are no longer than the GM lines so don't know what's up with that.....

The front air is plenty strong anyways (like I've said before, GM knows how to make air cold) so with a heavy heart I decided to stay with castrated rear air. There has been a slow leak, have had to fill it twice this summer. Second time the refill only lasted about 5 days so figured the leak might be big enough to easily spot now.

I could see the cut high pressure line and a fitting on the stub with a little green dye dripping off it so figured the leak was in the block offs.

At lunchtime I will post pictures of both what I used for a repair and the repair used by someone before.....

 

[AEdelheit]

Hmmm following!!

 

[CBari]

Pardon my AC ignorance, but why must aluminum lines be used. I know some lines on my tractor are rubber lines. They might not be OEM not sure but it would sure beat aluminum that the road chemical eats up.

 

[mwilson]

Pardon my AC ignorance, but why must aluminum lines be used. I know some lines on my tractor are rubber lines. They might not be OEM not sure but it would sure beat aluminum that the road chemical eats up.

Cost probably. Even the Rear HVAC lines in the Class 8 trucks are aluminum, I suspect rubber hoses would be more problematic (before the warranty period expires at least....)....plus all the aluminum lines are connected by plastic separators and have several quick connects which probably makes it far more efficient to install when building the vehicle....Daimler calls the rear line sets "Cassettes".....
I know steel lines for the rear heaters don't last three years, already been down that road with an older Caravan that I had...

 

[mwilson]

Possibly weight and resistance to vibration are factors as well....

 

[mwilson]

Well I apparently didn't get an overview shot of the underhood plumbing.

What the deal is that the rear A/C lines are connected to spurs off of the front lines under the hood. You could change the underhood lines over to a pick up set up for example but I think the block solution is cheaper UNLESS you have something wrong with one of the front lines, then a changeover might make sense....

Each spur has the standard one bolt flange and sealing washer combo that most GM's use.

I did some hard core surfing and finally settled on these as a durable solution....

https://www.amazon.com/gp/product/B06X9F3GXS/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

 

[mwilson]

Now for what I removed...

High pressure line capped..

Notice the extra effort expended in trying to squeeze the line closed...

 

[mwilson]

Then this gob of brass was the final seal...

And as you can see it didn't work as the dye and oil left some residue on the way out through..

 

[mwilson]

The low pressure or suction side was even more crafty...they simply disconnected the fitting and stuffed a plastic plug in there along with a rubber cap from something (which I destroyed while trying to get it out of there) and then bolted it back together...

Plastic plug...

 

[mwilson]

So once I got that mess cleaned up and the suction line cut off back by the accumulator I installed the block off kit....

Low pressure block off

High pressure block off

 

[mwilson]

Put it under vacuum and had a small leak. Re-tightened the low pressure plug and leak stopped. I suspect that the spur opening was a little distorted form the plastic plug and rubber thing being forced in there....

2nd Vacuum down...

 

[mwilson]

All good now!!! We'll see if it holds more than two days.....

I'll try to get an overhead shot tonight but the locations are as follows..

High pressure spur = right in front of the accumulator

Low pressure spur = right beside the front of the rh exhaust manifold.

 

[CBari]

Mike thanks for the reply you have me wondering why my tractor has rubber lines actually more like hydraulic hoses. Like I said probably not OEM which wouldn't surprise me considering this tractor has had a fire on it.

 

[mwilson]

The rubbers hoses might be a result of an A/C kit where tractor cabs are sold as an add on so the A/C would be an add on as well??? Maybe?? Then the hoses can be cut to length depending on how and where they are routed and the ends are put on afterwards..

The Thermoking Tripac APU's have rubber hose for that reason, way too many possible configurations to ship anything pre-made.....

 

[JR]

The rubbers hoses might be a result of an A/C kit where tractor cabs are sold as an add on so the A/C would be an add on as well??? Maybe?? Then the hoses can be cut to length depending on how and where they are routed and the ends are put on afterwards..

The Thermoking Tripac APU's have rubber hose for that reason, way too many possible configurations to ship anything pre-made.....

Our cranes also have rubber lines in the A/C side. They are braided type hydraulic looking hoses.

I've always wondered why OEMs don't use that copper nickel stuff instead of aluminum. I really can't see aluminum being any cheaper? But who knows.
The wife's Mercury had a pin hole in the high pressure line, about 6 ft long over all with several bends. The line itself cost over $200 plus labor as I don't have the proper equipment to do the work. A/C work is the only time my vehicles will see the inside of a shop. I'd just rather do it myself and know it's right.

Mike is that your vac pump in the picture above?

 

[mwilson]

Yes, I bought it several years ago. I wish I had purchased a bigger one as this one struggles to hit 30. That's where you need to be to boil the moisture out of a system that has been open....IF you leave it long enough it will pull 29 1/2 but I was rushing last night and the system was not completely empty when I started the repair so it got a quickie......

 

[JR]

I've been looking at investing in some tools. Between all of our vehicles and immediate family somebody always got problems :-laf
Just this year the Mercury was down and as of yesterday the Bug. I'm thinking it's time to get off the pot and pony up.

 

[mwilson]

I can bring them to work and use the big Snap On rig we have here but it tends to be in use all day when it's hot and I don't want to tie up shop equipment when it is needed elsewhere.

So over the years I have purchased decent Snap On gauges, a dye kit, the vacuum pump, scales, etc....if the system is still charged fully I will take them to work and suck it out with the reclaim machine. But usually they are dry or darn near it before I start. I also buy the R-134 in the 30lb can, much cheaper in the long run.
The worst thing is that the 30lb cans are designed to dispense liquid and have to be inverted to do so. The GM's could care less but the Dodge products will build head pressure when filling and you have to go slow and easy.
A scale is a must with R-134a, even being off 1 oz can affect system performance.

 

[Tuesdak]

The front air is plenty strong anyways (like I've said before, GM knows how to make air cold)

Not to pick on you but this isn't true. The Big Three need to take AC seriously and they don't. This be what I direct this at. Works well for Maine maybe. Come on down to Phoenix, AZ, oh, about now with the Monsoon humidity and 105+ temps and understand why foreign automakers have kicked the big three nearly out of the market. That be getting away from the obsolete for R134A orface tubes that simply give it up when it gets over 105 degrees out. I have the older design 2002 Yukon (before they plumbed the rear suction line into the accumulator later that model year) tore down in my garage from a shredded compressor. Yeah system full of 'debris hairballs'. Prior to that the slugging hurt the compressor and it wouldn't bring the high side up. I have the DeSlugger kit on it now.

My 2003 Dodge Ram does better in hot weather when they are both working. Regardless the GM system suffers from the inability to keep it from being a sweat box over 105 degrees outside when waiting for passengers in the parking lot due to low engine RPM at idle contributing to the lack of AC cooling and liquid slugging the low mount compressor on startup that has blown compressors clean in half and/or snapped the AC belt tensioner clean off the engine. (2008 may have the extra stretchy belt design to work around the problem w/o a tensioner.) Some 2008 systems on GM started to go to the better expansion valve systems, but, the rear expansion valve and orface tube up front has always been a mess.

You are correct about the rear lines being something you don't want to remove ever. This is actually an improvement over the older aluminum lines with the steel nut But the 2002 TXV in the rear still used this brain-dead obsolete steel nut design in a near impossible to service location. The compressor debris clogged condenser removal is a SOB over older years requiring most of the front end (grille and passenger headlights incl the supports) to be removed. The rear HVAC box is easier to split open than the older years.

Improvements to the system to make it work well: Engine RPM raised to 650 in gear and 750 Park Neutral from the CAFE joke of 500. Electric pusher fan shoehorned in, VOV variable orface tube, and alternate industrial refrigerant. Then, yes, it works well in climates you really Need AC in.

While you are tore into it you should change out the fragile with age plastic "T" fittings on the heater core before they blow out. This is where the rear heater hoses come into the front heater circuit. Not a fun job to get the old ones off as the releases are the first to "SNAP!" w/o doing anything...