Rear A/C leaks?
03-29-2010, 11:59 PM
#1
Three Wheelin'
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Rear A/C leaks?
Hi folks,
I'm currently working on repairing and converting to 134a the A/C system in my newly acquired '88 S4. A recent writeup in the service history I got with the car says something like, "system has a massive leak, maybe at the rear A/C, and also needs a climate control switch... not currently usable." Interestingly, there's a new climate control switch just prior that in the service history, so that part may be incorrect.
Anyway, the previous history also included installation of leak detection dye in the system. I've pulled the passenger side seat and also pulled the cover off of the rear evaporator. I found a pale puddle of dried flourescent compound around the flange where the lines go through the floor. I also found spatter everywhere along and around the lines, but I think this is from spray glue or something... it doesn't look like any reasonable leak pattern. Lastly, on the rear evaporator, there are three thin lines that run into it from the expansion valve, and one of those has a bright pattern of dye on it.
So, questions :-) :
1. Have you guys seen flourescent spray glue?
2. Any thoughts on the puddle at the flange?
3. Are there seals at the rear evaporator that could be replaced? It looks like those lines screw in, but I wanted to check with people that had tackled this before? Any other suggestions on repair here, and also on things to do while I in there?
Thanks,
Paul
I'm currently working on repairing and converting to 134a the A/C system in my newly acquired '88 S4. A recent writeup in the service history I got with the car says something like, "system has a massive leak, maybe at the rear A/C, and also needs a climate control switch... not currently usable." Interestingly, there's a new climate control switch just prior that in the service history, so that part may be incorrect.
Anyway, the previous history also included installation of leak detection dye in the system. I've pulled the passenger side seat and also pulled the cover off of the rear evaporator. I found a pale puddle of dried flourescent compound around the flange where the lines go through the floor. I also found spatter everywhere along and around the lines, but I think this is from spray glue or something... it doesn't look like any reasonable leak pattern. Lastly, on the rear evaporator, there are three thin lines that run into it from the expansion valve, and one of those has a bright pattern of dye on it.
So, questions :-) :
1. Have you guys seen flourescent spray glue?
2. Any thoughts on the puddle at the flange?
3. Are there seals at the rear evaporator that could be replaced? It looks like those lines screw in, but I wanted to check with people that had tackled this before? Any other suggestions on repair here, and also on things to do while I in there?
Thanks,
Paul
03-30-2010, 02:38 AM
#4
Chronic Tool Dropper
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Paul--
There are o-rings at the connections to the rear evap/expansion valve, at the bulkhead fittings that pass through the floor, at the solenoid valve under the pass seat. All will need to be replaced. There are o-rings where the rear lines connect with the main lines in front of the pass footwell/firewall, less-than-obvious connections at the fuel cooler too. I spent a long day getting everything resealed and rebuilt. Good news is that mine will freeze my fingers ten years later.
PET probably has a diagram of all the o-rings needed. When I did mine years ago, I asked Dave Roberts to just send me everything I'd need. He did a great job on o-rings, missed just a couple that are part of the compressor manifold connections to the compressor itself. They don't show up in PET but were easily available locally so no problem. Get the hoses rebuilt with barrier hose as part of your fun.
There are o-rings at the connections to the rear evap/expansion valve, at the bulkhead fittings that pass through the floor, at the solenoid valve under the pass seat. All will need to be replaced. There are o-rings where the rear lines connect with the main lines in front of the pass footwell/firewall, less-than-obvious connections at the fuel cooler too. I spent a long day getting everything resealed and rebuilt. Good news is that mine will freeze my fingers ten years later.
PET probably has a diagram of all the o-rings needed. When I did mine years ago, I asked Dave Roberts to just send me everything I'd need. He did a great job on o-rings, missed just a couple that are part of the compressor manifold connections to the compressor itself. They don't show up in PET but were easily available locally so no problem. Get the hoses rebuilt with barrier hose as part of your fun.
03-30-2010, 11:09 AM
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Three Wheelin'
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Hi Doc,
I've got the PET diagram, but it does not show any breakdown details of the evaporator itself. I guess I'll just need to pull the evaporator and see what happens when I remove those screws....
Cheers,
Paul
I've got the PET diagram, but it does not show any breakdown details of the evaporator itself. I guess I'll just need to pull the evaporator and see what happens when I remove those screws....
Cheers,
Paul
03-30-2010, 12:18 PM
#6
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No need to remove the evaporator unless it's to get the wrenches on something. Pull the cover off and you'll see the expansion valve connections, and the routing for the lines is pretty obvious. Get the pass front seat out early and get the rugs out there so you can work on the connections through the floor and on the solenoid valve. Add some foam pads to support the evap unit and you'll avoid a buzz/rattle when it's all together.
03-30-2010, 01:28 PM
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Sorry Doc, but I think nobody read my initial post.
I found clear signs of a leak near where the first thin line (passenger side), from the expansion valve, comes into the evaporator. I was asking whether there were replaceable seals where these thin lines connect.
(Edit) Let me correct that. Upon rereading my initial post, I see I wasn't very clear. My appologies.
I found clear signs of a leak near where the first thin line (passenger side), from the expansion valve, comes into the evaporator. I was asking whether there were replaceable seals where these thin lines connect.
(Edit) Let me correct that. Upon rereading my initial post, I see I wasn't very clear. My appologies.
Last edited by SQLGuy; 03-30-2010 at 02:30 PM.
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03-30-2010, 02:22 PM
#8
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Hmmm... thanks for this info. If those lines are copper, and the evaporator is aluminum, there must be some seals involved. Copper is also way easier to solder... and I have a decent amount of experience at that...
This is the copper and brass intake manifold and injector sockets from my in-work motorcycle FI project. The copper and brass fuel rail is now done too. This is the second generation manifold I'm making for this project. I ran a previous, similarly homemade, copper manifold for a couple of years, but I think there are some benefits to be had from this new design.
This is the copper and brass intake manifold and injector sockets from my in-work motorcycle FI project. The copper and brass fuel rail is now done too. This is the second generation manifold I'm making for this project. I ran a previous, similarly homemade, copper manifold for a couple of years, but I think there are some benefits to be had from this new design.
03-30-2010, 03:17 PM
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SQL--
It's been a long long time since I've been in that system so I'm a bit fuzzy on your question. There are o-rings between the expansion valve and the evap coil connections. If (when...) they leak, they will mist oil onto the surrounding bits. That oil with the dye in it is what you look for with the UV lamp. I had no dye in the system so no obvious leaks, but I did sniff the whole system for leaks with an electronic detector after charging it. Those extension tubes from the evaporator are the same material as the evaporator itself, so if there's a fracture there you should be able to find it easily. That evaporator is small enough and easy enough to remove that you can pressurise it wth air and bubble-test it in a bucket of water.
Interesting fab work on the FI motorcycle intake. Generally, I try to avoid using copper on car pieces because it work-hardens from any vibration and is subject to cracking, expands at odd rates with local heat, etc. But it's simple and easy to do prototyping and experimenting so long as you know the limitations. I notice the FI nozzles are set up for o-ring seals at the supply end, and don't appear to have retaining ring grooves on them. What's the plan for holding the nozzle to the manifold and for holding the fuel supply fitting onto the nozzle?
It's been a long long time since I've been in that system so I'm a bit fuzzy on your question. There are o-rings between the expansion valve and the evap coil connections. If (when...) they leak, they will mist oil onto the surrounding bits. That oil with the dye in it is what you look for with the UV lamp. I had no dye in the system so no obvious leaks, but I did sniff the whole system for leaks with an electronic detector after charging it. Those extension tubes from the evaporator are the same material as the evaporator itself, so if there's a fracture there you should be able to find it easily. That evaporator is small enough and easy enough to remove that you can pressurise it wth air and bubble-test it in a bucket of water.
Interesting fab work on the FI motorcycle intake. Generally, I try to avoid using copper on car pieces because it work-hardens from any vibration and is subject to cracking, expands at odd rates with local heat, etc. But it's simple and easy to do prototyping and experimenting so long as you know the limitations. I notice the FI nozzles are set up for o-ring seals at the supply end, and don't appear to have retaining ring grooves on them. What's the plan for holding the nozzle to the manifold and for holding the fuel supply fitting onto the nozzle?
03-30-2010, 04:00 PM
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Three Wheelin'
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Hi Doc,
No, the leak I'm seeing with the UV dye is cleary at one "squid" line entrance to the evaporator... nowhere near the expansion valve. There are, it looks to me, three nipples where these lines connect to the evaporator, and the one at the passenger side end of it looks like it was painted with dye. Everything else is either clean, or has a very light spattering.
For the previous manifold and fuel rail, I put a lot of dyno and road time on them and had no problems with any cracking. The only thing shown in this picture for the supply end is the injector sockets (made by turning down, drilling out and through, and a bit of other lathe work, from off-the-shelf PEX water connectors). The brass flanges that hold the retaining clips are part of the finished fuel rail, which includes some 1/2" copper pipe and fittings, with the sockets soldered into the rail and the flanges soldered to the ends of the sockets. I'm pretty sure I have some pictures of that in my camera, but I don't have it with me at the moment.
Part of the difference between the new setup and the old one is that with the new one I'm aiming the injectors as much as possible towards the intake valves. This make for injector alignment that is offset by about 15 degrees from straight-ahead for the 2/3 injectors, and about 30 degrees for the 1/4 ones. It was a real PITA to get all the sockets properly aligned on the new fuel rail! But it's done now.
Here's the previous fabbed fuel rail (which used a different design for the injector sockets), and the Hyundai fuel rail from which I got the injectors:
No, the leak I'm seeing with the UV dye is cleary at one "squid" line entrance to the evaporator... nowhere near the expansion valve. There are, it looks to me, three nipples where these lines connect to the evaporator, and the one at the passenger side end of it looks like it was painted with dye. Everything else is either clean, or has a very light spattering.
For the previous manifold and fuel rail, I put a lot of dyno and road time on them and had no problems with any cracking. The only thing shown in this picture for the supply end is the injector sockets (made by turning down, drilling out and through, and a bit of other lathe work, from off-the-shelf PEX water connectors). The brass flanges that hold the retaining clips are part of the finished fuel rail, which includes some 1/2" copper pipe and fittings, with the sockets soldered into the rail and the flanges soldered to the ends of the sockets. I'm pretty sure I have some pictures of that in my camera, but I don't have it with me at the moment.
Part of the difference between the new setup and the old one is that with the new one I'm aiming the injectors as much as possible towards the intake valves. This make for injector alignment that is offset by about 15 degrees from straight-ahead for the 2/3 injectors, and about 30 degrees for the 1/4 ones. It was a real PITA to get all the sockets properly aligned on the new fuel rail! But it's done now.
Here's the previous fabbed fuel rail (which used a different design for the injector sockets), and the Hyundai fuel rail from which I got the injectors:
03-30-2010, 07:33 PM
#11
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Certainly looks like two different metals to me. I'll probably pull and (attempt to) disassemble my evaporator tonight. I'll let you know what I find.
03-30-2010, 08:02 PM
#12
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usually the the copper lines will leak where they are sealed into the aluminum portion of the evaporator.
.( Flush the evaporator out first)
To fix this go get some Flame master fuel tank sealant its available at you local aircraft supply store.
then use some acetone to clean the mating areas, scuff with a red scotchbrite pad then reclean the joint then apply the selant to the outside of the joints put the unit in the sun to cure it may take a few days to reach full cure.
The Flame master sealant is also useful to repair the outside of the fuel tank if it should develop a leak at the T fittings where the vent hoses connect to the body of the fuel tank
.( Flush the evaporator out first)
To fix this go get some Flame master fuel tank sealant its available at you local aircraft supply store.
then use some acetone to clean the mating areas, scuff with a red scotchbrite pad then reclean the joint then apply the selant to the outside of the joints put the unit in the sun to cure it may take a few days to reach full cure.
The Flame master sealant is also useful to repair the outside of the fuel tank if it should develop a leak at the T fittings where the vent hoses connect to the body of the fuel tank
03-30-2010, 08:06 PM
#13
Team Owner
this is the first choice
http://www.flamemaster.com/Technical...s3204r_tds.pdf
This would be second choice
http://www.flamemaster.com/TechnicalsPDF/cs2415.pdf
Also since you have the system apart consider replacing both of the lines that come/go to the compressor as the end crimps will usually be leaking or will start leaking due to heat from the engine compartment and also replace as many of the O rings as possible including the ones under the car where the rear lines plug into the inside of the car
http://www.flamemaster.com/Technical...s3204r_tds.pdf
This would be second choice
http://www.flamemaster.com/TechnicalsPDF/cs2415.pdf
Also since you have the system apart consider replacing both of the lines that come/go to the compressor as the end crimps will usually be leaking or will start leaking due to heat from the engine compartment and also replace as many of the O rings as possible including the ones under the car where the rear lines plug into the inside of the car
03-30-2010, 08:13 PM
#14
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Like I said, it's been almost ten years since I had it apart. IIRC, the rear and front expansion valves are identical. If you are planning R-134a, the current replacement valves are 'tuned' for the R-134a vapor curves. Valves are current for BMW and I'm sure other cars, so they are not unreasonably priced. Put a new one in the front for sure.
Post pics please.
Post pics please.
03-30-2010, 08:35 PM
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Hmmm... I don't know that I have a "local aircraft supply" shop, but we'll see.
I also found, though, that there are a few solders and fluxes designed for soldering copper to aluminum. I'd actually feel better about a metal-based repair than an epoxy one, so I think I'm going to experiment with some scrap copper and aluminum pieces along with some solder from ACE and see if that results in a reasonable joint to try inflicting on my evaporator.
If not, I'll probably be heading towards the airport. :-)
Thanks,
Paul
I also found, though, that there are a few solders and fluxes designed for soldering copper to aluminum. I'd actually feel better about a metal-based repair than an epoxy one, so I think I'm going to experiment with some scrap copper and aluminum pieces along with some solder from ACE and see if that results in a reasonable joint to try inflicting on my evaporator.
If not, I'll probably be heading towards the airport. :-)
Thanks,
Paul