AC Refrigerant Leak - Thermal Expansion Valve (TVX)

Well, after 170K glorious miles, my beloved 07 DCLB SR5 4x4's AC started getting hot. I recharged it with refrigerant and a few months later, its hot again so I know I have a leak.

I started crawling around looking for the source of the leak, and judging by attached picture, I'm pretty sure I found it. My initial research seems to identify this as the Thermal Expansion Valve - this is on the passenger side right where the lines pass through the firewall, into what I believe is the evaporator under the dash.

My question is, has anyone had this problem before? If so what steps were done to remedy this problem? It seems you can remove the rubber bushing, unscrew the lines, and I'm hoping I have an O ring or something leaking but hey, this is Tacomaworld and I'm sure someone can give me more advice or has done this before

Appreciate it

 

Under those plastic clamps are 2 O-rings on each hose joint. You may just be leaking from there. If it was my truck I’d start by replacing those O-rings, recharge, and re-evaluate.
Side note: ensure the system is fully evacuated before removing those plastic clamps. I had one blow out on me when disassembling once and it was not fun.

 

Many thanks for your help - did you have to unscrew the lines and remove or you literally popped open those plastic clamps and replaced an O ring? Where did you buy your replacement O rings from?

 

You literally just pop off the clamps and pull the hoses apart. I didn’t buy the O-rings I was doing a repair on a customer’s vehicle. IIRC I replaced one of the hoses...

 

Many thanks again sir - would anyone happen to know a part number or source for these O-rings? my google search is not finding much

 

You will need to pull a vacuum on the system after repairs are made. Otherwise a compressor will likely be in your future.

 

Evaporator core developed a leak in 2017; Took over a year, and three recharges, to find it...

Whole dashboard had to come out!

What's really weird is that it blew ice cubes on the far left vent (driver's side) and got gradually warmer the further right you went. Far right vent would range from blowing kinda cool air to humid outside air...

 

A good AC Shop should be willing to sell you the correct o-rings.

This is what to expect when you get into it:

 

Why? I think an explanation would benefit futue readers and you seem knowledgeable.

Also

I checked today, cleaned the area up, and started the truck to purge the system. As soon as I turned on the A/C refrigerant and dye spewed out of those plastic connections so much it dripped onto the below exhaust. I purchased some generic A/C O Rings kit from the autoparts store. Tomorrow when it's light out I will open the plastic connections and have a look. I'll document and report back

 

anytime you expose the a/c system to the atmosphere (ie take a line off or replace a part) you have to pull a vacuum on the system for a minimum of 10 min to boil the moisture out (30 min is better) otherwise you'll overload the desiccate bag in the dryer with moisture and cause issues

you also must be sure system is discharged, and wear safety glasses because it can spray oil when disconnected with a low amount of pressure in there

a vacuum pump and manifold gauges can usually be rented to do the job properly

 

Agreed moisture is no bueno in an HVAC system. Along with this air does not compress at the same rate as refrigerant and needs to be removed. The presence of oil and air in a system can lead to the refrigerant oil becoming acidic and reducing compressor life. This is particularly true in systems where the electrical windings are exposed to the refrigerant, like most non automotive applications. In addition the cooling capacity will be greatly reduced. Most professionals will try to attain a 500 micron vacuum and see it hold. This will ensure moisture/air has been removed and the system is leak free. In my opinion you have done a nice job identifying the problem, should go ahead and pull it apart, slap some o-rings in it and then take it to a knowledgeable shop and have it charged.

 

I was able to take off the clips and attempt to replace the Orings. I say attempt because I didn't like the fit of the smaller lines orings so I ordered another kit. I also chipped a small peice of the clips so if anyone can let me know where to find those let me know.

Visually the stock Orings looked fine - see pic. I took other pics along the way and I'll put together a write up on disassembling / reassembling everything soon.

Many thanks again everyone for sharing your knowledge and experience.

 

That lower right small o-ring looks creased ( damaged ).

 

after pulling / testing with the vacuum - When refilling with refrigerant, should I be adding any oil for the compressor?

 

I have been told no by a very reliable source.

@CurtB would probably have much better info than I.

 

Yes it does. Always replace any used O-rings. They can look fine and still leak.

No. You didn't lose enough oil to matter. If you add oil, how much do you add? Too much oil displaces the amount of freon the system holds, reducing cooling capacity.
Those small O rings can seem too tight, but they are probably the right size. Put a drop of any clean oil on a finger and rub the O rings. They will go on easier and will seat better.
The chip in the clip? not sure but if it still locks just put a good zip tie around it.
Edit: your system takes 21 ounces of R134A. If you have the lines off, I hope you capped them in some manner? Otherwise more moisture and air enters the system. If you didn't, pull a vacuum for 30 minutes and let set for a leak test. If ok, start the vac pump again, open the gauge manifold and let that pump run. Overnight will not hurt. 2 hours would probably be ehough, provided the ambient air temp is above 70f.

 

Thank you to CurtB and JimmyH

I get the Orings today. I will put a drop of some clean oil on them and re-install hopefully today. Then I'll pull a vacuum and see if it holds.

I was planning on using the old zip tie method on the clip - Should be fine. I figured out after removing my first clip that you can insert a flathead screwdriver into the slits on the clip and pop them open.

I will update the thread later on with the results.

 

I did not cap them- didnt realize I had to. I was planning (as per a chrisfix video below, that actually uses a 2nd gen tacoma) to pull a vacuum, let sit for 30 minutes and see if pressure changes, then let vacuum pump run for 2 hours assuming it holds. Ambient temp here in south florida is well over 70, probably be closes to 80-85F when I do this. I will then recharge with 1 full bottle of R134A plus whatever weight % of the 2nd bottle to get to 21OZ

Edit - Should I add UV dye when refilling?

https://www.youtube.com/watch?v=Pdq8JAlct6s

 

From your pics, the green color looks like you already have dye. A black light will instantly confirm that. It will glow like an old hippie poster.
Since you didn't cap the lines, let the pump run for at least 2 hours. The oil in the system sucks up water vapor very easily. It takes a good long vac pull to get it out. Provided that there are no leaks. A leak under vac pulls in air. Not good.
I'm not a fan of the vac test for leaks. Unless you have a micron gauge connected, a small leak will not show up on an analog gauge.
Getting more technical now huh?

 

I replaced the Orings, put everything back together and ran the vacuum. Dial pressure gauge maxed out at -25 , I turned off vacuum pump and after 1 hour dial still shows -25 seems to be holding so far. Ill buy some refrigerant hopefully tomorrow, run the vacuum for a good long while, then charge her up and see what happens.