artbuc

Good Morning Folks! Ok, I am in a wishful thinking mode. Wife says A/C is weak. Sure enough, steady stream of bubbles in the sight glass and suction line not very cold. Can't see the leak point but haven't looked too hard yet.

My first reaction is to top it off and see how long it takes to leak down, mainly because I do not know of a competent place to take it. Certainly ain't going to Lexus of Wilmington or Wilke Lexus. Those two places have shown me enough of their stuff.

Question: Is it possible that I have a very slow leak (after all she is over 10 years old) and a top-off could last a couple years? Even if the new charge leaks out in a few weeks, my cost to buy and recharge will be less than paying someone to do a leak check.

bob2200

Based upon previous discussions on this forum, I'd suggest visually checking the A/C condenser, in front of the radiator, for rock/debris damage.

It sounds like you know something about A/C, so putting in a can of refrigerant without gauges would probably, in my opinion, be OK, but does have a finite risk of overfilling.

I don't think the Lexus A/C system is unique and any trustworthy A/C repair facility should be able to work on it.

artbuc

Right you are!! Just took a good look-see. Compressor oil all along the bottom 1" of condenser. I would like to replace the condenser myself and go to a shop for evac/recharge but I don't if anyone would do that for me.

lexus114

i dont see why the wouldnt art,after all it is money in their pocket.i would also change out the (i cant think of the name of it) the thing that acts like a filter/moister remover for the system.and definitely have it evacuated like you mentioned.the 134 system is highly susceptible to any kind of moisture.

salimshah

If it is a slow leak, I really doubt you will be able to visually find it .... unless a physical damage which almost caused the break.

I would suggest going to an a/c specialist and have them add the dye and some recharge. The only time the LEXUS shop will have an edge is when there is tearup required.

Also, do it sooner as you dont want too much to leak out and get air in.

Salim

lexus114

yeah,and we dont want any more holes in our ozone layer art. oh,i forgot this is supposed to be the safe stuff

code58

It may or may not be road debris Artbuc. All of the condensers are made of such thin metal anymore, you really have to be careful when you handle them. I would definitely suggest changing it yourself. I don't think you'll like the bill if Lexus does the work. An aftermarket condenser would be fine, but I would like to see it before I bought it. The aftermarket trade now produces some very fine parts in radiators and condensers, not like it used to be- some really bad stuff. You just need to see it 1st.
Probably not going to be really easy to find a place to do the charge, at least at a reasonable price. I have all of the equipment and a 30lb. of R134 and would be glad to do the work free for you (the evac. & chg.), but I don't thing my hoses will reach from here to Penn.
The dryer doesn't have to be changed as long as the system isn't open very long. (minimal- just what it takes you to remove the bad and replace with good) When I worked in the shop I seldom replaced dryers because the insurance co. wouldn't pay for them and all you have to do to dry it out is put the evacuator on and leave it for 1/2 hr.- 1 hr. and that dries it out fine. Just work on something else while it's pumping. You could do it yourself if you have some knowledge of AC. If you have an air comp. big enough, Harbour Freight sells an air operated vacuum for about $20., now on sale for $12. or $13. and you can buy a half way decent set of 134 gauges and hoses with 134 valves for about $50. from them That's what I have for 134 and they work fine, especially for home. You couldn't find anyone to do the work for that I don't think. I use an electric pump which is preferable, but the venturi vac will work fine if you have the air and can stand the hiss. Good luck and let us know how it works out. By the way you may want to add just a little pag oil for what may be lost in the leak and in the old condenser.

artbuc

Geesh Roger, is there anything you don't know???

I can get a Denso condenser delivered to my house for $182. There are cheaper ones out there but I am sold on Denso quality and fitment. I called two shops who both where willing to do an evac/charge for $100-150. I had ruled out doing that myself because I assumed the vacuum pump would cost at least several hundred dollars. Changing out the condenser is simple job. Have to get some oil (Repair Manual says to add back 1.4 fl. ozs. of oil when changing out the condenser). I am a little leery about this because I know too much oil will kill a compressor whereas they can operate a long time with too little oil. A few years ago my house A/C evap coil sprung a leak and lost what looked like a whole lot of oil. The guy who replaced it said he never added back oil because he never knew how much was lost and the risk of too much oil is much greater than the risk of too little. It is now in its 4th season and still running great. But I digress, don't think I can buy individual orings but a kit will cost only $10-15 and a few bucks for compressor oil. I've always wanted an A/C vacuum pump and decent gages so maybe now is the time.

One of the indie shops I talked to has a great reputation. He will be getting back to me with a few quotes using different grades/makes of condensers, one of which will be a Denso. Will let you know what he says.

Edit: The Harbour Freight venturi only pulls 28.3 " mercury. I thought you had to pull close to full vacuum (29.9"+) to adequately evac an A/C system?

salimshah

Faced with a weak pump, evac, charge (some), evac again and then charge full. This may be done even with a good pump.

Salim

code58

Goodmorning Artbuc- I would say that isn't unreasonable at all for a Denso. I can bet the Lexus dealer isn't going to sell it to you for that. I too have a high respect for the Denso brand. I probably wouldn't have even suggested aftermarket if I had known you could get Denso delivered for that.
If you have a competent shop that will do the evac and charge for $100., that's not bad at all. As long as they don't charge you an arm and a leg for 134. At $150., it's your call as to whether you want to get the equipment so that you are not caught in this spot again. The Harbour Freight is perfectly fine for home work. The venturi vac is not capable of 100% of what a pump vac will do. but the 28.3 is perfectly fine, it doesn't have to be 29.9. I never did figure out why, but once in a while you would pull a vacuum that you weren't able to get a full 29.9 no matter how long you left it on. The only thing I could ever figure was that the seals are made for pressure primarily, not vacuum, so a seal that would hold pressure perfectly might not hold a full 29.9 vacuum. I always left the gauges on for 10 or 15 min. after I had evac. to make sure there was zero loss (indicating no leak) while I did other things. Used vacuum pumps aren't easy to find but I would look on Craig's List or like places, because pumps don't wear out very quick. You could always make your own out of an old (good) donated refrigerator compressor, Mine is a commercial vacuum with feet and handle but it looks to me like it is made from that very thing. Don't remember the brand right now. Most of the ones they sell now are smaller and horizontal, but I'll also bet they won't last as long as a commercial refrigerator pump. Be interesting to know, because as I think about it, their primary purpose is compression, not vacuum.
The oil- I agree with what you've heard, not probably necessary if not much lost, but I don't ever add more that 1-1/2 oz. Oil is carried throughout the system though, so condenser does have some. As far as "O" rings, you should be able to buy individual at a "real" parts store. Make sure they are for 134, not just regular "O" rings. Good luck AB on whatever you do. Remember, you could just "dump" a can for now to buy yourself a little time, I'm sure that would be safe since you're seeing steady bubbles.

artbuc

Very interesting. This is why I enjoy DIY so much. Yes, the $$$ savings are great, but getting to learn so many new things and satisfaction out of doing it yourself are the real pay-offs for me.

Found an article from a self-proclaimed auto A/C expert who said he has done "thousands" of evap/charges. He said you have to leave vacuum on at least two hours to make sure all water is boiled off. Another article said you don't need a vacuum pump at all. Just connect the A/C system to your engine vacuum (he recommended the brake booster vac line) and let the engine idle about 20 minutes. He didn't say but I guess the most vacuum you could get with this method would be about 23-24 ".

Roger, your experience says some systems can't hold full vacuum but hold refrigerant pressure fine. That tells me you will accomplish very little by holding vacuum for two hours. In fact, you will do harm by giving the drier a chance to load up with moisture as outside air slowly leaks into the system.

Edit: This article seems reasonable and well-balanced:

Air Powered A/C Vacuum Pumps
Question: Can I use an air powered vacuum pump instead of the more expensive electric vacuum pump? What's the difference.

The simple answer is yes, provided you have an air- compressor with enough rated CFM to operate a venturi pump. Check with the manufacturer of the pump for their recommendations. Typical requirement for a venturi pump is around 4.5 CFM at 90 PSI.

In comparison, a conventional electric pump has many benefits over the venturi counterpart.





Ease of Transport


An electric pump has no compressed air requirement, so there is no need to have any additional equipment. Something to consider if you plan on using your pump in multiple locations and don't feel like lugging some big compressor around with you.


Noise Levels

Between the steady sound of rushing air, and the constant noise of a straining compressor, you might end up with something that sounds like a full blown construction site. Worth considering if you have neighbors and plan on doing late night work.


Moisture Removal


The purpose of a vacuum pump is to remove air and moisture from the A/C system. If the goal is to remove moisture, you might have a hard time with an air powered venturi vacuum pump. As a test, we used a large commercial compressor dialed in at over 150 PSI., and we were easily able to maintain the suggested air requirements. The vacuum produced by the venturi pump wasn't even enough to register on our Yellow Jacket micron gauge. That means we were not able to reach any vacuum above the LCD vacuum gauge starting point. That's something most electric pumps can do in very short order.

... A little more on moisture removal

At sea level, water begins to boil and change into a vapor state at 212 degrees Fahrenheit. If we increases the pressure we can raise the boiling point of water. An example of this would be the typical automotive cooling system which uses a 15 lb. radiator cap to maintain a design pressure. In that system, the idea is to raise the pressure and therefore raise the temperature at which the cooling liquid will boil. If we wish to lower the boiling point of liquid, we simply remove the pressure that's on top of that liquid. That's how we boil water out of an air conditioning system. We use a vacuum pump to bring the system to a level of near perfect vacuum so the water will boil off and be carried away as a vapor. It's important to note that ambient temperature has much to do with the point at which liquids will boil under vacuum. The greater the temperature, the fewer microns of vacuum will be required to start the boiling process. If you've been keeping note, you know that non condensables (air) and moisture are two things you definitely don't want in your a/c system.

The chart below shows how temperature plays a role in the level of vacuum needed to boil water.

Inches of Mercury
Boiling Point of Water °F

26.45
120

27.32
110

27.99
100

28.50
90

28.89
80

29.18
70

29.40
60

29.66
50

29.71
40

29.76
30

29.82
20

29.86
10


All values are at sea level. Subtract 1 inch for each 1000 ft. above sea level

Opinion...


Venturi pumps are certainly popular with the do-it-yourself mechanic since cost is often times the biggest factor. I'll give these pumps some credit since they can remove a substantial amount of air from the system if you have a decent compressor. Pulling a vacuum on the system is what's most important in terms of end result to the DIY'er.


Regardless of sales literature, I believe you won't be able to boil much water out of an automotive system with the vacuum level produced by a venturi pump. I was able to see that by using my micron gauge. I believe air powered a/c vacuum pumps aren't very well suited for use in an automotive service shop unless you plan on hacking these things apart to make other cool air powered vacuum devices. We have several very useful items in the shop that derive their power from the guts of a venturi pump.





Summary
If you plan on servicing A/C systems, and want professional results, invest in a good electric vacuum pump. It's not uncommon to get ten or more years of service from a good electric pump. As an option for the do-it-yourself mechanic, some tool rental companies now rent electric vacuum pumps on a daily or hourly basis. That may be a better option versus overworking your air compressor for an hour or more, just to get mediocre results.




--------------------------------------------------------------------------------

code58

Ah AB, we've gotta stop meeting like this, People are gonna start wondering why we carry that venturi pump with us wherever we go.
That article is a good and well balanced one.
I doubt that you could pull 23-24 Lbs. on an engine vacuum at idle, probably closer to 19- maybe 20. To say that that is just better than nothing is giving more credit probably than it deserves. I wouldn't want him doing my air charge. You may remember a short while back that I mentioned a mechanic (independent) that they would have come in to the shop (BMW body) that I worked in quite a few years ago to do our A/C work, dash and a few things like that. I noticed one day that he didn't evac the A/C, he just dumped on it. When I asked him about it he said he never bothers to evac. I had done A/C work before that, but the shops always had the equipment. We were a BMW dealership but also did all of the body work for the Mercedes and Volvo which were close by. I don't have to tell you, that day I got the bosses OK and bought my own equipment and did MY OWN A/C charges and until I retired, ALWAYS did my own in the shop. I won't ask what state(s) some of these guys are from. Bet the shoe stores don't do very well in those areas.
I agree with the articles assessment of the venturi evac., I only mentioned it because it would at least give you a way to pull some vacuum on the system and get rid of the air. I didn't really think it would do much to boil the moisture out. That's why I suggested doing the drain and change quickly so that the system was open as little time as possible. Remember, the desicant is there to do the job of absorbing the moisture that does get in if it hasn't already been contaminated by previous opening and improper service. If I had done a quick swap like that, I didn't worry about leaving the pump on longer than 20 min. or so. If the condenser had been ruptured in the accident, Then I would leave it on for an hour or more while I did other work. I think that the tech that leaves it on for 2 hours does not get much work through his stall. Nothing wrong with leaving it on that long, it's just not feasable in a busy shop. To those that worry about getting moisture in the system when it has a leak like you do, when the pressure in the system (even though low) is greater than atmospheric, it's not possible for air or moisture to enter.
Good luck Artbuc, let us know what you decide.
Roger

artbuc

I found this on another DIY forum. Supports what Code58 said about systems that won't hold vacuum but will hold pressure. Interesting!

Comment:
Any suspect refrigeration system should be "pumped down" to check for leaks. That means the refrigerant is removed, if there is any left, and a vacuum is pulled on the system. If it will not hold a vacuum, it will not hold refrigerant.

Response:
this is true BUT i have seen systems old vacuum but not hold pressure .. putting negitive force on a leaking seal sometimes seals it under a vacuum but when u put postive pressure on the seal with pressure it will leak ...

code58

Artbuc- the circumstances that I had experienced were pretty rare, and involved cases where it wouldn't pull the FULL 29.9 no matter how long you left it on. They would pull high 28's or maybe 29., but when I would shut the valves down to isolate the system to the gauges, it would hold vacuum steady, no drop at all. Normally, most current systems don't hold a lot of refrigerant, 1.2 to 2.0 lbs., probably less, and my pump will pull that size system to full vacuum in 30-40 seconds. When they used up to 4.0 lbs. it seemed like it would take 3-4 times as long. Course I was using shop equipment then too.
Concerning the above bold- On a warm day and especially before electric fans on everything, I have seen pressures get as high as 250-275 lbs unless you had a big Patton fan on the condenser. When they hit 300 I begin to get a little nervous. I have seen it twice, that took a little figuring to find out what was wrong. I'll save that for later. You can see the 29" vacuum is no match for the high pressures you can see on a hot humid day.

artbuc

Wow. Just found out ND-Oil 8 (Toyota Part # 08885-09107) is $120 for 250cc (8.4 oz). I've read where PAG 46 is an acceptable substitute but I will talk with Lexus. Any comments?