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Leak testing empty system Pages: 12

Wayne on Sat December 08, 2007 1:07 AM User is offline

Year: 1983
Make: Porsche
Model: 944
Engine Size: 2.5
Refrigerant Type: R12

I have an evaculated R12 system (currently at 0 psig) and I want to identify any leaks and their location without first charging with R12. Is there any problem with pressurizing the system with dry nitrogen for leak testing? I know I can do a vacuum leakdown test, but that will not allow me to find the location of the leak.

Wayne

Chick on Sat December 08, 2007 5:18 AM User is offlineView users profile

You obviously know you have a leak.. So I would use a couple ounces of R134a, pressurize the system with dry nitrogin and use a sniffer to find the leak, then recover the mix into a waste tank, repair the leak and then recharge with R12. Using R134a is fine as long as you don't run the system..If you don't want to do that, then just pressurize and use soapy water, but it does take longer...Hope this helps..

-------------------------
Chick
Email: Chick

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

Freedoms just another word for nothing left to lose

Dougflas on Sat December 08, 2007 8:48 AM User is offline

The EPA will allow the use of R22 as a trace gas with N2 to find leaks. This mixture dies not have to be recovered; they will allow you to vent it. R134 is less damaging to the atmosphere so I would gander they'll allow you to vent this mixture also. Give them a call to verify.

If you recover thses mixtures, what will you do with them to dispose ofthem? No one will take them. By the way, this is an excellent method to leak test. One major problem with trying to leak test with a vacuum is that you are "pulling" a shaft seal inward which may elide leakage. You want pressure outward and the N2 method will do that.

Edited: Sat December 08, 2007 at 8:50 AM by Dougflas

Wayne on Sat December 08, 2007 1:05 PM User is offline

Hi Guys:

Thanks a lot for the comments; they help a lot. I guess that maybe 100psi of N2 should be reasonable?

The 944 I am working on is now 25 years old (bought it new in '83; now has only 74,000 miles). The car sat for the last 7 years without use. When I finally got it back on the road, the AC did not work and there were a lot of bubbles moving through the sight glass (but looked clean). Took it to an AC shop and they charged me $50 to tell me that the compressor is leaking and needs to be replaced (wanted about $1,000). I did not know enough at the time to ask if they were certain the leak was in the compressor rather than a connector. Thinking that I was probably going to have to learn to do this myself ($1k out of reach), I asked them to discharge the R12, so it is now empty. I now realize that this was a mistake; should have taken in home and leak tested it myself!. Anyway, I plan to refill with R12 rather than R134a since the condensor on these cars is very small and R134a does not work so well according to the experience of a couple of people. I just bought a dual manifold gauge set for R12-R134a (Robinair) and I have enough R12 in small cans; I have a small vacuum pump and the Haynes manual on auto AC.

So, I could use some advice. With this history of 25 years old, what is the best approach? One would be to leak test it according to one of the suggested procedures using dry N2, find the leak, and if it is at connector, replace the seals; if it is in the compressor, buy a rebuilt from ACkits (along with a dryer). Considering the age, should I go through and replace all connector seals (Oring kit from ACkits) whether or not a leak is found? Is there a means for evaluating the Nippondenso 6E71 compressor on the bench? I could do a vacuum leak test on it, but that won't tell me if it is working otherwise. If I found a leak, should I just get a rebuilt?

Thanks for any help

Wayne

tony1963 on Sat December 08, 2007 7:35 PM User is offline

I've done many retrofits and generally are very pleased with the results. On something of that vintage, I would disassemble the system and flush the condenser and evaporator core. I believe that this system uses an expansion valve so install new parts as follows:

1.) Reman compressor/clutch assembly.
2.) Expansion device.
3.) Receiver/drier unit.
4.) All o-rings and seals.
5.) All switches.

By the time that you chase down which part leaks, etc. you'd be time and money ahead to replace all of the parts listed above. On all AC jobs that we do, we have been replacing all of the electrical switches. It is really a shame to do a system and then lose the refrigerant due to a faulty switch.

I'd use R134a anytime without hesitation.

-------------------------
Grove Automotive Group, Inc.

An Alabama Corporation

Wayne on Sat December 08, 2007 8:34 PM User is offline

Thanks Tony:

Do you think I should just replace the compressor and expansion valves without even bothering to test them? The expansion valve is not so expensive, but the compressor is. Regarding flushing, there is a simple aerosol can flush available. Do you think this is adequate, or should I take it to a shop to have it flushed?

Wayne

tony1963 on Sun December 09, 2007 2:16 PM User is offline

My advice is to replace the compressor, too. Keep in mind that time takes its toll on any sealing surface, including the seals in your compressor.

From what I can see, I don't think that you are being quoted a competitive price on your compressor. I did about 2 minutes of research and found one less than half what you were quoted.

Replace it all.

As far as a flush agent, everyone has their favorite but I prefer isopropyl alcohol which is "rubbing alcohol" in common terms. I buy it by the quart and use it in my flush canister with good results. It is environmentally friendly and will clean the parts. I follow with a long blast of shop air, a 2-3 hour evap cycle, then shop air again. I also pull a strong vacuum before I ever put the system together.

USE PRECAUTIONS AS THIS PRODUCT IS FLAMMABLE BEFORE, DURING AND AFTER USE! Dispose of properly and use adequate safety precautions. If you are unsure, use a professional.

-------------------------
Grove Automotive Group, Inc.

An Alabama Corporation

Edited: Sun December 09, 2007 at 2:20 PM by tony1963

TRB on Sun December 09, 2007 2:27 PM User is offlineView users profile

Tony what was the shop going to do for that $1000.00? My opinion is its a little tough to suggest this shop was charging improperly. If you don't know what they had planned for the repair. Cheapest is not always the best repair! We've seen many posts over the past few years where cheap ended up costing them in the end.

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

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com


Edited: Sun December 09, 2007 at 4:19 PM by TRB

bohica2xo on Sun December 09, 2007 2:59 PM User is offline

Good grief, talk about making a small issue into a huge problem...

Wayne:

The information in your second post is really what we needed to see - the whole picture.

A system may leak .5 ounces per year, and be perfectly fine. As small as your system is even if it was fully charged when you parked it, you could be 4 ounces undercharged. The presence of bubbles in the sightglass indicated a partial charge, perhaps just below the critical charge level.

You can't un-ring the bell however. At this point, you should replace the dryer. Your system uses mineral oil, and you should add back the oil lost in the old dryer.

There is no reason to rape this vehicle with a retrofit. It will not work well, and the cost of doing all of the work properly is far more than some R12.

Your "compressor leak" may be a shaft seal, but then again it could just be accumulated attrition. Replace the dryer, add some UV dye, charge it & run it for a few months. Keep an eye on the sightglass. Use the UV lamp to look for actual leaks.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

TRB on Sun December 09, 2007 11:40 PM User is offlineView users profile

Quote
Originally posted by: Texaserick
You can also use Freeze 12 from Pep Boys I believe. The can diameter will fit in an R12 side piercing can tap. We used tons of this stuff for checking older cans instead of R12.

Freeze 12 is basically R134a. Unless I planed on changing the oil and accumulator/drier I wound not suggest cross contaminating a system. Yes I know they say Freeze 12 is a replacement for R12.



-------------------------
When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

Wayne on Mon December 10, 2007 12:20 AM User is offline

Thank you guys for the input. Since it is now empty, I think I can find replacement shaft seals for the Nippondenso 6E171 in the car and do a minor rebuild. Based on your comments, this sounds like a reasonable thing to do. Anyone know where I can find an O ring kit? The car only has 70K and the AC was used very little (as I just learned, that may be the problem!). The bearings, reed valves, etc may be fine. I will replace the dryer and O rings on the fittings I take apart and leak test with N2 and a little R22 or R134a (just enough for leak test with a Tek Mate). I really don't want to replace the expansion valve unless really necessary, since it is tough to get to on this car. Then evaculate and refill with R12. If I keep track of the amount of oil in the compressor and dyer, then I can add that back. Is it OK to add that amount of oil directly just to the compressor before reassembling the system?

Thanks again

Chick on Mon December 10, 2007 2:23 AM User is offlineView users profile

Dude, you can do all that work if you want, and I'm sure Ackits.com can hget you the compressor seal kit, but really, follow "bohica2xo" advice, change the drier add back two ounces to it, pull a vacuum and if holds, charge it up.
"IF" you decide to change the seals yourself, have a camera and takes photo's of every step of the way. Changing the front seals on them is different than GM compressors, as the I believe the compressor has to come apart and done from behind? But I'm not sure, never did one on a denso yet. I personally would not try refurbishing a compressor unless you have experience doing them..When I was growing up I had a small box of pocket watches that I tried to fix... Special tools are needed to change seals in compressors..Unless you really want to get into it, (buying the tools etc) just price a compressor from the guys at AcKits.com.. Of just do as bohica2xo recomended..Change the drier and charge it up...Just my opinion...

-------------------------
Chick
Email: Chick

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

Freedoms just another word for nothing left to lose

NickD on Mon December 10, 2007 10:50 AM User is offline

I agree that having the remaining R-12 removed was a bad mistake, my God, man, your system had positive pressure and that is a wonderful sign, with zero pressure, moisture and crap and leak in causing more damage. And like Bohica stated, you have no idea to the extent of the leak, was your system bubble free even seven years ago? I would have topped it off with R-12 first, least tried putting in a couple of ounces and watching the sight glass. Guys like GMtech with a charging system would have recovered it first, looked in the book and determined precisely how much refrigerant was lost.

Pretty common knowledge that all MVAC systems leak, a question I had, is what is an acceptable leak. Doing a web search on this subject, found an EPA site that stated with R-134a, common for private vehicles to lose 10% per year and commercial vehicles to lose 50% per year. I consider that major, my oldest R-134a vehicle is now ten years old, still blows ice cold air and with a 10% loss per year or leaving 90% to the tenth power would show a loss of 65%! You don't get much cooling with that kind of loss.

So you have a compressor leak, well how much? Was the system ever charged before since you had this vehicle from day one? Would find out where you are first and go from there. Only had to add about 7 ounces to my 92 Deville when it was 14 years old, that's only a half ounce per year, that was a couple of years ago, still doing fine.

Regarding my own AC shops around here, amazed at some of these guys speaking with such self-confidence and being complete idiots, none of those guys are here on this board helping other people, shame you run into people like that.

Wayne on Tue December 11, 2007 3:13 AM User is offline

OK, no question that I really screwed up having the system emptied. The system had never been refilled or serviced since new. I know, really, really dumb, but I trusted the guys at the AC shop that it needed a new compressor, and I thought I could do that myself, but did not want to discharge R12 into the air, so had them remove the R12. I will certainly put in a new drier, but I hate to fill it with really expensive R12 and find out that they were correct about a significant compressor leak and have to dump it again. I found instructions on how to replace seals on a very similar Denso unit on the Pelican Porsche site, and it did not look too bad; no special tools required. I think I should at the minimum remove the compressor for a vacuum leak test; if there is a leak, attempt the seal replace. What do you think?

Wayne

bohica2xo on Tue December 11, 2007 4:45 AM User is offline

What do I think?

I think you are a glutton for punishment.
Perhaps you should pop that engine out of there, and replace the rear main seal. After all, it is as old as the compressor seal & requires no special tools to change....


Your 25 year old system still had a measurable level of charge. That is tighter than some 5 year old systems now. Dodges leak more refrigerant through the METAL parts than that.

I would get a fresh dryer in it, some dye & oil - and a full charge of R12. It is really not that expensive, and there is still plenty of it around.


B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Edited: Tue December 11, 2007 at 4:45 AM by bohica2xo

tony1963 on Tue December 11, 2007 6:10 PM User is offline

I must admit that I would probably charge $2,000 to do the job in the shop. My advice was based upon an already empty system and an owner who appears to want to do the repair himself, or so I thought.

We do not service any R12 systems with R12. If it needs service, I retrofit the system. R12 is quickly becoming obsolete and not worth the hassle. While there are some differences in performance between the two, the difference is not significant among some models, others it is.

My advice is retrofit. However, do as you see fit and good luck!

-------------------------
Grove Automotive Group, Inc.

An Alabama Corporation

TRB on Tue December 11, 2007 7:55 PM User is offlineView users profile

Quote
Originally posted by: tony1963
R12 is quickly becoming obsolete and not worth the hassle.

Have to disagree with this comment. R12 is widely available and has come down in price over the past couple years. Still a very viable option on vehicles which were designed to run R12.



-------------------------
When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

tony1963 on Tue December 11, 2007 8:45 PM User is offline

Low demand = low price.

-------------------------
Grove Automotive Group, Inc.

An Alabama Corporation

TRB on Tue December 11, 2007 8:52 PM User is offlineView users profile

Sure, but your comment was "R12 is quickly becoming obsolete". I don't agree with that comment. R12 is still the best refrigerant for R12 designed systems. Most of us have converted systems and had success. But it's not the only option in my opinion.

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

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

Wayne on Wed December 12, 2007 2:08 AM User is offline

OK, slowly getting the picture here. I just bought enough R12 to fill it (about $85), so maybe I will give it a try after replacing the dryer and after doing a simple vacuum leak test (just to make myself feel better). A general question: how useful is the sight glass on a manifold gauge set? As far as I can tell, it only allows one to see the flow of refrigerant into the system while charging (correct?). If so, does not seem all that important a consideration when purchasing a gauge set. My old dryer has a sight glass for looking at the flow of refrigerant through the system, but unfortunately all the replacements I can find do not. Is Robinair equipment decent in general?

Wayne

bohica2xo on Wed December 12, 2007 4:03 AM User is offline

The sightglass on a gauge set will not replace the sightglass in a system - and yes it is of very little value. Robinaire is good equipment.

This Dryer would appear to have the sight glass on it. Call AMA and make sure.

B

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

NickD on Wed December 12, 2007 7:01 AM User is offline

Japanese brought back the sight glass in the late 70's and I even have one in my 82 Chevy P30 motorhome, used in a TXV system and is located in the receiver that is located after the condenser and before the TXV valve. A very useful tool for visually showing that you have solid liquid flowing into the expansion valve, I like it. But there is restrictions in it's proper use.

First off the idea is to charge the system until the sight glass is clear, the receiver is capable of handling 2-4 ounces of extra refrigerant, depending on the vehicle and that is in the book, but this is strictly a reserve and by adding additional refrigerant to fill the receiver, you do not get additional cooling. Back in the old days when R-12 was 75 cents a can, after clearing the sight glass, would add that additional amount. Just in case there was a small leak, would have that extra reserve to stay cool say on a long trip, but with the price of it today, don't do that anymore, but first let's cover the restrictions.

First and most important restriction is the when using it, the ambient temperature must be at least 80*F, I prefer more like an 85*F day, if the temperature cools in the 60's lower 70's, even in a properly charged system, you will see more bubbles, it's cooler and the refrigerant condenses. If you charge for a clear glass on a cool or cold day, you will be way overcharged on a hot day;

Second and equally important factor is your AC system must be clean and all fans operating properly, you cannot charge properly if your condenser is full of bug, fan on working, or a lot of debris buildup on the evaporator. What were they thinking with the evaporator, fresh air intake that sucks in all kinds of bugs and vegetation is chopped up by the squirrel cage fan blade and deposited on the vents of the evaporator. Normally the blower motor can be removed so you can get in there to at least clean off the face of the evaporator. I have gone as far as using a leaf blower ducted taped to one open vent with the engine running to get vacuum so the dash vents are opened with a shop vacuum, but talk about the 30's dust bowl days, dust, dirt, debris, chopped up leaves were flying all over the place. Without proper air flow through the evaporator, you do not get proper sight glass readings. Much prefer my HVAC system where once a month, can easily slide out the filter and clean or replace it, not so easy in a vehicle. Found I could easily remove a panel on my motorhome and have complete access to both the heater core and evaporator, and it's outside of the interior so can quickly blow that clean.

Also a good time to hand spin the blower wheel and you may be in for surprises here, these motors have a brush cooler tube, on a car like an 86 Maxima or a Honda, even my Supra, the blower motor has screws on it, but all were packed up with debris and took an effort to spin the blower wheel, good cleaning, chance to oil the wicks, brushes looked good and easy to spin the blower wheel afterwards. On vehicles like a Continental or a DeVille, had no choice but to get out my CC and buy an entire new motor with a blower wheel firmly attached. I can open these, but can't put them back together again, blower wheel on the DeVille with a very weak base was melted on the shaft, any kind of prying would breake that weak plastic before the blower would start to move, GM may have saved a 1/2 cent on a snap ring, but they certainly teed me off in the process.

After all this you are ready to charge and with the doors open, blower at max, AC on, and the engine running at 2,000 rpm, would charge until just a few bubbles were still present. The reason for this, is on an equally warm day, a week or two later, under the same conditions, can pop open the hood, pull the cap off the sight glass, doors open, blower at max, and AC on, just view the sight glass to learn if there are more bubbles, if so, I know instantly if I have a leak and time to do something about it.

In a vehicle like my 88 Supra with a very well documented AC section in the manual can also connect the gauges to verify a clear glass under different ambient and humidity conditions with vent temperatures given, I like this as I know if the system is performing like the factory wanted it to. In a GM or Ford manual, just dump in so many ounces with a list of excuses you can give to your customer as to why your system isn't functioning the way you think it should, I don't like that.

So I hope this helps, a sight glass can be a very useful tool, but has to be used properly.

Wayne on Thu December 13, 2007 12:46 AM User is offline



Bohica: Thanks for the tip; I will call AMA tomorrow to check on this; would really like to have the sight glass!

Nick: Thanks very much for the helpful comments on the use of the sight glass. I have really learned a lot on this forum, and I sincerely appreciate the time everyone has taken to help me out. I hope to tackle this job sometime before Christmas with a lot more understanding than I had at the beginning! I will let you know how it comes out.

Merry Christmas!

Wayne

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