AC leak in car

[atgcpaul]

My wife's car has not been able to hold the refrigerant for several years now.
If I fill it up with one of those DIY refrig kits, the system will pressurize but
the AC doesn't cool for very long. It's been a year since I last tried this. As
you can tell, it hasn't been a big priority for me since she walks to the train
and rides that to work. If we take a long trip we use my car or if she is home
during the week, I ride my bike to work--only when it's hot. This is really only
an issue in the summer.

Now that we're expecting our first kid, we really need to be a 2 car family
with AC in both cars.

Her car is a 2000 Nissan Sentra and is using the new refrig, not freon. I'm
definitely not a car guy and would probably have new AC installed if my
mechanic (who I do trust) told me to.

Here's what I'm thinking, though, to diagnose the problem myself before I
take it in. If I try to fill it up one more time and the system does pressurize
and the car cools even for just a short moment, then the compressor still
works and they just need to find the leak and fix it. If I can't get it to
pressurize (there's a gauge on the refrig can), then the compressor is
probably shot, too, and they have to find the leak and replace the compressor.

Sound like a plan?

[gsmittle]

[snip]
Here's what I'm thinking, though, to diagnose the problem myself before I
take it in. If I try to fill it up one more time and the system does pressurize
and the car cools even for just a short moment, then the compressor still
works and they just need to find the leak and fix it. If I can't get it to
pressurize (there's a gauge on the refrig can), then the compressor is
probably shot, too, and they have to find the leak and replace the compressor.

Sound like a plan?

Sounds like a plan… I had to do the same thing to my old Suburban for years. Turns out the leak was in the compressor and it bought the farm after about four years. Had to replace the compressor ($400—I have an honest mechanic). On the positive side, the AC worked great for the last three years I owned the car.

If you can afford it and Mama isn't showing too much yet, now might be the time to look for a new car. (I'm really good at spending other people's money) If you're obviously looking for a family-mobile, the salespeople turn into hungry sharks with you as dinner.

Hope all this helps. If not, remember free advice is worth exactly what you pay for it.

g.

[Uncle Cracker]

If you have been out of refrigerant for a year, it is quite possible that many seals and other components that are designed to be under constant exposure to refrigerant have dried out or seized, and your problem may now be much worse than it was when you "parked it". This problem is one that someone who is "not a car person", and does not have the specialized training and equipment, has little chance of performing a thorough diagnosis, much less any actual repair. I'd advise you to turn this over to a pro that you trust, and be prepared for some bad news...

[cabinetman]

If you have been out of refrigerant for a year, it is quite possible that many seals and other components that are designed to be under constant exposure to refrigerant have dried out or seized, and your problem may now be much worse than it was when you "parked it". This problem is one that someone who is "not a car person", and does not have the specialized training and equipment, has little chance of performing a thorough diagnosis, much less any actual repair. I'd advise you to turn this over to a pro that you trust, and be prepared for some bad news...

That about sums it up. I wouldn't waste my money on another can.
.

[master53yoda]

The front shaft seal on all belt drive compressors is an oil seal. If the system has leaked out in all likelihood that seal is bad. Another item that your not catching is that if the system has been flat it has air which is a non-condensable in the system. this will cause the system to overpressure and prevent it from cooling. You need to take it into a shop and have it worked on. They will be able to put the system in a vacuum to remove the air and probably replace the seal in the compressor. this is not necessarily an inexpensive fix.

good luck

[rjwaldren]

Since you know that it's leaking and apparently pretty badly, charging it would be the equivalent to intentially venting, IMO. That's not legal even with the newer refrigerants, I would guess your using 134a. Depending on your view that's may help you decide how to proceed. The laws do allow for topping off systems with minor leaks in limited situations, I wouldn't consider this minor.

The main issue with the loss of refrigerant is that in leaking system air and moisture is introduced. They both change the pressures within the system, with actual liquid moisture being the worst to have hit the compressor inlet. Moisture also breaks down the refrigerant causing acids within the system. In order to clean this out it must evacuated (after the leak is repaired) to draw out the air and boil off moisture and likely flushed to remove contaminants. The time the problem has existed is also your enemy here. And adding refrigerant at this point would simply be feeding the moisture in the HCl acid machine.

I would suggest just taking it in for proper repair. If you spend the money for a topoff kit and maybe a UV dye to find the leak it won't change the procedure required for the tech to actually make the repair. The only difference with be that he shouldn't charge you for the refrigerant he does remove. I would hope that his refrigerant fees are lower than the canned retail product prices. If the compressor is bad they should find that straight away and give you the option on how to proceed from there. I doubt the cost of them identifying a bad compressor (if you decided not to proceed) would be much different than the cost of supplies to check it yourself (at least at my local auto box stores)

[atgcpaul]

OK. Thanks for the suggestions. I already had an extra can so I figured I'd
try it out before taking it into the shop. Sounds like even doing that would be
a waste of time.

We thought about getting another car (SUV) but both of these cars run great,
are under 70K miles, get regular checkups, haven't racked up any major
repair bills, AND they're both paid off. The Nissan still gets 30+ mpg. Once
we found out how much daycare per week would cost, the new car went out
the window.

The next time I take it in for an oil change, I'll ask the mechanic to give me
an estimate for the repair. Maybe by then, Fall will be here and I won't be
motivated until next Summer.

[LCHIEN]

a professional can find the leak with dye and or a sniffer. then they can fix it, evacuate it and fil with oil and refigerant.
Putting a can in a system that has lost all pressure is probably a waste like the previous respondents have said.

[jabe]

I agree with rjwaldren, letting this go for so long creates more damage to your a/c system. All a/c systems are a closed loop system which should not be contaminated with no outside source. The refrigerant has oil in it to keep all your seals & O-rings plyable so it won't dry out & crack so the more U use your a/c the longer it will last. Now with leaky seals/O-rings it introduces moisture & air into the system which degrades the parts of you a/c. So it will damage your evaporator core, dryer, compressor and all the o-rings & seals thus costing U more to repair. My older brother is a retired auto mech who specialized in a/c repairs.

[chopnhack]

All great advice, but being that the car is ~11 years old you might want to look over other items that as a whole tend to add up $$ such as rubber fittings and seals all over the car (not just mechanical), condition of tires, brakes, belts, hoses. Are the shocks starting to sag at all, has the transmission been flushed and filter changed around 60k? The decision to keep the vehicle can be costly as well , DAMHIKT... If the car is garaged and in great shape then kudos, it might be worth investing in. If like my 1999 with 79k miles on it, well... its seen better days

[LCHIEN]

just a reminder to all to run your A/C every month or so to keep the seals lubed and the A/C in good shape. Its not to hard to do that with normal weather here in Houston... but you guys up north might need to be reminded.

[mpc]

Most a/c leaks will accumulate a wet/greasy mess. Look at the joints in all of the a/c hoses/pipes for messes. If grease is everywhere (as is common on older cars) then you'll have to clean all the joints and re-fill one more time. A pro shop might do exactly this - with a ultraviolet (UV) dye added. Simple Green works well to cut through most engine grease by the way.

I do the repairs on my car's a/c systems - when the original refrigerant leaked out, rather than fix only the bad joint, I replaced every o-ring in the system: if one is old enough to have died, the others are probably on their last legs too. I'd rather do the work once and not have to worry about leaks for another 10 years. I replaced the rubber hoses too.

O-rings eventually fail and leak. The hard rubber a/c hoses often get hard/brittle at their ends, where they fit into those crimped-on caps. If you've never seen how a high pressure hose fitting works, it's basically:
* Metal pipe threaded on one end (with the o-ring trapped in there) to mate with the another pipe.
* That metal pipe ends in a barbed pipe.
* The rubber hose fits tightly over the barbs
* Instead of using a typical hose clamp, a cylinder shaped metal piece is used. This fits over the end of the hose; a special tool crimps grooves into this cylinder... the grooves are spaced similar to the barbs of the inner pipe. This makes a really tight seal.

Unfortunately, when the rubber gets old and dries out, it shrinks a bit so the outer cylinder doesn't clamp as well. Flexing the hose (which happens when the engine "leans" as you rev it or start it) exacerbates this problem. Often you can "test" a hose by flexing it near the outer cylinder, listening for leak sounds.

There are a few o-rings in the evaporator core - the radiator-like part under the dash (typically) that actually cools the air. These o-rings aren't subjected to engine bay temps so they fail far less often - which is fortunate because replacing them is a big labor expense. You may gamble on not replacing them when doing all the others... it's a pretty safe bet.

To do the job yourself, and to do it right, you'll need to be able to:
1: safely/properly unbolt each joint. Usually simple - just use two wrenches just like any plumbing job.

2: If the rubber hose joints leak, take the hose to an a/c shop, NAPA, etc. and have the rubber part replaced. They'll slice the metal cylinder sleeve apart, replacing the sleeve and the hose with new "barrier" style hose - required for today's R-134a refrigerant but compatible with the old R-12 freon as well. They'll re-use only the original barbed fitting/pipes on each end.

3: Use R-134a rated o-rings - basically blue or green ones. They'll work with R-12 as well. The black ones are too porous for R-134a. I'd replace the receiver/dryer too; they have a finite lifetime.

4: when re-assembling, wet the o-rings with a/c system oil as you install them. Otherwise they can rip/tear as you tighten the joints.

5: with the system totally assembled, connect an a/c pressure gauge set (two gauges).

6: Ideally the system would be flushed out with nitrogen. This helps flush out any moisture from the atmosphere that might have gotten into the system.

7: Pour or inject the proper quantity of a/c compressor oil into the system. There are two types of oil: one for the old R-12 refrigerant and one for R-134a. Use the one that matches the refrigerant... even if your car WAS R-12 originally and you're converting it to R-134a you'll need oil compatible with R-134a. The oil is "picked up and carried by" the refrigerant; R-134a won't carry the older oil.

8: Apply a vacuum pump to the system fully evacuate it - takes a minimum of half an hour in most cases. Then shut off the vacuum pump. Let the system sit for some time - hours if possible - and verify the gauges don't budge. If they move, you still have a leak.

9: Connect the gauge input hose to a source of refrigerant. Leak a little of the refrigerant where the hose joins the gauge set (loosen the fitting slightly while the refrigerant tank is open) to flush air out of that hose. Then re-tighten the input hose. Open the gauge valves and allow refrigerant to flow from the pressurize refrigerant tank into the car. Pro shop equipment will measure the weight and/or volume of the refrigerant so they know how much went into the car. You'll probably just count cans of refrigerant. If using the cans, stick them into a pan of hot (but not boiling hot) water; that'll raise their temps and thus the refrigerant pressure in the can so you can get more out of each can.

10: once one can is in the system, close the needle valve at the top of the can, remove the can, and replace it with a new/full one.

11: Turn on the engine and set the a/c to max cool, lowest temperature, full recirculate. There should be enough pressure in the system for the a/c compressor to engage: most cars today will NOT run the compressor if the refrigerant pressure (and thus refrigerant quantity) is too low because no refrigerant flowing through the system = no oil flowing with the refrigerant either.

12: stick a thermometer into a center dash vent. Monitor the air temps coming out of the system as you fill with the second refrigerant tank.

13: the factory service manual for your car, or the manual that came with the gauge set, will show the proper "suction side" and "discharge pressure" for your a/c system as a function of outside/ambient air temperatures. Use these as a guide... adding refrigerant until your gauges indicate those pressures. You'll probably need a helper to hold the engine RPMs up a little. Watch the thermometer we stuck into the dash vents... if that temp starts rising, the system has just passed "enough" refrigerant.

mpc

[woodturner]

Since you know that it's leaking and apparently pretty badly, charging it would be the equivalent to intentially venting, IMO. That's not legal even with the newer refrigerants, I would guess your using 134a.

FWIW, that's an interpretation. The law does not prohibit adding refrigerant to a system that is known to be leaking, regardless of the degree of the leak.

As written, the law does not equate adding refrigerant to a leaking system with intentional venting.

An example of "intentional venting" is cutting the lines on a refrigerator to vent the refrigerant. Of course, if you thought it was empty when you cut the lines, it is not "intentional" or illegal.

[woodturner]

8: Apply a vacuum pump to the system fully evacuate it - takes a minimum of half an hour in most cases. Then shut off the vacuum pump. Let the system sit for some time - hours if possible - and verify the gauges don't budge. If they move, you still have a leak.

Good description of the process.

Many vacuum pumps will leak enough to cause this test to fail. To avoid this issue, attach the vacuum pump through the charge port of the manifold guage, evacuate the system, then shut off the charge port to isolate the pump from the system.

For the DIYer, a cheap source for a vacuum pump is the compressor from an old freezer. Repair shops will often give you one. Sweat on a few fittings and you have a reasonable low volume vacuum pump. It will take a little while to pump down, but it works fine.

[atgcpaul]

....
mpc

Wow! Thanks for the detailed instructions. I wish I was up for this myself. I
can build most anything in wood and can put together most anything if given
instructions and enough time. However, this is something where there WILL
be parts leftover.

This one is definitely going to the pros.