jmrjames

It sounds like the solution is to burn money to cool off.

Using dye seems so DIY and messy compared to an electronic sniffer used by professionals which can detect leaks that dye might not escape from or be seen leaking from. Especially after several dye tests have been performed.

Am I wrong about by not turning on the rear AC that there will be no flow of freon through that part of the system.

When it is hot and humid here I am very happy that my rear AC works

Z928328

The car is going back to the shop on Monday- From there- They can see where the dye leaks out using their UV lights torch- Now after seeing SQL post of the rear AC- I might think the rear AC may be the main cause-I will be Asking them to fully check the Rear AC.

Also some strange odor seems to be coming from rear AC. Not too sure....

They claim- They change the evaporator on a 911 & 944 & BMWs. The 928 should be no difference & will take 3 days of labor- Costs 300-400 plus labor charge.

It seems I'm not the only 928 from the auction sales to have suffer this problem. Few 928s already visited this shop & also lose out freon.They confirm it's the evaporator in the dash but they did not work on it as they do not stock the parts & owner have no source to find the parts. So that means I have to buy the parts- & ask them to install.

Z

SharkSkin

It's not unusual for cars that have been sitting for a long time to have issues with the AC when started... seals dry out, etc. The 928 may be no different in terms of the basic function of the system but changing out the evaporator is, I'm guessing, VERY different. Do those other cars require removal of the whole dash, instrument pod, etc? How did they confirm that the problem is with the evaporator? Note that with a sensitive sniffer, a leaky expansion valve can register as a leak at the evaporator because of proximity. Went through that exact scenario with my car. The AC tech told me that it could be either the valve or the evap, we both agreed that I should change the valve and re-check. As it turned out, that fixed the problem.

Bill Ball

A new evaporator is a lot more than $US300-400, if you can even get one. I have no problem with hoses and all of the seals, but I'd want clear proof the evaporator is leaking before I did that part. With a leak this big any decent AC shop should be able to sniff freon through the vents on the lower side and in front of the evaporator box. The freon sniffers have a flexible wand that can get inside the box and sniff right on the evaporator coils.

jmrjames

He said he was informed that is was the evaporator by the folks who just filled the system without doing a vacuum hold test or by even using dye or anything else for that matter. Did you see the o ring pictures ?

Now someone uses the dye and discovers his first charge was leaking out at the rear expansion valve.

He has not mentioned anyone using a sniffer other than a nose to detect an odorless gas. Must be that dash evaporator from all of that dye on the front rug. Couldn't be that all of the parts where not changed or installed correctly.

Heck with 3 days of labor fees coming my way to learn how to remove a 928 dash I have to agree with them that it is the evaporator. Maybe I could buy a few sniffers then and still make a nice profit and hide the new evaporator out back.

Dude you need to stop talking about the "other" cars as you were told before. They will be back soon enough maybe even after you are done with this "problem". Maybe they already went to a real AC shop by now. This is common maintenance for the age and little use of any car.

I just also wonder how long that system and new parts had time to absorb the humidity there. How much oil is in the compressor and other things.

I have a nice bridge here that I will sell you and you can keep all of the tolls to pay for it.

Sorry but in this case I believe Ron White "You Can't Fix ______"

dprantl

A leak in the evaporator is *very* *very* rare. Consider that the evaporator is a component that is completely protected and surrounded by shrouding inside the car and is never really exposed to the elements. The only way they really fail is through years of constant vibration breaking the tube welds. Usually most other components fail before the evaporator. Almost always it is the condenser that leaks, since it is pounded by oncoming air and everything in it any time the car is being driven.

Dan
'91 928GT S/C 475hp/460lb.ft

SQLGuy

Depends which evaporator. The way they made the rear ones, or at least the rear one in mine, with copper tubes pressed into the aluminum tubes, leaks are not uncommon.

I never had a problem with 928 front evaporator, though. Maybe those are built differently.

WallyP

Z,

Any competent shop with a decent sniffer could find the leak in less than fifteen minutes. Why do you want to hand your car over to an incompetent shop that doesn't even have the basic equipment required to service air conditioning systems?

Is there no other shop that you can use?

Z928328

Hello Wally,

There are many AC shop around here & this particular ones was recommended by the mechanic who did my TB & also word of mouth by many people- Even Toyota, BMW & Merc dealers bring their customer's cars to this place if the cars have AC problem. This place seems proper.

Most AC shops here are doggy & many fake freons from China are sold here.That's why I'm not risking it.

The last time that I bring my car to the AC shop( 2 times) have the electronic sniffer.but did not detect leaks.

I will ask them to check the rear AC on Mon. -It seems I can hear some hissing or whatever sound coming from there & also some weird smell.



Z

WallyP

If they use the sniffer, they should find the leak.

The smell from the rear may be the refrigeration oil leaking along with the R-12.

As has been mentioned, the rear evaporator is known to leak more often than the front evaporator, due to the way it is made. There is a mixture of aluminum and copper in the evaporator, with different thermal expansion rates.

The hissing may be normal, especially if you were using the rear A/C. An air conditioning system works by building up pressure on the high side, and allowing the Freon to spray into the evaporator thru a restriction (the expansion valve). After you shut the system down, there will still be high pressure on the high side until it slowly bleeds off thru the expansion valve.

And, to answer an earlier question, the rear A/C will have system pressure (not high pressure, just the normal static system pressure) all the time. The solenoid valve just keeps the high pressure from reaching the rear expansion valve, but the other side of the evaporator is open to the rest of the system.

Z928328

Wally,

I follow your advice & also JmrJames- I finally find a AC shop on the other side of town which is near my home.

They have the electronic sniffer/leak detector. & I also hand the car over to them for the whole day today.

They flush out the rear evaporator & soak it in water- no visible leaks. & Check the hoses, condenser, No leaks etc etc.& also they did not trace any Dye done by the other shop the other day.- They fill it up & trace it with the sniffer- It's the front evaporator that is leaking. He also can track the front evaporator leaking near the front expansion valve area. (Strong beep)

they have the parts( One unit left)- Costs 500 $ & 300$ on labour charge. Todays checking - He did not charge anything as they are some old friend of my parents.

I should have visit them earlier. :P. So Monday- They will start doing it & by Tuesday- I can collect it.

Z

mickster

That's what I call good "Car-ma!"

SeanR

If the leak is at the evaporator, near the expansion valve, it might be that the previous install of the expansion valve (which can be tough to fit) that the seals at the rear expansion valve were kinked and are not sealing.

Check those seals before you pull the evaporator. I know you've had that done, but there have been a couple of times this has happened to me.

WallyP

I agree with Sean - the expansion valve will have to be pulled before the evaporator can be removed anyway. That means that this check is quick, easy and essentially free - and could possibly save you hundreds of dollars and many potential problems from having the dash disassembled. All they have to do is to pull the expansion valve first and look carefully at the O-rings and connections.

Z928328

OK- I noted down - Let's hope it was that. Monday- I sent my car very early morning So they can start the work.

When they refill the car just now to test of it holds the charge- They use one machine(with dial gauges on it) to check the pressure- It was losing out fast. & the sniffer trace at the evaporator area(middle). He can peep at bit the front evaporator from the engine & he says how he wish it has screw from there so it can easily access & replace.

The mechanic ( An experienced car air con specialist from the Philippines)- He said he's done an evaporator change on one red 928 S4 & few Porsche(2 944s & 968 to be exact) belongs to expacts(oil co workers). He knows what to do.
He also mention he pulled out a customer's Ferrari evaporator on a F355.

LOL--- the good thing is I can drive 20 mins to visit the car ever time :P

The car had the timing belt down last 2 weeks & the workshop is about 45 mins drive from my place. & I can't always monitor the car.


Z-