1997 Cadillac Deville A/C Repair

Tiny
MATTBRADY
  • MEMBER
  • 1997 CADILLAC DEVILLE
  • V8
  • 2WD
  • AUTOMATIC
  • 89,000 MILES
Need to know - when you take a car your car in for a/c repairs - is it standard practice to leak test the system before doing any work?

I took my caddy in cause a/c had quit working. Compressor was noisy and had a burnt bearing smell. Clearly there was a problem with compressor and it was changed. Morning after I took car home I heard a soft hiss under the dash and then a soft "pop" and a cloud of freon(?) Come up from the right side of the engine (hood was open to jump car). Took car back and was told I had an evaporator leak.

Called another mechanic who said system should've been leak tested before compressor work was done. Said he always does this as compressor went out for a reason and no sense replacing compressor if there's a bigger problem, etc.

I told my mechanic this and he said he couldn't leak test system with shot compressor. I think he could've - but I don't know.

Short/long - 2 quesitons:

(1) Is it standard practive to leak test a/c systems before doing repairs, and

(2) Can you leak test an a/c system with a shot compressor?
Do you
have the same problem?
Yes
No
Wednesday, July 15th, 2009 AT 5:06 PM

16 Replies

Tiny
BUDDYCRAIGG
  • EXPERT
Yes and no.

Let me type out a long answer to spell check it, and i'll be right back
Was this
answer
helpful?
Yes
No
-2
Wednesday, July 15th, 2009 AT 6:52 PM
Tiny
BUDDYCRAIGG
  • EXPERT
Generally when you charge a system, and especially when you replace a part.
You "suck it down" , meaning you attach a vacuum pump to the system. And let it sit there.
This does two things,
It helps to remove any moisture, as water will boil at lower temps when it's in a vacuum, think of the reverse of a pressure cooker, where water doesn't boil because it's under pressure.
Second, if there is a big leak you will notice it, and if you leave the system in a state of vacuum with a gauge on it, you can even detect small leaks, if you leave the gauges on it long enough.

Saying that.
Putting the system in a vacuum is very mild pressure (about 32 inHg)
compared to what happens on the high side when the compressor is running (about 250 psi)

So it is completely possible that your car was just fine when it left the shop the first time.
And the failure happened later.
Even sitting with the engine off, a fully charged system has about 75 psi in it.

So.

No

kinda.
You do a vacuum test, (see above)
and a few, and I really mean a few specialty places have nitrogen leak testing equipment.
Was this
answer
helpful?
Yes
No
+1
Wednesday, July 15th, 2009 AT 7:05 PM
Tiny
MATTBRADY
  • MEMBER
Thanks for feedback. Clarification please?

(1) My mechanic told me when I picked up the car that he'd put a green dye in the freon so he could see leaking with a black light - if I had a leak. He said he thought I might have a leak - since compressor went out and no freon in system when he went to do repairs. He told me to drive the car for a few days and then bring it back it so he could give it a once over for leaks.

(2) The morning after I brought it home I started it and that's when I heard the soft hiss under the dash and then hiss/pop/cloud of freon (?) On right side of engine. Cloud of vapor was not green - so not sure about the green dye claim he made.

(3) Having said all that - I have 4 questions:

(A) If you were given a car with a noisy compressor to fix - would you have evacuated the system/noted leaks and not gone any further until leak situation had been discussed?

(B) Since a/c was blowing cool (not cold) right before it quit and I smelled burned bearings - is it likely that freon leaked out slowly and a/c was able to still blow cool right up to the time the compressor crapped out?

(C) Hissing sound ("soft" sounding - but still noticeable) under the dash never occurred before. The morning after I brought car home was first time I heard. Could the mechanic, while repairing the compressor/charging the system, overcharge the system/pop a seal? Only reason I ask is I never heard the hiss before and his voicing a concern about a system leak/coming back to me telling me for sure evaporator has a leak after I took car back makes me wonder if he did something to cause hiss/leak to occur. Thoughts?

(4) Since Caddy's not worth much - would this be a good time to try CryoSeal?
Was this
answer
helpful?
Yes
No
Thursday, July 16th, 2009 AT 9:53 AM
Tiny
BUDDYCRAIGG
  • EXPERT
I'll address these two together.
With the system not being very cold, it could have had a slow leak, or the compressor could have been weak.
If you have a very slow leak (as you suggest you may have in B) It is hard to find without using dye.
When you put the dye in the system, the results are not instantaneous, the car has to be driven and the AC has to be used for the dye to circulate in the system. Sometimes for weeks.
So discussing the cost to repair any leak was not an option, because no leak had been proven.
PS, it is a very small amount of dye, you would not have noticed a green vapor.

More likely what happened, your system had a slow leak and was low on freon, or the compressor was weak. The system hasn't had to deal with normal operating pressures for a long time.

Once the system had the correct amount of charge, a weak component finally failed. It happens all the time with pressurized lines, a very weak part fails, you repair that and then the next weakest part fails.

You can try it if you want, but I don't have much faith in snake oil products.

Finally.
By what you have said so far, I feel that Your mechanic didn't do anything wrong and has followed standard operating procedures.
But ultimately, If you don't trust him, then go with your feelings and find a different one. You both will be better off.
Was this
answer
helpful?
Yes
No
-1
Thursday, July 16th, 2009 AT 12:27 PM
Tiny
MATTBRADY
  • MEMBER
(1) If you were given a car with a noisy compressor to work on - would you evacuate the lines/put system on a vacuum/note if vacuum held before proceeding to replace compressor?

(2) Since car is now hissing/popping/releasing a cloud of vapor on the driver side of the engine when it runs (compressor is on passenger side) - could it be that the orifice wasn't replaced/is clogged and/or something other than a leak in the evaporator is causing the hiss/pop/vapor under the hood?
Was this
answer
helpful?
Yes
No
+1
Thursday, July 16th, 2009 AT 12:47 PM
Tiny
BUDDYCRAIGG
  • EXPERT
No.
If the system is holding enough pressure for the compressor to run, then it's going to hold enough vacuum to pass that test.
Or
If a car comes in with a locked up compressor,
9 times out of 10 the seal on the compressor is damaged and would fail a vacuum test.

Is this hissing/popping/releasing a cloud of vapor thing on going?
It should only happen one time, after that the freon has leaked out and it cant do it again.

And could you clarify, in one post you said it was coming from the right side of the car, and now you said it is on the driver's side.
Was this
answer
helpful?
Yes
No
Thursday, July 16th, 2009 AT 2:05 PM
Tiny
MATTBRADY
  • MEMBER
(1) Compressor was making noise - i.E. It was turning but I think innards were shot. May not have been able to test for leaks in this condition?

(2) On the noise/vapor - Hiss/pop/vapor release happened when I started car up morning after I brought it home from mechanic. It happened twice. One hiss/pop/vapor release then a second hiss/softer pop/much smaller release of vapor.

Insofar as the hiss/pop/vapor on driver side when compressor's on passenger side issue goes - any ideas?

P.S. - My bad on using right side. I meant the issue's on the right side of the engine if you're standing in front of the car. Figured it would be better to start talking like a mechanic - i.E. Use driver/passengerr side instead of left/right.
Was this
answer
helpful?
Yes
No
Thursday, July 16th, 2009 AT 2:59 PM
Tiny
BUDDYCRAIGG
  • EXPERT
Sure, he could have tested for leaks, but it would have passed. And I'm going to bet that he knows that.

Was this vapor close to the radiator or back near the fire wall? But right now I cant think of anything on the right side.

We say left and right also, but it's as you are sitting in the car, not standing in front of it.

So the roadside, driver's side and left are all the same,
as is curbside, passenger's side and right.

Now to really mess with your head.
The left side of your engine is pointing towards the front of your car, and the right side of the engine is facing the rear of your car. :)
Was this
answer
helpful?
Yes
No
Thursday, July 16th, 2009 AT 3:32 PM
Tiny
MATTBRADY
  • MEMBER
Thanks for input so far. Need some clarification so gonna ask questions a little different/provide some add'l info along with so I can stop bothering you :)

(1) If someone brought you a car with a noisy compressor and, as you proceeded to evacuate the freon you found no freon in the system - would you assume the system had a leak and leak test the system before you did the compressor replacement as a matter of course?

(2) If after replacing the compressor you sent the car home and your customer came back next day telling you he'd heard a hiss/pop under the hood and saw a puff of vapor come up on the driver side of the engine halfway between the radiator and the firewall - would you suspect there was a problem with the compressor you'd just installed or what?
Was this
answer
helpful?
Yes
No
Friday, July 17th, 2009 AT 10:25 AM
Tiny
BUDDYCRAIGG
  • EXPERT
I've answered this question twice already. I'll try a different way of explaining myself as well.

These two facts in your question cannot exist at the same time
"a car with a noisy compressor and, as you proceeded to evacuate the freon you found no freon in the system"
There are sensors on the car that keep the compressor from coming on if it's out of freon.
So if the compressor is coming on, I know the system holds at least some pressure. And a vacuum test would not show any problems.
Now I'll offer you a alternate scenario.
Car comes in.
AC system is empty,
I circumvent the safety switch to see if the compressor will engage.
The compressor makes noise.
I replace the compressor.
Put dye in it.
Charge the system.
Since the compressor was bad, it most likely had a bad main seal as well.

If another leak is found, I would give the customer another estimate.
If no leak is immediately found, I would send it home. Comfortable with the knowledge that the dye will help pinpoint the leak if/when the customer comes back.

I would try to duplicate the problem to determine the failed part.
Was this
answer
helpful?
Yes
No
Friday, July 17th, 2009 AT 3:39 PM
Tiny
MATTBRADY
  • MEMBER
10-4. But the compressor wasn't running when I took car to shop. A/C had stopped running and I smelt a burned metal smell so I never re-engaged the a/c. I just took car to shop and, with just the engine running - there was noise coming from the compressor and the mechanic said I needed a new compressor.

All I'm asking is this:

Before he yanked the compressor - should he not have evacuated the system and in so doing discovered the leak in the evaporator (which is what he now says I have and what he now says caused the a/c system to lose freon and compressor to fail)?
Was this
answer
helpful?
Yes
No
Friday, July 17th, 2009 AT 3:50 PM
Tiny
BUDDYCRAIGG
  • EXPERT
I'm sure he evacuated the system, as it's the law. That is not doing a vacuum test.
Should he have performed a vacuum test?
I would not have.

And further more. From what you have told me, it is my opinion that the evaporator was still in working order when it left the shop.
You witnessed the very moment that it failed the next morning.
Was this
answer
helpful?
Yes
No
Friday, July 17th, 2009 AT 4:03 PM
Tiny
BUDDYCRAIGG
  • EXPERT
What's the name and city of the shop,
I want to check them out on the better business bureau website.
Was this
answer
helpful?
Yes
No
Friday, July 17th, 2009 AT 4:15 PM
Tiny
FACTORYJACK
  • EXPERT
Not to stick my nose in this business, but I have been reading this and have some input. It sounds like the vehicle was brought in with a drive plate sheared, and compressor seized. There should have been some noise, smell, degraded performance leading up to this. It is not customary to assume there was a leak since the system was still trying to operate. To add to system dynamics, you can have a leak under pressure, and not under vacuum, or vice versa. Think of a connection or o-ring, as it is pulled down it is pulled together and may not lose vacuum, when under positive pressure it spreads and leaks. A leak test can cover both vacuum and pressure. Have you identified where this leak is, the evaporator is on the passenger(right) side firewall where the large line, and small line enter a case. If you had a evaporator leak, it would more than likely expell into the passenger compartment. My guess, if it leaked after the repair, the shop kinked a line, left a connection loose, used wrong o-ring seals, or somehow the condenser got punctured. There is nothing on the right side, other than the high side line to the condenser. Two connections, one at the orifice tube, and one at the condenser. Was there metal in the system? The reason I ask, is sometimes shops opt to put a filter in the line. This filter is placed in that line in a location that is at the technicians discretion. The line is cut, and the filter is attached with compression fittings. If you had a pop/hiss/vapor, you should also have oil to show where the leak is. It sounds like the shop don't want to admit, or assumes, it did nothing wrong. That is my two cents, if I stepped on any toes, let me know.
Was this
answer
helpful?
Yes
No
Friday, July 17th, 2009 AT 10:54 PM
Tiny
MATTBRADY
  • MEMBER
Gstacey - you seem to have a much better handle on what my situation is than buddycraig. You have any idea why hiss/pop/vapor would occur on driver side of engine shortly after starting up car morning after I brought it home? Seemed pretty strange to me - that and the fact that when I came home there was a large bolt on the drive where the car had been sitting - obviously a part the shop did not install but left loose and it fell out when I drove off!
Was this
answer
helpful?
Yes
No
Monday, July 20th, 2009 AT 11:36 AM
Tiny
FACTORYJACK
  • EXPERT
Without being able to physically inspect the vehicle myself, I would suspect that some part of the job was done incorrectly and/or poorly. Like I said in my most recent post, there is nothing but a high side line running on the left(drivers) side of the engine. Have you inspected it for a damaged line and/or signs of oil. If the refrigerant leaked, it carries the system oil with it, that was the vapor that was seen. If the shop just replaced the compressor, nothing should have been touched in that region. As I said also, did they install a filter in the line? This is often installed after catastrophic compressor failure, in attempt to prevent any rogue metal particles from reaching the replacement compressor, the line is cut and filter installed using compression fittings. It sounded to me all along, that the initial diagnosis and repairs were done accordingly, but that something went wrong. They told you it needed an evaporator, usually those don't pop, they slowly leak, and how did they come to that conclusion. There is a pressure relief valve on the back of the compressor, it lets off at pressures of approximately 525psi to prevent system damage. If the shop is saying that it is not their fault, and something else failed, have them show you where it is leaking. Otherwise, have a second opinion.
Was this
answer
helpful?
Yes
No
Monday, July 20th, 2009 AT 10:33 PM

Please login or register to post a reply.

Recommended Guides