Cause of Evaporator leak?

[Z2TT]

Hello,

I have seen so many cars with leaking evaporators. I'm wondering how is it possible for the tube to be punctured. I can understand leaks from O-ring seals that go hard over time but I don't understand why evaporator cores leak, I mean the tubes aren't that thin are they?

I'm going to replace a leaking evaporator on my Lexus LS400 with another one, But I don't want it to just begin leaking again.

Thankyou.

[abbsnowman]

Aluminum coils are week and considder the bending and tweaking going on as your car goes down the road.
Make sure the coil is "comfortable" and not jammed when you install it. If there is room for some foam to soften the ride, put some in.
Abbs

[desA]

Assuming an aluminium fin - aluminium tube construction:
Galvanic corrosion, in the presence of water, with the aluminium tube being sacrificial to the fin, will very often result in early tube pitting corrosion.

If aluminium plate evap construction, then fatigue cracking could be the place to begin looking. The second area would again be galvanic corrosion between fins & plate surfaces.

Reason for galvanic corrosion:
The galvanic potential of the fin & tube (plate) alloys changes after brazing. This often results in the tube (plate) becoming sacrificial relative to the corrugated fins. Many manufacturers are too 'cheap' to use corrosion-controlled fins, which can reverse the galvanic potential imbalance - resulting in the operational galvanic problems. Other manufacturers simply do not understand the corrosion mechanisms & just copy-&-build products they see in the marketplace.

[vtmpnate]

On the contrary desA, I think manufacturers understand the corrosion process all too well. It helps sell more parts, and keeps people like us in business! Besides, the savings from not using any form of corrosion protection translates to a whole lot of profit right from the get-go! just my 2 cents

[Magoo]

Z2TT.
They are designed to fail within 10 years and probably sooner, the perfect car/vehicle is designable but they would not sell many after market saturation.
The coils are so thin you could spit a hole in them. Add corrosive atmospheres and leaks are common.
In eccence cars are designed for a limited life, and that includes the A/c.
I had a wagon with a 100 K warranty, 105k and things failed fell off and as a trade-in worth zip. Was not impressed, never since bought a brand new wagon.

[desA]

On the contrary desA, I think manufacturers understand the corrosion process all too well. It helps sell more parts, and keeps people like us in business! Besides, the savings from not using any form of corrosion protection translates to a whole lot of profit right from the get-go! just my 2 cents

:D

There are specific accelerated corrosion-life tests in the automotive industry e.g. the SWAAT test - this is pretty aggressive - for new automotive products.

Japanese cars are typically designed to a 3-5 year lifespan. Not sure about the export vehicles.

[Z2TT]

Would it be safe to assume that on the large scale that the evaporators are produced, that some may be more prone to failing, and some may not?

[vtmpnate]

You're right, desA, I do recall reading that off the old Sanden Daruma brochures back in the late 80s. Perhaps I should have said "better" rather than "any" form of corrosion protection. And then of course there is the luck of the draw, whence a fraction of coils manufactured will fail faster than others.


:D

There are specific accelerated corrosion-life tests in the automotive industry e.g. the SWAAT test - this is pretty aggressive - for new automotive products.

Japanese cars are typically designed to a 3-5 year lifespan. Not sure about the export vehicles.