20V Radiator Plastic vs Metal?

paul fernandes paulfern2000 at yahoo.com
Thu Jan 23 09:54:25 EST 2003

Hello to all,
I just stepped in to see how the list is doing and right off I see this one
and since I was just sitting here waiting for a shipment to come in well
here it goes..

I'm a  professional in this business, design engineer working for a world
wide VERY big
heatexchanger company. There are several things to consider here first off.

- plastic tanked radiators are still one the industries most reliable units.
 but there are some after market units which use cheaper grade plastic in
the tanks
which will cause what some of you have seen in the past.
Also within the last ten years the materials used for these tanks have
improved so
if your radiator is say from a 1988 Audi 5000 it can be the case that it was
built with
the inferior grade of plastic PA6.6 for example and or with a lower glass
filled content.
Another point to add and this is based upon tones of hours in testing and
We have noticed that lately (with the last two years) that glycol mixtures
have gotten more
aggressive...this means acidity levels were found in the glycol..the reasons
for this it is not indented.
This was all started by OEM manufactures to upgrade or improve their
warranties ...well we notice
that these new glycols are so aggressive they start eating the tanks
(plastic) structure from inside...
Anyone scared here yet??????? this of course can weaken your plastic tanks
or even eat away at the
tanks gaskets.

I am not quite sure how the automotive industry (OEM) is handling this but I
can tell you that
not too many radiator or heatexchanger business will like it either...
their are alternatives of course and this is to watch out which fluid you

The main drive to aluminum was two fold mainly, weight reduction and
price followed but was later "eaten" by tank cost.

- Metal tank radiators:
I had actually posted something about this on my site but no one ever
bothers to look a heatexahnger
part of the project so oh well.
the plain truth is "metal" radiators are made up of the following...and this
is as a general industry rule.
+tanks copper / brass
+core , copper/brass (copper air centers / brass tubes)
+header (clinched thing) must be made of steel .....
 Now first questions is why steel header? obviously strength is the number
one rule...also steel and copper have neutral
chemical reaction (proven thru testing) ...other materials like aluminum
tend to have nasty chemical reactions with other alloys and start to break
down..(this is to technical and will not go into here.)

Now the good thing about metal radiators..obviously copper brass in this
case..there is no doubt that they perform way better then
aluminum cores...why since when did aluminum conduct better then any copper
or steel...heat or electricity for that fact..think about it...
now what the industry does to counter affect this is build aluminum cores
bigger then the metal ones..this helps out in the Heat exchange DELTA.
bad thing about metal cores is: corrosion..of coarse...now this on is more
theory then practical but OEM's insist on it
even thought we have seen some nasty failures on aluminum as well.

The last and not least is cost issue.
metal versus aluminum, normally the aluminum is cheaper to build but is
offset by the high cost of plastic tank mold...VERY HIGH COST..
in the end these two are actually identical in price so we should actually
see no or little  difference in price..

Hope this helps some...and sorry for the long details...
my shipment is still not in so I  lost nothing..

Paul Fernandes
(Luxembourg - Europe)

----- Original Message -----
From: "Scalmanini Steve" <sscalmanini at yahoo.com>
To: <200q20v at audifans.com>
Sent: Thursday, January 23, 2003 8:50 AM
Subject: 20V Radiator Plastic vs Metal?

> It may be true that "The Nissens all metal radiator
> actually has a higher rate of failure than the
> stock AKG radiator", but what's preferable, a
> part with a higher failure rate but that won't
> fail suddenly and completely, or one with a lower
> rate but that commonly fails completely and
> without warning and would leave you stranded
> (and is more expansive)?
> The necks/nipples won't break off of a radiator
> with metal tanks but they might seep at their
> seems sooner than one with plastic tanks.  I'll
> bet the metal ones aren't really "all metal", but
> instead have metal tanks crimped onto the metal
> heat exchanger with a gasket in between, just like
> the ones with plastic tanks.  I doubt that they're
> actually soldered together like we might assume
> from the proverbial old days.  So with one more
> metal surface against that gasket to corrode, vs.
> the more inert plastic one, I would expect those
> with metal tanks to fail at that gasket seal sooner
> than those with plastic tanks.
> Can someone who got one of the metal ones tell the
> list exactly how the tanks are attached?
> The bottom line is, IMHO, I'd rather risk a slow
> failure with warning than a sudden failure that
> would leave me stranded.
> Comments?
> Steve
> Ukiah, CA
> Patrick Anderson ptanders at attbi.com Wed, 22 Jan 2003
> The Nissens all metal radiator actually has a higher
> rate of failure than the stock AKG radiator. ...
> Sent: Wednesday, January 22, 2003 1:55 AM
> ... what are the pro and cons of the AKG OEM
> radiator and the all metal Nissens?
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