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I just replaced radiators in both my Ford Escorts - one has been "eating"
radiators. Brochure that came with the new after-market radiators said
ought to be 0.1 (zero pt one) volt max measuring from raditor to gnd. I
called - tech service said 0.3 (zero pt 3) was really their max. Mine was
0.5 (zero pt 5), so I ran a #22 piece of RV-6 wire from top of radiator
(attached to aluminum top frame with screw) back to negative battery
terminal. No "delta voltage" now!
I have never understood exactly how the voltage was being generated. Now,
with Bill Dube's explanation, I have to say I understand a bit more than I
did before. However, . . .
My radiators were both on the rubber donuts on the two lower mounting points
on frame of car. The rubber radiator hoses completed the isolation of the
radiator from the engine block. That only leave the coolant as the
"electrolyte"between the aluminum head and cast iron block of the Escort
engine.
I now wonder if running water with John Deere coolant conditioner (water
pump lub and anti-corrosion additives as good as Prestone eth.glyc) acted as
a "better" electrolyte and caused more rapid (6 months from "new" to
"replace") damage to my radiators in that one car. I think I can correlate
the repeated rapid failures to when I switched to JD coolant cond. & water.
Remaining questions:
1) Is the "ground wire" from radiator to negative terminal of battery good
enough to totally eliminate this "galvanic cell" action?
2) Forgetting about the type of coolant, and focusing just on the rubber
donut bottom mounts/isolators from frame, why would that isolation or lack
thereof alter the "galvanic action" "equation"?
3) And, I should mention that the Haynes manual shows a bolt in the
aluminum head for a grounding strap or cable from head to somewhere -
neither Escort had this bolt/cable, just the empty hole in the head. Could
that "have been" or "still be" a problem for my radiator life?
David Carter
----- Original Message ----- From: "Bill Dube" <bdube@al.noaa.gov>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Wednesday, May 25, 2005 9:52 AM
Subject: [FlyRotary] Galvanic action (was: radiators as jugs 4)
The main problem I see is that the radiators are not electrically
isolated from the aircraft frame and engine block. There is no vibration
isolation either. This can cause serious problems with metal fatigue and
with corrosion driven by galvanic action.
The vibration from the engine will fatigue the fins and tubes and
perhaps the inlets.
The electrical connection between the radiator and the engine
block competes the circuit on a galvanic "cell". The dissimilar metals of
the engine block (cast iron and/or aluminum) and the radiator (copper or
aluminum) along with the water acting as the electrolyte form a very
effective battery (cell, actually). The current flows in the circuit and
eats the crap out of the radiator.
I would see this problem often when I was a car mechanic
(previous
life). Folks would remove the radiator, and then replace it without the
rubber grommets. About a year later the radiator would become Swiss
cheese.
Similar things happen to household water heaters that are
improperly installed.
Bill Dube'
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