[xj-s] update coolant leak

this is an update on my continual coolant leak after
shutdown. as you may recall, I changed all hoses, new alum
radiator, electric fans, tstats, etc and after 2 months
developed an annoying leak only after cooldown. about one
cup of coolant each time. after weeks and months of
replacing lower rad hose again, retightening hose clamps
etc, I was finally able to remove the new alum rad and
surprised to find when that it leaked at both sides of
radiator.

i thought that was the least possiblity given that it was
new. I also made sure all copper tubing on top bleed valves
were open, and especially the connection to main filler
there is a coolant hose that comes off there, made sure that
was open.

the shop just returned my fixed radiator, and I am now
watching it for leaks.

apparently the leaks were caused by electrolysis, and from
what I read can take as little as 2 weeks to start leaking.

i just wanted to post to others that if you have a new alum
radiator, as opposed to recored oem, these radiators can
conduct electricity and create eletrolysis and eat away at
your internal welded seams.

i have switched to HOAT hybrid organic acid coolant zerex
g05 and also added no rosion product that should help.

i am also going to have my radiator tested for electrical
current as I dont want to go thru this again.

so if you have an alum radiator, and new electric fans…

caution, make sure there is no electrolysis happening in
your system radiator or it can and will cause a leak…

hope this helps somebody.–
1990 Jag XJS 5.3L v12 Coupe
baltimore, United States
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apparently the leaks were caused by electrolysis, and from
what I read can take as little as 2 weeks to start leaking.

The only way you can get electrolysis is if the radiator is grounded.
The OEM radiator is not grounded, it’s mounted entirely in rubber.

– Kirbert

// please trim quoted text to context onlyOn 10 Feb 2012 at 6:33, nwmgnt2011 wrote:

In reply to a message from Kirbert sent Fri 10 Feb 2012:

I agree all rad … have rubber stops but it is possible
that edges of radiator touch chassis and my fan shroud now
has dual fans electric so some type of stray current caused
electrolysis…–
1990 Jag XJS 5.3L v12 Coupe
baltimore, United States
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I agree all rad … have rubber stops but it is possible
that edges of radiator touch chassis and my fan shroud now
has dual fans electric so some type of stray current caused
electrolysis…

Yeah, so make very sure that your electric fans are NOT electrically
connected to the radiator, and add plastic shims or whatnot to make
sure the radiator doesn’t electrically contact the chassis. It’s
easy to confirm when done; just use a VOM to check ohmage between
radiator and chassis. If it doesn’t look like an open circuit, it’s
got a connection somewhere that you need to disconnect.

– Kirbert

// please trim quoted text to context onlyOn 11 Feb 2012 at 13:37, nwmgnt2011 wrote:

In reply to a message from Kirbert sent Sat 11 Feb 2012:

I don’t think you can ever completely isolate the radiator
electrically because the coolant mixture itself is a conductor of
electricity. With a sensitive digital ohmeter, you will always
read some value of ohms (although it maybe in the megohms) just
like you would between your left and right hands with the ohmeter
probes. Therefore, there is an electrical path from the radiator
via the coolant to the engine block even if the radiator is
completely isolated from the chassis.–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Austin, TX, United States
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In reply to a message from lockheed sent Sat 11 Feb 2012:

I just measured my new rad with fans etc installed and reads
approx 1.35 Meg Ohms with battery off car. The battery is off due
to me repairing some floor rust ready for the spring I hope but too
cold to weld and waiting for warmer weather !–
The original message included these comments:

I don’t think you can ever completely isolate the radiator
electrically because the coolant mixture itself is a conductor of
electricity. With a sensitive digital ohmeter, you will always
read some value of ohms (although it maybe in the megohms) just


95 XJR6, 94 XJS 6.0 coupe, 04 XK8 ,99 Ka
Croydon , SURREY, United Kingdom
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In reply to a message from 540itouring sent Sun 12 Feb 2012:

To measure electrolysis need to measure voltage in coolant?
Anything more than .1 v . Is not good…any experts pipe
in I am just swing what I heard…I don’t know what
resistance means in rad itself…–
1990 Jag XJS 5.3L v12 Coupe
baltimore, United States
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To measure electrolysis need to measure voltage in coolant?
Anything more than .1 v . Is not good…any experts pipe
in I am just swing what I heard…I don’t know what
resistance means in rad itself…

In order for electrolysis to affect the radiator, there must be a
complete circuit for electricity to travel. The presumed cause of
such electricity is two differing metals in contact with an
electrolyte, forming a battery. So, presuming the coolant is the
electrolyte, and the aluminum radiator plus some other metal in the
coolant circuit, perhaps the steel of the crossover pipe or the brass
of the heater core, forms a battery, this still wouldn’t cause
electrolysis if there’s no way for current to flow from one metal,
through the coolant, to the other metal, and then back to the first
metal. It’s that last step that requires both metals to be grounded
to complete the circuit. If the aluminum radiator is electrically
isolated from the chassis, the current could come in through the
coolant itself, but it can’t get back out, so no current flows, and
hence no electrolysis.

Even so, this type of electrolysis normally works pretty slowly, and
I’m led to believe that the case in question involved a radiator
being damaged very rapidly. That would normally mean that, rather
than these materials forming a weak battery and generating tiny
currents, the system is somehow applying system voltage (12V) through
that coolant to the radiator. That’ll eat up material in a big
hurry; it basically becomes an electroplating process that erodes
material away from one place and electrically deposits it in another
place. But that would involve somehow applying 12V to the radiator
without it being grounded so the current would have to flow through
the coolant to get to ground. That would be a serious error, but
more to the point if it involved the incorrect connection of some
piece of electrical equipment, such as an electric fan, that fan
would not work because the coolant wouldn’t carry enough current for
it to operate. If it even turned at all, it’d barely move. Hence,
it would be readily apparent that it was connected incorrectly.

In short, I find the entire explanation that these leaks were the
result of electrolytic corrosion to be highly suspect. Far more
likely they were the result of manufacturing error.

– Kirbert

// please trim quoted text to context onlyOn 12 Feb 2012 at 3:40, nwmgnt2011 wrote:

I just measured my new rad with fans etc installed and reads
approx 1.35 Meg Ohms with battery off car. The battery is off due to
me repairing some floor rust ready for the spring I hope but too cold
to weld and waiting for warmer weather !

That sounds right to me. I’m not sure what difference the battery
being in or out would make.

If it measured 1.35 megaohms before it developed leaks, I would
seriously doubt the conclusion that the leaks were caused by
electrolysis.

– Kirbert

// please trim quoted text to context onlyOn 12 Feb 2012 at 1:32, 540itouring wrote:

In reply to a message from Kirbert sent Sun 12 Feb 2012:

oh I was not the one that measured the ohms…i measured dc
voltage on the radiator and got 0v.

but I want to mention several thoughts…from what i
understand new alum raidators do not flex well, and aside
from the electrical issues, the flexing of the car might be
cause for rapid leaking at seams?

now for the electrical issues. the manufacturer suggested i
ground the radiator…

the radiator did not come with a ground strap, but I have
read that some do. our radiators are rubber insulated at
both top and bopttom, so there is some confusion as to
whether one should ground an alum radiator or not the ground
it…

i will say that after testing a ground, I had other effects,
i.e. better coolant gauge readings i.e. not spiking above N…

could it be possible that there is some current in the
coolant solution, and this causes some inaccurate readings
in the coolant sender to the gauge?

the vendor also suggested adding an additive norosion, to
help prevent electrolysis in the coolant.–
1990 Jag XJS 5.3L v12 Coupe
baltimore, United States
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In reply to a message from nwmgnt2011 sent Sun 19 Feb 2012:

‘‘from what I understand new alum raidators do not flex well’’

I don’t know of any that do - that’s why they are basically mounted
in rubber so that the body can flex without transmitting the
flexing to the radiator.–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Austin, TX, United States
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In reply to a message from lockheed sent Sun 19 Feb 2012:

My fixed–alum radiator has a slight leak right side
somewhere I can see small trail of coolant at this point
add alumina bars leak. I am running low on patience with
this coolant system I hate add something but pinhole
hissing sometimes makes this a possibility–
1990 Jag XJS 5.3L v12 Coupe
baltimore, United States
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but I want to mention several thoughts…from what i
understand new alum raidators do not flex well, and aside
from the electrical issues, the flexing of the car might be
cause for rapid leaking at seams?

Well, first off, the radiator is supposed to be mounted in rubber.
The idea there, besides the electrical isolation, is so that the
chassis can flex WITHOUT flexing the radiator. In fact, the radiator
is supposed to be softly mounted so that it can serve as a harmonic
damper and damp out vibrations through the chassis.

Second, there’s a diagonal strut out in front of the radiator. It
might be worth checking that it’s in place and properly mounted.

now for the electrical issues. the manufacturer suggested i
ground the radiator…

the radiator did not come with a ground strap, but I have
read that some do. our radiators are rubber insulated at
both top and bopttom, so there is some confusion as to
whether one should ground an alum radiator or not the ground
it…

Wow, I certainly wouldn’t ground one. Perhaps the manufacturer wants
it grounded so you’ll be buying another radiator from him in a few
years!

i will say that after testing a ground, I had other effects,
i.e. better coolant gauge readings i.e. not spiking above N…

A ground on the RADIATOR had these effects? If so, you’ve got
problems elsewhere! You need to be checking the grounds on the
ENGINE.

could it be possible that there is some current in the
coolant solution, and this causes some inaccurate readings
in the coolant sender to the gauge?

Not if the coolant sender is grounded. And since the coolant sender
is screwed into the engine, there’s only one way it might not be
grounded…

– Kirbert

// please trim quoted text to context onlyOn 19 Feb 2012 at 7:21, nwmgnt2011 wrote:

In reply to a message from Kirbert sent Sun 19 Feb 2012:

there is a pinhole leak that has developed on the right
side…i did not ground before this happened…

it is a trickle of coolant on the spoiler, not enough to
drop to the ground, and sometimes, there is a slight hissing
sound…

for these pinhole type leaks, is it possible to use bars
leak aluminum radiator product?–
1990 Jag XJS 5.3L v12 Coupe
baltimore, United States
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