I need a quick rad to gnd verification.

[CajunKenny]

Hi all!

I was just wanting someone to post what resistance they have from battery ground to your radiator.

Mine is directly shorted and wanted to see what variances are out there if any. Just for reference, I have a Koyo.

In case anyone is wondering why, my concern is stray currents taking out the rad core.

Thanks...

 

[jetjock]

The stock radiator is isolated from the chassis...

 

[Mk3runner]

That's the rubber mounts.. No current. Do you have your mounts? Maybe the lower ones are missing.

 

[CajunKenny]

Thanks for confirming jj!

 

[CajunKenny]

That's the rubber mounts.. No current. Do you have your mounts? Maybe the lower ones are missing.

This was isolated when first installed. I had to grind on the upper mounts a bit; but, was able to get it done. When I checked it, I was surprised that it was shorted and it's just been long enough that I couldn't totally remember.

 

[CajunKenny]

Just for reference: The best I can get is ~3.4k. I'm sure some of the continuity is due to the conductivity of the coolant. That's what I'm hoping anyway...

I still can read a full 12v when grounding to the rad...??

If anyone else that has a similar setup can verify, that'd be great! My reference points were the alternator housing and the side of the rad.

Thanks again!

 

[Poodles]

radiator is touching the chassis somehow...

 

[CajunKenny]

That's about the only thing it can be. I guess I should pull it out and put electrical tape on the sides and put an insulator on the top and bottom edges of the chassis. We have some really good edge insulation at work.

Still hoping someone will be able to post their measurements...

 

[jdub]

Any amount of current will turn an aluminum radiator into a sacrificial anode...that means you will corrode a hole in it in short order. Suggest you isolate the radiator ASAP.

 

[CajunKenny]

So should there be NO continuity at all between a full rad and chassis?

Coolant is conductive; but, does anyone know how conductive? My rad may be isolated from the chassis with the exception of the coolant...? I guess the best test would be to drain it, then measure.

I was hoping to get around that by comparing someone else's findings.


EDIT: I just measured and I've got a solid 78k between the rad and alternator housing and ~1.3meg between the coolant in the rad and the alternator housing.

 

[IJ.]

"stray current"

 

[CajunKenny]

Yeah...

Ok. I took more measurements. Here's my findings for anyone interested.

Rad > Alternator Housing = ~1.05 meg (don't ask me why it's different from the last time )

Coolant > Alternator Housing = ~2.2 meg

Coolant > Rad = ~1.4 meg

That leaves very little current to eat at my rad core. Hopefully...

 

[slidebabyslide]

interesting thanks

 

[jdub]

Think about this Kenny...the problem is a current path between the thin aluminum of the radiator and the coolant (yes it's conductive). Any other measurements does not tell you squat. With a current path through the radiator, the coolant acts as an electrolyte removing metal from the anode (the rad) and deposits it on the cathode (engine block).

Over time you can figure out what happens...on the thin metal used in a radiator, it doesn't take long. Instead of asking "is this too much current", the question should be "what do I need to do to the radiator to isolate it from the current path". Don't head off on an abstract vector and focus on the problem.

 

[IJ.]

The tubes in an average Al rad are 20thou thick so it doesn't take long to errode enough to leak.

From memory the max allowable was .5Mv anything over that means trouble.
(someone will correct me if my memory has it wrong and you can't use a Digital MM to test it)

 

[jetjock]

Your radiator appears isolated. The real question how many mv are there between battery negative and the coolant itself. Take off the cap and stick the probe in the coolant. Don't let it touch the radiator....

 

[CajunKenny]

Rad unmounted and leaning toward the engine (not touching anything) = 240mv (coolant > neg battery terminal)

Rad fully mounted = 230mv (coolant > neg battery terminal)

 

[GrimJack]

Instead of asking "is this too much current", the question should be "what do I need to do to the radiator to isolate it from the current path". Don't head off on an abstract vector and focus on the problem.

Or "What can I mount inside the radiator that will become the sacrificial anode before Aluminum?"

 

[IJ.]

Rad unmounted and leaning toward the engine (not touching anything) = 240mv (coolant > neg battery terminal)

Rad fully mounted = 230mv (coolant > neg battery terminal)

WOW :aigo:

My local shop showed me one of their Rads that leaked in 2 weeks @ 100mv, time to start checking ALL the grounds in the car <hint look anywhere body work has been done>

Hope you didn't use a Digital MM to test?

 

[CajunKenny]

No body work has been done to the car.

Yes, I did use a DVM. A Fluke 87.

What is needed instead of a DVM? An analog meter?