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Coolant Testing With A Multimeter

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Gary Lewis

Coolant Testing With A Multimeter

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Have any of you tried this?

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

BigBrother-84

Re: Coolant Testing With A Multimeter

Never even thought it was possible!

Jeff / 1984 F350 Crew Cab 4x4/5.8L w351 4V/ T18/ D50 4.10 front/ 8' bed.
Restored 2019-2022.
Nicknamed «Big Brother 1984», due to its soooo-looong shape & nod to George Orwell's 1984 famous novel.

mat in tn

Re: Coolant Testing With A Multimeter

I'm going to look into this. it does seem to have some validity in theory as electrolysis is capable of generating a voltage. becoming a battery of sorts. grounding seems to be the big potential question. is the coolant in the block not grounding to the block?

Gary Lewis

Re: Coolant Testing With A Multimeter

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Please let us know what you find, Mat.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Coolant Testing With A Multimeter

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In reply to this post by mat in tn

mat in tn wrote

is the coolant in the block not grounding to the block?

I think the theory is that rubber hoses and plastic tanks isolate the radiator and heater core from the truck as a whole.

People make too much of this IMHO
There's not much potential there and it could be eliminated by a single strand of wire as fine as a hair.

(see my response to Bradley's "idea" of annular boosters, or Gary fretting about where to monitor voltage)

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Ifitaintbroke

Re: Coolant Testing With A Multimeter

Interesting story from one of my coworkers who used to be a Ford dealership mechanic: They had this truck that kept going through heater cores, and they couldn't figure out why. An engineer who happened to be there looked at it, and stuck a voltmeter into the coolant. Read 1v. They flushed the system, and used distilled water(which I would think they should have done in the first place) and the truck was fine after that. That's what I was told anyway...

Bradley
86 f250 supercab longbed, 4x4, 460 bored to 472 cubes, ported heads, ARP rod bolts, EFI pistons, 5.08/5.41 lift 114° lobe separation flat tappet cam, notched lifters, Smith Brothers pushrods, stock rockers, Eddy Performer intake, Holley 1850 or 3310 depending on mood, custom curved points dizzy, MSD analog 6al triggered by Pertronix module, zf5 swap, 3g alternator, custom instrument cluster, dual tanks with 38 Gal rear for 57 Gal of fuel capacity, far too much more to mention.

98 Ranger standard cab, rwd, 5-speed, 2.5L, glass pack muffler, dual plugs wired to fire at the same time, coming up on 300,000 miles before too long.

Averaging 26-27 mpg.

South Georgia.

mat in tn

Re: Coolant Testing With A Multimeter

this sounds plausible and I was going to run a couple tests in the shop today, but I got distracted by one of the resurrections.

Gary Lewis

Re: Coolant Testing With A Multimeter

Administrator

I, too, was going to run some tests today but didn't. I have relatively new coolant in Big Blue, but that in Blue is quite old. Better test and see what I can find. And I'll do it with three different DVMs.

Gary, AKA "Gary fellow": Profile

FordFETruck

Re: Coolant Testing With A Multimeter

Yeah, I've done this over the years. Seems like a pretty good test. I've tested the old IAT green coolants that I had a surplus of, and I had them go to .6 volts within 2 years. The G-05 coolant I have in all but one of my vehicles (it's G-05 also but dyed red for MoPaR use) and the older the coolant the higher the voltage was. A few months ago, I put new coolant hoses on my truck, I had .3 volts at highest before (3-year-old G-05) I replaced the coolant I drained with fresh and didn't bother flushing the rest and it went down to like .1 volts.

1986 F250 351W, C6, 10.25 Semi float 3.55 gear, 250K Miles

FordFETruck

Re: Coolant Testing With A Multimeter

In reply to this post by Ifitaintbroke

Ford had a big problem losing heater cores out of the Crown Victoria/ grand marquis/ town cars for a long time because of the alternator grounding through the coolant when the lower alternator bolts would become corroded between the bolt threads and alternator case.

1986 F250 351W, C6, 10.25 Semi float 3.55 gear, 250K Miles

ArdWrknTrk

Re: Coolant Testing With A Multimeter

Administrator

In reply to this post by Ifitaintbroke

Ifitaintbroke wrote

Interesting story, a Ford dealership mechanic had this truck that kept going through heater cores, and they couldn't figure out why....

My truck kept going through heater cores (10 in all!) and I got to stay close to my friend Rick Piper who inherited Portchester Auto Radiator from his father.

Turns out I had a tiny crack between an exhaust port and the spark plug.
It would only open up if I was romping on it and had to back off suddenly.

I got to where I could change it and have the coolant system buttoned up in 15 minutes.
This was back in the day, when Modine still made brass heater cores and Rick would pressure test every one before it left his shop.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.