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6.5L Diesel Engine Discuss the 6.5 GM diesel engine & associated components. Automatic transmission questions & problems belong in the 4L80/85 - 4L60E - 6L90 Transmission Forum

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Old 02-14-2020, 10:18 PM   #11 (permalink)
DieselPro
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Dang, I'm good! You might find a coolant temp sensor back feeding the current to the wires. It might be bad as well even though it works.

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Old 02-15-2020, 04:10 AM   #12 (permalink)
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While I love the potatoes and antifreeze theory, I believe you should be looking at grounds. Since we don't know the type of instrument you are using I'd say start with the basics, grounds, sensors then funny green men. I believe you will find your answer somewhere there. Something acting as a capacitor will only hold a charge until propery grounded. The fluid alone will ground the radiator, and shouldn't give off anything. Capacitors in radio equipment discharge rather rapidly unless your running amps etc. Look for a grounding issue, or an instrument fault. Good luck! And keep us posted.

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Old 02-15-2020, 04:17 AM   #13 (permalink)
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Also ya might want to check the battery disconnect, they are notorious for leakage.
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Old 02-15-2020, 11:26 AM   #14 (permalink)
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Quote:
Originally Posted by Caldiesel1 View Post
The fluid alone will ground the radiator, and shouldn't give off anything.
To test the voltage coming from the coolant place one lead from a digital voltmeter in the coolant and one lead on a good ground.

Now try this for grins and giggles. Disconnect the batteries and temporarily ground the two terminals together to effectively ground out the capacitors or whatever you think may be back feeding current. Connect voltmeter leads between the +- cables. Now the system should read zero. Now here is the believe it or not section. > If voltage comes back up disconnect a temp sensor (there are two) Does the stray voltage go away? Sometimes it goes into the wiring through a temp sensor. Should you change the sensor> Maybe.

Some of this info is pure speculation and some of it dead on. Believe it or not!

Most of my stuff comes from out of the box so you may have to do these tests to get to the bottom of it.

Keep in mind if your coolant is carrying voltage that some form of electrolysis is taking place and can't be good for your vehicle.
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Old 02-15-2020, 11:41 AM   #15 (permalink)
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Check coolant voltage with engine running to, shouldn't change but you can figure that out if it does.

Personally I think anything over .25 volts needs to be checked into... .4 volts is considered excessive.

http://www.familyhandyman.com/automo...-a-multimeter/
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Old 02-15-2020, 05:00 PM   #16 (permalink)
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Quote:
Originally Posted by DieselPro View Post
Dang, I'm good! You might find a coolant temp sensor back feeding the current to the wires. It might be bad as well even though it works.
You nailed it. I'm sure the radiator is making voltage and coolant is charged. I have the plastic coolant tank on the firewall. I insert a threaded rod into the coolant and check with a multimeter. With the positive probe on the rod and the negative to ground, it reads -0.025 volts. That seems bassackwards to me but that's how it is. Put the negative probe to the rod in the coolant and the positive probe to ground and it reads as positive voltage.

The positive leads to the batteries are completely disconnected. Now the charge in the truck electrical system is down to 0.03 volts identically stated by two digital multimeters.

I did change the coolant sensor a few years ago with a NAPA part. That doesn't mean it isn't bad again. I will definitely be changing the coolant soon. I siphoned some out a year or so ago to see how it looked and I added a bottle of Wixcool that I had laying around for a while. Not sure why I even wanted to do that since it was a leftover from my old Ford 7.3 IDI. I called Wix and they said it was cool to do. The coolant did look good but I didn't check the pH.
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Old 02-16-2020, 02:42 AM   #17 (permalink)
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Snore.......we went from 10ths of volts to 100ths of volts. I'm not sure what your after here? Got an aluminum radiator? You have electrolysis, got a copper core radiator? You have electrolysis. Not to mention heater cores and hard lines. If you're worried about battery discharge it would take 3 years to discharge a 800 amp hr battery.
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Old 02-16-2020, 11:08 AM   #18 (permalink)
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If this discussion is boring to you, you are cordially invited to quit reading it at any time.
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'94 K3500 Silverado DRW long bed crew cab 4X4 with most of the options
Bought on 3/23/11. Current mileage 161,805
It came with new 6.5L TD Goodwrench crate motor dealer installed at 99k miles and 4L80-E trans rebuild at 135k miles
G80 4.10 rear, 225/75 16 tires
New Stanadyne FSD on 3x6x1 aluminum heat sink, remote mounted above and behind the bumper.
Heath Turbo Master, Hayden SD fan clutch & trans cooler
Diamond Eye 4" exhaust, GlowShift diesel combo gauge. Analog EGT, Digital Boost & Trans Temp
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Old 02-16-2020, 11:03 PM   #19 (permalink)
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SRR. I receive these highlighted posts from the website. I read them to further my knowledge in doing so, I ask questions and give my opinion. I ask the question of what's the end goal to the post because I want to understand the objective, the goal of the final outcome. This is what I've learned so far, it's an older truck, it has an electrolysis issue. You suggested sending units which I believe has merit but my friend DR Vasilio, who is a retired GM engineer says it ain't so. Dr V says to check some of the sensors you have replaced and you'll be surprised. At the end of the day I want to absorb the final outcome to this post, it also made me look at investigating my fleet of vehicles and equipment. I haven't been able to get even close to .03, but I'm still in the process of checking all the water cooled members of my fleet. Since you are not the original poster I'm not sure why you've responded. I know it's politically popular to attack instead of answer the question but you are not in a position to answer the puzzle. It seems to me that you have never gone through a critique, peer review or debriefing, and if you have you forgot the nature to the quest for understanding and knowledge.
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Old 02-16-2020, 11:25 PM   #20 (permalink)
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I had a temp sensors that had opened up on the inside and the coolant was being subjected to 12 volts.

Been so long ago I can't give you any specifics but it is possible.

At the time I couldn't keep a heater core in the truck over a year before it started leaking.

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