temp gauge fluctuates
 

OK I'm curious how accurate the factory gauges are. I've got a 98.5 24v 3500 , when on the freeway the gauge fluctuates between about 170 and 200, usually it'll stay right at 190 but sometimes it goes up a little and cools a little. I'm more curious if its a bad gauge or if I'm having real cooling issues that need addressed. any advice is helpful. I've got an aftermarket gauge to put in I just haven't yet because I'm trying to get all 3 first before I put them in.

When mine started doing that kind of shenanigans it was a bad thermostat. I have a scan gauge ll and it shows the OEM gauge to be pretty darn close.

I had a sneaking suspicion that it could be the thermo. Sounds like I should look into putting a new one in. And may as well instally gauges while I'm at it.

The ScanGauge II, like Russ said, it a very nice setup. I would look into it, it also has some very cool features at a reasonable price.

I'll look into that as well. eventually I'd like to have a programmer that displays all that important stuff but for now I have aftermarket gauges.

edge juice with attitude will display engine readings..

my adrenaline with pulse monitor shows engine readings too.

some temp fluctuation is normal.

pretty common to see a good 10+ degree drop in coolant temps when the tstat opens then closes... these trucks have an overkill cooling system that works almost too well.

if you have ever got your truck fully warmed up and gone under the hood, you will notice that one half of your radiator gets warm, but the other half of it is cold to the touch... they work amazingly well at dropping the coolant temps to ambient air temps when they are clean :tu:

that rush of cool liquid causes engine temp to drop fairly quick. As for gauge accuracy: the factory gauge is electronic. it merely displays what the ECM is reading from the sensor.

all gauges on your dash are digital gauges, they just display analog style. so gauges are only as accurate as the sensors telling them what to display.

That's good to know. I just don't want to blow a head gasket. I can't afford that shit at the moment. Would the fact its been in the teens and twenties the last week or so have any affect ?

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And also its not the cooling off that bothers me its when the needle goes above 190, I've had bad luck with cooling systems in the past so when I see it move above 190 I get stressed out lol

mine goes up to 205-206 then drops to 190 and starts back up again lol

That's basically what mine is doing. like damn near exactly what it does lol

Duracrap tstat purchased, will be installing tomorrow. Also going to pull my radiator out and clean all the crap out of the fins, I think that might have a little to do with my issues too.

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New thermo is in an working correctly , sadly this did not fix my issue, but after having a friend use his laser thermometer on it we've discovered that the sensor is the culprit. New gauge will get put in next weekend and if that doesn't fix it then I'm out of ideas.

So who can help me figure out where the sensor is that runs my gauge, I've hear its a single wire on the back corner of the head, but I can't find any wires or sensors on it that could be it. I've found a large plug in the head that I've heard is where its supposed to be, any info is helpful I need to figure this out asap.

Better buy a Cummins Tstat or you'll be replacing it again.

I'm not concerned with the thermostat at the moment i got the failsafe one so at least it'll fail shut if it fails. that doesn't answer key question about where the other sensor is.

Well truck finally threw a code tonight. P0118. Ect voltage high input. Basically the wiring is jacked going into the plug and needs fixed. not to worried at the moment since I'm wiring my glow shift setup tomorrow.

ok so got the glowshift gauge hooked up and the temperature is still fluctuating, except tonight on my way home from work it hovered just under 200, then dropped to 180 and stayed at 185 for the rest of my drive ( 40 minute drive, did it around 25 minutes in). can you guys think of anything, i've bled the system 3 times. im starting to think either my water pump is about to shit the bed, or i have a blockage somewhere. I have no loss of power, no white smoke, and the coolant has never gone over 200 on my gauge. any help is appreciated, im really not wanting to do the HG but i will if i have to.