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Discussion Starter #1
My '95 12v has 260k miles. When on the highway cruising at 60 mph the stock temp gauge slowly climbs up to 190, then pauses and quickly drops down to about 150 (guessing here on the stock idiot gauge). It then restarts the slower increase to 190, pause then drops to 150 again.

What is happening here? Is this normal? I don't really like the thermal cycling that is going on here.

Outside temp was about 56, and I still have my grill plates on. Temp never went above the 190 point. Is my thermostat working correctly?

Thanks

Art
 

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Every 12V i've been in has done it... Only thing I know to do is pull the thermastate.. then good luck getting her to warm up though.....
 

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Discussion Starter #3
Every 12V i've been in has done it... Only thing I know to do is pull the thermastate.. then good luck getting her to warm up though.....

Thanks Nick, I feel better now that it seems to be normal. I'd still like to 'solve' the issue as to what's happening at least. Then work to fix it.

Art
 

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yeah I understand! I drove my moms 95 12v after 3 year and it freaked me out! Until I remembered they do that. And it did it from FL to CO.
 

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there is a tsb on that subject and it states the the oem sensor is very sensitive and with the radiator being so big when the T stat opens it is cooling the ECT alot and it does list a part # but i kinda like knowing that the T stat is working.
 

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Discussion Starter #6
Where is a good spot to plumb in an aftermarket water/engine temp mechanical sender?

That should account for the sensitive factory gauge.

'Kinda reminds me of the small block chevy engine with the single water outlet on the intake manifold. What would happen is one of the heads would be hotter and have more pressure and flow cutting off the opposite side's flow until it heated up more than the now cooling, flowing side. Then the flow sides would swap back and forth all the time. Not very efficient cooling with regards to hot spots etc. The fix was to pull water out of each head independantly from an hole drilled/tapped into the front of the head. Also increased flow on the exhaust side of things which also helped.


Also want to put in an oil pressure and oil temp gauge. Where to plumb???

Thanks

Art
 

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While on the heating cooling subject, last trip I made my temp guage on the dash started dancing then died.

Guess I'm going to focus on the sending unit at the back of the engine. ??

Nice location, at the back behind the fuel filter Afc and a whole lot of other stuff.:thud:
 

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Fluctuation is normal :thumbsup

my Guage reads about 30* low,..

I just replaced the thermostat with the new part number, and i got a new temp sender,... that thing is so far back i cant even reach it,..:CRY:

its in my glove box,....lol
 

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Fluctuation is normal :thumbsup

i got a new temp sender,... that thing is so far back i cant even reach it,..:CRY:

its in my glove box,....lol
I thought it was a rather rediculous location. They could have drilled that hole anywhere.

Pull the engine out to change sensor.:lol3:
 

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They all do the up and down dance. Mine has been doing it since new. I added some wetting agent to the radiator and that evens it out a lot. The oil pressure is not controlled by the computer, as in the newer trucks, it's a standard oil sender/gauge setup so it reads fairly well. Just replace sender if you worry about it. I have a maintenance gauge I use when I want to check it. If it's an automatic, put in a tranny temp gauge rather than oil temp. More useful info. By the way, is the KDP tabbed? If not, do so right now!!
 

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my 96 moves about 20 degrees. i would think if you have 40 degree difference your thermostat is needing to be replaced.
 

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The up and down gauge fluctuations is actually a good thing, it tells me that the thermostat and radiator are working OK. :D

I replaced the factory 190 thermostat with a new Cummins 180, and the needle still does the up and down movements, only now it doesn't go up that much.

I also added an Autometer mechanical water temp gauge, and the readings match up pretty good with the factory dash gauge. I plumed it in to the hot line of the heater core using a brass T, not the best setup but it works.

An easy way to add an oil pressure gauge is to use the plug on top of the oil filter adapter, right next to the turbo feed line. The readings will be about 20psi higher here than at the OEM sensor location on the side of the block, but still you know for sure you have oil pressure.
 

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Discussion Starter #13
The KDP was done by the last owner. He also put in Isspro EGT/Boost/Trans oil temp gauge pod, so less work/oney for that.

I want to get more reliable gauges for the reliability aspect as well as I want to really see what's going on in there with different outside temps and towing loads etc. I'll probably also get a rear diff oil temp as well. Again for interest's sake, and there's some damned long steep hills in BC Canada.

I think there is a oil plumbing point right on the oil filter housing, so that one is easy. I'll have to be more creative with the il temp plumbing into the oil pan, unless there is already an unused Cummins oil temp plumbing point.

I'll try the water wetter soon.

Stock oil temp gauge unreachable... that really sucks. Sounds like originally a Cummins placement where it was previously accessible in other applications, and was never moved until maybe later applications like the 24v change.

So the computer controlls the output to the water temp gauge? Interesting.

Thanks

Art
 

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Discussion Starter #14
The up and down gauge fluctuations is actually a good thing, it tells me that the thermostat and radiator are working OK. :D

I replaced the factory 190 thermostat with a new Cummins 180, and the needle still does the up and down movements, only now it doesn't go up that much.

I also added an Autometer mechanical water temp gauge, and the readings match up pretty good with the factory dash gauge. I plumed it in to the hot line of the heater core using a brass T, not the best setup but it works.

An easy way to add an oil pressure gauge is to use the plug on top of the oil filter adapter, right next to the turbo feed line. The readings will be about 20psi higher here than at the OEM sensor location on the side of the block, but still you know for sure you have oil pressure.
Thanks, I didn't innitially see your post on the second page abou the oil pressure plumbing. Yeah, I'd rather have a more accurate oil prussure to what the bearings are seeing.
 

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What exactly is a KDP?
 

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What exactly is a KDP?
KDP = Killer Dowel Pin.

There is a dowel pin that locates the timing gear box to the block that wasn't a tight enough press fit. It sometimes vibrates out and falls into the timing gears ... thus the name. If you are lucky, all it will do is break out the side of the timing gear box.

This is the very first thing that ought to be fixed before other modifications.

There are a couple ways to fix this before it falls out. One method can be done without even pulling the timing gear box cover, but it requires a jig to locate the place to drill a hole in the side of the timing gear box.

Do a search on "killer dowel pin" and you will get hits.
 

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i have the same problem except that on my 98 i start the truck and the temp just sits on 140 and after like 30 mins of driving it will slowly raise up inbetween 140 and 190 then creeps back down is this normal???? does anyone elses sit at 140?? thanks
 

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mine goes up and down too... but only since I got a new radiator!!!
 

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i have the same problem except that on my 98 i start the truck and the temp just sits on 140 and after like 30 mins of driving it will slowly raise up inbetween 140 and 190 then creeps back down is this normal???? does anyone elses sit at 140?? thanks
Yea, mine reads low,...140-165 and moves slower after i installed the new thermostat,
i have a new temp sender but it looks like a pain to install so i am putting it off,....lol

.
 

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I think that the gauge fluctuations are due to the sender being located away from the thermostat
 
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