DAM YOU T-STAT??? help with wierd coolant temps - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 11 (permalink) Old 11-27-2007, 11:36 PM Thread Starter
 
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DAM YOU T-STAT??? help with wierd coolant temps

Ok my truck is doing some wierd ****.
Its a 06 lbz gmc and it has 40k on it.
The temp gauge in the dash started fluctuating the other day it never usually goes above the 180? mark (the next mark up from 160) . I was towing so i considered it normal even though its never happened before.

So i unhook the trailer and go out for a bit and again the temp gauge is reading in the 12 o clock position with no load in the bed and trailer unhooked it will go from the 180 mark then to 12 oclock then back down then up again then back etc etc. So I check the coolant level its perfect check coolant color again perfect.

I then realized i can monitor coolant temp through my six gun so i put that on the gauge will read in the 12 o clock position but the six gun will show a temp at 180-186 max this on the highway with 38-50 degree ambient temps.

I dont know where the hell to start because normally if its a tstat it gets stuck open not shut??? Could it be the sender?
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post #2 of 11 (permalink) Old 11-27-2007, 11:37 PM
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Quote:
Originally Posted by germantoy
Ok my truck is doing some wierd ****.
Its a 06 lbz gmc and it has 40k on it.
The temp gauge in the dash started fluctuating the other day it never usually goes above the 180? mark (the next mark up from 160) . I was towing so i considered it normal even though its never happened before.

So i unhook the trailer and go out for a bit and again the temp gauge is reading in the 12 o clock position with no load in the bed and trailer unhooked it will go from the 180 mark then to 12 oclock then back down then up again then back etc etc. So I check the coolant level its perfect check coolant color again perfect.

I then realized i can monitor coolant temp through my six gun so i put that on the gauge will read in the 12 o clock position but the six gun will show a temp at 180-186 max this on the highway with 38-50 degree ambient temps.

I dont know where the hell to start because normally if its a tstat it gets stuck open not shut??? Could it be the sender?
Are you still under warranty?
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post #3 of 11 (permalink) Old 11-28-2007, 01:16 AM Thread Starter
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Unfortunately im over my warranty so the dealer said since the truck has 40k on it
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post #4 of 11 (permalink) Old 11-28-2007, 12:49 PM
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It is normal. The needle is fairly sensitive in a narrow ECT range from 170-190. There is a 5 degree segment where the needle will move more than it should. You are just straddling that area.

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post #5 of 11 (permalink) Old 11-28-2007, 06:24 PM Thread Starter
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Is it strange that this is happening now with 30-40F degree temps outside?? What can I do to remedy this?
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post #6 of 11 (permalink) Old 11-29-2007, 02:19 AM Thread Starter
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also my gauge will read a couple ticks over 160 but yet the coolant temp from my gauge will be reading 120-140 this is from a cold start to warm up.
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post #7 of 11 (permalink) Old 11-29-2007, 12:46 PM
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It happens when cold because your thermostat is staying closed most of the time, as it was designed to do. When it cracks, there is a cold surge, due to the radiator being supercooled in that time. You are watching the stat open and close. It is not a bad thing, but admittedly GM should have deadened the gauge in that range.

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post #8 of 11 (permalink) Old 11-29-2007, 03:00 PM Thread Starter
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Bee as always you have been super helpful yourr a gentleman and a scholar thanks
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post #9 of 11 (permalink) Old 11-29-2007, 03:15 PM
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There is something you can do. If you drill a 1/16" hole in one of the thermostat flanges, you will keep a slight amount of coolant moving through the radiator. That would reduce the cold surge when the stat cracks open.

If you had the scan gauge you could see the actual ECT that is causing the oem gauge swing, it would likely be reading between 175-180 IIRC. It is an odd latency that a lot of manufacturers fix by designing a small bypass hole into the thermostat.

Be careful not to drill a larger hole, because then you will run cold.

The other solution is to don a winter front.

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post #10 of 11 (permalink) Old 11-29-2007, 07:31 PM Thread Starter
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ya i just thought it was odd that it was running the warmest ive seen it, in the coldest season that ive owned it (bought in june)
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