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Discussion Starter · #1 ·
Well, I am not sure what to try from here. I just replaced my thermostat for the second time with another Delco 132-55 (GM 14077122), and the truck still will not warm up above 160F. I have a Vintage Air system with a block off valve in the heater circuit, so there is no flow through the heater core unless you activate the heater, which I have not been doing. Its been in the 60s in SoCal, so I would expect the truck should have no problems warming up without a radiator block off.

The truck starts and runs fine, but I am getting ~14 mpg and I think getting the engine up to proper operating temp might make that 1-2 mpg better. Also, it seems like oiling system performance and consequently engine life would be improved at the correct temperature. The truck has got awful mileage for years, but I just recently installed temperature gauges and was previously unaware of the cold running issue.

My water temp gauge reads just over 160F after a long drive (sender in factory location), and the IR thermometer reads 165F at the thermostat housing. Oil temp gauge barely registers at 140F (sender at the plugged boss above the oil cooler lines), and the fittings in the oil cooler lines measure 145F on the hot side and 80F on the cold side. I think I can rule out defective gauges at this point, based on all the readings showing the engine is running cold.

Is there any way the coolant can bypass the thermostat? Am I just getting defective thermostats? I can't comprehend how the engine could run at 160F forever with no coolant circulation...

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Well it could be a lot worse, you could be fighting a over heating truck...

I wouldn't worry about it and be thankful, if you want more heat place cardboard in front of the radiator and carry on and consider yourself lucky...
 

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Mine is cold blooded also. I put my thermostat pickup in the front of the crossover tube threaded hole. I second sctrailrider it could be worse lol.
 

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Discussion Starter · #4 ·
Lol fine, you're right and it could be worse. I just don't understand how it can possibly run below the thermostat temperature if no coolant is being allowed to circulate.

And the truck gets awful MPG, and I think the low engine temperature is partially contributing to that.

The difference between 160 and 195 may not be enough to matter, but lower oil temp will cause higher viscosity and generally poorer engine lubrication. I'd really like to get this running at the design temperature but am not sure what to try. I'm going to block off most of the radiator with cardboard and see if that helps. Hopefully it won't keep my AC from working..
 

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Maybe try to ensure there is not an air bubble in the coolant system
 

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Discussion Starter · #6 ·
What is the best way to purge air from the system?
I usually just remove the radiator cap, warm up the engine, and then blip the throttle while watching for bubbles in the radiator cap opening. When the fluid is moving and there are no move bubbles for 3-5 min, I replace the radiator cap and run it.

Is there a better procedure for this?
 

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Doesnt sound like a bad idea! I usually squeeze the hell out of the top rad hose (when cold) when rad looks full and get a few more pints each time.. Maybe someone else with a different procedure will chime in.
 

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I have a large aftermarket aluminum radiator and I can confirm, my truck is also cold blooded.

I'm considering getting rid of the mechanical fan in lieu of electric fans to help it warm up at idle and low speed driving. The cardboard is a good idea too for higher speed driving.
 

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2007 Klassic CCSB 2500HD. Six-gun w/speedloader, iDash, and EFILive.
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If you really want to know, you can pull the tstat and put it in hot water to verify the temps at which it opens and closes using a thermometer.

My dad's had the same issue but swapping it out with a new one did the trick. The spring was just weak.
 

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Not sure how the Vintage Air system fits into this equation, or how the block off plate might affect anything. When you turn on your heater, does the blower give you hot air? Or have you already got it figured out? And you're right about your mileage. 14 sucks for a N/A 6.2. My 83 gets 20 with 4.10s, SM465, pulling a loaded trailer.
 

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Your engine fan may be the problem. The clutch can fail in the engaged condition and all that cold air will cool your engine down. I've had several fan clutches fail over the years on 6.2, 6.5, and Duramax engines.
 

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I have a large aftermarket aluminum radiator and I can confirm, my truck is also cold blooded.

I'm considering getting rid of the mechanical fan in lieu of electric fans to help it warm up at idle and low speed driving. The cardboard is a good idea too for higher speed driving.
I can promise you the aluminum radiator isn't the issue. My 6.2 had a large aluminum radiator and never had an issue getting to temp. That being said I was running a later 6.5 thermostat housing in my truck. I had a few crappy stats that wouldn't let the truck warm up. The last one I ran was almost the opposite. It would warm up a bit hot then open late and drop it down. Made climbing a hill loaded fun, climb then drop and we were good the rest of the hill!
 

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x2 on the stuck fan and bad t stat or wallered housing.. the fan draws quite a bit of power...double whammy.
 

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Just bought a fan clutch. Nearly
$45 before shipping on rock, searched eBay and got one for $26 us made new in box.
 

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Lol fine, you're right and it could be worse. I just don't understand how it can possibly run below the thermostat temperature if no coolant is being allowed to circulate.
It is circulating, it would be overheating for sure if it wasn't.
Take some temp readings off the cylinder head, like right side rear as this cylinder runs the hottest.

If you want to know for sure, put the thermostat in a pan on the stove and note at what temp it opens. I bet even though it's a 190 degree stat it's opening at a lower temp.
I'd also bet that stat is made in China...
 
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