Since it was 10F this morning and going to be the same or colder tomorrow morning I figured I will get some statistics on how well a winter front works. I want to get mileage and time as to how long it takes to hit 190F. I will do a constant 55mph for these tests and be on the road within a minute of starting.

Today was without a winter front going straight into 20-30mph headwinds at 10F. Although synthetic oil seemed to not do anything at 20+F, you will notice that it cranks slower now that the conventional oil I am running starts to get really thick, you can even see how long it takes for it to get oil pressure. So synthetic does have it's place in the colder temps.

My EGT's were around 680F at 55mph when the engine was still under 130F, this proves how thick oil and cold surfaces make an engine have to really work. On the return trip with the engine at 190 and still at 55mph, the EGT was around 400F.

http-~~-//www.youtube.com/watch?v=vvVo4QMXX4Y

For some reason I read your posts as you referring to that little hose as the bypass.. Whoops!The spring may look like its good, but I am quite certain its fatigued. I highly doubt water flow is stronger than the spring. When I changed my OE thermostat it looked no difference, and felt no different than the new OEM one, but it sure works a whole lot different. You may never find out what is actually wrong, other than its worn out. The reason the temps read different is sensor location in relation to coolant flow with the bypass open, or closed is a little different (at least I would presume so).

For some reason I read your posts as you referring to that little hose as the bypass.. Whoops! The spring may look like its good, but I am quite certain its fatigued. I highly doubt water flow is stronger than the spring. When I changed my OE thermostat it looked no difference, and felt no different than the new OEM one, but it sure works a whole lot different. You may never find out what is actually wrong, other than its worn out. The reason the temps read different is sensor location in relation to coolant flow with the bypass open, or closed is a little different (at least I would presume so).

My guess is that is was crap from new (something I read about more often with non-OEM thermostats). That photo is from the service manual I downloaded from the downloads section.

I'm not talking about your external bypass, but the internal one. When the thermostat is closed the bypass takes the coolant from the head and feeds the water pump thru a passage. When the thermostat opens the thermostat will block that bypass and force the water pump to suck from the radiator, when thusly pulls coolant from the head. If the 5.9 V8 doesn't have the same internal casting it wont operate the radiator bypass properly. $30 vs 8$.. how much do you value your time? Even at minimum wage your time has exceeded $22 worth of labor. The symptoms you are describing are classic failed thermostat, high temp spikes and swings. I didn't realize it opened late, so weak may be the wrong term, so maybe slow is better.. My original tsat was very slow to react, big spikes, but it never dropped below 180*.

Where are you getting the 180* temp from???? I know for a fact, that my truck will cool down to 160* or less if I let it idle in real cold weather. I still have the OEM stat..........yeah, it's 6.5 years old!!!! When I had the Juice W/Attitude on my truck, it monitored engine temp. When I would start her up cold, the engine temp would go to about 203-204* before you'd see the temp drop.......which would be the stat opening. I could see the same on the OEM idiot gauge. From there it would osscilate back and forth a bit until the system "equalized" a bit. Equalized is not a good word, but it's all I can think of now. I wish I could keep my trucks temp at 180+ without the high idle kicking in!!

Without a fan, I can keep it at any temp I want idling, it slowly warms up and will eventually hit 210 (as high as I let it go while testing that theory, and that was at 10F). BUT, if I turn the heater on full blast, it will drop down to 160 eventually. It would be neat to have some sort of thermostat on the blower motor since full blast will cool it and leaving it off will let it heat up and I don't want to sit in there monitoring it to keep it right at 190.

Electric Fans?

No I want the blower motor in the cab to be my "electric fan" while idling. What fun is an electric fan on the radiator that everyone else has, plus it will be heating the cab rather than the atmosphere. Its pure genius

No I want the blower motor in the cab to be my "electric fan" while idling. What fun is an electric fan on the radiator that everyone else has, plus it will be heating the cab rather than the atmosphere. Its pure genius

I wonder what your going to do in the middle of summer towing a heavy trailer and its 110-120*F outside???

and you coke up your bearing on the turbo cuz you didnt idle it down..be surprised on how many people dont know to do that.....wether they have owned diesels before or not...lot of people have told me that they didnt know that...just saying....

--- Update to the previous post...

What hose? The little 5" long hose that goes from the top of the thermostat to the upper radiator hose? That hose is for bleeding the air out. Has a fancy fitting on the end.. I have a movie on it earlier in this thread..

The thermostat that is junk has 2 springs and 2 discs, the one that goes in the housing, and the one that goes in the bypass. Now what I want to confirm is that when the engine is cold, that bypass should be OPEN, so the disc should be pulled back and out of the way and not sealing it off, right?

Then as the engine gets to 190 and the thermostat opens, the opening motion pushes the whole middle of the thermostat including the bypass part so that the small disc is pushed up against the bypass to seal it off, right?

Now, I put the temp probe where that bleed hose is so it is right on top of the thermostat, I can stick my finger in the hole the probe is in and touch the thermostat. I put the junk one in and drove. As you can see in the video, the sensor on the back of the head goes to 220 or more, but the other sensor I am talking about (one on the floor) that is by the tstat never got over 200, and when it opened it would only drop to 175. It takes a while for the wax to cool as I noticed in the boiling test, but it was 200 for a long time which it should have been partially open, but for some reason it seems like it just pops open all the way.

I am going to let the truck cool off and run the same test with the good tstat.

Hmmmm, crazy idea here. Is there a chance that the tstat cracks open partially like it is supposed to do, then is somehow forced open by water pressure or anything? Then the temp just gets so cold it finally has enough force to pull it shut. Is that what you meant by faulty spring? It seems to be just as hard to push as the other one but I don't know if something else is happening with it when it gets heated up.

http-~~-//www.youtube.com/watch?v=lCQWbdOIpnI

Yes I know White01, read my posts.. I am not looking for the right thermostat I know which one is right I am trying to figure out what is wrong with the one I have. Readddd my posts! I've reiterated everything 5 times.

iiiight....i have read and read and read them...figure i would help out with the scratching of the head ...what is wrong with it...:moon::lmao: weeeeee haaaawww!!!!

http-~~-//www.youtube.com/watch?v=lCQWbdOIpnI

Good lord that has a wide and wild swing too it...

that's what i thought...that is quite the shock to the system huh?hot to a cooler temp?

that's what i thought...that is quite the shock to the system huh?hot to a cooler temp?

Even my older NAPA stat only gots to maybe 204*F then pops open suddenly and falls to as low as 188*F one time... After that it hang right at 193-197*F...

I watched the video again, I really think its just a faulty thermostat, and maybe a slightly sensitive gauge. On a side note, get an alignment and fix your brakes!

Turn the truck off because I will have no reason to leave it idling because the engine will stay warm.......................You accommodate your needs based on the season, same as you having to take your winter front off when summer hits

Running without a fan in summer is bad ju-ju!

No I want the blower motor in the cab to be my "electric fan" while idling. What fun is an electric fan on the radiator that everyone else has, plus it will be heating the cab rather than the atmosphere. Its pure genius

relay in an adjustable thermostatic switch, like those for electric radiator fans. Then, you can set your temp you want the fan to switch on/off. Put it on the HIGH setting wire. Like this: http://www.jegs.com/i/JEGS/555/52125/10002/-1 Additionally, ISX.. Have you tried another 'new' tstat from the same manufacturer of the 'junk' one? Just comparatively testing two of the same?

relay in an adjustable thermostatic switch, like those for electric radiator fans. Then, you can set your temp you want the fan to switch on/off. Put it on the HIGH setting wire. Like this: http://www.jegs.com/i/JEGS/555/52125/10002/-1 Additionally, ISX.. Have you tried another 'new' tstat from the same manufacturer of the 'junk' one? Just comparatively testing two of the same?

I need that temp switch! No I haven't tried any but the 2 I had. Seems like it is hit and miss if they work properly or not.

so, to add to this thread, I replaced my thermostat Saturday. (must say, it took all of 2 minutes, and I think I lost about 4 ounces of coolant, at most..)I drive about 6 miles to work, and the truck never leaves 140* COLD mark, even if I plug it in.The old tstat looked fine, and wasn't stuck open, like I thought it might be. Oh, the Stant tstat, $30 at Manny, Moe and Jacks.. At least it came with a new o-ring gasket.. whoopty-freakin-doo..So, I drove in to work this morning.. By the time I got to the jobspot, it was ~170-180*F. YAY! That's in 24*F temps, and being plugged in last night. Tonight, I'll not plug it in, and see what it does tomorrow, as it's supposed to be a repeat of today.BTW, the old tstat: I might try to test it tonight, if the wifey will let me put the tstat in one of her pots.. I'll add pics shortly.

This is what came out of the truck. I failed not getting a pic of the one that went in. It looked different.. No lower disc, and the valve-portion, or actual "gate" was much narrower.

Sent from my HERO200 using Tapatalk

I took the thermostat out one time and mine did the same thing. Went 7 miles and just barely moved the gauge, it was still under 140 in 80F weather. I doubt your thermostat is stuck open though. How fast are you driving? I just went to town and back at 30-40mph (snow) and I just barely made it to 190 after 20 miles. Once the engine is warmed up, they don't seem to have much problem keeping warm as long you don't run the heater on full blast. I was on the interstate once and I don't have a fan on the engine and I pulled over for a bit waiting on someone and I didn't have the heater on to dissipate any heat. Just idling it was building heat (it hit 210F eventually), and it was only 10F out. Maintaining heat and getting it hot are 2 different things. I can pull a trailer and get it hot in a few miles or I can drive like I did today and the engine just doesn't work hard enough to get hot, plus having the heater on full blast takes heat away from the engine also. Let us know how you drive for those miles to work, it could be a big factor.