Ok, so I replaced my water pump, t-stat, housing, hoses, belt and added coolant filtration. Went from stock (I think) to the 203 stat. Oh yeah, changed to the red Prestone HD ELC. I have an Edge Insight and added a coolant sensor to see the actual temp. Is it normal for the coolant and oil temps. to be nearly the same? The other day it was about 40F and both temps were running 195 to 205. Even when driving 'easy' on the way home from work the oil was around 200 when I got home, and leaving it idle for 5 min. doesn't really drop the temp. much. I was under the impression that's a little high for the turbo when you shut the engine off? I'm not sure exactly how the fan clutch works either, but I've noticed that the fan is spinning all the time, is it only supposed to spin at high temps? I bring that up, b/c I was wondering if it is bad or was damaged when I changed the water pump? Any insight would be greatly appreciated. Thanks all!

 

I would expect coolant and oil temps to be fairly close due to the oil cooler (oil/coolant heat exchanger). It's normal for the fan to spin when the engine is running. When the temps get a bit warmer, the fan is designed to lock up and you will definitely notice a difference in sound.

Out of curiosity, why did you choose to go with the 203 t-stat? I believe I've read a few posts here and there where folks have had problems with the non-OEM t-stats (something about the stem length or maybe some other issue....)

 

you water should be about 203, and the oil will be close.
i will not go to the 203 because it is so hot here and will make the oil hotter and degrades it faster.

 

From what I have heard it is for better fuel mileage, I am like you I would rather have my truck run cooler. It is hot enough out here most of the time.

Here is the .pdf link from Dieselsite. http://www.dieselsite.com/pdffiles/fuelmpggains.pdf

 

i think the 203 is like other mods some like it others dont.

 

If you can get temps at the turbo down to 200 degrees before you shut it off your doing great! Good luck with that though. Install a egt gauge before your turbo and those 200 degree temps your seeing will seem low. I will let mine idle, if it's been working hard, to get the temp down to 300 or just under. During driving your turbo is seeing temps all over the place sometimes over 600-800 derees, higher if towing heavy.

 

I was meaning more toward oil and coolant temps. not EGT's, but your info. is good to know also. thanks.

 

Those temps are normal, it is for me and my 203*, its been in my truck for about 75,000 miles now. As for mileage gains, I've never noticed anything, to many other factors play into it for me personally, fuel condition (BTU's) heavy foot, idling, speed, exct. As for the stem sizes, Dieselsite sells the correct size thermostat for our trucks so anywhere else for the 203* I'd measure.

 

There was a guy on here that heated the oem and 203 stats in boiling water. The oem opened all the way, the 203 didn't. He had more than one to so I thought I'd just pass this along.

Chet

 

I think I know why some people claim slightly better fuel economy with a warmer engine. I just found this information today - bear in mind it's for big rigs, but the concept is the same.

 

so what is a good oil temp. to safely turn the truck off? I understand that too hot oil temp. at shut off is bad for the turbo.

 

Just turn it off... Todays oils do NOT coke like older oils do.

How many MILLIONS of trucks out there that are run harder then ours, and they have no gauges... They pull into the rest stops and shut down.

Turn the damn thing off.

If you have run it hard pulling all day then give it a few minutes to calm down and turn it off.

 

As others have noted on living in high temperature climates, I also live in an area of high desert were temps can reach over 100 for as much as five months a year. A few days ago it was 85 and its only February. I just purchased a stock thermostat but I am wondering if removing the thick insulation from the hood would aid in ventilating the engine compartment and possible help to keeps temps down.

 

It will not help... Mines gone, but only because it was torn to shreads from blown IC boots at 45psi+...

 

Like Joe (CSIPSD) mentioned. Coking oil is the concern. The temperature of the oil is only partially significant. The idea is not to shut the engine off when the turbo is really hot. If the turbo is really hot when you shut it down the heat transfer on the shaft and bearings will heat the oil coating them (which is no longer flowing). This can lead to coking. The newer oils do not have problems with this like in the past. Coking is basically like cooking the oil with hot parts. If the part is really hot, it will breakdown the oil and sear it on the parts.

Here is a good explanation: Coking Oil, Coking Oil 2

Due to the wheelbase on my truck I usually back into most spots. I have found that the time it takes to stop, throw it in reverse and park is plenty of time to get the temps down to under 400*. Unless you pull a long hill, then shut it off at the top, you will most likely not ever see a problem.

Here is a picture from an OBS Turbo I rebuilt. There is a slight amount of coking on the area closest to the turbine wheel. Beyond that there was little to no signs of coking at all. So you are pretty safe in just shutting it off.