It was 21 degrees here this morning, and when I go to start my truck I scroll to the oil temp display, and my oil temp is only 34 degrees? Can anybody else comment on my possible low reading?

 

Unlike the 7.3 where the block heater heats the oil, the block heater on the 6.7 is attached to the water jacket. Most of your oil is lying in the bottom of the pan all night so will be closer to air temp.

jammer

 

Imagine that you had a 900 watt kettle(most draw about 1500) and that the kettle was about 750 lbs of compacted graphite iron filled with 28 quarts of liquid, exposed to a temperature of 21 degrees and a possible wind chill. I do not think you should expect much more of your block heater.

 

-37 here, and the truck starts (plugged in) like it was 70.

--
Gordon

 

Our temp last night was 11 degrees. Truck plugged in oil temp at start up was 48 degrees. Truck sat outside at work today for 10 hrs not plugged in,temps were 19 degrees, on start up oil temp was 27...interesting thing is my tran temps seem to stay very close to oil temps.....so far anyway....only has 350 miles...we'll see.

 

I understand that the heater is not going to keep the engine hot, but I was expecting something more than that. Only a 10 degree swing between ambient temp, and oil temp? My tranny temp was only 1 degree off of the oil. If the heater is working then shouldent the oil in the motor be warmer than in the transmission? Or does it warm the trans too?

 

In the first reply to your thread Jammer did a great job explaining why the oil temperature is so cold.


The block heater warms the primary cooling system, which in turn is also responsible for transmission cooling. It would make sense that convection would provide a small degree of circulation that may or may not slightly warm the transmission cooler. Not sure.

But as far as engine temperature, believe me the engine is getting warm. I can track coolant temperatures with my ScanGauge. From this I can tell you that three hours on the block heater at 0 degrees F will yield an engine(coolant) temperature of over 60 degrees.

And with the coolant at 60 I may see an oil temperature of 15-20 degrees. This is normal.

The block heater is heating your engine, you're simply looking at the wrong gauge.

 

As stated in a previous post, the block heater heats the coolant in the block and not the motor oil which sits in the pan below the block. What you are witnessing is perfectly normal for a "block" heater. If you want warm oil then you will need to invest in an oil pan heater, but since our pans are composite plastic, i am not sure that such a beast exists yet that will remain attached to the pan.

 

I wonder why a oil heater is not used? Guess it's not needed. On our Cummins Engines (ISX) they have both oil and coolant heaters.

 

It would be nice but I don't think it's needed. Remember that adding an oil cooler to a composite pan would be more costly.

I believe the primary purpose of a block heater is to keep the combustion chambers from getting so cold that the fuel doesn't want to ignite.

I've started mine at -10 with and without the block heater, and there is a noticeable difference. For me the block heater is simply a tool to get better fuel economy, as this engine really doesn't need it for the vast majority of the temperatures we see up here in the winter time.

 

I was curious what my block heater would do during our cold snap here in Houston. I plugged in the block heater a few hours ago just to see what, if any, temperature differential there might be. I read this thread and went out to the truck to see if there was any effect to be detected by using the block heater.

Right now ambient temperature is 31F with a stiff North wind. My transmission temperature is 19F and my oil temperature is 51F per my Information Screen. I did not start the truck. Hopefully this information does not cloud the issue.

 

I have not plugged my truck in to date. It has started nicely down to zero. Tonight's forecast is for -10 or so. I will be plugging in tonight.

Regards

 

It was -12 here last night. I had engine heater plugged in all night.
I checked oil temp before start up, it was 28.
60 seconds after I started the motor, it shot to 90.

Clearly the heater is working, the temp sensor for the oil just isn't seeing it until the motor circulates the oil.

 

I was thinking about this a bit last night as I was standing in a 40 mph, 15 degree wind. It is interesting that they decided to heat the water jacket. By design it draws heat away from the engine. I am willing to bet that things like orientation to the prevailing wind has a big impact on the temperature delta you can expect to see over ambient.

Think about that big radiator facing into the wind, cooling down all that heat a 900 watt heater can produce. If the "block" heater is only heating the water, I wonder what impact the near frozen oil has on providing sufficient lubrication during that critical start-up period.

From my experience flying small airplanes, the goal was to get that oil warm enough to insure that during the first couple of minutes of operation we could get pressure and flow to the critical elements. Wonder what is different on a truck engine?

 

It doesn't work like that.

Remember that the thermostats are traditionally connected to the upper radiator hose, which comes into the water pump from the top side. Convection is going to push the hot water to the upper areas of the engine where it will be blocked by two closed thermostats. The only way warm coolant could get to the radiator is if there was heating action near the bottom of the block so that warm water could work it's way down the lower radiator hose.

But the block heater isn't at the base of the engine, it's in the passenger side cylinder bank. Presumably for this exact reason.

Block heaters always heat the cooling sytem and are VERY common on diesel engines of all shapes and varieties. Oil pan heaters are also common, but much less so than block heaters.