Thermostat

[AH64ID]

Yes there was a TSB that converted it from a sender to a switch. 

 

@Mopar1973Man have you ever had a smarty on your truck?

[Mopar1973Man]

15 hours ago, AH64ID said:

Yes there was a TSB that converted it from a sender to a switch. 

 

@Mopar1973Man have you ever had a smarty on your truck?

Once long time ago. Still to this day the CCD network tool, mechanical gauge, and dash cluster all appear to agree. Only time the pressure is questionable during the use of my high idle switch.

Edited January 11, 2018 by Mopar1973Man

[AH64ID]

3 minutes ago, Mopar1973Man said:

Once long time ago. Still to this day the CCD network tool, mechanical gauge, and dash cluster all appear to agree. Only time the pressure is questionable during the use of my high idle switch.

 

Interesting. My understanding is that the Smarty will apply the TSB for a switch and an algorithm based dash gauge. I wonder if you have it and it's just closer than current trucks are.  I do know that the 2nd gen's I've seen aren't nearly as inaccurate as the current flash for my truck. 

 

I know that when I bought my truck it was more accurate than it is now, and actually fairly correct 80% of the time. There was a update in one of the software revisions that modified it's operation again and now it's only accurate on a warm motor at about 1300 rpms. 

[kzimmer]

I hate that they did that.

[Dodgeih]

Mine has  had a smarty and my oil pressure seems to work as a sender rather than switch. I have not had the most recent Flash from Mopar. Also this. Just kind of crossed my mind. there are kind of two things I was thinking about oil temp. does anyone have any idea what oil temps a loaded semi truck runs? And also when these trucks were made when these trucks were made synthetic, or conventional oils for that matter we're not nearly as advanced as they are now. I feel that they can withstand a little higher temperature than oils 20 years ago. and also for that matter typically pickup trucks with diesel engines get their oil changed way sooner than then the oil needs to be changed anyway.

[dripley]

My 02 oil pressure gauge has always acted like it is reading the true pressure, but from my reading here I was convinced it was a product of the ECT and rpm making it look that way. I seem to remeber a video of the early mpg fooler here and when it was turned on and the temp gauge changed so did the oil pressure. @Mopar1973Man was that not you that i learned that from?

[Mopar1973Man]

ECT has a effect on the oil pressure reading when colder. But comparing the actual oil pressure, CCD network message and the cluster the number are fairly correct till the engine is cold. Then the oil pressure reads high when the ECT is fooled even though the oil pressure is actually lower. Normal run though it good enough for indication of pressure.

[AH64ID]

9 minutes ago, Mopar1973Man said:

ECT has a effect on the oil pressure reading when colder. But comparing the actual oil pressure, CCD network message and the cluster the number are fairly correct till the engine is cold. Then the oil pressure reads high when the ECT is fooled even though the oil pressure is actually lower. Normal run though it good enough for indication of pressure.

 

 

So yours doesn’t display actual pressure. If it’s ever false it’s the flash. 

 

It may indicate in the proper range when warm but there will be no warning of a low oil pressure condition. Generally speaking it’s not an issue on these motors thou. 

[Dodgeih]

@Mopar1973Man if it worked as a switch, when the ecm was fooled with the high idle switch in 6cyl mode, wouldn't the oil pressure rise on the dash, just like the temp falls? If it worked as a sender then the op would be unchanged with any position on the high idle switch..

[Mopar1973Man]

1 minute ago, Dodgeih said:

wouldn't the oil pressure rise on the dash, just like the temp falls?

 

Yes. It does show a rise even though real pressure doesn't change. This the only time I see skewed numbers. As long as the temp is not fooled then the numbers appear correct. 

[AH64ID]

19 minutes ago, Mopar1973Man said:

 

Yes. It does show a rise even though real pressure doesn't change. This the only time I see skewed numbers. As long as the temp is not fooled then the numbers appear correct. 

 

They may appear correct but it's still a useless gauge, and that's what sucks with how Dodge/Ram does it! Oil pressure could be 10 psi at 2500 rpms and you wouldn't know until it was too late. 

[pepsi71ocean]

On 1/9/2018 at 4:37 PM, AH64ID said:

Since there is all the talk about 200° thermostat's I'll chime in. 

 

Dodge/Ram went to a 200° thermostat with the MY10 trucks. This was done to help increase fuel mileage,  and presumably reduce emissions/regens. 

 

The hotter the engine the more efficient a diesel engine should be. For this reason I always said that I would switch to a 200° thermostat in my truck once we had fan control with UDC. 

 

Well we have UDC fan control and I will not be swapping out to a 200° thermostat. Dodge/Ram only ran the 200° thermostat for 3 years and that made me wonder why, especially since it should yield a more efficient truck. 

 

So I started doing a little research and the only thing I can come up with is that while the motor might be slightly more efficient the oil temps got too high while towing and they were seeing oil issues related to heat. There is nothing definitive thou. Oddly enough when the trucks went back to a 190° thermostat they also got an oil temp gauge (thou I cannot determine if they are real or fake). The newer trucks also have a much more aggressive fan schedule than the older ones, that keeps the coolant and oil temps lower. 

 

On a 2nd gen, or a non custom tuned 3rd gen, you won't have the ability to change the fans lockup temp and a 200° thermostat will cause the fan to operate more even thou the temps are in the normal range for a hotter thermostat. 

 

So that's my 0.02. 

 

 

 

I will say this, I have done some hauling with the 200F in the truck and I've yet to see anything over 210 for a open temp. and even so towing heavy stuff I see 197-202 with my 200F t stat in.  The highest continual use I saw was towing a flatbed along I-78 from Reading PA to new jersey with my coworkers ford exploder on the back, and that was 215 at 70mph, under full boost.  But it never went over that, and quickly dropped back to 197-202 when on flat ground. 

Conversely Our freightliners routinely see 220-230F climbing the same grades.

 

Granted i do believe that the volume of coolant and the efficiency of the system is more then the load I put on the engine, but even towing a 12,000lbs 5th wheel camper this September I didn't notice anything abnormal, even with the 200F in. 

 

Even so, I do believe that for most of us here, a 200F will benefit more then it could do harm, and the GVWR of the engine and the coolant system as @Mopar1973Man man has said vastly exceeds the capacity of our trucks. 

[AH64ID]

54 minutes ago, pepsi71ocean said:

 

I will say this, I have done some hauling with the 200F in the truck and I've yet to see anything over 210 for a open temp. and even so towing heavy stuff I see 197-202 with my 200F t stat in.  The highest continual use I saw was towing a flatbed along I-78 from Reading PA to new jersey with my coworkers ford exploder on the back, and that was 215 at 70mph, under full boost.  But it never went over that, and quickly dropped back to 197-202 when on flat ground. 

Conversely Our freightliners routinely see 220-230F climbing the same grades.

 

Granted i do believe that the volume of coolant and the efficiency of the system is more then the load I put on the engine, but even towing a 12,000lbs 5th wheel camper this September I didn't notice anything abnormal, even with the 200F in. 

 

Even so, I do believe that for most of us here, a 200F will benefit more then it could do harm, and the GVWR of the engine and the coolant system as @Mopar1973Man man has said vastly exceeds the capacity of our trucks. 

 

Yes likely it does no harm, but without an oil temp gauge it's nearly impossible to say. 

 

The biggest negative effect you'll see is excessive fan operation, especially since 99's came with 180° thermostats. 

 

Fully open on the 200° thermostat is about 215-217°, so that's why you hit 215° and stayed. The 4th gen trucks with 200° thermostats start to cycle the fan at 212°, but I bet your starts engaging around 195-200°. Since it's not ECM controlled you likely won't see much engagement when empty, but as soon as you apply a load the fan will be working a lot more. 

 

Yes the cooling systems are pretty darn large for these trucks and can support around 400-450rwhp sustained. I've been WOT for 5-6 miles at 23K GCW up a 6-7% grade running 2500 rpms and my ECT didn't hit 215° ( I engage the fan at 208°), and Cummins says I can run it up to 225° before running out of heat rejection.  I'm really curious what oil temp will be on those same long pulls. 

 

[pepsi71ocean]

7 minutes ago, AH64ID said:

 

Yes likely it does no harm, but without an oil temp gauge it's nearly impossible to say. 

 

The biggest negative effect you'll see is excessive fan operation, especially since 99's came with 180° thermostats. 

 

Fully open on the 200° thermostat is about 215-217°, so that's why you hit 215° and stayed. The 4th gen trucks with 200° thermostats start to cycle the fan at 212°, but I bet your starts engaging around 195-200°. Since it's not ECM controlled you likely won't see much engagement when empty, but as soon as you apply a load the fan will be working a lot more. 

 

Yes the cooling systems are pretty darn large for these trucks and can support around 400-450rwhp sustained. I've been WOT for 5-6 miles at 23K GCW up a 6-7% grade running 2500 rpms and my ECT didn't hit 215° ( I engage the fan at 208°), and Cummins says I can run it up to 225° before running out of heat rejection.  I'm really curious what oil temp will be on those same long pulls. 

 

I don't doubt, but I've rarely heard the fan lock up up here.  I though all clutches locked up at 215/220?

[Mopar1973Man]

12 minutes ago, pepsi71ocean said:

I though all clutches locked up at 215/220?

 

That about when my fan locks. 

[AH64ID]

212°  Is the max allowable temp with a 180° thermostat, from Cummins, so that seems high. 

[pepsi71ocean]

On 1/12/2018 at 4:49 PM, AH64ID said:

212°  Is the max allowable temp with a 180° thermostat, from Cummins, so that seems high. 

 

Except our clutches are based on radiator temperature. That radiator needs to start passing heat past the clutch first. 

[Mopar1973Man]

Bingo. 3rd gen fan clutch is based off coolant temperature sensed by the ECT sensor. As long as the flow from the thermostat is low the fan will not lock on the 2nd gen. It will cool to fast before the fan senses enough heat to lock even partially on cold winter day.

[AH64ID]

2 hours ago, pepsi71ocean said:

 

Except our clutches are based on radiator temperature. That radiator needs to start passing heat past the clutch first. 

 

Exactly, which is a benefit at low loads and why I said just cruising it likely won’t cycle the fan too much more,  but on a hot day where the a/c and intercooler are already heating the radiator up you might get some fan operation while empty.  

 

But when the motor is working hard the hotter the thermostat the hotter the radiator. The radiator is getting fed coolant at least 20° hotter than it was when the fan clutch engange temp was designed, and that’s going to make it engage more often any way you look at it. A partially open 200° thermostat can make for a hotter radiator than a mostly open 180° one.

 

Aside from fuel mileage it shouldn’t hurt anything having the fan work more, I’m simply pointy out that it will operate more often. 

 

Looking at the 1999 FSM the fan will engage when the radiator discharge temp is 160°-179° F. When the radiator is getting fed 180° coolant that will take a while to get to, but at 200° it wont take as long. A 180° thermostat should only be putting 200° coolant into the radiator at very high sustained loads, whereas a 200° thermostat doesn't put coolant any colder than 200° into the radiator. 

 

46 minutes ago, Mopar1973Man said:

 It will cool to fast before the fan senses enough heat to lock even partially on cold winter day.

 

We're talking about year round operation of a 200° thermostat. In the winter it likely won't ever lock on an empty truck without a winter front, but in the summer or with a winter front it might. 

 

I've read about guys, on this forum, having there fan come to life in the winter with a winter front on, and that was likely with a cooler thermostat which means a cooler engine bay. With a 200° engine it doesn't take much radiator heat to get the engine bay to hold 160-179°. 

 

With my MM3 I can watch all of the underhood temp sensors and even in the winter it doesn't take much to warm up that engine bay. As soon as the radiator cracks I get 20°+ warmer IAT's from the radiant heat of the radiator by the intercooler, and the intercooler is ahead of the radiator in the airflow. That's all without a load on the motor. 

Edited January 19, 2018 by AH64ID

[ofelas]

Never did find a warmer than 180f stat for my 12v first gen, so I swapped in a second gen stat housing and use the appropriate stat.

 

Here ya go -

 

1st gen 12v - 180f 54mm diameter stat (has a tapered seat bypass & 2 jiggle pins) Cummins p/n 5292738.

 

2nd gen 12v - 180f 63mm diameter stat (has a disc bypass & no jiggle pins- uses the one way check valve to purge air) Cummins p/n 3928499/Mopar 05014568AA.

 

2nd gen 24v - 190f 58mm diameter with disc bypass (I initially ground this down to 54mm for my first gen but it's too deep to fit inside the 12v head) Cummins p/n 3946849/Mopar 05015708AC.

 

I use a 63mm NOS Mopar # 3418459 in my second gen stat housing, its 195f, and is identical to the Cummins second gen stat in weight & construction, except that is doesn't have the bypass disc or bypass tapered seat.

 

It's commonly available replacement is NAPA 532090/Stant 13479.

 

I'm not concerned about the bypass function, as its only there to close & prevent flow through the bypass passage when the thermostat is open & provide 100% flow through the rad hoses.

 

The bypass hole is too small to make a difference to cooling flow whether closed or open; its primary function is to ensure a bit of coolant circulation when the thermostat is closed, to help avoid hot spots while warming up.