[rebar]

I'm going round and round trying to find a suitable T-stat for my 97. I don't want the 180 and I understand cummins never made a 190 degree for the 12 valve, but I really want to try one to gain mpg and reduce heat cycles.

Ive read some have installed a 195F NAPA #532090 for a 440 Mopar. And another guy a Murray 15479 which I cant find.

But has anyone installed the cummins 24v 190 degree stat 5015708AC in a 12 valve? Or what stat did you install to raise operating temperatures and how do you like it?

Thanks!

 

[alanack6795]

440 one fits 24v one does not fit.

 

[rebar]

Thanks.

The napa THM 532090 (440 stat) is superseded by THM 291 which I just installed and will run tomorrow.

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 (ofelas ground this down to 54mm for his first gen but it's too deep to fit inside the 12v head) Cummins p/n 3946849/Mopar 05015708AC.

I found some new info but wonder if the 3418459 there talking about is the same 440 stat I just installed.

This solution has been reported by Gerry Willomtzer <[email protected]>: 195 degree t-stat Dodge PN 3418459 intended for a 70's gas engine

 

[ofelas.5z]

I wish I'd have checked the seating depth of a perfectly good 24v stat before grinding the diameter from 58mm to 54mm; I eventually went to the 63mm ID second gen stat housing for my first gen to accommodate the 190ish stats available.

Yes, the 341849 is the one you need. I've seen some stamped 192f & others stamped 195f.

Two variants of the above stat - one with the exposed shaft/spring, & an
HD one with a shrouded body, similar to the Cummins unit.

Pics here - https://www.cumminsforum.com/forum/...stem-balance-genuine-mopar-vs-fleetguard.html

None of the aftermarket stats have a bypass closing disc; but it's not essential at all.

It's good to bypass during warmup - the NAPA/Mopar/Stant stat's lack of a bypass disc doesn't prevent the bypass flow - when the stat is closed, the bypass is open, and fulfills it's primary function of circulating a trickle of coolant through the head. The Fleetjunk engineers should have made the rear freeze plug divert as well, but that's easily fixed. On my setup, I divert the stagnant #5 & #6 coolant to my heater core inlet via a Keating Machine tapped rear freeze plug.

When temps dictate, and the stat opens to regulate temperature, the bypass closes - this doesn't really cut down flow through the upper rad hose; I've heat gunned the difference back to back on the same day before & after the stats opened. The tiny bypass doesn't really have a chance at affecting a fully open stat's monster flow that these very stout water pumps facilitate.

Thanks.

The napa THM 532090 (440 stat) is superseded by THM 291 which I just installed and will run tomorrow.

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 (ofelas ground this down to 54mm for his first gen but it's too deep to fit inside the 12v head) Cummins p/n 3946849/Mopar 05015708AC.

I found some new info but wonder if the 3418459 there talking about is the same 440 stat I just installed.

This solution has been reported by Gerry Willomtzer <[email protected]>: 195 degree t-stat Dodge PN 3418459 intended for a 70's gas engine

 

[rebar]

I wish I'd have checked the seating depth of a perfectly good 24v stat before grinding the diameter from 58mm to 54mm; I eventually went to the 63mm ID second gen stat housing for my first gen to accommodate the 190ish stats available.

Yes, the 341849 is the one you need. I've seen some stamped 192f & others stamped 195f.

Two variants of the above stat - one with the exposed shaft/spring, & an
HD one with a shrouded body, similar to the Cummins unit.

Pics here - https://www.cumminsforum.com/forum/...stem-balance-genuine-mopar-vs-fleetguard.html

None of the aftermarket stats have a bypass closing disc; but it's not essential at all.

It's good to bypass during warmup - the NAPA/Mopar/Stant stat's lack of a bypass disc doesn't prevent the bypass flow - when the stat is closed, the bypass is open, and fulfills it's primary function of circulating a trickle of coolant through the head. The Fleetjunk engineers should have made the rear freeze plug divert as well, but that's easily fixed. On my setup, I divert the stagnant #5 & #6 coolant to my heater core inlet via a Keating Machine tapped rear freeze plug.

When temps dictate, and the stat opens to regulate temperature, the bypass closes - this doesn't really cut down flow through the upper rad hose; I've heat gunned the difference back to back on the same day before & after the stats opened. The tiny bypass doesn't really have a chance at affecting a fully open stat's monster flow that these very stout water pumps facilitate.

Great info ofelas, thanks..

What's odd is one hit I get searching 3418459 shows this, which looks almost identical to the napa THM 291 I just installed. And another hit shows this style which Im guessing is the better of the two?

I'm interested in Keating Machine tapped rear freeze plug you mentioned. It helps cool 5 & 6 better, or relives pressure? I guess I need to read this, but right now Im going to refill distilled water and take her for a drive. Might also install the new ofv to and maybe new T6 etc etc.

My goals with the stat is to raise my operating temperature from my 160-170 to 195 and stabilize the temperature swings. Mine weren't swinging, but took forever to get up there and also hopefully gain some mpg doing so. Do you have any tips or mods regarding p-pump mpg?

 

[thor363]

ofelas, got any pics of how you ran from the Keating plug to heater core inlet? I've got that Keating rear billet also, and wanted to do something similar.

 

[ofelas.5z]

I prefer the second link you posted.

The rear freeze plug port helps circulate the stagnant coolant near #5 & #6. Faster heat with the slightly hotter coolant delivered straight to the heater core to boot.

There's folks far more knowledgable than I could be as far as P-Pumps.

Tire pressure, alignment, 1700-ish cruising rpm and a clean air/fuel system is all that I can contribute

Great info ofelas, thanks..

What's odd is one hit I get searching 3418459 shows this, which looks almost identical to the napa THM 291 I just installed. And another hit shows this style which Im guessing is the better of the two?

I'm interested in Keating Machine tapped rear freeze plug you mentioned. It helps cool 5 & 6 better, or relives pressure? I guess I need to read this, but right now Im going to refill distilled water and take her for a drive. Might also install the new ofv to and maybe new T6 etc etc.

My goals with the stat is to raise my operating temperature from my 160-170 to 195 and stabilize the temperature swings. Mine weren't swinging, but took forever to get up there and also hopefully gain some mpg doing so. Do you have any tips or mods regarding p-pump mpg?

I installed a 90 degree brass push lock on the Keating freeze plug & used high temp 5/8" heater hose wrapped in convolute tubing directly to the metal inlet of the factory water valve leading to the heater core on my first gen. I don't use the factory steel tube going to the water valve as it's plumbed to my remote mounted ATF to coolant heat exchanger.

One could also T the rear freeze plug outlet into the factory heater core line.

ofelas, got any pics of how you ran from the Keating plug to heater core inlet? I've got that Keating rear billet also, and wanted to do something similar.

 

[rebar]

My test run was good and just like advertised, the napa THM 291 worked great and performed to my expectations first time out. This engine has probably never seen these temperatures, so I dropped the dino and switch to T6.

I'm under the impression that these motors run most efficient around 2000 rpm imo. Or at least that's my number, giving me the green light to cruise 75:wink2:

I sold a intercooled 1st gen I rebuilt years ago that towed my previous rig like it was nothing. On the way back on a empty stretch of interstate I put the throttle down "just to see".. 16K# combined 14' tall 24' toyhauler, nv4500 3.54 and as I approached 100 mph 2800 rpm, my egt's kept dropping like the motor wanted more. I was sold, and also averaged over 15mpg running over 75 that 2400 mile trip.

Notice at the end of the vid how the temp never drops lower than 190 when slowing or stopping like the first stop (175 which was higher than where my factory stat ran), where it must not have been completely up to temp maybe? Anyway, real happy..

https://youtu.be/h3BMDBaIt1M

 

[EXSwap]

Just when I think I've got everything I want to use with my motor figured out, y'all come around with some really great info. I swear I learn something new here every day. Thanks!

 

[ofelas.5z]

rebar - good to hear.

Mileage wise - I'm not sure how much better fuel fuel economy on a mechanical engine is due to a hotter stat, or the fact that I do a fan/clutch delete for the winter months.

 

[JarodTLG]

I just PM-ed you back, but I'll also post here for others benefit/curiosity.

I put a 5015708AC in my 97 12 valve. I'm the 2nd owner, and I do not have all the service records so I'm unsure what has been done to it, like if a different tstat housing was swapped in or what.

However, the 180 stat which was marked as a cummins part, and appeared it had been in the truck for a while and the 190 degree one with the part number I listed were identical. looked literally like the same part except for age and the markings indicating part number and temperature.

I initially tried a Stant in the truck to get the temp up a little, which had a terribly small opening when the stat opened up, which ultimately ended up with insanely wild swings to the peg on either side of the gauge. it came out immediately.

I then got the 24V stat.

I compared to the OE one, it fit into my 97 housing nicely, not loose but the same as the one I took out. had a nice rubber gasket just like the old one I removed on it so I feel it sealed up good.

Truck now runs right around 190, where before it ran right around 180, sure it swings a little to and fro, but I understand that's normal regardless of stat.

Fuel economy hasn't changed. nor has performance, or really anything to a point I've noticed from seat of pants and basic math mpg calculations. My economy has always been terrible though, Tennessee roads towing customers stuff around hurts it bad.

Takes a while to heat up same as every other diesel I own.

Heat blows very nice and hot air once its warmed up, probably will be even better once I replace the heater core I suspect has a small pinhole in it.

 

[ofelas.5z]

Jarod -can you post the part # of the 180f stat you removed, and a picture perhaps?

 

[JarodTLG]

I'll see if I can locate it. I know I kept it, just gotta figure out where I put it

 

[Radialinflow]

I just tried a 190 degree thermostat for a 5.7 hemi in my 95 12 valve tonight it seems to regulate pretty well. I tried a 195 stant super stat last week and it regulated temp quite well but it uses a bleed notch instead of a jiggle pin and was causing double the warm up time. Can't have that. I also have a 1/2" hose running from the rear freeze plug Keating machine plate to the water pump inlet and a 1/2” hose running from the port on the head where the factory jiggle pin is down to the water pump inlet. The design of the cooling system is pretty crude on these engines they have almost no recirculation causing extremely uneven

 

[Radialinflow]

temperature through out the engine. The other issue is the gauge is reading coolant at the halfway point as it travels through so the gauge always reads low when the thermostat is open.

 

[BSH]

I'm running a Mishimoto 190, definitely helped mine run a little warmer.

 

[BSH]

Mishimoto MMTS-RAM-94H Dodge 5.9L Cummins High-Temperature Thermostat, 1994-1998

 

[Radialinflow]

Cool I was thinking of trying one if those next maybe. Does it hold a steady temp?


Sent from my moto g(6) using Tapatalk

 

[BSH]

Ya, I was finding on slightly chilly days the temp gauge would sit in the middle until I got on the highway then it would drop and the heater would cool down as well. This seemed to help for sure.