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How far up the temp gauge should I let my hemi get?

3K views 15 replies 7 participants last post by  PolkaPower 
#1 ·
I was offroading this weekend, and noticed that when I was running high rpm and high throttle, the gauge would get to about the 3/4 mark, where it normally would be at the middle mark. As soon as I'd back off a little, it would return to the center.

It's not near the red mark, but I never know how much bluff (if any) they have with those. If I get motivated, I'll pull the scangauge off my motor home and put it on the WK so I can read an actual number instead of that idiot gauge.

Additional info:

I wasn't worried about it, but I'm curious. I didn't get any hints that the vehicle was too hot (didn't smell funny, didn't steam or gurgle, didn't click and bang when I shut it off, etc.).

I never hear the electric fan, but it pretty clearly is working because of how quickly the temp drops when I ease off the throttle, and it doesn't depend on moving to cool. When I say I never hear it, I mean I don't notice and I know I have poor hearing from my Ranger years. I will make a point of getting out to notice next time I run it.

I didn't try turning on the A/C to force the high speed fan on (I assume that works on this rig). I know that adds more heat load, but it can demonstrate that the cooling system is up to snuff and if it chose to, it could lower it's temperature. I'll try that next time.
 
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#2 ·
I wouldn't let it get ANY hotter than the middle mark.

Of course that's not always pOssible.
I remember a member here who said he installed a cooler thermostat and bought a tuner capable of setting the fans to go full in at a cooler temp to protect against over heats.

All that said, my hemi over heated from a cooling system failure and it cost me $7k for a new one. Tuners and thermostats are cheaper than that...
 
#3 ·
I wouldn't let it get ANY hotter than the middle mark.

Of course that's not always pOssible.
I remember a member here who said he installed a cooler thermostat and bought a tuner capable of setting the fans to go full in at a cooler temp to protect against over heats.

All that said, my hemi over heated from a cooling system failure and it cost me $7k for a new one. Tuners and thermostats are cheaper than that...
That's scary. I'm assuming my thermostat is full open during these climbs, but maybe it wouldn't hurt to drop one in there on suspicion.

What temp thermostat are people putting in these?

FYI, my radiator and hoses were replaced by the dealer just before I bought it (about 1,000 miles ago) in case I didn't mention that.
 
#4 ·
I think I'd hook your ScanGauge up to it first to see what the "real" temperature is. Although the 07's haven't had the same dropped valve seat issue that the 05-06's have (at least I haven't heard of any), overheating at any time is not a good thing. Both my Hemi's are early models (05 LX and 06 WK) and I run 190* thermostats in both and have the fans kicking on quite a bit earlier than stock....running full blast by 215*F. I also have DashHawks on both vehicles and they normally run ~188-195* and in the summer, with the air on and ambient temps around 100*, the highest I've ever seen either one is ~210*

Also, have you checked the cap, and have you lost any coolant. I've had issues with both caps and thermostat housings. It might not hurt to check the cap and pressurize the system to insure both are holding pressure properly. I've recently replaced the t-housings with Billet Technologies units and replaced all the "screw" clamps with stainless "T" bolt clamps. Keep us posted on your findings.
 
#6 ·
IIRC right at the 12 o'clock mark on mine is something around 210º. Entirely too hot for normal operation IMO. I have a 190º stat in mine now and can watch the temp cycle right around 194 regularly and have my fan settings at 195, 198 and 200 for low/med/high.

As for the trans temp, a bluetooth OBD2 reader is cheap as hell and so is the torque app. Here's instructions for setting torque app to read 5-45RFE temp: http://www.jeepforum.com/forum/f67/working-torque-app-trans-temp-4025474/

I find that the formula must be slightly off. Leaving my garage in the morning at ~60º the app shows ~70º trans temp. So far in normal driving the app has been showing me ~130-135 after a half hour.
 
#11 ·
Agreed, and the more I follow the trans temp the more I notice it follows a trend with ambient.

I should be dragging a my trailer at ~3000lb this weekend through some awful hilly two-lanes this weekend and I plan to keep a curious eye on temps. Also curious if the occasional 'bumpalong' shows up more. Somewhere in the 2 or 2P kickdown it does it and I just flat don't like it.
 
#12 ·
Thanks a bunch for all the input. I've put my scanguage on and towed a light load of rocks on pretty level ground, staying under 50mph, but keeping the gears low and rpm up. It was about 210 to 220 at the middle mark, which is where I'm used to seeing it. Again, this is a device, not god, so that number may not be correct.

I don't get any other clues of overheating, such as the bottle overfilling, or bubbling, or losing fluid, or the vehicle feeling hot. I've had many rigs before that would cook you if you opened the hood after a warm trip. Often I can hear the clicking and banging of hot metal changing dimensions after I shut down, but this really doesn't. Once in a while the exhaust pipe clicks, but not under the hood. This one simply doesn't strike me as overheating.

I cleaned out a muddy soup from my nearly new radiator, and now it looks beautiful, but the temp gauge is in the same area. I'm more comfortable with a low temp T-stat than I am a n ECU program. I know people have that stuff well understood, but I don't want to risk my warranty unless I have to. The fact is, if this hemi commits suicide and I haven't screwed with it, it will probably cost me $100 and I'd end up with a better motor. Once I mess with the controls, I own the results.

I'm going to get out my laser temp guage and start seeing what other stuff is getting to. I also want to figure out if the fan is coming on and when.

Is it hydraulic? Does it have multi-speeds?

Thanks in advance.
 
#13 ·
my CRD has been getting to 3/4, started last summer and the one hot day we have had so far this year it went to about 5/8

i thought about changing my fan solenoid or buying a whole fan assembly off a wrecked one if i could find it..

with using the dash command app i was reading average 210, most i saw was 216...but from what has been posted here [in another thread] thats nothing too overly serious
 
#14 ·
The fan on 5.7 and 3.0 models is hydraulic. You'll know if it's on high...it moves air!

ALso, I forgot the address earlier that the cooler you see in front of the condenser is actually the power steering fluid cooler. The trans cooler is part of the condenser, look closely and you'll see that it's two circuits and the upper portion is the trans cooler.
 
#15 ·
I finally got out wheeling again since installing the scan gauge (I can't go alone for health reasons, and nobody has had time). The gauge was going to the 3/4 mark at times, but that never exceeded 236, and I was actually hearing the fan move more air and the temp would go back to 218 or lower quickly once the fan started working hard. As before, I never got any sign of an overheat. I'm not going to worry about it; everything seems to be working the way it was designed. Besides, it wouldn't break my heart to build a custom hemi, so the thought of dropping a valve seat is more a concern about how to get home that day. Now that my tow dolly is here, I'll be dragging it with the F150 or motor home, so all I need is a ride back to my truck.

My scan gauge doesn't read transmission temperature, so I can't give a number there. Since the 545RE is common in big Dodge trucks with big tow ratings, I'm pretty sure I'm not over-working it.
 
#16 ·
Mines gotten to 216 going slow off road. I don't like it. My ZJ doesn't go over 210 with the ac blasting.

I would worry more about the transmission temperature the the motor because you know that's heating up nicely.
Chrysler is notorious for not providing adequate transmission cooling and they did not build it from the factory for sustained slow off road use. Heat kills transmissions.
I use torque to monitor the traffic temperatures. I don't know how accurate it is but it does provide a baseline to go off off and that got to 218 the same day.
I added a B&M transmission cooler after that.
Now it hangs around 140 highway.
I don't wheel my wk though, that was a one time thing. Too much stuff to go wrong and too complicated.
That's what I got the zj for.
 
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