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padgett 03-01-2012 09:56 AM

Pentastar Thermostats
So far I have found at least two different thermostats for a Pentastar, 05184570AH and 05184651AF both of which seem to consist of three seperatable pieces, a housing (water neck), ring, and thermostat.

On the forums I have seen mention of a 186F and 195F units but the part books do not give set points.

Just as data points, watching with both a scan tool and the EVIC, I did not see the thermostat open until 207F when it dropped to 199F (yes Virginia I know the difference between a fan turning on and a thermostat opening, this drop was waay too fast for a fan). This explains the over 200 temps I am seeing on the Interstate and has nothing to do with fans.

Is this what others are seeing ? Thermostat opening is obvious even on the EVIC, look for a slow steady rise during warmup followed by a sudden drop of 6-10 degrees F.

Just a thought and need to check with an IR sensor. If the coolant sensor was reading high, that would expain why after a long warm up the oil temp is 20 degrees below the coolant temp. My experience (of course it is dependant on sensor location) is that oil temp runs higher or equal to coolant.

The proper set point is one thing a service manual should tell you but wanted to check here before I complain. Right now over 200F operation is OK for the moment but when summer comes and long term it is not good for anything under the hood (may be why the battery is under the passenger seat).

And another point: I have seen mention that the two-stage oil system drops to the low pressure at 158F. Looks like that is 158F OIL temp not coolant.

J13ntv 03-01-2012 11:21 AM

Re: Pentastar Thermostats
I have the hemi which can be a different ball game for all that I know, but do know my coolant temp is 199-203 running, and gets as high as 224-226 idlings, before the fan kicks on high and it starts to come back down.

My oil also runs a little below, equal to or higher then coolant the few times I have watched it since I switch to mobil 1 synthetic.

GTREVINOWK2 03-01-2012 08:17 PM

Re: Pentastar Thermostats
I can confirm the above statements we just finished messing with the otc scanner

padgett 03-01-2012 10:14 PM

Re: Pentastar Thermostats
1 Attachment(s)
OTCs are nice, I have a couple of 2000s for my OBD-I GM cars. Also DiaCom and Moates PC cables with C.A.T.S. software. Been playing with car computers for a while now but old school UV Proms. Flashing sounds lots easier (if can avoid bricking).

For the Heepderow (my first OBD-II) I have an OBDwiz cable and CD for my netbook. $29.95 + free shipping from Amazon. Below is a screen shot, am still tweaking the display a bit to get more on the screen & need to find the Chrysler codes for the tire monitor. Then will be putting together some playthings like a SRT type 0-60 timer - easy with a clock and MPH readout. This is going to be phun.

Been doing a little more testing and suspect the coolant sensor may be reading a bit high, oil temp may be more accurate. Will find out more precisely when the new thermostat assembly gets here (on back order). Wouldn't mind if does read high, would bring some things (including the fan) in earlier. Easier than programming.

Sometimes it is handy to play games with sensors, some companies have made names and a lot of money just messing with the IAT. However there is no substitute for a little reprogramming (my Reattae all have 180F thermostats & bring low fans in at 185F and high at 189F. Everything under the hood and in the engine lasts longer. Running cool is important in a Florida summer.)

Of course while I know GM computers, I don't know Chryslers. Never needed to before. (but if a tire shop can flash, it can't be hard to find out).

BTW, which statements can you confirm ? Yout wants to know.

padgett 03-10-2012 10:32 AM

Re: Pentastar Thermostats
2 Attachment(s)
OK, thermostat arrived. For some reason known only to Chrysler the waterneck/o'ring/thermostat is all an assembly that does not meet industry standards such as SAE J634a.

It is marked "195" which is pretty much an industry standard since the 1950's. I have found that using a 180 makes everything, particularly rubber parts such as belts and hoses, last much longer.

This means the thermostat starts to open at 195F but is probably not full open until about 205 which explains the 199-206 I am seeing in a 45 mph or greater cruise at 70F (fan not needed). I have seen recorded temps of 210 without the needle on the tach cluster reaching the center mark.

The picture below shows a disassembled thermostat. All you would need to change the setting is a different pellet assembly but are not sold that way and doubtful the aftermaket would have an interest.

Looks like with some mods to the housing a 44mm Stant Superstat could be fitted, since smaller than to O'ring the only difficulty I see would be clamping it in place.

Does anyone know if a 180F thermostat is available for the pentastar engine ? Overseas perhaps.

dlillie87 12-03-2013 09:42 PM

Re: Pentastar Thermostats
Padgett, have you found a 180 thermo for the pentastar yet? Im looking as well

mswlogo 12-03-2013 10:01 PM

Re: Pentastar Thermostats
Where is the temp sensor relative to the Thermostat?

How do you know the temp sensor isn't wrong?

Or the Gauge?

If you run your engine under temp you can really mess up it's efficiency.

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