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  #1  
Old February 11th, 2018, 16:04
BALTANAKT BALTANAKT is offline
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New Motor Running Cool

Hey All,

My '91 XJ is running cooler than it should be. Was wondering if I could get some thoughts.

- Warms up to 195, drops to 160, and repeat
- Heat works, but on cool side (indicating cool temp reading is accurate)
- New thermostat (Motorad)
- New water pump (NAPA)
- New radiator (SPECTRA PREMIUM/COOLING DEPOT CU1193)
- New fan clutch (GPD)
- Coolant is full
- System burped twice

At this point I can only imagine the thermostat isn't doing it's job properly or the system is just cooling too efficiently.

Any other thoughts?

Thank you
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  #2  
Old February 11th, 2018, 16:17
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Hypoid Hypoid is offline
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Re: New Motor Running Cool

Verify the temp with an external thermometer?
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  #3  
Old February 11th, 2018, 17:47
BALTANAKT BALTANAKT is offline
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Re: New Motor Running Cool

@Hypoid,

Yep. Hose temp corresponds with the gauge.
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  #4  
Old February 11th, 2018, 18:53
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techno1154 techno1154 is offline
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Re: New Motor Running Cool

Quote:
Originally Posted by BALTANAKT View Post
Hey All,

My '91 XJ is running cooler than it should be. Was wondering if I could get some thoughts.

- Warms up to 195, drops to 160, and repeat
- Heat works, but on cool side (indicating cool temp reading is accurate)
- New thermostat (Motorad)
- New water pump (NAPA)
- New radiator (SPECTRA PREMIUM/COOLING DEPOT CU1193)
- New fan clutch (GPD)
- Coolant is full
- System burped twice

At this point I can only imagine the thermostat isn't doing it's job properly or the system is just cooling too efficiently.

Any other thoughts?

Thank you
I had two of the discount store brands that did that which was especially annoying in the winter of 2002 in Connecticut. I changed to an OEM thermostat 16 years ago and still going like the first day. Others recommend the Super Stant brand ass having good luck with them.
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1996 XJ; 4.0L; AW4; NP231; SYE; D30 and D44; ECTED; 4.10 gears; 30X9.5 -15 BFG/AT/KO; 3" lift; Rusty's LCA; JKS ADJ UCA; Kevins ADJ Track bar; Drawtite Front Receiver; Dual Electric Fans; Dual Battaries.
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  #5  
Old February 11th, 2018, 22:07
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Green Mesa XJ Green Mesa XJ is offline
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New Motor Running Cool

On a different vehicle I had a Motorad open too cool. It was supposed to be a 180 deg but I was having trouble with the temp being too low, when I swapped it out I tested it it appeared to open all the way at 164deg.

Iíve used super stant in our jeeps with no problem but if you can find oem that will probably be better.

Oh I just saw a thread somewhere where they used some kind of reduction device to control the flow to keep the temperatures right. I look around for it later.


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  #6  
Old February 11th, 2018, 22:15
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Green Mesa XJ Green Mesa XJ is offline
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New Motor Running Cool

Found it. It was at the MJ forum, they placed restrictors to help control erratic temperature fluctuations, like from 215 to 160.
I canít post the link since Iím reading it with this same app, i can link to it later if youíd like.


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  #7  
Old February 12th, 2018, 05:32
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cruiser54 cruiser54 is offline
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Re: New Motor Running Cool

Living in an area that the temp can be 0*F to 110*F I have found no better thermostat than the one from the dealer. 52028186
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  #8  
Old February 12th, 2018, 06:07
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alexgalexg alexgalexg is offline
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New Motor Running Cool

If it's bouncing around you might have air trapped. Bleed it and see

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  #9  
Old February 12th, 2018, 06:25
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cruiser54 cruiser54 is offline
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Re: New Motor Running Cool

It woulda bled all the air out after a few heating and cooling cycles.
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  #10  
Old February 12th, 2018, 06:50
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BCKNBLK BCKNBLK is offline
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Re: New Motor Running Cool

As cruiser stated, any remaining air would have escaped through normal operating cycles. If I were in your shoes, the first step I'd take would be to take out the thermostat and test it in a pot of water on the stove with a thermometer. They are not accurate as you will see, including the OEM units that draw more faithful followers. But they SHOULD be reasonably close. If it is close enough that you are happy with it, re-install it. Then test the coolant temp sensor. You can look up online the resistance readings that are acceptable for a good piece, or just toss it and purchase a new one, install. If that does not help the situation, then look at installing a restrictor as one of the guys mentioned above. You can find a couple good examples online of how to make it, its pretty simple and quite effective. But only add a restrictor as a last resort, because the basic cooling system, if assembled with good parts, should operate well without the restrictor. I've just gotten done with a rebuild a little while back, and almost all of the cooling system components were replaced as part of the project, and it is amazing how narrow the coolant temperature band is. Once it reaches operating temperature, I never see the needle move, and I do not use a restrictor.
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  #11  
Old February 12th, 2018, 06:58
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Re: New Motor Running Cool

I have a chart with the values.

But, I'm telling you. I installed 3 Super Stats in each of my Jeeps a few years back. They all took a long time to heat up and had temp swings.
So, I got all of them replaced under warranty and installed the new ones.

Same deal.
Bought one from the dealer and installed it in one Jeep.
Warmed right up to 195 in less than 3 miles on a 20* morning. stayed there with maybe a needle width of fluctuation.

Needle stays in the same spot on hot days also.

Installed one in each of the other Jeeps and duplicated the results..........
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  #12  
Old February 12th, 2018, 08:05
BALTANAKT BALTANAKT is offline
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Re: New Motor Running Cool

Sounds like a thermostat swap is in order.

Man, nothing like pouring cooling all over the front of a brand new shiny clean engine.

Thanks fella's
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  #13  
Old February 13th, 2018, 18:21
BALTANAKT BALTANAKT is offline
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Re: New Motor Running Cool

New thermostat from Jeep dealer today. $34.

Came in a MOPAR box but was made by MOTORAD. Same brand as my current t-stat.

This new one has the vent hole where as my current t-stat does not.

I put it in a pot of water and it seemed to open/close at 195*.

Will install as soon as I can and report back. In other news, averaged 13mpg over last 124 mi. Hoping this is due to running cold as all sensors are new and it did 18mpg before swap. -_-

Current t-stat part #: MOTORAD 300195
New dealer t-stat part #: MOPAR 83501426-AD
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  #14  
Old February 13th, 2018, 19:33
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cruiser54 cruiser54 is offline
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Re: New Motor Running Cool

Quote:
Originally Posted by BALTANAKT View Post
New thermostat from Jeep dealer today. $34.

Came in a MOPAR box but was made by MOTORAD. Same brand as my current t-stat.

This new one has the vent hole where as my current t-stat does not.

I put it in a pot of water and it seemed to open/close at 195*.

Will install as soon as I can and report back. In other news, averaged 13mpg over last 124 mi. Hoping this is due to running cold as all sensors are new and it did 18mpg before swap. -_-

Current t-stat part #: MOTORAD 300195
New dealer t-stat part #: MOPAR 83501426-AD
It seems that MotoRad makes different stats for the OEM market versus the aftermarket.
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  #15  
Old February 15th, 2018, 18:22
BALTANAKT BALTANAKT is offline
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Re: New Motor Running Cool

UPDATE: Mopar (Motorad) Thermostat Results

Installed new thermostat from Jeep dealer today. I am bummed that this new one still has me running cool.

Temp Inside Vehicle:



This is it's highest reading. It will drop down a needle width when I accelerate from a stop.

Temp on Front of Thermostat Housing



Temp on Thermostat Sensor



Temp on Sensor at Back of Head

170* (no photo)

Thoughts
  • Very strange that the dealership part was made by Motorad (same make as my first thermostat) rather than MOPAR.
  • I think my poor gas mileage (13mpg) could be attributed to running cool
  • I could try a NAPA thermostat
  • Maybe my pump is too powerful
  • Maybe my radiator is too effective

Any thoughts?
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