Question:

So I have a 1990 XJ with a straight six in it. up until recently I have had a overheating issue in the city as well as off road. Recently I had to replace my water pump so while I had the XJ torn up, I thought I would upgrade some of the cooling system.

So I,

-replaced the oem pump with a Hesco High Flow Pump



-connected a "puke" tank to the pressurized overflow tank (this was so the water would be poured into a tank allowing the water system to be completely full allowing for better heat absorption)



-I ripped out my AC system which included the radiator in the front of the engine radiator. This allows for better flow of air
- and I put Lebaron Hood vents in.

Now my XJ has a 195 degree Super Stat in it but my problem is on the highway and city I'm running cold. My temp gauge says Im running at just above the second tick mark on the water gauge.



I have noticed that if I just idle, the temperature gauge will clime to what I think is 190-200 degrees



but as soon as I start moving the temp declines either to a point between the second tick mark on the gauge and the 210 mark, or colder. I also noticed that the gauge reads past 210 once I turn off the engine and let it sit for a minute.



I have been researching and trying things for the past couple weeks but haven't found anything yet that will help.

So far I have tried.
- burping the system (several times)
-squeezing the radiator hoses, which I can feel the surge in the opposing hose
-replacing the water/ani-freeze mixture with more ani-freeze
-flushing the heater core
-damming up part of the front grill

I also checked the hoses going to the heater core and both of them get very hot. The hoses going to and from the radiator also get hot, but not as hot as the hoses going to the heater core. I believe this is because they are much bigger in diameter? I also have a 1995 XJ thermostat cover so I could use the threads on the side for the coolant temperature sensor and put a ball valve in its place to make burping the motor easier.

If anyone has any ideas or solutions they have found work, I and my gas mileage would thank you.

 

I would verify the temp with an I.R. temp gun pointed at the t-stat housing. Most wouldn't complain that they are running cool. But I would verify to make sure if your gauge is read right.

 

i hooked up a mechanical gauge in my renix (with no cooling system "upgrades"), and it basically showed the same as your factory gauge. then i put in a factory mopar t-stat (replacing the one i drilled a 1/16th hole in ) and it evened out. fwiw, i don't think there is anything 'super' about the Stants...

 

Went through 3 "super" stats. Friggin' junk. Ran too cold. Put factory stats in my 3 Jeeps. All is well.

 

It's true. Factory t-stat is the way to go, I had a 180 in before cruiser here convinced me to get a factory t-stat and my jeep had difficulty making it to the first tick. After the new one was in it stays at 210 steady.

 

Why would it stay at a steady 210 with a 195 stat in cool Oregon ambient temps? A 195 stat should be wide open, or very close to wide open at 210, no?

 

With the mods u've done and cool Oregon ambient temps, your gauge seems to be displaying about right with a 195 stat. Factory gauges r notorious for inaccuracy (close but no cigar). R u still running your heater occasionally?.......that will lower coolant temps a little.

 

Thank you all for your feedback! I am planning soon to take the thermostat out and bench test it to see if its opening up at the correct temp. at that point I may just get a OEM replacement if it seems to have the results it does from what all of you are telling me. Also, that picture for the gauge is great! Ive always wondered what it was actually reading. I'm planning on putting a Stewart Warner temp gauge in there soon. I don't usually ever turn the heater on unless its a dyer situation (I got stuck up in the snow for 7 hrs alone once and the heater was my life line)

Once I bench test/replace the thermostat Ill let you guys know what the results are. Again thanks for your input!

 

the temp your engine operates at is not just determined by 'when' the t-stat opens, its also determined by the amount of flow through the unit itself. you might bench test that stat and see that it opens at xxx degrees and think all is well, but how much flow goes through a Stant @ 195 might be different than whats being allowed through the mopar stat at the same temp. a friend of mine (with a 5-speed 90 like mine) was also complaining about running too cool during this past winter (not good when its -30 celcius). we replaced his also with a mopar stat, and all is well. ($32 canadian)
anyways just food for thought,

good luck man.

 

Remember, u can't just stick a temp gauge in there (unless it's a mechanical gauge).....u must install the sending unit that came with the gauge (if it's an electrical gauge).

 

So I finally installed my Stewart Warner Water Temp Gauge along with a new thermostat purchased from the dealer ahem stealership. It was a bit more expensive than I was anticipating. After I installed the gauge, sender, and the thermostat, I now run at 195 degrees in the city (the temp fluctuates as the thermostat opens and shuts) and a constant 195 degrees on the highway (no movement of the needle). I have a feeling the other thermostat was wide open. I haven't bench tested it though. Thanks for all your help everyone!

 

Those are good thermostats. Whaddya have to pay?

 

I had to pay $25 for the thermostat and seal. Not horrible, just a bit more then I was anticipating. I did like how the thermostat had a mechanism to allow air to pass by. It was a hole with a piece of metal in it that when air was behind the thermostat the hole would be open and when water was behind the thermostat the hole was closed. So far it has been a good thermostat.

 

Seems to me the 195 Mopar stat may be opening early if coolant is 195 at hi-way speed (motor working reasonably hard). The Stant SuperStats (I always test before installing) are closed at their rated temp thus giving a operating temp slightly above (2*-3*) their rating (using a digital gauge and depending on operating conditions).

 

I was wondering about that, but something I considered was the temperature gauge sender is in the back of the engine and the thermostat is at the front of the engine. I am assuming that the reading at the back of the engine and the reading at the front of the engine are a little off. My thoughts were the front of the engine may be a little hotter because the water from the back of the engine flows towards that point thus picking up more heat. I haven't proven that, but just looking at the loop it made sense. Soon I want to move the temperature sender into the thermostat housing for the most accurate reading.