So my 90 xj will still get a bit warmer than I think it should. Only an offroader slower speed vehicle. I was told to take out thermostat to help it stay cool, so the coolant is continually circulating. So I did. My question is does not running one keep it cooler or not. Is it better to let it work asit should with thermostat or run without?? So far in my renix I haveanew aluminum radiator, bottle delete with upper hose cap and overflow. Somtimew it will get over 200*+ with both fans running. So should I put the thermostat back in or does it run cooler without.

 

Thermostat are to keep motor at certain operating temps . Removeing it will make engine run cooler. At the same time mpgs are gonna suffer from not reaching normal operating temps. Id check operation of fan clutch seeing how slow speed coolings the issue.

 

I vote for thermostat back in..

Wait and see what others say..

Ant...

 

x2

 

Provided your thermostat is working properly, it will have no affect on your temperatures beyond the temperature it's designed to open at, typically 195º f. So, running without it will not reduce overall temperatures. The purpose of the thermostat is to prevent coolant from circulating until the engine reaches operating temperature. After the thermostat is open, the rest of your cooling system takes over to maintain that temperature.

 

x3

 

X4

 

You could always upgrade to quality, high CFM electric fans. Put them on a toggle switch. Also try hood vents.

 

How's the water pump? Fan clutch?
How far over 200 deg? 200 isn't abnormal.

Agreed with F1, removing the T-stat does nothing once the coolant temp hits the thermostat rating. Removing it only slows the warm-up process.

 

I would keep the thermostat in, I believe I have been running an 180 degree thermostat, and the 4.0L stays at 180 even in stop and go commute traffic with the factory electric fan running on the drivers side. At higher speeds the engine stays at 180 with just the clutch fan.
For slow speed you need to make sure the electric fan is pulling air through the radiator fins to cool the engine.

 

First off, use a 52028186 stat from the dealer.

Ever had the water pump off? Fins could be partially rusted off.

How is it on the highway?

When you say both fans are running, I'm confused. You mean the stock fan is turning and the electric fan has also come on?

 

Forgot to say, brand new water pump. I had a new thermostat installed at first and was getting to hot, 240ish. Took it out and it took a lot longer to get that high. Rig will never me on road, just slow speed crawling. Clutch fan is in good working order and electric fan is on a toggle. Mpg is not a concern,
I suppose I could reinstall and seehow it goes this time around, it hasnt been in since I added upper hose cap and deleted the bottle

 

Operating temp for the 4.0 is 200-210 on the gauge. Think spec is like 205. So use the stat specified by the MFG. IF your rig doesn't maintain the correct temp FIX the problem, causing it to run hot or cold.. Maybe you need to DEKETE the mechanical fan for an Efan, maybe add some vents.

 

Get a factory stat in there. How do you know your fan clutch is good?

Want a stout fan clutch? Get a Napa 272310.

 

My 98 runs 210 no matter what, highway, stop and go traffic, 10 degrees outside, always 210, i even switched from a 180 thermostat to a 165 for a while and still 210