Jeep Wrangler Forum banner

Thermostat removal?

9K views 32 replies 10 participants last post by  Dirtybird1998 
#1 ·
While technically my overheating issues are behind me, in the heat of the Arkansas summer I'm still running about 230 on the highway instead of the 210 I would hope for. Have any of you run without a thermostat before? I don' know if more coolant flow would help or not, or if I just don't have enough radiator surface area. The radiator is very clean inside and out, so that isn't an issue. Switching back to the stock fan cured my overheating, so I proved that lack of airflow was the cause. But I'm at a point where I can't increase the air flow anymore. Removing the tstat is easy and it could be installed during winter months.
 
#2 · (Edited)
No, don't remove the thermostat. Yours might simply not be opening fully, I'd replace it with a new 195 (non-failsafe) high-quality thermostat like a Stant SuperStat. And no, don't be tempted to try a lower temperature thermostat like a 165 or 180 degree model which can't force or help an engine to run cooler on a hot day.

Some aftermarket radiators can make it difficult for the engine to run cool enough. Also, is your fan shroud in good shape and installed? A missing or damaged fan shroud can cause overheating problems.
 
#4 ·
While technically my overheating issues are behind me, in the heat of the Arkansas summer I'm still running about 230 on the highway instead of the 210 I would hope for .
You're overheating issues are not behind you if you're at 230°
If you're only hitting 230° on the highway, it could be a flow problem, that could be causing the lower radiator hose to collapse (do you have a spring in the lower rad hose?)

As suggested, first install a new 195° thermostat.
You say the rad is clean inside and out, but, AFAIK, there is no way to really tell if there's blockage inside — How old is the radiator? Might be time for a new one. Could also be the water pump — in any event, 230° is hotter than I would want it running.
 
#5 ·
As indicated there are many reasons to run the T-stat. Running a T-stat slows down coolant flow allowing time for proper heat transfer from the radiator; as well as numerous engine performance reasons.

Start with the basics:

Check cooling fan operation first.

Check for mud or debris in condenser fins(big problem from vehicles we get from the South). Flush out thoroughly from the back side.

If it gets hotter the faster you go check for grille obstructions. Even a sunk winch can deflect airflow over the hood and away from the grille.

I have two LS3 builds in the shop now with Warn power plants, driving light's, led bars and winch controllers obstructing 80% of the grille airflow, they will be relocated. We have done airflow testing on the JK and now have a dual fan setup that helps lower under hood pressure.
 
#9 · (Edited)
The thermostat is a new one (installed at the beginning of my overheating issues). I think the right answer is the grill being obstructed. The second thing I did was removed my grill inserts, and that help a lot, especially on the highway. Makes sense now.
I was wrong about the temperature, it runs about 210 (center of gauge) until its been running for about 15 minutes, then creeps up to 220 and that is where it stays.
The thermostat change is easy, I'll try another new one (Jerry's recomended one) and maybe take the winch cover off to see if that helps with airflow. I'd hate to have to remove the lights, but if they gotta go they gotta go.

Its worth mentioning that I went ahead and flushed the systsem out this weekend, but after running two bottles of radiator cleaner through it for a couple of hours it was not bad at all, barely any rust at all. I knew that going in but feel better since this vehicle is new to me. I was surprised at how little coolant the system actually holds. I can see why it is very easy to put too much antifreeze in it (which is bad). It took less slighly less than a gallon of unmixed antifreeze to make up a roughly 50/50 mix.
 
#10 ·
FYI the 4.0L engine has a plug on the drivers side of the block towards the rear-down low about 2" higher than the edge of the block where the oil pan bolts on. It is like a pipe plug and mine had a 3/8 hex in the center for an allen head wrench or bit. If you remove it you may be suprised how much junk/rust may come out-AND-you will get all of the old flush water out, so your refill will be new coolant mix.
 
#12 ·
I've spent over 30 years in the Southwest stuffing high compression V8 engines in small engine compartments like the Jeep JK. We have developed single, dual and on occasion three pass radiators to control coolant flow through the cooling system. We offer single, dual and quad cooling fans to meet the cooling demand.

OE manufactures, especially the Germans, have run multiple T-Stats as well as computer controlled T-Stats for years. The goal is to control the flow through the system for maximum heat exchange, cold emission warm up cycle, hot protection mode, etc. Without this flow control the cooling system would not work properly, maybe in a 1949 Ford but certainly not in a modern computer controlled vehicle which is dependent on precise operating temperatures.

So while I appreciate your observation that the heat exchanger transfers BTU's, without coolant flow it would not matter, both are required for the cooling system to work.

In the old days we would overdrive the water pumps on engines that idled low to keep the coolant flowing. Today we see a marked improvement with our dual pass radiators, allowing the coolant a little more time in the radiator. Electronically controlled T-Stats are becoming more popular for the reasons indicated; it's all about getting the engine to the proper temp, fast cold start up, intake valve temp control, and combustion temps for best efficiency and emissions.

Airflow is another discussion with the pressure zones inside and out of the engine compartment. The usual problems we have with the JK are plugged condensers, grille blockage and on occasion plugged radiators. Also on the 3.8 JK's the single wound cooling fan uses a voltage divider to get two speeds. It is common for the voltage divider(fan resistor) to burn out leaving only high speed. Check to see if you have two distinct fan speeds, if you only have high the fan is not properly staged from off-low-high. If going from off-high(due to the bad divider) the inductive current kick can exceed 75 amps melting the fan motor connector or high speed fan relay connector, we see this a lot in the SW.
 
#13 ·
First, your issue might be your thermostat. Pull it out, stick it in a pot of boiling water and see if and when it opens. It doesn't take much for a thermostat to go bad. Water boils at 212. If it doesn't open when it starts to boil, it's more than likely your thermostat that is the cause of your current heating woes. I've run cars without thermostats including my other car which is a Euro sedan. It runs very close to normal temps with the thermostat gone. Mine was a bad thermostat but I didn't know it at the time. I need to put a new one in but on that car, taking it out was a close to three hour job. It might be the fall before I get around to it.
 
#14 ·
I've run cars without thermostats including my other car which is a Euro sedan. It runs very close to normal temps with the thermostat gone.
I'll wager you did not coast off a 10,000 foot mountain in sub zero temperatures with your foot off the accelerator for 15 miles and see similar temps?

For the record Chrysler states " An engine should not be operated without a thermostat except for servicing or testing. Operating without a thermostat causes problems. These are longer engine warm up time, unreliable warm up performance, increased exhaust emissions and crankcase condensation. This condensation will lead to sludge and wear."
 
#16 ·
Right now in Arkansas WE WISH we had some sub-zero temps! :)

I've pretty much determined that I don't suffer from lack of coolant flow, but lack of air flow across the radiator. I didn't get the chance to work on the Jeep last night and won't tonight either, but Wednesday I'm going to start by pulling off the winch cover to see what, if any, difference that makes.

I purchased the Jeep in September of 2014 and drove it 300 miles home without a hiccup. It wasn't until I installed an electric fan in the winter that I had any issues, at least that I was aware of. Just prior to installing the electric fan I installed grill inserts that had aluminum billets in them and a new winch complete with winch cover. It took me a few months, but as spring approached it became obvious the electric fan, despite being Hayden's largest (17") and most powerful model available, did not pull in enough air.

So all the additions I made during the winter months have come back to haunt me during the summer, my first summer driving this (or any) Jeep. It may be, as a previous post suggested, that I have some amount of blockage within the engine passeges. For the moment I have to accept that if I do I have to work around it. The vehicle has just 80k miles on it and at least the parts that I can/have seen... the radiator interior and thermostate housing, are clean.

For now I'm going to remove the winch cover and see what difference that makes. The new thermostat that Jerry B. suggested is on the way. I've already removed the billets from the grill (which helped quite a bit when I had the electric fan installed, BTW).

I gave some thought to putting the electric fan on the front side of the radiator, although I think that might be counter productive. It can be used as a pusher or puller and the wiring is already in place, the unused fan just sitting in the garage.

I'm thankful that with the stock fan back on it I'm at least not in the danger zone anymore, 220 give or take is the very highest it has run since. I'm just hoping to get it back down to 210 as it was when I bought it, maybe even 200. I appreciate all the helpful advice you folks have to offer!
 
#17 ·
Removing the T-Stat for testing is valid. I actually do drive up a mountain quite often LOL. My test drives take me to the top of Lee Canyon, about 9,000 feet. I start in Vegas and ambient temp can be 115*, by the time I get to the top of the mountain it's in the 60's or 70's. In winter when it's 40* in Vegas it's usually in the 20's or lower at the top.

It's a good 15 miles uphill with little relief so it's perfect to test the cooling systems on our V8's, high altitude, high temperatures, heavy load.

On way down I downshift into 5th or 4th(6 speed auto) to hold 55 mph. Even on a warm day the ECT drops to 185* with a 195 T-Stat. On a cold day I have seen ECT drop into the 160's WITH a 195 T-Stat. And this is with a large V8 which produces more heat.
 
#18 ·
Ok you guys are getting all technical, but let me throw this out there. Any chance that the temp sending unit or gauge may be the problem? Just wondering.
 
#19 ·
How did you determine the temps? A mechanical gauge, or scan tool? Do not go by the dash mounted temp gauge, it is nothing more than a replacement for an idiot light.
 
#23 ·
I have a reader that may tell me the temp as reported by the sensor... but then you have to wonder how accurate the sensor is.

The part of me that was awake in science class says that when my temp gauge indicates around 240 - 250 and I smell antifreeze and hear a gurgling sound, its pretty dang close to being accurate.

Wife called and said the Jeep was dead this afternoon when she wanted to go for a joyride. No juice in the battery, she says. Grrrrrrr. I retraced my steps from my test ride on Sunday and I know nothing was left on.
 
#24 ·
The part of me that was awake in science class says that when my temp gauge indicates around 240 - 250 and I smell antifreeze and hear a gurgling sound, its pretty dang close to being accurate.
Problem is, with the TJ gauge, where exactly is 240°?
I was surprised to see that 220° is between the "1" and "0" of 210, I would have expected it to be just past the "0" (and if my TJ is past the "0", it's running too hot)
 
#25 · (Edited)
Once in a while I think too much worry, hand-wringing, and analysis is expended on some stuff that is unworthy of too much worry. I'm all about instrumentation and love all the cool gauges on an aircraft panel but so long as the indicators are all pointing roughly in the vertical position, as engineers design them to do when conditions are good, life is good for me. Which is one reason most of the gauges in our cars, spacecraft, and aircraft went back to analog displays with pointers instead of all numbers. The digital numeric readouts that started appearing in the eighties made everyone worry and have to think too much. Life is good for a pilot and driver when all the gauge pointers are pointing roughly straight up. :)
 
#28 ·
The B-52 cockpit looked like a scene from the Airplane movie... gauges on top of gauges on top of gauges. 8 engines, each having about 6 gauges for various functions. What was cool was they have a "Master Caution" light in the middle of the instrument panel. If anything is out of spec it lights up a nice bright yellow. Same function as the Jeep "Check Gauges" light. Gotta love it.

Very perceptive post, Jerry.
 
#26 ·
Today of all things I've had the same problem I believe. Everything running just fine & then I noticed my temp. gauge start climbing past 210. I could smell antifreeze too. Pulled over to check everything out as soon as the check gauges light came on (luckily I was in a good area).. Come to find out, some how that top hose running into the radiator got so hot and looked about pinched & goosenecked causing a blockage. Going to be replacing that hose along with my thermostat. Clutch fan has tension so it's good to go. I limped it home & it did not go past 210 degrees. Anybody had something similar?
 
#27 ·
Not on a Jeep but on a Miata, (don't judge). I had an overheating problem I was trying to chase down. Couldn't figure it out. Finally took it to a guy that had worked on Mazdas. He figured out that the structure of the bottom radiator hose was toast. Anytime I pushed the Miata to highway speeds, the hose would collapse and create a blockage. Once the hose was replaced, it stopped overheating.
 
#32 ·
It is good to have a scanner capable of reading "real time" from sensors. As far as temperature goes-it is also good to have a decent IR thermometer-to check engine temps-as well as exhaust (in the case of cat failure, or some one already gutted it), things like that. Besides men require various tools and toys. It is only right and in most successful marriages the wife know this also. We men like Pick-ups jeeps, motorcycles,tools/toys-women like luxury cars,sports cars,jeeps,shoes/jewlery/clothes,etc. .Just the way it is IMO.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top