The myth: low temp thermostats, electric fan conversions & "performance" radiators

[jodomcfrodo]

Your needle should sit above 210 most of the time, especially with hot outside temps and the AC on. This is 100% normal.

In terms of heatsoak, how should a TJ behave? I know when I was out crawling on a hot day, if we stopped for a few minutes and I shut off the Jeep, I would pop the hood to let it cool off a bit. While heatsoak comes down to mostly physics, is there anything I can do to allow my Jeep to cool off faster? (Hood Vents wouldn't be a bad start I guess). My Jeep just never really seems excited to start after heatsoaking.

 

[Chris]

In terms of heatsoak, how should a TJ behave? I know when I was out crawling on a hot day, if we stopped for a few minutes and I shut off the Jeep, I would pop the hood to let it cool off a bit. While heatsoak comes down to mostly physics, is there anything I can do to allow my Jeep to cool off faster? (Hood Vents wouldn't be a bad start I guess). My Jeep just never really seems excited to start after heatsoaking.

You could get hood vents, yes.

But let me tell you this... @Jerry Bransford and Blaine are wheeling in arguably the harshest conditions in the U.S. down in Johnson Valley. nowhere that you or I wheel even comes close to that.

If they are doing that with stock cooling systems and no hood vents, then why would you or I need any? We wouldn't...

The hood vents would cut down on heat soak though, yes. But it's not going to improve performance or anything.

If your Jeep has trouble starting when it's hot, that's something unrelated to the cooling system. Sometimes it can be the injectors becoming heat soaked, but you can fix that by wrapping them with insulation material. It could also be issues related to your fuel pressure / fuel pump as well.

 

[jodomcfrodo]

You could get hood vents, yes.

But let me tell you this... @Jerry Bransford and Blaine are wheeling in arguably the harshest conditions in the U.S. down in Johnson Valley. nowhere that you or I wheel even comes close to that.

If they are doing that with stock cooling systems and no hood vents, then why would you or I need any? We wouldn't...

The hood vents would cut down on heat soak though, yes. But it's not going to improve performance or anything.

If your Jeep has trouble starting when it's hot, that's something unrelated to the cooling system. Sometimes it can be the injectors becoming heat soaked, but you can fix that by wrapping them with insulation material. It could also be issues related to your fuel pressure / fuel pump as well.

It doesn't have trouble starting at all, but it just doesn't sound good when it does. Almost sounds like a rod knock when I start it in the heat. I assume because the oil is thinner, but it has no problems running completely fine after a half second. Only happens on days over 85 degrees after a few minutes of heatsoak.

I need to wrap the #3 injector as well. Likes to shake around sometimes. The transmission is never happy in the heat, but I'm going to leave that down to the NV3550 just being a loud transmission. Everything in my Jeep is just louder in the heat, but it all works perfectly fine.

 

[Chris]

It doesn't have trouble starting at all, but it just doesn't sound good when it does. Almost sounds like a rod knock when I start it in the heat. I assume because the oil is thinner, but it has no problems running completely fine after a half second. Only happens on days over 85 degrees after a few minutes of heatsoak.

I need to wrap the #3 injector as well. Likes to shake around sometimes. The transmission is never happy in the heat, but I'm going to leave that down to the NV3550 just being a loud transmission. Everything in my Jeep is just louder in the heat, but it all works perfectly fine.

I don't know man... that not good sound shouldn't have anything to do with the oil (unless something like your oil pump is failing and not getting oil to where it needs to be). That's indicative of a bigger problem, and possibly even warrants a thread of it's own. I've been in some super, super hot situations and never had that sort of noise when I started my TJ.

As for the transmission, I put a Derale transmission cooler on mine, which helps tremendously. I'm not sure if you can install one on a manual transmission though, but that would be worth looking into. What you're describing isn't normal... even with the heat.

 

[jodomcfrodo]

I don't know man... that not good sound shouldn't have anything to do with the oil (unless something like your oil pump is failing and not getting oil to where it needs to be). That's indicative of a bigger problem, and possibly even warrants a thread of it's own. I've been in some super, super hot situations and never had that sort of noise when I started my TJ.

As for the transmission, I put a Derale transmission cooler on mine, which helps tremendously. I'm not sure if you can install one on a manual transmission though, but that would be worth looking into. What you're describing isn't normal... even with the heat.

The transmission I'm not worried about. It has redline fluid in it and its a one year old rebuilt unit. Not really that big of a deal, especially considering the NV3550 is known to be a loud transmission when idling in neutral (which is the only time it makes the noise).

The engine is going go when it goes. It has 225,000 on it. Its been making that noise since I started driving it 3 years and 43,000 miles ago. I just find it weird because it runs flawlessly. Revs quick, has plenty of power, and makes very little noise (besides starting in the heat). I should probably do some research. If I can't find anything I'll grab a video next time its hot out and post up here.

Overall, my Jeep just makes sounds in the heat, making it nicer to drive in temperatures under 85. I hate driving it in the heat a lot of the time if I'm turning it on and off a lot.

 

[Chris]

The transmission I'm not worried about. It has redline fluid in it and its a one year old rebuilt unit. Not really that big of a deal, especially considering the NV3550 is known to be a loud transmission when idling in neutral (which is the only time it makes the noise).

The engine is going go when it goes. It has 225,000 on it. Its been making that noise since I started driving it 3 years and 43,000 miles ago. I just find it weird because it runs flawlessly. Revs quick, has plenty of power, and makes very little noise (besides starting in the heat). I should probably do some research. If I can't find anything I'll grab a video next time its hot out and post up here.

Overall, my Jeep just makes sounds in the heat, making it nicer to drive in temperatures under 85. I hate driving it in the heat a lot of the time if I'm turning it on and off a lot.

It's possible with that sort of mileage on the engine that your rod bearings (and other internals) are starting to get worn down. The heat could indeed be causing it to be worse, that's true.

The nice thing about it is that you can get a fully remanufactured crate engine for around $2000 when the time comes to replace your engine. Had to do that on my XJ!

 

[jodomcfrodo]

It's possible with that sort of mileage on the engine that your rod bearings (and other internals) are starting to get worn down. The heat could indeed be causing it to be worse, that's true.

The nice thing about it is that you can get a fully remanufactured crate engine for around $2000 when the time comes to replace your engine. Had to do that on my XJ!

Just watched some videos on 4.0 knocking. Sounds nothing like that thankfully. I might have to test starting without the clutch and with the clutch to see if its the transmission. I have the fuse pulled so I can start with it in neutral. I start it without the clutch about half the time so I wonder if its the hot transmission making that noise and not the engine. Never makes any noise when cold starting or on days under 85.

It hasn't been hot around here so I may have to wait to test this but I'll definitely post if I can't find anything conclusive.

 

[Chris]

Just watched some videos on 4.0 knocking. Sounds nothing like that thankfully. I might have to test starting without the clutch and with the clutch to see if its the transmission. I have the fuse pulled so I can start with it in neutral. I start it without the clutch about half the time so I wonder if its the hot transmission making that noise and not the engine. Never makes any noise when cold starting or on days under 85.

It hasn't been hot around here so I may have to wait to test this but I'll definitely post if I can't find anything conclusive.

It very well may be coming from the transmission. While I don't own a manual, I've heard enough of them in person to know that that transmission is much louder than the type of manual transmission you'd find in something like a Miata, that's for sure!

 

[bobthetj03]

The NV3550 sounds like a box of rocks in a tumbler. Mine has been noisy like that since the day I've owned it @38K miles. Now has 160K miles.

 

[jodomcfrodo]

The NV3550 sounds like a box of rocks in a tumbler. Mine has been noisy like that since the day I've owned it @38K miles. Now has 160K miles.

Does yours get noticeably louder after long stretches at highspeed or on hot days? I notice that as mine gets hotter, it gets noisier. I can't hear it very much at all in the winter if I'm driving at low speeds.

 

[Steven_Olson]

Chris, I think he meant to block part of the airflow to the radiator. I'm not sure how a 195 degree thermostat would allow the engine to run at 188 degrees. I would think it would warm up to 195 degrees then open the thermostat which would cause the temp to drop and the thermostat to close then repeat.

I am using an obd2 reader and the Torque app on my phone to monitor the engine temps to eliminate the cheezy dash guage. It does cycle up and down but the highest it's gotten was 209 on a 85 degree day with the ac on high. I'm wondering about changing out the thermostat, thinking it might be hanging open a bit too much. I'd rather have more cooling capacity than needed than not enough.

Sent from my SM-N950U using Tapatalk

 

[Cudabnu]

Newbie here, Thanks for the info! my 3 row aluminum radiator was just delivered yesterday, returning it today for a stocker!

 

[Chris]

Newbie here, Thanks for the info! my 3 row aluminum radiator was just delivered yesterday, returning it today for a stocker!

Wise move! You'll be happy you did. Those aftermarket radiators are garbage and don't last long. I've yet to hear of any of them lasting longer than a stock unit.

 

[dbxpete]

Where I live we get 120 degrees for about 4 months of the year and we offroad in the desert, climbing dunes and revving the engine high to be able to do so. down here we mostly have to do SOMETHING about the cooling as we get often cases of having to stop a trip for a bit to wait for the engines to cool down and not spew, especially with bigger heavier tires. down here we tend to change the coolant and use something (forget the name) that boils much later and doesn't expand as much or replace the rad. fewer of us change the thermostat.

I do understand that this is a fringe case and most people won't be revving at 4000 to 5000 rpm going up soft sand dunes at 120 to 125 degrees. it's brutal on heat and a matter of just not being able to extract as much heat with the rad surface area when the surrounding air is crazy hot and you are absolutely thrashing the engine (often on stock setup we get juuuust under the red section of the temp gauge). Also note that we only get the 4.0 down here, not the 4 banger.

EDIT: Probably worth mentioning that a big contributing factor is that the AC needs to be on maximum, full blast all the time so it contributes some too. turn it off and your jeep will probably make it through the day without overheating but you might not, hehe

 

[Chris]

Where I live we get 120 degrees for about 4 months of the year and we offroad in the desert, climbing dunes and revving the engine high to be able to do so. down here we mostly have to do SOMETHING about the cooling as we get often cases of having to stop a trip for a bit to wait for the engines to cool down and not spew, especially with bigger heavier tires. down here we tend to change the coolant and use something (forget the name) that boils much later and doesn't expand as much or replace the rad. fewer of us change the thermostat.

I do understand that this is a fringe case and most people won't be revving at 4000 to 5000 rpm going up soft sand dunes at 120 to 125 degrees. it's brutal on heat and a matter of just not being able to extract as much heat with the rad surface area when the surrounding air is crazy hot and you are absolutely thrashing the engine (often on stock setup we get juuuust under the red section of the temp gauge). Also note that we only get the 4.0 down here, not the 4 banger.

EDIT: Probably worth mentioning that a big contributing factor is that the AC needs to be on maximum, full blast all the time so it contributes some too. turn it off and your jeep will probably make it through the day without overheating but you might not, hehe

Yep, you my friend have a very rare case indeed.

I can see why in your case you would need to do something about the cooling system, since the heat you're dealing with combine with the high speed sand dunes is going to make for a seriously hot engine!

 

[dbxpete]

Yep, you my friend have a very rare case indeed.

I can see why in your case you would need to do something about the cooling system, since the heat you're dealing with combine with the high speed sand dunes is going to make for a seriously hot engine!

the good news is that this engine has thus far survived 120k miles while being taken to the desert almost every weekend for the past 6 years or so, averaging about 15 miles of dunebashing each weekend (minus the hottest month where we just cant do it). This engine really is bulletproof.

 

[mrblaine]

You could get hood vents, yes.

But let me tell you this... @Jerry Bransford and Blaine are wheeling in arguably the harshest conditions in the U.S. down in Johnson Valley. nowhere that you or I wheel even comes close to that.

I'm not going to speak for Jerry but I do not go to JV when it is hot. I made that mistake one time in July. Screw that. It was so hot in those canyons that we had a guy back up, hook the end of a rock 4 feet long, 1 foot in diameter and stand it up. It jacked the axle up almost 4 feet in the air. I told the guy standing in front to come back and check it out since it was pretty neat looking. He told me to piss off, it was too hot to walk that far.

 

[chino1969]

I fell for all of that BS years ago by installing those items on my 95 Cherokee. Did not make the same mistake with my 04 TJ. Also did not install a throttle body spacer or K&N cold air intake after reading many of the posts on this site.

 

[Chris]

I fell for all of that BS years ago by installing those items on my 95 Cherokee. Did not make the same mistake with my 04 TJ. Also did not install a throttle body spacer or K&N cold air intake after reading many of the posts on this site.

Smart man! We all live and learn. Been there and done that myself!

 

[Nightmare9]

I'm replacing my thermostat after getting a P1281 (Engine Cold too Long) code.
I have the Stant 45359 and I was watching a couple of videos on Youtube.
This guy drills a hole in the thermostat to allow and air trapped in the engine to escape. I guess there is a bypass on the side, but he thinks it is too low. Does anyone else modify the thermostat like this?