thoughts on engine temps (1 Viewer)

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1973Guppie

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I wanted to post up for opinions on a recent trip to the mountains and my temps in my my supercharged 1996 fzj80. AC on full blast the whole time.

ambient temp was around 95-100 degrees outside. Elevation of about 4500 and during the drive up the mountain at speed my truck was staying very cool, about 194-200 degrees. But once we pulled into the campground and were looking for our spot I was surprised when I looked down and saw that the engine temp spiked to 220. In order not to have the ac cutoff I quickly turned off the AC and blasted the heat. We were headed back on the roadway and within 2 to 3 minutes of travelling about 35 mph the temps went way back down and I was able to turn the AC back on and temps went back to 194.

So, at speed the cooling system is working great but curious if a spike like that is normal or not? I am running the landtank blue fan clutch with a 3fe fan.

I have plans to add some hood vents as well as an aux fan in the near future.

appreciate any opinions and how to mitigate issues. I would like to keep temps cool when rockcrawling etc as well. I guess time will tell if I have problems.

Noah
 
This happened to me yesterday. Freaked me out but I'm convinced my fan clutch just failed cuz it's not roaring.
 
thx Joey, so you think your fan clutch is toast? mine is only a few years old and was expensive! Is there a lag time when the fan clutch should kick in? I was doing some reading:

http://www.haydenauto.com/fan clutch tutorial-part 1/content.aspx

and it would sure make sense that the clutch was not engaging? we were driving around for about 10 minutes I guess at low speeds.
 
I've had similar issues when climbing to higher elevation (5300 ft or so), and then stopping but keeping the LC on. The temps spike around 212 for me, but just sitting there with the AC off drops it down to 198 or so quickly. I've not had to blast the heat to reduce engine temps yet. Brand new fan clutch and thermostat, nothing changed
 
I don't have a SC but I was recently camping at about 8K and noticed the same as you. I think it's the thinner air to a truck that's not acclimated.
 
What you experienced seems normal. Last weekend was one of the hottest I can remember up on the Rubicon. My temps were right about 200 at trail speed then my wife requested AC on. This was our first hot weather trip in our new to us 80. Although I do not have an aftermarket water temp gauge I did watch my tranny temp gauge climb from 150 to 180 with the AC on. I stopped to verify temps with my infrared thermometer and sure enough the water out tube was now 215 and Tranny pan about 175. Turned off the AC and temps dropped back and stayed good all day. However my wife was a little bit hotter!
 
What you experienced seems normal. Last weekend was one of the hottest I can remember up on the Rubicon. My temps were right about 200 at trail speed then my wife requested AC on. This was our first hot weather trip in our new to us 80. Although I do not have an aftermarket water temp gauge I did watch my tranny temp gauge climb from 150 to 180 with the AC on. I stopped to verify temps with my infrared thermometer and sure enough the water out tube was now 215 and Tranny pan about 175. Turned off the AC and temps dropped back and stayed good all day. However my wife was a little bit hotter!

I need my "witts end" decoder ring to make sense of this post!
 
This also happened to me yesterday right after I got off the highway. Water Temp rose up, A/C cutoff... so I turned the A/C off and it slowly came back down. Today, I changed my fan clutch and am looking to flush my coolant in the next few days. So far so good.
 
well went outside and rotated the clutch, seems to be working fine, hmmm, wonder if it takes a few minutes for the clutch to engage? I guess I will find out on our next trip out......

Keep in mind that the thicker fluid we add also takes longer to get into the parts of the clutch where it can do the job of creating friction to engage the fan.

Cruise along on the freeway for a while and the clutch probably totally disengages. And the water does its job of pulling thermal energy out of the block and head. The water pump does its job of pumping it through the radiator, where it is cooled by the high volume of ambient air flowing through it. That high volume of air, which never gets a chance to heat up much, is the same thing turning the thermostat on the fan clutch, disengaging it.

Now, abruptly stop the truck, and as a result, the airflow through the radiator, because the clutch is disengaged. Residual thermal energy still transferring out of oil/block/head into water, water pumping through system and radiator.. but without the fan clutch engaged it barely pulls air through the radiator which is what would turn the fan-clutch thermostat and make the clutch reengage.. and even once the t-stat turns the process of getting the fluid where it needs to go doesn't happen immediately.

So.. my personal opinion is this is why toyota didn't put 30k cst fluid in the clutches to start with. While that fluid will ultimately make the clutch engage more aggressively, (a function that could also be accomplished by adding ribs to the plates in the clutch if their engineers thought more engagement was necessary) it will take longer to engage because slinging that goop through the tiny holes in the clutch isn't easy.

Fwiw I haven't noticed my truck doing this.. but I haven't been paying ultra-close attention either. I'll keep an eye on it.
 
I need my "witts end" decoder ring to make sense of this post!
I appologize for using such big words. It was a hot day. I was going very slow on the Rubicon trail. My water and transmission temps were normal and stable (unchanging). I turned on the AC at my wifes request. My water and transmission temps then increased a good bit. I then turned AC off. Water and transmission temps then decreased. Findings: Turning the AC on during periods of very warm weather while the enging is working under conditions other than flat cruising will cause water temps to increase which will then cause oil and transmission fluid temps to rise. Solution: Select AC to "OFF" mode and open windows.
 
Side note: my post doesn't explain high temps at trail speeds with AC on.. that is most likely purely heat from the AC condenser preventing the radiator working effectively.
 
You people with your fancy superchargers and air conditioning...
 
Keep in mind that the thicker fluid we add also takes longer to get into the parts of the clutch where it can do the job of creating friction to engage the fan.

Cruise along on the freeway for a while and the clutch probably totally disengages. And the water does its job of pulling thermal energy out of the block and head. The water pump does its job of pumping it through the radiator, where it is cooled by the high volume of ambient air flowing through it. That high volume of air, which never gets a chance to heat up much, is the same thing turning the thermostat on the fan clutch, disengaging it.

Now, abruptly stop the truck, and as a result, the airflow through the radiator, because the clutch is disengaged. Residual thermal energy still transferring out of oil/block/head into water, water pumping through system and radiator.. but without the fan clutch engaged it barely pulls air through the radiator which is what would turn the fan-clutch thermostat and make the clutch reengage.. and even once the t-stat turns the process of getting the fluid where it needs to go doesn't happen immediately.

So.. my personal opinion is this is why toyota didn't put 30k cst fluid in the clutches to start with. While that fluid will ultimately make the clutch engage more aggressively, (a function that could also be accomplished by adding ribs to the plates in the clutch if their engineers thought more engagement was necessary) it will take longer to engage because slinging that goop through the tiny holes in the clutch isn't easy.

Fwiw I haven't noticed my truck doing this.. but I haven't been paying ultra-close attention either. I'll keep an eye on it.

thx for this, makes alot of sense, I would guess that if I would of waiting long enough at a standstill before heading out back on the road the clutch fan would have kicked in eventually. Will have to monitor things and wait for it next time. Overally I was really happy with the way the truck ran and cooled itself in really hot weather. Even headed up the grade on the 8E freeway at 75 mph my temps never got above around 204.
 
Might need to adjust at what temp the clutch kicks in. Mine kicks in when temp gets hot with no delays.

I have blue hub fan clutch with 30k fluid and the adjustment screw close to middle. Also make sure you have enough fluid in there.
 
Might need to adjust at what temp the clutch kicks in. Mine kicks in when temp gets hot with no delays.

I have blue hub fan clutch with 30k fluid and the adjustment screw close to middle. Also make sure you have enough fluid in there.
That might be the case. I set mine at around 190. Last weekend was the first summer test, climbing into the Sierra in 100* heat. Generally 195-200. Peaked at maybe 205*. Immediately dropped to 190 when coasting. I'm guessing I have about 12.5K in the clutch.
 
X2 you people with your new fangled SCs, air conditioning, and vehicles that run, with tires no less. Does anyone run an accessory or addendum electric fan? (Yes I understand you shouldn't have to...but does anyone?)
 
Keep in mind that the thicker fluid we add also takes longer to get into the parts of the clutch where it can do the job of creating friction to engage the fan.

Cruise along on the freeway for a while and the clutch probably totally disengages. And the water does its job of pulling thermal energy out of the block and head. The water pump does its job of pumping it through the radiator, where it is cooled by the high volume of ambient air flowing through it. That high volume of air, which never gets a chance to heat up much, is the same thing turning the thermostat on the fan clutch, disengaging it.

Now, abruptly stop the truck, and as a result, the airflow through the radiator, because the clutch is disengaged. Residual thermal energy still transferring out of oil/block/head into water, water pumping through system and radiator.. but without the fan clutch engaged it barely pulls air through the radiator which is what would turn the fan-clutch thermostat and make the clutch reengage.. and even once the t-stat turns the process of getting the fluid where it needs to go doesn't happen it.


If this is true then it would be easy to justify having an electric aux cooling fan triggered by the AC. It would provide some needed cooling for the period of time it takes for the fan clutch fluid to heat up again and reengaged.

When I did my test run with the orange fan clutch I noticed immediate cooling once I got to the top of the climb and pulled over. I didn't pay attention to whether or not the fan clutch was still roaring but I do have the JDM aux cooling fan installed.
 
The clutch valve moves pretty quick, like full stroke in less than a minute, should respond in almost real time. Thicker fluid has little if any affect on response time.

The temp sender is close to coolant out, so reflects load. When the motor is loaded, then dropped to idle there will be a temp spike, normal. If it more than you prefer, shift neutral or park and bring the idle up a bit until it stabilizes, even in hot weather should only take a couple of minutes.

The A/C takes heat out of the cabin and dumps it in front of the rad, so in hot weather, will see a corresponding temp rise. The incoming airflow to cool the rad will be hotter, also the rad output airflow will be hotter, so the clutch should step up. Unless the clutch is already full on, from excessive adjustment and/or not enough fluid viscosity, so no step up to be had.
 

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