Hot temps when crawling (2 Viewers)

[WCBlueSky]

I did the RavenTai temperature gauge mod, and I am consistently seeing hot coolant temps when it is hot outside, with the AC on, going slow (like crawling up a hill). If I move faster, rev the engine up high while sitting, or turn off the AC and turn on the heater, then the temps go down. I've never boiled out coolant or had the A/C shut off at 227 deg, but it seems like I'm running hotter than I should be, see picture below. According to the RavenTai temp mod thread, this is about 217 deg F, and I've got up to the top of the red in the past, which is about 227 deg F.

Here are some things I've replaced, but still having the issue:

• New TYC radiator, flushed cooling system, added new Prestone 50/50 mix
• New Aisin blue fan clutch, modified with 20K cst fluid and re-timed to open at 95 deg F per the Landtank thread
• New OEM radiator hoses
• New OEM thermostat
• New OEM radiator cap
• New OEM belts, tightened to ~80 lbs using Gates krikit tension gauge
• Aisin water pump has a manufacture date of 2017, no play in the bearings

Here are some tests I've done:

• Block test showed no combustion gases in the coolant
• Coolant pressure test held pressure. One intermittent tiny pinhole leak discovered
• Compression test good
• Checked timing, was advanced to 7 deg, set it back to stock 3 deg

From everything I've read, a modified blue fan clutch should fix this, but it doesn't seem to be helping. Any ideas would be appreciated.

 

[-Spike-]

If you haven't, you can fill the spaces around the radiator with open-cell foam and weatherstrip tape to ensure all the air is going through the radiator core, rather than around it. You can seal the rad to the core support, and also put some between the rad mounting rails and the rad core.

My system is as efficient as possible, but when idling in extreme heat it will occasionally get hot enough to shut down the A/C. I have a hand throttle, so I run the engine at 1200-1500 RPM when I'm not moving.

 

[WCBlueSky]

Thanks Spike, I will definitely put some foam in.

Do you think an electric pusher fan would help keeps temps down when I'm not moving? (I don't have a hand throttle.)

 

[Bludozer]

Do you think an electric pusher fan would help keeps temps down when I'm not moving? (I don't have a hand throttle.)

Arguably yes, but as @-Spike- said, if you're crawling at uber low speeds in peak summer heat, high temps are to be expected.

 

[-Spike-]

Thanks Spike, I will definitely put some foam in.

Do you think an electric pusher fan would help keeps temps down when I'm not moving? (I don't have a hand throttle.)

Sure, more air is better. Most electric fans don't move much air though, and putting one in front of the A/C condenser is not going to do a lot for the radiator. I have one (from a 100 series), the effect is minimal. I plan to put on two larger ones, but mostly for the A/C. A hand throttle is cheap and will take less time to install than a fan, and will do more for you. The downside is that it's not automatic.

 

[WCBlueSky]

What do you do when crawling down a steep rocky hill and you are mostly on the brakes, with virtually no throttle? Can you still use the hand throttle to rev up the engine?

 

[greentruck]

If you're running hot on a long downhill, you may have bigger problems. You really want to be able to go back to idle when moving downhill, too easy to get yourself into trouble otherwise.

 

[WCBlueSky]

Going down a hill at 20 mph or more, I have no problems. Going down a hill at 0.5 mph, when the engine is already heat soaked, I get rising temps.

 

[GreatWhtCrewmax]

Have you verified the the actual temps your seeing? Maybe the temperature sender is starting to fail. Maybe tee in an analog gauge to verify, with everything being new and a blue fan clutch I have a hard time believing it’s getting that hot.

 

[greentruck]

Going down a hill at 20 mph or more, I have no problems. Going down a hill at 0.5 mph, when the engine is already heat soaked, I get rising temps.

There's the possibility here that once you get the foam in place around the radiator, this should improve. If it doesn't, although you've tested, keep an eye out for the possibility of a failing HG.

 

[bicycleagent003]

If your rig is OBD2, I would suggest getting a cheap OBD reader and using the free Torque Lite app to see the actual coolant temperature. Even with that temp gauge mod, I think it would be helpful to have an actual F temperature number. You've done a lot of work on your cooling system, it's surprising you're getting such high numbers. Good luck.

 

[-Spike-]

What do you do when crawling down a steep rocky hill and you are mostly on the brakes, with virtually no throttle? Can you still use the hand throttle to rev up the engine?

I have the truck in low range and first gear. If it's moving at all, it's well over 1500 rpm. I don't run the hand throttle when in gear, unless I forget to release it. There are occasions where I move at idle, but they are rare and short.

On a side note, I don't ride my brakes if at all possible. I let the engine slow the truck. 5.29's help with that, but only 10% underdrive vs. stock gears and tires.

 

[WCBlueSky]

The high engine temps appear real. As a test, I drove around the city (outside it was 93 deg F) and then pulled into my garage with the A/C on and let the engine idle for a couple minutes. The needle rose to just below the red on the gauge. I used an infrared thermometer to measure, and everything was above 215 deg F: the upper radiator hose, the thermostat housing, the cylinder head...,which roughly matches the scale of the RavenTai gauge. I turned off the A/C and the temp quickly dropped back to normal while still idling.

 

[DSRTRDR]

how about you get yourself an Ultragauge and report your numbers ? - the simplest version costs around $80 - UltraGauge OBDII Scan tool and Information Center

 

[WCBlueSky]

94 is OBD1, unfortunately.

 

[80t0ylc]

I also have a '94, but am running 35's, significant armor(weight) and pull an off road trailer. The TYC made the biggest difference in my cooling system improvement efforts and I came to realize that the old brass/copper radiator had reached it's limit and the aluminum was more efficient. Looks like you're running the TYC so as @-Spike- mentioned, seal up the edges, so your fan shroud will channel the air throught the radiator. Last, but definitely not least, I've found that running in low range, especially when the engine is under load will keep the engine temps lower. You'll notice, with your new modified temp guage, that engine temps will climb with the slightest uphill grade. That's because the engine's working harder. Anything you can do to make it easier on this 1FZ engine, will pay dividends to keep it cool. I'll run low range, offroad, even though I don't need it, if I'm running 25 mph or slower to keep rpm's higher and the power shifting points that low range provides.

 

[baldilocks]

Or simply accept the fact that you can’t crawl in summer heat with the AC on. What you describe in the opening post, I experienced the first time I ran AC for my wife while creeping on the trail. I’ve left the AC off on the trail since then and coolant temps stay low.

 

[-Spike-]

Or simply accept the fact that you can’t crawl in summer heat with the AC on.

Oh hell no.

No.

On the other hand, I generally head to cooler climes to wheel in the summer, so I can't really talk. Wheeling in 110+ degrees is miserable no matter how cold the A/C or engine is.

 

[80t0ylc]

Or simply accept the fact that you can’t crawl in summer heat with the AC on. What you describe in the opening post, I experienced the first time I ran AC for my wife while creeping on the trail. I’ve left the AC off on the trail since then and coolant temps stay low.

Before I replaced my copper/brass radiator with the TYC, I couldn't even run the A/C with ambient temps above 95* on the highway. That kinda defeats the intent of air conditioning - doesn't it? Can't use it when you really need it. I'm able to use the A/C most of the time crawling. I've had to kick A/C on to keep my iPad from overheating using Gaia while in unfamiliar territory to keep me on track. I believe the combo of TYC, Wit's end tuned fan clutch & 5.29's plus concentrating on making it as easy as possible on the 1FZ allows me to run the A/C. Got to have it!

 

[baldilocks]

Oh hell no.

No.

Remember that when the engine coolant is hotter, the transmission temp also rises. That day I ran AC while on the Rubicon my trans temp went up to 175 before I turned the AC off. Not only are higher temps not good for transmission life, more heat is radiated up into the cabin floor. So your head might be cooler with the AC on but your feet probably won’t be.