Preventing overheating

[Dusty]

My well maintained 96 lx450 runs perfectly and does not overheat 99% of the time. But if pushed hard enough in the right circumstances it can get too hot and I am trying to find the most cost effective way to make my 1fzfe overheat proof.
I recently returned from a 4,300mile holiday driving aroung the western US (Co, Ut, Id, Mt, Ca) and the 450 was flawless and did everything I asked of it from bouncing down muddy trails in Montana and the Sierra Nevadas to cruising across the interstate as fast as reason and my radar detector would allow. On only 4 occasions did the truck disapoint; when the AC cut out over 3 passes. The pass that heated her the most was the I15 pass between Vagus and baker at 115 degrees outside with the AC cranked, 700lbs of family and gear, and cruising at over 80mph. I have a digital auxilary temp guage (from summit) plumbed into the upper radiator hose and it was registering between 205-215 degrees depending on terain before we got to the pass. As the 450 got farther up the pass so did the temp. I turned off the OD and let the tach climb to 3,700rpms. At 220 degrees on my guage the ac quit (yes i know it is suposed to do this at 226 degrees) and i continued to slow to keep the temp below 230 degrees. I had to stay between 55-65 mph and the AC kept itself off for about 20 min-not comming back on till we were over the pass and the temp had fallen below 220. Durring this pass incident the oem guage got to just below 3/4. I counted over 20 cars pulled off the road on this particular pass-probably all overheated.
I experienced similar ac cut out to a lesser extent on the way back over this same pass from Ca into Nevada and on the pass from Salmon Id into Montana and climbing into the Sierra Nevadas going to Shaver Lake from Fresno. In each of these situations it was hot outside, the AC was on, and the 450 was heavy and running hard.
This is the first time I have pushed my rig in such heat. This is the first time I have had the AC cut out. I believe my 450 is in top shape. I have had it for 2 years and 30,000 miles now. I have climbed this pass in the winter without a problem. I have climbed the 70 out of Denver on several occasions without a problem. But this is the first time I have climbed in real heat.
I would like to be able to climb passes using all 212 hp the 1fzfe has to offer. And I would like to do so in 120 degree heat with the AC on and 1000 lbs of gear aboard. AND I DONT WANT TO SLOW DOWN DEAR..."ITS MY TURN TO DRIVE AND I'LL GO AS FAST AS I WANT, WHEN ITS YOUR TURN YOU CAN DRIVE SLOWER".
So here are the options I have come up with:
1. huge auxillary oil cooler using a sandwhich adapter under the oil filter-possibly one with a fan
2. auxillary fan in front of radiator
3. Different radiator (this could get expensive)
4. listen to wife and slow down

In presenting this post I am assuming a healthy 1fzfe with a perfectly performing oem colling system can be overheated if pushed hard enough.
On another note I cant see how you guys with forced induction can possibly push your rigs hard for extended periods of time in the heat without overheating using the oem cooling system.
Any ideas?

 

[alaskacruiser]

I wouldn't assume you have a perfectly performing cooling system until you verify this is true. At the least:

1. Verify that your radiator isn't clogged or operating with severely restricted flow (this is apparently a common problem, esp. on the 95-97s with the alum. radiators, and esp. if you accidentally mix reg/green coolant without a proper flush)

2. Verify that your radiator fan clutch is working properly (search for more info). These can wear out.

Also, please specify more info about your rig, like mods and how many miles are on it.

 

[Dusty]

alaska
good point
-I have flushed the radiator 3 times since i got it and use eth glycol.
-I did the fan blade hold test and almost cut off my hand (use a welding glove)
-I have had my 96lx450 for 30,000 miles and have the lexus recorded service hx (i am the 3rd owner and both the prior 2 did their service at the dealer). i use M1 synthetic 5w40 and send my oil to blackwell labs for analysis-it is doing great. I have personally checked the valve clearances. I have a preluber on my rig and and auxillary trany oil filter.

 

[Dusty]

I believe my rig (with 130,000 miles) is running perfect. Is it not possible to overheat this motor as it comes from the factory if pushed hard enough? I immagine it is and I believe I am just the man to overheat it. Although I wouldn't trade my rig for any ford or chevy I also don't think the 1fzfe is bombproof. Can it be made cooler? I also know aluminum conducts heat much better than brass and cant see how the brass can make it cooler. Any objective data? Objective data is hard to come by with the oe guage.

 

[bjowett]

For serious duty.... only an engine oil cooler will suffice. I know the 1FZ already has one from the factory, but it's a oil to coolant unit... and that just places more heat into the cooling system. A good full flow external unit works wonders. I will be designing one for my 4.6L, I'll be happy to share the parts list with you.

 

[flintknapper]

I believe my rig (with 130,000 miles) is running perfect. Is it not possible to overheat this motor as it comes from the factory if pushed hard enough? I immagine it is and I believe I am just the man to overheat it. Although I wouldn't trade my rig for any ford or chevy I also don't think the 1fzfe is bombproof. Can it be made cooler? I also know aluminum conducts heat much better than brass and cant see how the brass can make it cooler. Any objective data? Objective data is hard to come by with the oe guage.

Other things to check are thermostat... (might not be opening all the way), radiator cap...(if leaking will let temps. rise more quickly), lower radiator hose...(at high speed can collapse if spring is not in good shape).

Aluminum conducts heat better, but does not dissipate heat as well. I did alot of testing with the help of Thermo-Dynamic Inc. on Aluminum radiators when we went to a Cummins M-11 diesel in Foretravel coaches.

We found that "core design"..those with the most favorable aspect ratio, outperformed the others regardless of material. We tested both aluminum and copper/brass. That was about 8 yrs. ago and at that time aluminum radiators had a much better core design than the C/B units.

All things being equal...I would choose copper/brass over aluminum if weight was not a factor. Maybe current technolgy has come up with a way to furnace braze copper/brass instead of soldering. If so...that would be my pick.

 

[Dusty]

Thanks Bjowett
Id like to see your parts list when you have it. I was thinking about doing a sandwhich adapter at the oil filter-is there another way to plumb it?. I was also thinking about getting a cooler that comes with an integrated fan and thermastat.

 

[RavenTai]

Thermal conductivity of other common materials:

Material Thermal conductivity W·m-1·K-1
Diamond 1000-2600
Silver 406
Copper 385
Gold 320
Aluminium 205
Brass 109
Platinum 70
Steel 50.2
Lead 34.7
Mercury 8.3
Quartz 8
Ice 1.6
Glass 0.8
Water 0.6
Wood 0.04-0.12
Wool 0.05
Fiberglass 0.04
Expanded polystyrene ("beadboard") 0.03
Air (300 K, 100 kPa) 0.026
Silica aerogel 0.017
Styrofoam 0.01

aluminum may conduct heat better than brass by almost twice but copper conducts better than aluminum by almost twice, the Tacoma radiator had copper fins not sure about the tubes but the metal air joint of the fins is where it really matters

I woudl still like to give a early "brass" radiator a close eaxmination see if it has copper fins not brass.

 

[Dusty]

We found that "core design"..those with the most favorable aspect ratio, outperformed the others regardless of material.

interesting. On that same note i recently read that fin and plate oil coolers (more expensive) work better than fin and tube

I know it is possible that my thermastat may be sticking and my lower hose may be squishing but to reemphasize my point...IS IT NOT POSSIBLE TO OVERHEAT A PERFECTLY GOOD 1FZFE IF IT IS PUSHED HARD ENOUGH? Are there not others out there that can overheat their well maintained rigs when racing up passes in loaded cruizers with the AC on?

 

[PHAEDRUS]

While mine is not a 1fze and has the older bus tranny it has been my expereince that the overdirve is your best freind in high temps. running hard in 3rd and 4th especially in rpms in excess of 3400 is a sure firee way to get my rig to start inching up in temps.
this is not just a function of the engine oil cooler but the tranny cooler wich routes into the side of the radiator. I would not be surprised if a aux tranny cooler solbved more of your problems than any engine oil cooler. I almost installed one prior to my last Moab trip (from the seattle area) Decided just to slow down a bit and had no problems.
if memory serves the amount of flow of trans fluid into the radiator drastically reduces once you are in overdrive. running hard in 3rd and 4th gear pumps more hot tranny fluid inot your overall cooling system and makes you run in higher rpms overall wich I think is leading to the issue you described.
Dave

 

[landtank]

I was driving around death valley a rew years ago in 130 deg weather. 4 people and gear for a cross country trip. The AC cut out twice, but that's it. After a few minutes it was back on for quite a while.

 

[alaskacruiser]

Dusty- I also have a data point: I was in Death Valley in '03. My rig was loaded with gear and 4 people, the AC was on all the time, and the temps were 110+. I intentionally asked for trouble by turning overdrive off and driving for extended periods at high RPMs, and my AC never cut out, nor did my temp guage move past the halfway point. My aux. temp guage read 220 max. Maybe important to note that this was shortly after a new radiator (OEM aluminum) and thermostat. Fan clutch is still original, though, and passes the "cut off your hand" test.

 

[landtank]

I intentionally asked for trouble by turning overdrive off and driving for extended periods at high RPMs

Wouldn't this help the situation by circulating the coolant faster?



And mine wasn't no "data point", just an acount of a past situation.

 

[PHAEDRUS]

Rick,
this circulates hot atf fluid into the rad faster, not the coolant.
although as I type this by nature the coolant would be movign faster, possibly having less time to discharge heat before returning back to the block???
Dave

 

[bjowett]

93 and up have a monster fluid to air tranny cooler in addition to the coolant piece... part of the standard tow package, if I am not mistaken...?

I'll post what I dig up asap.

 

[Rich]

In general, when climbing a steep slope, lower gear translates into more rpm which results in higher fan speed, which should provide more cooling.

Do note that with overdrive off, at least with the '97 tranny, the torque converter can lock in 3rd gear. Heavy throttle with unlocked torque converter will heat up the tranny fluid quickly.

I have only experienced the AC cutting out when fully loaded with expedition gear - all space behind the front seats filled with gear and temps ranging from 110 - 120.

On paved roads has only happened on climbs so steep that downshifting into 3rd or 2nd gear was required. Has also happened with same temps and load, but offroad in low range where the slope was extremely steep and vehicle speed, due to terrain, was around 5mph, resulting in very little airflow. This latter situation is where an aux electric fan would be beneficial. I wouldn't be surprised if I was due for a fan clutch replacement.

 

[Dusty]

Great help. Its good to know that others can heat their rigs till the AC cuts out. I immagine that if I replace the radiator my rig may possibly run cooler up hot passes but these recent overheating incident(s) represent isolated occurances taking place under extreme circustances (for me anyway). I can't justify replacing the radiator for what may very well be normal functioning for the 1fzfe. I consider 2 important points: 1st the 1fzfe has an AC cut out function so the designers knew it could overheat and second the engine only makes 212hp and a lead footeded individual like myself could easily use most of those for extended periods of time on inclines which may tax any reserve the cooling system had.
I'm thinking a bigger trany cooler and a fan driven oil cooler may do the trick.
Can you guys with forced induction race up hot passes without overheating? I know Cdan has an aux fan and methanol injection. I know some have intercoolers. What else are the blown dudes using to squelch the heat?

 

[MTNRAT]

OK here goes. If your cooling system is not operating PERFECTLY what you experienced will happen. IF it is working perfectly what you experienced will NOT happen.
I had the same problems.
I will bet dollars to donuts you need to replace the radiator. These things are notorious for failing especially if there has been any mixing of coolant types. While you are at it replace the thermostat.
So to sum it up:
-replace radiator with a 1994 3 core brass radiator part # 16400-66040
-replace thermostat
-possibly replace fan fluid coupling.
-use TOYOTA red coolant and make sure the block and heater core get flushed.
-flush rad, block and heater core every two years at least.
Even being supercharged and pulling a 4000 lb boat up the Coquhalla Pass in 100degree heat at 60-70mph no heat issues at all.
Before replacements I could get heat issues going up that pass at 40mph at 80 degrees.
Better safe than HG problems.
Cheers,
PS. Cdan can provide the parts at a great price.
Sean

 

[MTNRAT]

BTW I am of the belief that anyone haveing the AC cut out is because of a compromised cooling system. The AC is designed to cut out when things are not working properly. This helps protect the engine when something is wrong. I do not think this is normal.
Cheers,
Sean

 

[Dansan]

Having originally lived in Chicago then moved to LA, I'm very familiar with I70 westbound out of Denver and I15 around Baker, California. The problem stretch on 15 is up the hill out of Baker, to Las Vegas.

In August of 1999, I towed a dual axle U Haul trailer with about 2500 lbs of stuff and had an additional 750lbs inside the truck. My vehicle is a 1995 LC that had 75K miles at the time. All the way to California, the temp gauge never went above the middle and outside temps were 90 - 110 along the route.

The AC may have cut out, but it was imperceptable. Baker up to Halloran's summit is not the steepest grade or the greatest rise in elvation for a major road, but, it takes place in an area with unrelenting summer temps. I usually pass through it very early in the morning but I have still seen August temps in Baker at 6am, over 95 on the giant thermometer.

I believe I could tow in the heat of the day, but would only do so if I had to. Even with excellent maintenance, components wear over time. That journey will exploit any weakness in the cooling system and turn it into a major cause of failure.

I just replaced my coolant (Toy red and distilled water), replaced the PHH and thermostat. At 117K, the PHH looked fine to me except maybe for the beginning of a slight bulge. Perhaps, if we want to avoid HG issues, the fan clutch and the radiator themselves need to be PM items. After all, HG failure translates into a $2K and up repair for those not skilled or disposed to do it themselves.

Its interesting to read about designing a rig to routinely withstand the hottest and heaviest operating conditions but what is the real world cost benefit?