Fzj80 overheating on highway during summer months

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Hey y'all

So recently during this past summer I've been going to the ranch more and more often. It is about a 35 minute drive from my house to the ranch and in that drive my cruiser will start to overheat on the highway during the day, (temp outside is 93 and above). to combat from overheating I just turn on the floor heater in the back which seems to work. The drive home from the ranch at night it never even tries to overheat. I've replaced the thermostat and the fan clutch and neither worked. Driving around town during the day never overheats the truck either. It is just highway speeds that do. What could be causing this to happen? any input or advice is appreciated. The truck is a 1995 with 220,000 miles and the headgasket was replaced at 206,000 miles.

Thanks
 
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If only overheat on the highway, most likely not the fan clutch as the radiator should be getting enough air flow to cool. I had a similar situation, overheat on highway above 75, my temp gets up to 215-220 consistently, turned out it was the crappy CSF radiator i had just replaced since my OE blew @ 220k. Needless to say, i yanked the sucker out and straight to the trash and replaced with a Ron Davis....my temp been around 185-190 all day long with AC.
 

flintknapper

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If only overheat on the highway, most likely not the fan clutch as the radiator should be getting enough air flow to cool. I had a similar situation, overheat on highway above 75, my temp gets up to 215-220 consistently, turned out it was the crappy CSF radiator i had just replaced since my OE blew @ 220k. Needless to say, i yanked the sucker out and straight to the trash and replaced with a Ron Davis....my temp been around 185-190 all day long with AC.
^^^^^

I submit this is a common misnomer. The 80 series very much needs the fan to be working to help evacuate air from the engine compartment. Folks think that it is fine to have only 'forced air' working for them. More than one person has had to learn this the hard way. If you don't believe it, take your fan off and go for a drive at highway speed, report back.

Yes, its an oddity....I won't argue that....but its 'real world' when it comes to the 80 series.
 
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MoJ

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^^^^^

I submit this a common misnomer. The 80 series very much needs the fan to be working to help evacuate air from the engine compartment. Folks think that it is fine to have only 'forced air' working for them. More than one person has had to learn this the hard way. If you don't believe it, take your fan off and go for a drive at highway speed, report back.

Yes, its an oddity....I won't argue that....but its 'real world' when it comes to the 80 series.
I agree, after years of anecdotal observations, for what that’s worth. But I’m always curious as to the why.
 

Irish Reiver

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I think the "why" is because the front of the cruiser is like a brick and air forms a bow wave similar to what you would see driving through water. Air is forced over the hood and under the body and very without the fan very little would make it through the radiator. A good response from the viscous fan will pull air in through the radiator. If you see your engine temps rising as you get faster then it is a good sign that your fan needs some attention - probably a higher cst oil.
 

flintknapper

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I agree, after years of anecdotal observations, for what that’s worth. But I’m always curious as to the why.

I am not able to provide a technical reason/answer for it that would be convincing....so I won't try. But I DO know it to be true.

No doubt...Toyota did air flow tests before manufacturing the vehicle, but one of the first things to cross my mind (22 years ago) when looking for an 80 series was how SMALL a grill opening it had.

And the basic shape of the front end being rather 'boxy' has to be creating a 'pressure area' not especially conducive to good airflow either into or out of the engine compartment.
 
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You had a HG failure and left a 20 year old radiator in? If you did replace it then my apologies. Not trying to be a dick but that is the first thing I would replace with a oem. They are a limited life time item. Also i think the older pre 92 80s cant get oem anymore. They spend a lot of time trying to find a good quality radiator. I would definitely by a new oem while they are still available.

They are cheap compaired to a HG and you wont have to worry about it for the next 10 plus years if you dont break it or something. Obviously replace the fan clutch with oem. Even m.j if you just get a good used oem and put proper fluid in it. Thermostats are also so cheap and do wear out and stick. It is a normal baseline item if you have not ever replaced it.

Again not trying to be a dick but dont screw around withthe coolant system. It only takes one part to fail and you destroy your motor. To me the entire coolant system should be part of a normal baseline unless you buy it from some one with solid records of a recent replacement with oem parts.

I have been told that some high end German cars recomend a full coolant system replacement every 8 years. That kind of sucks but I would imagine you would never see problems from it following that kind of maintenance schedule.


To be honest I was chasing temp problems myself at one time. I replaced a few items. Things would get better and the worse and back and forth. After dicking around I just replaced every last part of the system with new oem parts including the radiator and water pump. Never had another problem and no more bandaid fixes. I could move on to other "fun" projects.
 
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The radiator thing is like cancer, small and hard to notice at first but keeps growing until one day something big is noticed. BTW, having went with brass for durability, seriously consider aluminum in choosing your replacement radiator if that's what it proves to be. It's worth a couple degrees better cooling and I wish I had that extra capacity for peace of mind.

BTW, the stock gauge is deadened to avoid alarming drivers, but is not much account for early warning. There is a mod (search Raven Tai gauge mod IIRC) that allows the stock gauge to get real and follow temps closely. Some form of Scan Gauge is even better as it will give you a digital readout that is even more precise.
just ordered a aluminium one today. after purchasing a obd2 temp reader I was a able see what the actual temp of the engine is. I found that my engine on the highway was hitting 210-212 while driving at 60MPH. I did 5 flushes of the radiator the next day with distilled water and the water coler came out the same dark brown every single flush. I figured im gonna start with the radiator first considering the fan clutch was engage fully when it needed to be. hoping this will fix the issue but even if it doesn't I'm happy to know that their is a new radiator in there. thank yall guys so much for the information and help. I will let y'all on know how it goes. Thanks
 
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You had a HG failure and left a 20 year old radiator in? If you did replace it then my apologies. Not trying to be a dick but that is the first thing I would replace with a oem. They are a limited life time item. Also i think the older pre 92 80s cant get oem anymore. They spend a lot of time trying to find a good quality radiator. I would definitely by a new oem while they are still available.

They are cheap compaired to a HG and you wont have to worry about it for the next 10 plus years if you dont break it or something. Obviously replace the fan clutch with oem. Even m.j if you just get a good used oem and put proper fluid in it. Thermostats are also so cheap and do wear out and stick. It is a normal baseline item if you have not ever replaced it.

Again not trying to be a dick but dont screw around withthe coolant system. It only takes one part to fail and you destroy your motor. To me the entire coolant system should be part of a normal baseline unless you buy it from some one with solid records of a recent replacement with oem parts.

I have been told that some high end German cars recomend a full coolant system replacement every 8 years. That kind of sucks but I would imagine you would never see problems from it following that kind of maintenance schedule.


To be honest I was chasing temp problems myself at one time. I replaced a few items. Things would get better and the worse and back and forth. After dicking around I just replaced every last part of the system with new oem parts including the radiator and water pump. Never had another problem and no more bandaid fixes. I could move on to other "fun" projects.
I completely understand now. You're not being a dick. But a little back story on this truck and me. I received this truck as a birthday gift for my 16th birthday. after a few months of owning it the HG went out and it was parked for about a year while I worked part time during high school saving my money to afford the parts and labor it was gonna cost to fix it. We took it to a local shop here who did all the work on the truck(HG wise) . Never in that process of getting the HG replaced did the shop mention replacing the radiator so I just never changed it.
 
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I also understand. Even if you did it yourself sometimes you can only do what you can do. We like to be on our soap box here on mud about maintaining these trucks. But life sometimes limits funds. Glad you are looking at it all now.
I completely understand now. You're not being a dick. But a little back story on this truck and me. I received this truck as a birthday gift for my 16th birthday. after a few months of owning it the HG went out and it was parked for about a year while I worked part time during high school saving my money to afford the parts and labor it was gonna cost to fix it. We took it to a local shop here who did all the work on the truck(HG wise) . Never in that process of getting the HG replaced did the shop mention replacing the radiator so I just never changed it.
 

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