Fzj80 overheating on highway during summer months (1 Viewer)

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Joined
Aug 25, 2021
Threads
1
Messages
9
Location
Corpus Christi Texas
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
 
What fan clutch did you install, OEM or aftermarket? A large number of members in similar climates drain the fan clutch and replace the fluid with higher viscosity fluid. Searching will give you numerous results.
 
You likely just answered your question, probably a long list of threads discussing the inferior quality of the aftermarket clutch.

When you say overheat: The A/C cuts off, steam from under the hood or just a high reading on a scan gauge?
 
You likely just answered your question, probably a long list of threads discussing the inferior quality of the aftermarket clutch.

When you say overheat: The A/C cuts off, steam from under the hood or just a high reading on a scan gauge?
alpologies, I've never used this site before. The gauge will just sky rocket when it occurs.
 
The aftermarket clutches are problematic, in fact many people modify or buy a modified fan clutch to enhance the cooling ability of an 80.

Does the AC cut off when this happens?
 
Check your radiator. Unless it was replaced after the HG failure, it's likely original. They develop areas of poor circulation that remain cooler than the properly functioning part of the radiator. Get one of those cheap remote read thermostats like Harbor Freight sells and examine the radiator for the cool spots after you've shut down having got it good and warm.

BTW, seeing the stock gauge in the red means that you've got something going on that needs pretty immediate attention.
 
The aftermarket clutches are problematic, in fact many people modify or buy a modified fan clutch to enhance the cooling ability of an 80.

Does the AC cut off when this ha The ac was blowing cold up until I turned the heaters on.
The ac blows cold up until the point I turn on the heaters to cool down the engine. It's never cut off
 
Check your radiator. Unless it was replaced after the HG failure, it's likely original. They develop areas of poor circulation that remain cooler than the properly functioning part of the radiator. Get one of those cheap remote read thermostats like Harbor Freight sells and examine the radiator for the cool spots after you've shut down having got it good and warm.

BTW, seeing the stock gauge in the red means that you've got something going on that needs pretty immediate attention.
He said it doesn't have a problem over heating during regular town driving...isn't that when the fan clutch is being used and not at highway speeds?
Really good advice on the stock gauge, they don’t move much until it is too late. And definitely needs immediate attention

My experience is the AC cutting off is the first sign it’s getting hot.

@bhsdriller brings up an excellent point regarding low speeds, however since it’s an aftermarket the fan clutch is the first thing I would change along with the radiator if it’s the original.

Have you added anything like lights etc in front of the grille?
 
Check your radiator. Unless it was replaced after the HG failure, it's likely original. They develop areas of poor circulation that remain cooler than the properly functioning part of the radiator. Get one of those cheap remote read thermostats like Harbor Freight sells and examine the radiator for the cool spots after you've shut down having got it good and warm.

BTW, seeing the stock gauge in the red means that you've got something going on that needs pretty immediate attention.
will try this, also i see it rise decently fast but as soon as the heaters turn on it drops back to operating temp. The only time the truck ever touched red was before when the HG blew. Since then I've watched the temp gauge as if its my spedometer just in case anything fails.
 
Really good advice on the stock gauge, they don’t move much until it is too late. And definitely needs immediate attention

My experience is the AC cutting off is the first sign it’s getting hot.

@bhsdriller brings up an excellent point regarding low speeds, however since it’s an aftermarket the fan clutch is the first thing I would change along with the radiator if it’s the original.

Have you added anything like lights etc in front of the grille?
Recently yes I have added lights but this issue occurred before the lights were put on. and no I didn't buy the lights before addressing the issue. I received them as a gift so I put them on anyways.
 
He said it doesn't have a problem over heating during regular town driving...isn't that when the fan clutch is being used and not at highway speeds?

That would seem to be logical but for some reason is not the case with our 80's. The 80's may be unique in how the body/front facia is designed where it builds high pressure in the front that doesn't allow air to pass unless it is pulled through by the fan. Earlier this year there were a couple of similar problems reported that were resolved with a new fan clutch or higher viscosity fluid.
 
Radiator cap
Radiator
Coolant condition
Coolant level
Hoses
Thermostat - properly oriented and functional
Water Pump
Fan clutch
Fan blades
Fan shroud
Unobstructed airflow to the grill
 
will try this, also i see it rise decently fast but as soon as the heaters turn on it drops back to operating temp. The only time the truck ever touched red was before when the HG blew. Since then I've watched the temp gauge as if its my spedometer just in case anything fails.
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.
 
Texas truck.

Needs engine coolant system flushed, replace radiator, order a blue hub fan clutch and mod with 20K CST silicone fluid. That should solve your issue. If not....plop a Motorad failsafe 170°F Tstat in it.

Its assuredly not just one thing. Remember your truck has a cooling SYSTEM and yours is no doubt in need of a good going over.

I am in similar Texas Weather, my vehicle has more than 100K miles more than yours and it runs 188-190°F on the highway A/C blasting.
 
Recently yes I have added lights but this issue occurred before the lights were put on. and no I didn't buy the lights before addressing the issue. I received them as a gift so I put them on anyways.

Since you have an OBDII truck, get a Scangauge so you can get an accurate reading of truck temp. The stock gauge is not reliable in any shape or form.

Make sure no air in system and thermostat isn't upside down.
 
Since you have an OBDII truck, get a Scangauge so you can get an accurate reading of truck temp. The stock gauge is not reliable in any shape or form.

Make sure no air in system and thermostat isn't upside down.
ScanGauge temp.jpg
 

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