Running hot at highway speeds. (1 Viewer)

[TEXASLAWMAN]

1997 170k miles, 35" tired j springs l shocks, brand new radiator, blue fan clutch, new thermostat, new hoses, new fluids.

With ac on it gets hot above 60mph without ac on it gets hot above 70mph.

Per scan gauge below 70mph with no ac gets to 193-198 degrees above 70 mph slowly climbs to 215 if I turn on heat it drops to 190s.

What gives....

 

[erse]

What is your exhaust set up? cats? Muffler? new/ old? clogged perhaps?

 

[Tools R Us]

... blue fan clutch, ...

This is likely your problem. In stock configuration that are not strong enough for hot weather. I would swap the fluid for 25-30K and see what that does.

 

[TEXASLAWMAN]

This is likely your problem. In stock configuration that are not strong enough for hot weather. I would swap the fluid for 25-30K and see what that does.

At highway speeds I thought the fan would be for lower speeds.

Also I took this fan clutch of my 95 that was set up exactly the same it did not run hot.

 

[TEXASLAWMAN]

What is your exhaust set up? cats? Muffler? new/ old? clogged perhaps?

Original exhaust but no error codes, power seems good.

 

[Tools R Us]

The '80 is fan dependent at highway speeds, especially with grades and A/C, in hot weather.

 

[Gabriel 71]

Up the weight of the oil in the fan clutch. I bought a blue fan clutch and before I even put the thing on took it apart and put heavier silicone oil in. It's more than likely your fan clutch.

 

[flintknapper]

I'd 20K that fan clutch for sure. And check to see that your CATS aren't degrading (You should have at least 100° F temp difference from in front of the cats to where they end, if working properly, check exhaust back pressure as well).

Then we can move on to other possible causes.

 

[450LX]

I just did a headgasket on my truck and wanted to clean the cooling system as soon as I got it back together. I used a product called Thermocure. I have always been skeptical of flushing agents, but holy smokes this stuff works. I flushed the cooling system with the hose and made sure to remove the block plug. After flushing I filled with distilled water and the quart of thermocure. I drove around getting it up to temp and let it sit for 6 days. Periodically I would start it up and let it idle to operating temp to keep it circulating . After those 6 days I flushed the entire cooling system again and was amazed how everything looked inside the radiator and thermostat housing, everything looked brand new! I put a little in the overflow tank and at the end of the 6 days you could see exactly how full The overflow tank was because the bottom on it was perfectly clean, but the top still had the 20 year old stains on it. The Thermocure removes rust and is biodegradable and doesnt have any harsh chemicals or acids in it, it's made for cooling systems. After doing the Thermocure my truck is running 179 degrees and if I'm hard on it the truck hits 185 on the scan guage. I don't know if this makes since but before the flush it took for ever to fill the cooling system. The water was going in slow and burping took for ever. After the thermocure the water and antifreeze mix fill went into the radiator so fast and took 3.5 gallons extremely quickly. I burped the system with the engine running and it took hardly any time at all compared to filling it up the first time. Like I said Im always skeptic of 'snake oils' but this stuff blew me away. Amazon and Summit sells it and it has almost all 5 star reviews.

 

[sleepycruiser]

Before I did a coolant flush I was getting a steady 185 degrees. After I get about 190 degrees. What higher temp should I be concerned about? What temperature would signify getting too hot?

 

[bloc]

"Too hot" varies.. depends how long and how the truck is operating when it happens, but 190 is nowhere near it.

 

[Kaninja]

215 is fine. It is when you hit 225+ sustained I would look at what is going on. What are the ambient temperatures outside when you are seeing 215?

 

[TEXASLAWMAN]

I'd 20K that fan clutch for sure. And check to see that your CATS aren't degrading (You should have at least 100° F temp difference from in front of the cats to where they end, if working properly, check exhaust back pressure as well).

20k or 10k in the fan clutch? I have both.

Then we can move on to other possible causes.

 

[TEXASLAWMAN]

215 is fine. It is when you hit 225+ sustained I would look at what is going on. What are the ambient temperatures outside when you are seeing 215?

It was humid and in the low 90''s

I did drain the fluid filled with 20% antifreeze and wetter than wet. She averaged 205-210 on the way back.

 

[flintknapper]

We are both in Texas (me in Deep East Texas). Pretty much like a Sauna where I live most of the year. I put 20K in my blue hub, made a big difference. Got that 'roar' back at start up, my highway temps are normally about 190° F in the summertime and rise to about 193°-195°F in town with A/C on.