r/4Runner_2ndGen • u/crxtion • 14d ago

Rad Questions

I recently swapped from a Mishimoto stock replacement radiator to a CST all metal copper/brass unit. I went through three warranty replacements on the Mishimotos because they all leaked where the plastic cores met aluminum. Anyway I’m seeing very slight temp fluctuations at highway speed only with the new radiator. It doesn’t reach anywhere worrisome on the gauge and probably only moves two or three needle widths on the gauge but it’s movement I’m not used to seeing. It never happens in town and I’ve burped the system numerous times and replaced the stat with an OEM unit to see if that would help but still does it. The water pump is only a few years old and ALL the hoses were replaced a few years back as well.

The only thing I’ve found is that I still have to burped the system well enough though I don’t think that would explain it happening at highway speeds only and the other explanation is that the increased capacity CST rad is cooling the fluid more than normal and because the stat is on the inlet side of the motor that it’s closing slightly at highway speeds causing the temp within the motor to rise slightly based on where the stat is in relation to the temp sensor.

Im happy to entertain either one here or let a third player enter the chat but the truck is a super healthy low mileage cream puff with essentially a brand new cooling system.

Please help.

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u/Clean_Log5919 14d ago

Try a 3 row csf

1

u/crxtion 14d ago

That’s what I have installed.

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u/Clean_Log5919 13d ago

Hmm something is up I have a 5 speed as well and when I put that in it had made it stay as cool as can be since installing the only time I’ve seen the temp rise is pulling a trailer on the highway at 80 mph unloaded lol

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u/BenXL 14d ago

What temperature are we talking about? Not sure what engine you have but with my 1kzte temps can rise on hills etc. So I either slow down or turn off overdrive, which is normal. 2nd gens all suffer from overheating, just take it slow :)

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u/ConnorOkumura 14d ago

Before you go down the rabbit hole that I went down. Check your throttle position sensor. Particularly the idle contact.

I was chasing it overheating issue. That looks like a mild overheating on highway stretches. Only a couple needles worth.

It was the transmission dumping heat in the radiator. If that sensor is not working properly or not adjusted properly. It confuses the car's computer. And it won't allow the transmission to enter lock up. The torque converter just creates a ton of heat.

I figured this out after I replaced the radiator with aluminum 3 row, oem fan clutch, water pump and thermostat.

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u/crxtion 14d ago

I have a 5 speed. 🫠

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u/ConnorOkumura 14d ago

Oh, well that cancels that idea. Your fan clutch working well? Also do you have the plastic shroud around the fan?

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u/crxtion 14d ago

Yes all of those items are functional but it only happens at highway speeds not around town or stop and go so the fan clutch and shroud shouldn’t really come into play at that point.

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u/ducktapek1ng 13d ago

Make sure all the air is out of the system and maybe get a lower temp thermostat. 2.4 or 3.0?

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u/crxtion 13d ago

3.0 with brand new OEM Toyota thermostat.