Radiator Theory

[qwkphkr]

Ok, so I have a 96 3500Hd. At 55 mph on a 60-70 deg day, the temp runs about 210-220, any faster and the temps go on up. When it's sitting it will run 180 all day long. It doesn't overheat in city driving, just when it gets to hwy speeds (usually 50 mph+ for 10 min or so). Keeping it at 55 mph will keep the temp steady.

I read that the aluminum radiator has a limited lifespan, something like 12 years and then no matter what the al is too corroded to cool effectively. My theory is that I need a new radiator, since it seems to work fine at lower speeds and Idle. The fact that it cools at idle tells me that the fan and thermostat are working fine.

Before I drop $230 on a rad, and installation price too, I wanted to see if someone could verify my theory.

thanks!

[JD_countryboy]

have you ever thuroly cleaned the outer fins of the radiator? If you cant force air thru the cooling fins, you will never cool the coolant. And does your fan clutch fully engage and lock up? What color coolant are you running, and whats the condition of the coolant?

[3bals]

Do all that stuff that JD said and see what happens. I had the same issues. It would get hot under load at speed. Washed it carfully with a power washer from the inside engine bay out, flushed, switched coolant (to green) and changed T stats. Went on a road trip with in bed camper to Utah in July. It over heated several times on the trip. It never boiled over, just got real hot.

Made it home put in a new radiator. Problem solved, never overheated again, but the damage had already been done. Cracked head(s), coolant leaked into cylinder, bent or broken rod(s) and/or rod bearings. Engine kaput!

[ZiGBlazer]

My truck was running warm, 210-225, when I bought it. Normal temps. When I dyno'd it temp shot up quickly to 235 before I let off. Normal driving wouldn't get it up like that, but a couple times pulling through the hills made it come up. I did a coolant flush when I got it (2004) with a new 195 thermostat. Last year I put on SSDs 180 thermostat, HD fan clutch, and D-max fan upgrade. I also pulled the radiator out and cleaned the living sht out of it. Hot tanked in and used some new chemicals on it. Had a pile, probably 2lbs worth of flaked junk, sitting on the ground when I was done.

Since it stays at 180 and only moved a couple times, once when I was pulling a 2 car garage 15 miles to my house at about 12mph, and the other when we get 10 inches of really heavy wet snow and I plowed a few driveways. Temp went up to about 215, fan kicked in sounding like a plane taking off, temp went back down to 180 within 15 seconds, fan kicked off within 30.

So, short story long, running on the highway you should have the airflow, if the outside of the radiator isn't plugged, meaning it is probably a radiator problem. There might be hope for cleaning it, but unless you have the ability to hot tank it and spend 1-2 hours trying, I'd say just get a new one.

[qwkphkr]

Thanks for all the info guys. I think I am going to replace the rad and t-stat before any more damage is done.

One other question, would a clogged catalytic converter cause overheating at hwy speeds?

[grancito]

Yes, restricted exhaust causes overheating.

[qwkphkr]

I am going to try a test pipe also then.:cool:

SS Diesel says that hot tanking is ineffective on an aluminum radiator...:confused:

the Antifreeze is green, so some maintenance has been done at some point. The heater core is disconnected so I'm assuming that it's bad and that's probably when they changed the fluid. No way to tell when that was though.

[ZiGBlazer]

Hot tanking usually is ineffective, but I tried some new chemicals and used 220 degree water to rinse it out good. Worked for me.

[flattire]

what brand of chemical did u use to soak and clean it

[ZiGBlazer]

I don't really know what chemicals they were. They were left by the venders for us to try out at work. I know one was some sort of acid soak foam. I haven't heard of many people getting aluminum radiators clean, and frankly am still kinda surprised it worked so well for me.

[CAdiesel]

My HVAC guy had some sort of cleaner in a pump sprayer. He sprayed it on and rinsed with water and the A/C condenser went from black to silver took all the crud with it. The only reason I bring it up is a place to start and the A/C stuff is aluminum just like the rad on these trucks. If I remember I will give him a shout and see if I can nail down what it was.

Side note: I'm pretty sure my radiator had build up in it plus it was springing leaks I believe this clogging was the cause of my blown head gasket.
IMO: Even though radiators are kind of expensive it can be cheap insurance to just replace it, plus if the heater was leaking it might not belong before the rad goes. Especially if you don't know the age and condition. Another thing make sure to use 50/50 antifreeze and h2o or you will shorten the life.