a while back the 81 was overheating around town. i figured it was the fan clutch but another unit didn't help. so i figured the radiator was clogged after the truck sat for so many years. i went to drain the radiator fluid and only a drip came out the drain, so i knew a clogged radiator was the cause. i had to pull the lower hose, a PITA because the metal fitting by the pan has been extended in a repair. anyway, directions said to fill the system with water and the additive, run it up to operating temperature, drain, re-fill with water, hit operating temp, drain, and refill with anti-freeze.

well after putting in water for the first time and dumping in the 'unclogging" additive, i can't get the darn truck to get all the way to operating temperature. the needle only hits 1/4 on the guage max. i waited for the weather to turn warmer, and even on a 70 degree day it won't heat up. i finally figured it must be 'unclogged' enough to keep from overheating, so i drained it. well, i tried. the drain on the radiator is still as plugged as before, hardly a drip from it!

so i believe i have a partially clogged radiator, not enough to overheat it yet, but enough to cause somewhat of a headache. do i pull the lower hose to drain it, flush the system and call it a day, or do i throw in the towel on the old radiator and get a new one? and if a new radiator is in store, should i get a stock replacement from the parts house or go with the aluminum units like on ebay?

Al

 

I would say a new one is on order, can't go wrong, and will prevent problems in the future.

$162 plus shipping at radiator.com

$164.67 shipped at radiatorbarn.com

As for the warming issue, did you drive it around? or just let it idle? If it is just idling it won't really warm up.

Have you tried sticking a garden hose in the upper hose hole, and undo the lower hose and see if water comes out. If it backs up and comes out the upper hose hole, then you def need a new radiator. If it flows fine, then it may just be the plug area clogged, but you never know.

 

i drove it around, and still can't get the needle above 1/4.

if the radiator is this clogged, should i be concerned about the water jackets in the motor getting clogged as well?

Al

 

If it's not heating up, are you sure the radiator is clogged?? I would think it wouldn't cool down if clogged.

Sounds more like your thermostat is stuck open to me.

 

First I would use a real temp guage to find out the true temp .. and not just realy on the factory guage ..

 

it was overheating very badly before i drained the radiator and put in a flushing agent. the radiator may be flowing better now, but it is still partially clogged (doesn't drain from the plug still). what has unclogged has stopped the overheating but now won't hit operating temperature.

should i swap out stats first, or just throw in a new radiator.

also, are 1st gen radiators any different then 2nd gen radiators? i really like the aluminum units on ebay but they mention only fitting second gen rigs. dosen't seem like they'd be that different....

Al

 

might need to check the inlet and outlet sides, I don't recall...I would do a new radiator, thermostat and water pump all at once...than you know you are good to go...

 

First you can trash the radiator cleaner you got waste of money. All you need is cascade dish washer liquid.
1 Just put a cap full in the radiator.
2 run the truck about 30 min.
3 take the top hose off and place a water hose in the radiator fill neck. (make sure the water is on not full blast.)
4 repeat if still looks dirty.
I also found out that the radiator that has neck with where the small hose hooks up is cheaper. I brought my radiator to the radiator shop and the guy brassed mine off and onto the new radiator. That is if you need a new one. A radiator shop can do wonders with a used radiator. Might want to try that first.