86 S-15 overheating

[Dibsing]

I have a 1986 GMC S-15 4x4 Gypsy with a 2.8 V6 TBI fuel injected.

Recently after driving it all winter i noticed that after about 10 mins of running the engine overheats, or atleast says it does. After seeing the gauge go from 40oC to 125oC i pulled over and popped the hood. The engine wasnt smoking or hissing like my old ford did when it overheated. There was Coolant in the resovoir and the radiator had coolant too. I limped home and made it. Next day i changed the thermostat, and refilled up the coolant to the top of the radiator (also replacing the radiator cap). it is still overheating today, so i went and bought a new tempurature gauge for 10$ at the local Canadian Tire. I also noticed that the top line into the engine from the radiator is extermely hot to touch, but yet the bottom line into the radiator from the engine is very very cool to the touch. Could a blocked hose be the problem?

[dugie6551]

Sounds like a blocked hose .... replace all the hoses and flush the radiator. You may want to also check or replace the heater hoses while you are at it.

[RahX]

Its probably a blocked up radiator. CAREFULLY feel around the radiator and see where the hot/cold line is and you found your block. You might be able to have a radiator shop unplug it but you might have to just replace it. Be careful tho that thing is HOT when its hot

[Dibsing]

I drained the fluid and checked all the hoses and they were clear and water flowed through easily. the radiator isnt plugged as that water flowed through smoothly as well. retested the thermostat and it opened at 98oC/ 192oF. After reconnceting and fixing some leaks with the hoses, it still was overheating at approximatly 110oC which when it started to climb. the top radiator hose is still quite hot but the bottom one is still ice cold. any other suggestions?

Thanks

[OverBoardProject]

Take it to a car wash and spray out the rad. If you have air conditioning you'll want to seperate the 2 rads, and then spray them both out 1 at a time.

I've seen 1 so plugged with some crap that it didn't have a chance of cooling properly

[sector95]

If it were my truck, my inclination would be to replace the radiator....especially if this is the original unit.... I mean it is 20 years old. Just because you can see coolant flowing doesn't mean it is flowing at the correct rate (this is one of the tests a radiator shop should perform on a suspect radiator). And as was suggested, your rad could be plugged in certain areas so that only a portion of it is flowing coolant. Try removing the thermostat and see if the truck still overheats....if it does or runs hot then you probably need a new rad.

Some other thoughts... the temp gauge.... is this an aftermarket installation or the orignal factory setup? Could be the sending unit has gone bad. Does your truck have factory A/C (whether it's working or not)? These engines are equipped with a fan clutch designed to "freewheel" under most conditions and engage when the air flow thru the rad reaches a certain temp. Again, if this is the orignal fan clutch, I'd replace it also.

Good luck and hope this helps...


mike
85S10

[RahX]

Re-read my post and try what i mentioned in it. Feel the radiator, it should be a fairly constant temp from top to bottom with no major drops. It will burn the crap out of you if you're not careful though. Another thing you might think about is the waterpump. I've seen those do weird things like the shaft breaks internally so there isn't a leak and nothing appears to be wrong but the pulley turns and the impeller on the waterpump does nothing. The fins may even be rotted off of the thing.

[Disturbed_One]

I did a cheap and cost effective flush to my '88 Nova

little car kept over heating with no a/c or anything



so I went and got a couple items from the local walmart
-gallon of vinegar
-gallon of distilled water
-gallon of antifreeze


I drained the raditor, filled it up with the vinegar, let it sit overnight and part of the day, drained all the crap out (dissolves the crap without harming the radiator)
took a water hose and finished flushing it out, then filled it up with some new antifreeze and water (distilled so I dont get any calcium bulid up)

though i dont drive that car much now a days, but I see I have to do it to my truck, so I dont risk that one overheating (didnt have to worry about it over the winter when I bought it)