My Truck Won't Stop Overheating =/?

Question

My truck is overheating, obviously. Idling, it doesn't over heat or if it does, very slowly unless I turn on the a/c and give it some gas.

I replaced the heater core last year..and no signs (antifreeze on passenger floor, etc) that it's bad again. I replaced the thermostat 2 days ago. The water pump is circulating o.k....

So what in the WORLD is going on?
My brother told me that there's probably air in the radiator somewhere. He said to fill it with antifreeze slowly..and it'll seem like I'm putting alot in there but to keep doing it to get the air out.

It DOES gurgle when it over heats. And then he said to let it overheat a time or two and it should be fine, but nothing's working and the radiator and hoses aren't leaking.

What in the WORLD is going on?

it's a 1989 1500 (Silverado) it's got a 350 in it if that helps at all...

I know absolutely NOTHING about fixing vehicles, the little I have done for it is a result of reading a whole bunch...as far as the engine goes, I got it with a new engine and transmission from a school that trains mechanics. It's run BEAUTIFULLY up until this point.

Answer 1

First off Check that Radiator Make sure is Isnt Plugged up Second of Are you Fans Weak? If so that Could be a problem Thrid off Squeeze the Upper Radiator Hose for a Few seconds and see does it have a strong surge if not its the water pump. if all that checks out get a Radiator Pressure Tester and Put it on and Run the Truck Does it have more then 5-7 PSI Pressure? If so Then your leaking Exhaust into the cooling system and that means you have a bad head gasket. If that doesnt find a soultion then just try a regular pressure test is you build it up 7 pounds and it leaks down but you see no antifreeze check for water in the oil if nothing this its a Leak around the Water Jackets, Thus being a Bad Head Gasket or Cracked Cylinder Head.

Answer 2

Well seems how you noted that you know NOTHING about fixing it, the best I could say is go to an ASE certified shop that specializes in radiator / cooling problems. Here is one thing you could try by yourself.
WITH THE ENGINE COOL!!!!!!!!, remove the radiator cap and then start your truck and let it run and run and run. Once the engine warms up it will "BURP" out all air out of the system. If it looks like the radiator is low on fluid, don't be afraid to use the garden hose. The system is supposed to be a 50/50 mix of water and antifreeze anyways. If this does not resolve the problem, then I can only suggest to take to the pro's. I have some other ideas, but you have to have the right tools to go any further. Good luck.

Answer 3

Hi, it's almost 20 yrs old. If you are not the kind to do regular maintenance then the internal engine water ports may be clogged. Requires top overhaul.
Another thing, I guess using a 350 in place of the original engine is another prob, your radiator may not be suited in size to cope with the extra heat. It's like putting a radiator for a Mini into a Mustang. Do the math.
Check your Head Gasket, sometimes overheating is due to a busted head gasket, top overhaul once again.

Answer 4

Sounds like a plugged up radiator with the year and high-mileage, if you haven't flushed it periodically. I would flush the cooling system and you may have to remove the rad and have it boiled out at a rad repair shop or replaced....make sure to properly fill the system and purge any air out. Also, test for bad head gasket possibly by doing a pressure test of the system---parts stores carry pressure testers. Finally, as a temporary solution, you can buy products like Water Wetter which lower cooling system temps by 20-30 degrees or so---motor home owners and racers use it.
http://www.racerpartswholesale.com/redline3.htm
Buy online or some parts stores or speed shops carry it.

Answer 5

Chevrolet had a batch of bad head gaskets in 1989-1990 but you ruled that out with newer rebuild. I wonder if they put the intake gaskets on backwards, blocking the front water ports, it's been done before. There are block offs in gasket that go to rear of engine. You could probably take out thermostat and poke a long thin screwdriver in there to check for block offs.

Answer 6

lets go through my check list easy things first 1 check your fan its a temp sensitive right check this with eng off try to turn fan by hand probally spins easy right when this type fan heats up then a built in clutch locks in and turns the fan harder. you could replace this fan with an old fasioned type w/o the clutch 2 with eng cold open rad cap fill almost to top run eng till its water is flowing smothly(take the thermostat out and hold it between your index finger and thumb then throw it out into a field as far as you can.until you are having prolbems because your eng is running too cold you wont need it trust me on this one i' ll explain over the phone [phone] back to your overheating now look at the water flowing past the open rad cap look for bubbles after a few min the bubbles should stop if not blown head gasket between exaust port and water jacket or worse crack head or block but probally not (just trying to cover all possibilities) with hood up and a/c on idleing you shouldnt overheat take it up to hot but not overheating then get a piece of mirror 4or5 in. or borrow your ladys compact place it in the exaust from the tailpipes it will instantly fog up then go away as the mirror gets warm look at mirror dry is OK lots of water dropletts bad head gasket or head dont jump to fast little moisture is ok stop Q. do u need to keep filling it up w/ water? no except when it overheats and blows its top OK doesent use water check no fog on mirror check no bubbles in radiator check use a lasor temp gague to check rad temp (veryfy rad is not part cloged) check eng timing set to factory specs cintrifugal advance and vacuum advance both working properly check fan clutch removed half check not yet idle rpm warm factory set calif emmissions temp placed with thermostat LOL check catalic converter not cloged check oil level to mark not over filled check rad system pressure test ok check (temp replace coolant recovery cap ) check compression check each cylinders should be all close look for 1 very high all eq. check your the answer to your prolbem is in your e-mail just kidding the impeller blades on your water pump are worn and rusted the pump isnt working to factory specs even if you see lotts of water circulating in rad i hope i was a help it also could be a combination of just a little bit of each of the things i listed good luck 1 thing at a time if you find it i would like to know what it was thanks rogerjimerson @yahoo.com

Answer 7

Could be a bad head gasket, letting exhaust into water jacket

Answer 8

with it warmed up ,run your hand over the webbed part of the radiator. if you feel any cool spots,then it is clogged. if so you will need to use a cleaner in it or take it to a radiator shop.