88 k1500 Overheat problem repalced evryhting! still not fixed! HELP!!!!

[.ben]

so i have an 88 k1500 with the 305 TBI andi decided to replace my entire cooling system since it was very old and alot of parts were corroded (wasn't getting any heat in winter, minor overheating when towing in hot summer conditions etc) so i replaced the Rad water pump heater core all hoses and thermostat....very soon after i started having serious overheating problems with the new parts first it was only when climbing hills and i thought it was just air in the system but it never got better never took anymore coolant so was still convinced there was an air lock in the cooling system somewhere so i backed the truck down a steep hill and manged to get some more coolant in after running with the rad cap off and such i also repalced the thermostat....again just to be sure i ddint get a dud....but it didn't solve the problem..... i eventually got frustrated trying everything i could think of and brought it to a mechanic....the mechanic called back a few hours later and told me i had a blown head gasket, cracked heads and probably a cracked block.....and said my engine probably wasn't worth repairing and recommended i look for a used engine....me and a friend walked by later and picked it up and tried to drive it home.....well before it would only overheat on the highway and on hills but now i could hardly drive it through town and keep the temp gauge out of the red....it had somehow gotten a lot worse than when i had dropped it off....
however....the truck runs absolutely perfect, no miss or anything lots of power it just overheats....i had trouble believing i had cracked heads cracked block and a blown head gasket on an engine that runs perfect....
so last night we pull it into the garage and run a compression test....all cylinders read 155 PSI....PERFECT....
what is getting ever weirder is that today i drove it again and once again it heated right up to about 3/4 on the temp gauge and i pulled it back into the garage and noticed something, the upper rad hose was hot, very hot, but the lower rad hose was cold so thniking maybe the rad i got was plugged i pulled it off and connected a garden hose to one side but the water went right through with no problems i then pulled the water pump apart and it looked perfect inside as well.... i then removed the thermostat and blew air through the block and out the holes where the water pump connected with a vacuum to see if there coolant passages in the block were plugged but it blew through with ease....




so anyone have any ideas? im stumped on this....i don't think its the cylinder head since it appears coolant insit getting through my rad or very little is getting through the rad becuase the rad wasnt even hot when the engine was overheated....

[Kennyray]

make sure that you got the right water pump. some rotate in the opposite direction and could cause overheating

[Kennyray]

check the rotation of the water pump, some rotate cw ans some ccw depending on the year and I can't remember when they switched

[.ben]

Originally Posted by Kennyray

check the rotation of the water pump, some rotate cw ans some ccw depending on the year and I can't remember when they switched

AH HA! good point i will examine both pumps again....

[leolkfrm]

Is the clutch fan working? pull the t-stat and fill the block with coolant, is the t-stat in upside down? when the cap is off do you see bubbles in the rad?

[.ben]

Originally Posted by leolkfrm

Is the clutch fan working? pull the t-stat and fill the block with coolant, is the t-stat in upside down? when the cap is off do you see bubbles in the rad?

i have come to the conclusion that the water pump i got is ether screwed or its turning in the wrong direction....

just flushed the entire system because it seems the old coolant was foaming now there is no foam at all but its still overheating and if you finch the upper rad hose and release you don't feel any coolant move through the hose....i will replace the water pump tomorrow and report back....thanks for the replies....

[leolkfrm]

if the t-stat doesn't open you won't feel coolant moving also

[.ben]

Originally Posted by leolkfrm

if the t-stat doesn't open you won't feel coolant moving also

the test was done while the engine was running and overheating.... and the t-stat was jsut replaced for the third time in 2 days i think i have the wrong water pump....

[gmctrucks]

Sorry to hear of all the problems your having im thinking they sold you the wrong water pump of coarse they won't admit it and if they did maybe they should give you a new motor that would be cool. Also since your truck is an 88 model maybe you should have your radiator rodded out I bet that will help as well more down the line.
Good luck! GMC
PS-Wrong water pump and you have paper work saying that the engine is messed up = a new engine from the parts store wouldn't that be something. I have also heard that running a vehicle hot it will take years off the engine.

[leolkfrm]

do you still have the old t-stat? take out the center and use the flat piece as a restrictive washer, coolant should flow all the time then, yet not to fast for effectiveness. It's only for helping diagnostics