305 overheating

[Walk518]

I’m new to the forum but long time creeper. I have a 86 short bed with stock 305 that recently starting trying to overheat ( according to the gauge). I’ve changed t-stat, waterpump, radiator, sending unit, replaced radiator & heater core hoses & gauge ,still try’s to peg out hot...?? I also flushed heater core & preformed block combustion test for blown head gasket. I’m not loosing any coolant and no signs of water in oil. I used a IR thermometer on block it read 180 and around 200 at the sending unit. Also the gauge would read 260 & the radiator cap would not be hot & I very careful opened cap & coolant wasn’t boiling & was circulating . I’m have no clue what to do next...?? Any help is greatly appreciated !!!

[Irish_Alley]

Welcome from Maryland.

Take a read here. A guy was just having the same issue
http://forum.73-87chevytrucks.com/smforum/index.php?topic=37894.0

[Walk518]

Tks!! Good read!!

[bd]

Next time the gauge indicates overheating, unplug the sender.  The gauge should drop below cold. 

Three different gauge senders were used in square body production.  Although for any given year the same sender was used in all gasoline fueled engines, the senders are not interchangeable between their specified years of use.  In other words, the sender must match the year of the gauge.  Do your best to verify that you installed the correct sender and gauge for your 1986 truck.  Otherwise, the gauge will return a false temperature indication.  Refer to Functional Tests of Factory GM Electric Gauges for specific details.

[Walk518]

Ok, I’m going to try that tonight. Tks!!!