Overheating issue

[Curtm220]

Originally Posted by special-K

Wholly thermostat Batman! I wonder why the L6s that never had the drilled thermostat never had this issue all those years

That's a good question. I had an inline 6 and never had an issue until I had to replace the radiator. After that the temp gauge would nearly peg before resting at its normal temp. After a new thermostat and still seeing e problem, Air under the thermostats was the only thing that made sense. Drilled the base and never saw it again.

[litew8]

What radiator did you replace with?

[Curtm220]

Originally Posted by litew8

What radiator did you replace with?

I replaced it with a stock one out of another truck that I bought from a buddy who had done a swap to a small block.

[litew8]

@sjburk Don't know why, but when looking at radiator caps for your engine I find both 13 and 16 psi. You mentioned having a 13, guessing that is what was originally on the 2 core. Looking at your picture it doesn't look like you have an overflow tank. If true, try sourcing one to catch that fluid and see if makes any difference (keeping hose submerged the tank's fluid when it fills).

Having too low psi rad cap can have an effect on how the system coordinates and increases the boiling point, so if it [cap] isn't faulty and is the correct psi, that should be ok and not interfering.

[Togan66]

When I drilled mine, I really thought I had an air pocket issue, so I was hoping to remedy that issue. It did the trick.

[special-K]

I guess what I'm saying is this drilled thermostat is a great remedy,but only gets around whatever the real issue is. Nothing wrong with that. I'm a whatever it takes kind of guy,but still would want to find out the actual cause at some pint.
Also,these trucks were never designed to run a closed coolant system utilizing an overflow tank,so just another band aid.
These are well designed trucks which have functioned reliably from factory. There were no design issues with cooling,so as built is still all you should ever need.

[litew8]

Yeah, and the 6 cylinder was never designed to use a thick three core radiator either without a shroud. They made 6-cylinder radiators specific.

[68 IRON]

If you bought the laser thermometer, give us your readings (about 6 or so) from t-stat to engine again. It should read roughly what your t-stat is set at to gradually cooling across radiator.

[Z10]

Originally Posted by 67 chevelle

Picture is worth a thousand words , YOU NEED A SHROUD , will solve your problem

You need a shroud. You're only pulling air through the radiator in front of the fan. A shroud will pull air through all of the radiator.

[sjburk]

Sorry, I had my truck in the shop welding in some new panels for quite some time. I got it back yesterday and bought an IR thermometer. I let the truck idle in the driveway, the needle went all the way to the hot side, I revved it up and it went back down and leveled at about 3/4 of the way at a steady idle. When the tsat got to around 185 the hose going to the radiator did get hotter. My temps when everything leveled out were, sending unit in head 250, head 250, block 225, tstat housing 230, tstat rad hose 175, water pump rad hose 150, incoming side of radiator 180, rest of radiator 100. That actually sounds reasonable to me, but please tell me your thoughts. Now I'm thinking the gauge or sending unit is off on readings. Thanks for your patience.

[litew8]

Auto Meter Mechanical Temp Gauge Installation -...

[68 IRON]

The lower and upper tstat housings should be about the same (180F) and through hose, radiator inlet slightly lower if not the same. You should have a 30 to 50F drop across the radiator depending on outside temp. Your tstat temp concerns me (should be closer to the tstat opening temp)...it shouldn't be 230F

[sjburk]

Well last night my friend had a get together so I decided to take old yellow, and I drove 60mph for 10 minutes there and 60 for 10 minutes back. On the way there the gauge never got up to halfway, on the way home it went all the way up for a moment but then went back down and again never got past half, I don't know what's up with that although neither times did I get out the IR thermometer.