Need help with overheating issue on my 77 k10 with sbc 350

[Lens77chevy]

I've replaced tstat water pump temp sensor temp gauge upper radiator hose bleed air out of system and it still runs very hot and also replaced radiator cap too I don't have a clutch fan so my fan runs all the time I cant figure out why I'm still running hot I flushed radiator water ran through clear. I'm at a loss any suggestions would be greatly appreciated thanks

 

[77 K20]

Running hot when? When driving up a long hill? When towing? When just idling?

Mine started "running hot" when idling or driving at low speeds. If I popped it into neutral and revved it up it would then cool off. In my case it was a bad head gasket.

There are test strips you can dip into your coolant to see if there is evidence of exhaust bubbling thru it. Or have it idle with the radiator cap off and look for bubbles.

 

[Charlie]

 

[Shorty81]

Are you using a shroud? I have a direct drive fan with a extension to position the fan as close to the radiator as possible. I use a 180 tstat and runs cool.

 

[Obwonkonobe]

I always put my sender in the manifold btw, and use a ir gun to double check the temp

 

[1987 GMC Jimmy]

Like it was touched on here, you need to verify your temp at the head where the sender is with an IR gauge. The combustion gas test with strips or with the solution and tester they have at the auto parts store would be worth doing.

 

[Rusty Nail]

Fan installed backwards?
Upside down?
Inside out?

Ah!
Radiator hose collapsing on itself mebbe? Does it gots a sprang in it?

Your flow is all jacked up somewhere ol boy. You ain't got none.

None.Flow.

 

[Blue Ox]

Here we go again. How much original stuff is left on this thing? You know, that surplus junk the factory puts on, like fan shrouds.

 

[Rusty Nail]

 

[roundhouse]

Usually if t runs hot while sitting still or driving slow it’s an airflow issue

Radatior , shroud or fan or possibly hot air being able to be short circuited back across the rad , because the rad and shroud isn’t sealed air tight to the core support and the hot air is coming right back around into the front of the rad again

If it runs hot while driving at highway speed it’s not an airflow problem side you got 70 mpg air over the radatior and engine , highway speed is a water flow problem

Collapsed hose , clogged rad , etc

 

[Lens77chevy]

Well I used a block tester and fluid did not change so head gasket should be good, I had already ran that test but forgot to put in original post. I have a fan shroud. It runs hot all the time my gauge used to peg hot right away but after replacing tatar and water pump gauge slowly gets hot and it seems to stay between 3rd hash and just before where the red starts. I'm thinking its my rad cause all my horses are good I have no leaks

 

[roundhouse]

You checked it with the laser thermometer ?

Or another gauge in the other head port ?
Or in the upper rad hose ?

Does it run hot sitting still ?
Or
While driving down the road ?

Sitting still is an airflow problem
Fan not moving enough air across rad , due to fan or shroud issues

Get some duct tape and seal up all the gaps between the shroud and rad
And also between the rad and core support
And tape some foam strips on top of the core support so when you close the hood no air can travel between the top of the core and hood

After that’s done you should be able to hold your hand in front of the grille and feel the air moving

Hold up a plastic grocery bag or some tissue paper and or should stick to the grill

If it does not , you’re not moving enough air

 

[4WDKC]

Well I used a block tester and fluid did not change so head gasket should be good, I had already ran that test but forgot to put in original post. I have a fan shroud. It runs hot all the time my gauge used to peg hot right away but after replacing tatar and water pump gauge slowly gets hot and it seems to stay between 3rd hash and just before where the red starts. I'm thinking its my rad cause all my horses are good I have no leaks

tstat? just because they are new doesn't mean they are always good or the right temp.

 

[1987 GMC Jimmy]

Yeah, I’d verify temp with a laser thermometer, maybe boil the thermostat if you have a kitchen thermometer to verify it, and if you’re concerned about a blockage, you can tee in a flush kit and back flush the system with a garden hose.

 

[Crispy]

I had a similar issue when I replaced the head gasket. Turns out my brand new Stant thermostat was NFG. First time in my life its happened. Ended up buying and boiling a new one to verify opening. Once it checked out I installed it and havent had an issue. This is no knock against Stant, I've never had an issue running their caps or thermostats until this last one.

Can you elaborate on your fan set up? I would start looking their before tearing into the engine again.