250 inline running hot at highway speed

[ViviensTractor5110]

Oooooo...I like that certainty....like a flat alum sheet in front of the crossmember ?

[ViviensTractor5110]

To cycle air in or block the bottom off?

[ViviensTractor5110]

Cooling is finicky work it seems. The things that work are oft counter intuitive.

[Boog]

Viv have you checked the ignition timing of the engine? If it's timed too slow it will run hotter and burn more gas too. Don't cost anything to check it.

[ViviensTractor5110]

I must display my ignorance....I've never done it....all I know about the process is its a light on the balancer....I've had the ignition apart and back again with good luck....as a side note...my vac advance looks super crusty...maybe swap that out before I time it?

Thanks again

[geezer#99]

Originally Posted by ViviensTractor5110

To cycle air in or block the bottom off?

To create a low pressure area below the motor so the air will flow thru the rad.

[MagmaJct]

Is it just my imagination, or has this thread gone from the realm of likely causes of the OP's problem, into the realm of insanity?

Actually the thermostat keeps the coolant in the engine until it warms up, then it opens and flows to the radiator.

Just so...got me...the resistance theory still serves though no? I don't know. Today we troubleshoot

My bet is internally clogged radiator. Also outside. Bugs and crap will block the air flow through the fins. With trucks this old there's no telling what you will find.

The gob of gasket maker I blew out of there supports that logic. Thanks Boog

Thanks guys...hope to diagnose today...

You can buy a flush kit that has a fitting that you splice into the heater feed hose, i used to drain my coolant and fill with water, then hook my hot water tank up with a hose and fire up the truck and let it flush.

Bought a flex fan too which knocked off about 5 degrees Still 210ish when wrapped out at 70 mph

Put an air dam right under your rad and watch the temp drop.

Oooooo...I like that certainty....like a flat alum sheet in front of the crossmember ?

To cycle air in or block the bottom off?

Cooling is finicky work it seems. The things that work are oft counter intuitive.

To create a low pressure area below the motor so the air will flow thru the rad.

Somehow, the thread went from diagnosing a problem, to throwing crap at it. Is this what we learned in school and texts on proper troubleshooting? A stock configuration needs only stock solutions. What can cause an engine to overheat? Why is removing the thermostat so commonly the prescribed solution, and why doesn't it work?

Well, think about it for a moment. Thermostats are designed to open at a certain temperature. 160F, 185F, 190F, 195F, and so on. If the coolant leaving the engine is over 200F, here's what we can surmise. The 160F thermostat is fully open. The 185F thermostat is fully open. The 190F thermostat is fully open, and so on and so forth. There is no real value in installing a cooler thermostat, or removing the thermostat!

The argument is often made that the thermostat restricts flow, therefore, removing it will increase flow, and bring the temps down. This logic is flawed in a HUGE way! This logic assumes the thermostat is the cause of the restriction! Perhaps in some high HP engine, this might be the case. But I suspect the OP has a near stock setup.

In which case, the odds are great something is broken. Be it a clogged radiator, clogged engine cooling passage, or a bad pump. Perhaps a collapsed hose. The lower radiator hose has a spring in it to keep it from collapsing. Perhaps it rusted out. A temporary fix will not solve the problem if the problem is poor coolant flow.

[ViviensTractor5110]

I'm Just going to set it on fire in the driveway.

[Capt404]

Just a question, do you have a fan shroud on the radiator? Could be I
the difference in temp

[ViviensTractor5110]

I don't and finding one is like finding a unicorn...I may endeavor to adapt or fab one

['68OrangeSunshine]

Originally Posted by ViviensTractor5110

I don't and finding one is like finding a unicorn...I may endeavor to adapt or fab one

That's because L6s don't really have one, just the ''Finger Guard'' bolted to the top of the radiator bulkhead.

[ViviensTractor5110]

That was what I thought...with the availability of parts...surely if there was one then...one could be had now....does the finger guard play a part...other than fingers?

['68OrangeSunshine]

Originally Posted by ViviensTractor5110

That was what I thought...with the availability of parts...surely if there was one then...one could be had now....does the finger guard play a part...other than fingers?

Yeah, a little bit, but not like the nylon/fiber ducted fan shrouds on the V8s.
I don't know if a V8 fanshroud will do you any good, there's so much airspace in the engine bay with the L6, that it's almost like it's aircooled.
For the record -- I have a built 292 [30 bore, Cam, bigger valves, 4 bbl carb] and I live in Arizona year round. I run a Flex Fan, good coolant mix, 3 tier V8-size radiator, 195* T-stat, mechanical water temp gauge w/pickup in head . And I'm not running hot. It did run hot when I first was breaking it in after the rebuild. The most surprising gain was by going to the 195* thermostat [had been 180*] and by using more water in the coolant mix. I was on the coolant-heavy side 70/30 or 60/40. Now it's 50/50 or 40/60.

[Custom/Ten]

Magmajct, Sanity! X2 stock 250's don't need after market parts to keep cool. You have a clog or a bad part, my 250 overheating prob was not an overheating prob at all, just a bad gauge. Find the problem and fix it.

[ViviensTractor5110]

I'm going to douche the block and change the pump...between that and a new radiator....think I'll be money