250 inline running hot at highway speed

[ViviensTractor5110]

Ok boys....here we go,
Bought my 69' stepper...ran great around town...but always a little hot on the highway....55-60 mph it creeps into the 220 range....so after a cab swap and lots of body work...I've been driving her again...trying to increase drive ability I yanked the housing...no thermostat....ok.
So I dump a 160 in it and it's only mildly better.
Is this a dwell time in radiator issue that a more restrictive thermostat may cure? The PO was a tool so there's no telling what his motivation was...and for good measure there was a gob of purple gasket maker snot that came out of the rad drain cock when I bled it down.

Your knowlet is always appreciated

[ViviensTractor5110]

Knowlet.

[EARNHARDT#3]

Knowlet?

[swamp rat]

All a thermostat does is keep coolant from circulating untill the temprature imprinted on the thermostat is reached, when its open its pretty much out of the picture at that point and the rest is related to the flow of coolant

A good radiator repair shop can test the flow of the radiator, i would think the only other coolant posibility would be clogged up engine cooling jackets from not running a 50-50 antifreese mix over the years, a warn impeller on a water pump or just old antifreeze.

One other posibility is that the temp sending unit may have been replaaced with an incorrec one

[ViviensTractor5110]

Thanks swamp.

Knowlet is power.

[ViviensTractor5110]

Coolant systems suck. Hoping for an easy fix. I should flush that block huh?

[88Ironduke]

I believe there is a "dwell" time to the inline 6 where water flow is concerned. I might be wrong but the Stovebolt guys say that the water needs to stay in the 250 head long enough to pick up heat. Due to the length of the head and the way the passages actually flow water when a thermostat is out the water is in and out of the block but the cylinder head doesn't see the flow rates back at number 6 cylinder. Can't confirm it though.

If it was mine I would start with pulling the water pump. Cool thing is you can see the #1 cylinder bore and the internal passages very well.. If it looks like a chia-pet growing in the water galleries you have found your problem. Flush the radiator and block, throw on a new water pump for giggles and see what happens. The stock 2 core is easily up to cooling the inline 6.

Paul

[ViviensTractor5110]

Awesome 88...May be my route...tempted to stick a 195 stat in there and see how much truth there is to the matter....if a the 160 pops at 160...and a 195 at 195....surely this must mean the possibility is there that the restriction offered by a 195 May keep the the coolant in the radiator longer and thus below 195....making full open a rarity....suppose we will see....though I am the type to do a pump for good measure

[ViviensTractor5110]

There's always the possibility of a lean condition too...buty plugs look right and and I can kill a tank of gas like nobody's biz...so leaning toward a clog...a pump or a curse.

[chevy_mike]

Where is the temp sender at? On my wagon, I thought I was running way hot. The sender was in the head. IR temp check at the radiator was showing the correct temp. I moved the sender to the t-stat housing and the gauge showed the correct temp.

Just a thought.

[ViviensTractor5110]

I'm in the stat housing

[ViviensTractor5110]

Mech sunpro cheap easy

[swamp rat]

Originally Posted by ViviensTractor5110

Awesome 88...May be my route...tempted to stick a 195 stat in there and see how much truth there is to the matter....if a the 160 pops at 160...and a 195 at 195....surely this must mean the possibility is there that the restriction offered by a 195 May keep the the coolant in the radiator longer and thus below 195....making full open a rarity....suppose we will see....though I am the type to do a pump for good measure

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

[ViviensTractor5110]

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

[Boog]

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.

[ViviensTractor5110]

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

[Dirt's72]

Take the cap off and you should be able to see if the radiator cores are plugged by looking inside with a flashlight. If there's a lot of white scale build up it may just be plugged. You can go to the dollar store and get some works toilet cleaner. Dillute it. Take out the radiator and lay it down with that stuff in there. Set it in the sun for a while.
Or if it is clean in the radiator maybe your water pump is pumping the coolant to fast through the radiator not allowing it to cool in the radiator long enough.

[lowbucktrucks]

Thermostat also restricts the flow of water, slowing it down.

[ViviensTractor5110]

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

[swamp rat]

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.

Another trick my diesel mechanics instructor taught me is to buy some no sudzing soap like dish washing soap, if its crystal forum dilute it into water so its all liquid, add it into your system (just soap and water) and run it for a while, drain and flush.

[ViviensTractor5110]

I said f it and bought a radiator. Triple alum on e bay 150. Stuck a flashlight in it and watched it run...pumping well at idle but crusty. If the pump is tired hopefully this will buy time for me to rebuild the 292 I have stashed.

[ViviensTractor5110]

Bought a flex fan too which knocked off about 5 degrees

[ViviensTractor5110]

Still 210ish when wrapped out at 70 mph

[ViviensTractor5110]

Thanks for the info swamp.

[geezer#99]

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