Truck running hot

[special-K]

My`72 K2500 has a problem when it`s hot out.The tempurature runs up when it`s good and hot outside,only.I can run it easy and it will climb slow on the interstate.On back roads I drift it in neutral on hills to get along.
It had a flex fan/solid spacer and I switched to another fan w/clutch yesterday.It ran ever hotter.I just went out and got a new clutch and put it on.But,the other one seemed fine.I had a t-stat housing seap and I fixed that,too.The thermostat is working fine.I wonder if the TH350 could be running hot for some reason causing this.I haven`t checked timing,but it runs fine on regular with no pinging.It did it last summer,too.
Any suggestions?It doesn`t use water and runs cool except when temp get near 90.

[ksjh1316]

I had a similar situation on another vehicle and it was the water pump that was bad. Seam that years of driving had caused internal problems with the prop and when it was cooler outside it could cope fine but when temps spiked I would run into overheat situations. The water pump never leaked or made a noise but when it wa pulled there was little functioning internally on it

[MyakkaJeff]

Do you have a fan shroud on the truck? Also the fan should be just inside the shroud edge. Sometimes switching fans goofs this up.

[clay68c10]

How hot is it actually running? The factory temp gauge isn't very accurate. Mine would hit red at 185-190, which isn't hot.
What radiator do you have? If you don't already have one, I'd say go with a 4 core. That should keep a small block cool.

[68gmsee]

Here's what I checked and did on my 69 with 350/350 with no shroud some years ago. They're in the order I remember doing them one at a time. (some already mentioned above.)

1. Flushed radiator and refill with 20-30% antifreeze.
2. Replaced radiator cap. Make sure you get the right pressure one.
3. Replaced lower radiator hose.
4. Replaced thermostat.

Still ran hotter than I liked so replaced water pump and had a 4 core radiator put in.

On my 68 GMC with 6 cyl and 3 speed, I did the first two and also replaced thermostat. It helped it some. I also bought a temp reading radiator cap from Auto Zone and found out it wasn't getting above 190 so I forgot about it.

[steelhorse]

Anything 200 and under is fine for these trucks,most new cars run up to 220.Check the temp with a manual gauge if you can those old gauges arent that accurate.If it is still overheating it sounds like the radiator is either partially clogged or to small.If you look in the radiator and see a bunch of buildup in the passages time for a new one.

[OrangeCrush1970]

I had a bit of an overheating problem similar to this and I had a small clog in the radiator (I run a 4 core for a 400 on my 350). I pulled the radiator and had it rodded out and rebuilt and the over heating stopped. While chasing down the overheating problem I replaced my 180 degree therm w/ a 195 degree therm and my stock temp guage runs a tad higher than before... the truck has run perfectly since.

edit: sorry this does not answer your question but i thought it may add some clues to the chase.

[estig70]

Originally Posted by ksjh1316

I had a similar situation on another vehicle and it was the water pump that was bad. Seam that years of driving had caused internal problems with the prop and when it was cooler outside it could cope fine but when temps spiked I would run into overheat situations. The water pump never leaked or made a noise but when it wa pulled there was little functioning internally on it

SpecialK,

I agree with ksjh1316 about the water pump itself and the prop.

Could also be the radiator as orangecrush1970 says, and make sure you have that fan shroud on there as 98gmsee mentioned.

Let us know what you find out.

Eric

[gn4u2c2]

http://images.google.com/imgres?imgu...US276%26sa%3DX

[jott_06]

i'm having the same exact problem with my camaro. Yesterday it started getting hot when i was running around town like it does every summer so i went home and got the electric fan i bought for it out and put it on and wired it up on the front of the radiator pushing air and i left my flex fan pulling like it should. I got the car out today and it did the same exact thing. Runs about 215-220 degrees. I redid everything on the car last spring so i know there are no problems with radiator and such. I have a Griffin aluminum radiator on it thats only been on there less than a year and now two fans all new hoses, and the motor was built last spring. I think i might try one of those water pumps from summit racing that is supposed to flow more water

[SteelMohawk]

Special-K it must be something in the water, because my truck is acting up and has never had a cooling issue before.

[special-K]

Something in the water.... Maybe it`s got algae?

Thanks for all the input.The temp will go as high as you let it.Gotta take it easy or it`ll overheat.Only when above,say, the upper`80s.It has sensitivity issues.I`ve scheduled with a therapist.

After posting this it hit me that I should have the radiator rodded.It`s the big ole 4-core and worth that,either way.
If it still heats up I`ll look into the water pump.But,I think a reeamed core will do it good either way.

It have an aux. trans cooler and runs through the radiator.Those lines feel just right,barely warm.

Another thing...I actually burned up the original motor in this truck in`01,the year I bought it.It got way hot on the hiway in between my glances at the gauge.I had been running it pretty hard.I saw a chunk of water pump gasket gone and assumed it let go causing me to lose my water rapidly.I saw the gauge was in the hot zone,shut it down and managed to drft it over a mile right onto the next exit,which would cool it quite a bit.That thing was still blazin`hot.I wire loom was melted to the intake.Once it cooled and I put water in,it was all clackety in the valvetrain.Water in oil,the works.The block was warped/heads trashed.I put this motor in in`04,but never ran it alot because I had bought my Highland that summer for my driver.I think it`s this radiator that did in the last motor.It`s fine up to a point.

May it is something in the water,like hi alkaline building deposits...

[Boog]

Tim while you have the rad out for cleaning why not replace both the hoses as well. That bottom hose should have a spring in it to prevent it collapsing shut. It may have rusted away in the current hose. I have had that happen with one that sat a bunch.
Also that fan clutch you put on. Is it a centrifugal or thermostatic type? The thermostatic type is by far the best for most stock type applications. I know, I know, everybody has their opinions on which is best as well but it's hard to beat.

[68gmsee]

It's global warming.... as some people would say.

[LONGHAIR]

I would say that it is time for a clean-out and inspection.
As a general rule...hot at low speed is an air-flow issue and hot at higher speed is a coolant flow issue.

Assuming of course that it really is hot in the first place, which was somewhat touched on earlier.....Rodding the cores and replacing the hoses at the same time is a good idea, it certainly can't hurt anything.

[special-K]

Hoses are new.It`s a thermo clutch.I have the rdiator out for dropping it off Monday morning.Oh,and someone asked about a shroud and,yes,factory shroud.I`m sure after the radiator guy does that I`ll know.I`m expecting him to say,"Man,that thing was clogged."

[ChevLoRay]

My '65 Chevy C-10 had a 4-row core radiator in it, back in Oct. 77, when I did something stupid and had to put a new water pump on it. Ever see a fan belt get twisted while it's running? It gets effectively shorter and puts some "pressure" on the shaft of the water pump....and a bit of a wobble results. Sure did like the way those glass packs sounded....just before the "incident".


Anyway, when I went to pick up the radiator (based on when I was told to come back), ole Hutch says, "C'mere....you gotta see this". Uh-Oh. He put the air pressure to the radiator and dropped it back into the water. It looked like it was carbonated. Heck, it didn't even leak before I took it to him!! So, after $150 and another day, I had a re-cored radiator.

[LONGHAIR]

V-belt roll-over is usually from serious over-reving. I have seen it a few times. Most of them the belt wasn't as tight as it should have been though. Long distances between pulleys can make it more likely too.

[special-K]

I run the Z28 alternator pulley.