running hot

[jetfixr]

I recently bought a 70 c10. I took it out for the maiden voyage today just to make sure everything works ok. At highway speeds it was running about 195-205, in light traffic 210 and climbing. I would like to see it run 20 degrees cooler, I noticed in the glove box there was a empty box for a 185 degree t-stat. So I am assuming it has a 185 degree t-stat in it. So I am trying to figure out why she is runnin' so hot. One thing I did notice was that the fan shroud had approximately a 20 inch opening. While there is a 7 bladed steel fan that is only 15 inches in diameter. Is that normal? Also the fan is not centered in the shroud there is about 1 inch clearance on top and about 4 inches clearance on the bottom. Could this be the reason for the problem? The radiator is a 3 core but I was really driving easy so I wouldn't figure it should have a hard time keeping up.

[69GWC]

I stuck a 160 t stat in mine and a 18" clutch fan on it and its SO much better now I am so glad I did this, mine had the same little steel fan on it and it moved half the air (it seemed anyway) and its so much quieter now without that fan roar.
I would say atleast change out that fan for a larger one for starters.
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[jetfixr]

Yeah, that would seem to be the easy fix, only problem is the fan is not centered in the shroud. There is 1 inch clearance on the top and 4 inches on the bottom. So changing from a 15 inch fan to a 18 inch would push fan into the shroud. I am wondering if it is normal to have a fan that is not centered in the shroud like that?

[PanelDeland]

First check actual temp.The sender or guage may not be accurate.Also knowing what engine,rad etc may give someone an idea.I suspect the shroud isn't the right one and/or the shroud/fan aren't matched from the discription.The fan should have 3/8-1/2 in clearance around the fan to shroud,The fan should set halfway into the shroud.Timing can also affect running temp as can A/F ratio(air Fuel mix).

[69GWC]

Not sure mine was centered just fine, I have about a 1" all the way around on mine.
My truck also was a 6 cylinder and is now a 350 truck so that could be one reason for the difference I guess.
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[Lee H]

As paneldeland stated you need to verify the actual temp with a mechanical gage or an IR gun. These gages are not real reliable. Mine reads in the max but is really 185 degrees.
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[jetfixr]

It has a radiator cap with a built in thermometer, it is pretty darn close to the engine temp gauge. I would tend to think it is running a little hot. If the radiator fan/shroud is incorrect anyway, may as well try and fix that and see if the temp drops. I will try an IR thermometer too, but I would like to get the correct fan and shroud for more efficient cooling as well. I live in a hot climate

[GASoline71]

Just changing a t-stat to a lower degree won't help.. Oveheating means the cooling system is not up to snuff. If the radiator is the original 40 year old unit that came in the truck stock... it prolly needs to either be recored or rodded out.

The correct fan and shroud will definately help out a lot.

Gary

[Stocker]

^^ x2

You can run a 195 t-stat without overheating if the other stuff is good.

Your fan needs to be centered in the shroud opening, with a tighter gap all around. The fan should sit halfway in & halfway out of the opening.

7-blade fan sounds good, but is it fixed-blade or clutch-fan? Either one will cool, but a fixed-blade is loud and it robs power & wastes fuel.

[mud.man.rj]

As important as a shroud is I don't have one on my big block just the small plate that sits over the top of rad and runs 185 all day, make sure the rad cap is the correct pressure first then also make sure the fan is close enough to the rad to pull the air threw. Is the water pump working properly, belts tight enough, just a few extras to think about besides the good ones already listed by others. Make sure the bottom hose isn't collapsing when warm, I run a spring in mine.

[jetfixr]

Thanks for the input guys I will tinker with it tommorrow a bit and see what I come up with, think I am going to pull the t-stat out. I will run without it just for troubleshooting purposes. If it still gets hot, I can at least eliminate the t-stat from possible causes.

[mud.man.rj]

Yo should run a t.stat no matter what, use a 160 at least because the water pump needs resistance to pump properly, some cases no T.stat will actually run even hotter, then there is real confusion, so throw in a 160 then check again with all the references everyone gave. Good luck.

[davepl]

If it's running hotter than the current T-Stat value, changing the T-Stat can't and won't change it.

There are three main causes of overheating, in this approximate order of likelihood:

- People messing up the shroud
- People adding larger engines without upgrading the cooling system
- Corrosion or parts failure in the cooling system
- Retarded timing

I can't tell you how many times I've seen people throw parts endlessly at a car or truck that's not cooling well, all the while ignoring the fact that the shroud is missing, or broken, or the fan doesn't match the shroud.

Make sure that (a) you have a good shroud, (b) that the fan fits the shroud with an inch or so around the edge max, (c) that the fan is at the proper depth in the shroud (usually about 1/2 way in), (d) the shroud is sealed to the rad so that any air pulled by the fan MUST come through the radiator.

Did I mention I'm a big advocate of shrouds?

Imagine you were trying to pick stuff up with a shop vac. If you were six inches away and there was a big hole in your hose, you wouldn't be surprised if it wasn't working. Similarly, for the fan to actually pull air THROUGH the radiator.

Now, all that preaching done, if it's not cooling on the highway my theory might be wrong, but it sounds like it's doing -better- on the highway than in the city.

[jetfixr]

Dave, I would really like to get the correct shroud and fan. My problem is, the shroud that is in the truck right now looks like the one most of the chevy truck stores carry. It has a 20 inch opening, but the fan is only 15 inches and WAY off center so this does not allow for me to put in a larger fan. The water pump dictates where the fan will be located because the fan is mounted on the water pump pulley. The motor is a 350 out of a 1983 truck. I don't know how I would go about moving the fan around. My only thought is at this point to scrap the current fan and go with electric. If the fan and shroud are not the cause of my problems, I will be out a bunch of money and the truck will still run hot

[Frkypunk70]

I had same trouble with mine, especially when summer weather came. My truck would approach 200. I didnt have a shroud and then my clutch froze up on my fan. I had a shroud laying around and went to a u- pull it place and grabbed a Jeep electric fan. I can run it on the hottest days now and she never gets over 175. Easy mod and fixed the warm weather driving problems. Just a suggestion. Btw I did my fan install even though I have a long water pump. So it is possible. Good luck whatever you end up doing.
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[Dunenutt]

Is your trans mount in good condition? If it is broken, it will kick the fan toward the top of the shroud. New motor mounts with old trans mount will do it too.

[VWNate1]

In my years as a Journeyman Mechanic , I find the cooling system dirty followed by incorrect time are the two most likely causes .

I now use Citric Acid Powder mixed with distilled water to clean cooling systems , it takes a day and some labor but , every inch of the block will be shiny clean ~ no red silt anywhere .

It gets rid of solder bloom in the radiator too and cannot damage any alloy parts , making it a nautural for Imported engines .

It's been 103° + here of late and my '69 has no shroud and the gauge sits down low where it ought .

Just a thought as for me , it's easier than yanking the radiator & letting some goof damage it .

[sleepertruck72]

[QUOTE=VWNate1;5542796]In my years as a Journeyman Mechanic , I find the cooling system dirty followed by incorrect time are the two most likely causes .

I now use Citric Acid Powder mixed with distilled water to clean cooling systems , it takes a day and some labor but , every inch of the block will be shiny clean ~ no red silt anywhere .



VWNate1,
Do you replace all hoses, pump after using this mixture ? Or just refill with coolant/water ?

Jetfixr,
I have a used oem fan shroud off a 72 C10. If you come pick it up its yours...

[VWNate1]

That's the beauty of it ~ it cannot damage the rubber or alloy parts of your cooling system ~ those who foolishly use vinegar , often get pin hole leaks because vinegar eats the solder .

Citric Acid cannot .

After it's clean , I do one last flush with baking power to ensure 100 % neutralization .

Then I refill with the coolant mix .

[TobyArnot]

Originally Posted by VWNate1

In my years as a Journeyman Mechanic , I find the cooling system dirty followed by incorrect time are the two most likely causes .

I now use Citric Acid Powder mixed with distilled water to clean cooling systems , it takes a day and some labor but , every inch of the block will be shiny clean ~ no red silt anywhere .

It gets rid of solder bloom in the radiator too and cannot damage any alloy parts , making it a nautural for Imported engines .

It's been 103° + here of late and my '69 has no shroud and the gauge sits down low where it ought .

Just a thought as for me , it's easier than yanking the radiator & letting some goof damage it .

I just found this post and would really like some more info on this Citric Acid Powder. What's the deal with a flush and where can you find the "stuff"? It sounds like what I'm looking for.
.
Thanks for your time

[Lemield]

I'd like to know more about the Citric Acid Powder procedure too!

[VWNate1]

O.K. ;

Here ya go :

I bought a 75 # box of it in San Bernadino , you can buy it OnLine , Flea-Bay , Baking and Candy Making Supply Stores etc.....

Time and labor are the hardest things , the more diligent you are , the better it comes out .

[yuccales]

Originally Posted by Dunenutt

Is your trans mount in good condition? If it is broken, it will kick the fan toward the top of the shroud. New motor mounts with old trans mount will do it too.

^This^ Also could your front clip/rad support mounts be in bad shape letting your rad support settle down?