I'm getting HOT!!

[flyboyjack]

Well, I tried searching for answers. Couldn't find what I wanted/needed. I have an all original 71 C10 and 350. Temps are fine when driving, but get me stopped at a long light or worse, stop and go traffic here in southwest Florida and in a matter of a few short minutes, and I mean SHORT, the water temp goes all the way to the right. It doesn't knock, but if I shut down it of course gets hotter and will "buck" a little on start up. As soon as I start moving even 15-20 MPH, all is well. Original radiator. New cap. New 160 thermostat. What am I missing? Got 100K on the engine. Remove and clean the radiator? Change fan blades? I would like to stay "old school" and not go electric. Help please!

Thanks

[dmjlambert]

Hmm. I would suspect the fan clutch based on what you're saying. Did the problem start at some point? What changed?

[Warrens69GMC]

Fan shroud? 7 blade fan?

[WorkinLonghorn]

No expert, but is the radiator clear of debris in front, no mass of insects or other objects? Is there and old A/C condenser with the fins all folded over in front? Is the fan shroud intact and firmly attached? Lower Hose not collapsing from the internal wire corroded away? Water pump old and ineffective (is it weeping at all from the shaft area)?
I had this problem like you describe and if memory serves (rare) it was internal blockage inside the engine and I think I tried running a cleaner through it. Another time it was just a water pump with the vanes all corroded.

[Stocker]

Need a bit more info on your setup..... is there a fan shroud, what type of fan is it (clutch, fixed-blade)? Pics might help too. Is it a new problem?

[davischevy]

Shroud and fan clutch would be my first suspects.

[mikeshome]

Sounds like clutch fan if you are running one.

[jimijam00]

That shroud needs to be sealed up against the rad, and the fan should be the right size for the shroud and the blade half in and half out of the shroud. I run about 20% coolant and 80% water. Got a good Hayden HD clutch too. No need for a 160 thermostat. I've got a 180 and mine runs 180 all summer long, including in temps of 100ish.

[flyboyjack]

Hey Folks,
No bugs in the radiator and the fins are in very good shape. Fan shroud intact and set up properly with blades half into the shroud. Water pump is making zero noise and there is no weeping, etc.. I have not checked the bottom hose for collapsing. This overheat problem seems to have always been there since I bought it 18 months ago. It didn't seem as severe as it does now,... so I'm thinking as a lot of you that the fan clutch needs to be replaced. I'm fairly confident it's OE. So it's probably due. Then if the overheat continues,...I'll look for blockages or have the radiator boiled out.

Thank y'all for your inputs. Have a great Memorial Day.

Jack

[rockyrivermark]

May also want to add cleaner kit and backflish to cooling system to clean it out. Sounds like that’s overdue anyway.

[Steeveedee]

If it doesn't overheat running on the road at speed, your radiator is not clogged. I've seen the fan clutch mentioned. Does your truck have one? It's easy to diagnose. Just put your hand where you can feel the air flow. Weak flow will be obvious. Also, when the engine is hot, and turned off, see if you can spin the fan. If so, the clutch is shot.

[special-K]

Originally Posted by davischevy

Shroud and fan clutch would be my first suspects.

The fan is for moving air when the truck isn't moving.

When you have poor flow due to clogged radiator the truck will run hotter the harder you run it. Going up hills or hiway cruising above a certain RPM. I don't think you'd be cooling down at 15-20 mph if it was bad flow. Plus it doesn't actually overheat, right?

[flyboyjack]

It does not actually overheat,...the OEM gauge goes right up tp the max limit on the hot side of the temp gauge. So far the needle has not moved into the white band. ( I do not have a laser temp, so I'm relegated to trusting the gauge which I do not like to do). New fan clutch ordered and will go in tomorrow. I will also run cleaner through with a backflush as well.

Thanks all for everything!

[Jrainman]

this is my way of looking at it , if I was doing a fan clutch, a few more bucks a few more bolts and I would do the water pump , and if I decided to do a engine and rad flush, again a few more bucks and few more bolts new hoses and I would also do the T/stat , but hey that is just me if I do not know how old all the cooling system parts are they all get changed ,Why risk a expensive engine fail ,when a hundred fifty bucks gets me all but the radiator

[tdangle]

I also think its the fan clutch. Let us know when you swap it out the results.

[68 P.O.S.]

You should switch your vac advance to a manifold vac source to help the engine run cooler. Helps with mileage too. You have to set it up correctly first tho, you can't just switch ports or it won't work right. Also, advancing your timing helps with engine cooling. What's your timing set at?

[Sheepdip]

Originally Posted by Jrainman

this is my way of looking at it , if I was doing a fan clutch, a few more bucks a few more bolts and I would do the water pump , and if I decided to do a engine and rad flush, again a few more bucks and few more bolts new hoses and I would also do the T/stat , but hey that is just me if I do not know how old all the cooling system parts are they all get changed ,Why risk a expensive engine fail ,when a hundred fifty bucks gets me all but the radiator

All good answers to the culprit but I'm with Jrainman, have seen many bad water pumps show the same symptoms. Simple test.... you can pull your radiator cap let it warm till the stat opens and observe your flow at different engine speeds.

[rockyrivermark]

Get a $20. IR temp gun and get temp at stat housing where it meets the intake.
Guessing at the temp isn’t helpful.
Check clutch if have one on fan.
I added a pusher electric fan with 185 stat switch works great and quiet
Shuts off at 165. Spal brand.

[special-K]

A properly operating fan clutch, water pump, and rest of OEM system works well to keep these trucks plenty cool, same as electric fans. Just have to fix what's wrong. There is nothing wrong with the how the OEM system was designed

[Richard2112]

Originally Posted by special-K

A properly operating fan clutch, water pump, and rest of OEM system works well to keep these trucks plenty cool, same as electric fans. Just have to dix what's wrong. There is nothing wrong with the how the OEM system was designed

It's true there's nothing wrong with the OEM systems My fan is a 5 blade direct drive and moves plenty of air. In the cab it sounds like a hurricane under the hood but I know it's working.

[flyboyjack]

Originally Posted by Richard2112

It's true there's nothing wrong with the OEM systems My fan is a 5 blade direct drive and moves plenty of air. In the cab it sounds like a hurricane under the hood but I know it's working.

I removed the old fan clutch. Figured the OER clutch would be easy to install. But with gorilla hands and slots instead of just holes for the bolts to go through,... it’s a bear!!!! I still plan on a “flush”. Then if all else fails,.. the water pump. And I noticed all the fan blades had bent tips so I straightened them all out!! ( just kidding)!
Posted via Mobile Device

[68 P.O.S.]

Originally Posted by flyboyjack

I noticed all the fan blades had bent tips so I straightened them all out!! ( just kidding)!
Posted via Mobile Device

[D.PASSMORE]

I run a 180 deg thermostat in my engines. Seems to balance out the temperature when cruising or stopping at lights. Another thing is try to keep a good 50/50 mix coolant - distilled water. To much anti-freeze seems to make an old Chevy motor run warmer than needed.

[special-K]

I always run 180s, too

Originally Posted by flyboyjack

... And I noticed all the fan blades had bent tips so I straightened them all out!! ( just kidding)!
Posted via Mobile Device

Me too! And I noticed the blades were spaced irregularly so I tore it apart and got them spaced evenly. Man what a bunch of work. I should have just gotten another fan

Plus, that big thing all around the fan blocks air from the engine and makes it all go to the fan. I'm not worried about the fan getting hot... DUH?

[RustyBucket]

I also have GORILLA HANDS... W/ 5 thumbs on each. It's way easier to start washers & nuts on studs than trying to hit a bolt hole you can't see. Diddlin' & pokin' a hole you can't see can be fun but not bending over the front of your truck. A good hardware store should stock 5/16" SAE/USS studs in a variety of lengths. SAE(fine thread) end screws into the pump flange, washers & nuts on the front. There have been a few threads about replacing bolts w/studs. Seems like one of the auto parts chain stores sell a set of studs/nuts & washers in a little pkg. A guy with GORILLA HANDS & 10 thumbs could nick his old fragile radiator with the fan & clutch assy. Don't ask how I know.