Fan Clutch issues. 460BB

[*13*]

Ok, Ive been running circles for the last month. I bought a 79' F250. Shorty after it began to run hot. I changed the
thermostat(high flow) & the antifreeze. Still hot
Changed the fan clutch. Ran ok for a couple days then hot, again.
Changed the water pump. semi ok for a couple days & getting hot again.

I'm beginning to think its the fan clutch, for the following reason. I can hear the fan pulling hard, at startup. as the truck warms is mellows out. I run on the highway & it now runs a little warm. When I pull off the highway I can't hear the fan pulling anymore & its getting warm.
When I changed the pump last week, it had sat for a couple weeks. the motor would get warm, then cool itself back down. Now, that isn't happening, again.

The obvious questions...
I am not losing coolant.
No coolant in oil or from exhaust.
No remanufactured parts. Pump & fan clutch were new replacements(heavy duty).
The new coolant looked clean when removed from the system.
I have the big radiator & it looks super clean
the water pump has a new backing plate.

So, questions.
What are the chances one would get a new fan clutch that is defective?
& is there anything I'm maybe not thinking of?

[Tom Wells]

13,

Don't have a clutch-type fan - it's electric.

The only heating problems have come from air trapped in the engine; several heat/cool cycles with topping off the reservoir in between fixes it.

If you have the thermal type fan clutch, it's supposed to help when the engine is warm, and not so much when it's cold.

That's more than I know about that!

Tom

[*13*]

Thank you for your thoughts.
The truck doesn't have a reservoir. I "think" the air is out. I'll check it again, tomorrow. I have refilled the radiator after running it a few times.
the fan clutch I have has a lifetime warranty. I'm swapping that out tomorrow.
The clutch is thermal, it has the spring on front. I pulls hard at startup. Still spins when warm but doesn't seem to have the same energy. I'm judging this by the noise level.
We'll see tomorrow...

On another note. I pulled a few of the plugs & they look as they should..Good!

[120mm]

Originally Posted by *13*

Thank you for your thoughts.
The truck doesn't have a reservoir. I "think" the air is out. I'll check it again, tomorrow. I have refilled the radiator after running it a few times.
the fan clutch I have has a lifetime warranty. I'm swapping that out tomorrow.
The clutch is thermal, it has the spring on front. I pulls hard at startup. Still spins when warm but doesn't seem to have the same energy. I'm judging this by the noise level.
We'll see tomorrow...

On another note. I pulled a few of the plugs & they look as they should..Good!

I drive Land Cruisers, and they are notorious for capturing bubbles in the cooling system. Some things I'd recommend:

Put a filler "T" in the highest hose in the system and fill from that while the engine is running.

Get the front end up so that the rad cap is the highest point in the system, and fill from there, with the engine running.



Get one of these things and use it, following the instructions.

[DanEC]

Timing plays a big role in how cool an engine will run. You might check the timing. And if it has vacuum advance on the distributor I would make sure it functions and is hooked up to full manifold vacuum and not ported vacuum.

[*13*]

I'll check these things. Thanks. I think I need to invest in a temp gun, as well. It's all strange that it ran fine for the first couple weeks that I had it & then started getting hot.
The clutch fan wasn't operating properly. The thermo spring wasn't even connected. Now with the fan clutch operating properly it still sits higher & than it did, originally. When at highway speeds it runs a little hotter then, cools back off a bit when at lower speeds. the temp sender is new.
The timing should be good but, maybe the advance isn't pulling properly.
The radiator tank is easily the highest point in the system. sitting on an incline might be worth a try to double check for any air in the system.

[DanEC]

You should notice a big difference in how long the fan spins when you shut the engine off while still cold - and shut it down when it's good and warm. I don't remember the old rule of thumb exactly but it's something like the fan should stop within 1 to 2 revolutions of the engine stopping when hot. When cold it might spin for several seconds.

[*13*]

Good to know. I can already see a difference. It's not pulling hard at startup.

[raider390]

With a fan clutch usually if temp goes up on surface streets bad fan clutch, at freeway speeds plugged radiator.

[Dirty Harry]

Any chance that the bottom radiator hose has gone soft and is collapsing at higher rpm?

[MKS427]

Did you have the radiator cap tested? If it is marginal, it may explain an intermittent problem.
When does the issue occur, at idle or speed?

[*13*]

Haven't tested the cap or bottom hose. Here is the latest.
Yes, after a freeway run to work, about 15 min at speed it's overheating & won't bring itself down. Work commute is about 20+ min total. I put my hand over the radiator & it feels cool. Still has coolant in it.
So, Last night I took surface streets home. about 30min. It ran a little warm until about 5 minute from home, then it spiked. Turned it off & let sit for a couple minutes. Start it up & it quickly drops into the warm area again, not hot. Ran it the rest of the way home. A couple times when I revved the motor for a seconds, the needle would drop a few degree. Then work its way back up to where it was.
It's seeming to me like there isn't free flow of coolant. As if it's restricted then , completely clogs up at times, when its warm.
Sound logical?
The radiator looks clean, & the old antifreeze didn't show signs of excessive sludge?

[DanEC]

That could fit the symptoms of a soft, collapsing lower radiator as mentioned above.

[*13*]

Yeah, I could see that making sense. I'll have look at that, Thanks!

[40k Later]

If you can touch the radiator that would indicate no hot engine coolant has entered and therefore I would say you have a "Bubble" or trapped air. Run it with the cap off until it burps. If that doesn't work have someone rev it up slowly with the cap off and see if the flow increases. That will tell you if your bottom hose has collapsed. If after you rev it, flow slows, your bottom hose is tango uniform.

I'm thinking air is trapped and not a fan issue. Please let us know what you find

[*13*]

ok, got the truck on a slope & ran it till it burped. Seems to be running better. Neither hose is collapsing. I checked them in the warm running state. Not even distorting, visually. I'll give it a few days & see where were at. It's been back & forth to work, a couple times w/o issue. Now to the windshield wipers....Older vehicles....

[cycleguy55]

My BBF 460 came w/o a thermostat. I bought and installed a high flow thermostat that had a small poppet valve in the plate to allow air to escape. I also drilled a couple of extra 3/16" holes in the plate to allow air through, though it does take longer to warm up than I'd like (especially when the weather is cool).

Check out the tech tips at https://www.stewartcomponents.com/in...formation_id=6

[*13*]

Originally Posted by cycleguy55

My BBF 460 came w/o a thermostat. I bought and installed a high flow thermostat that had a small poppet valve in the plate to allow air to escape. I also drilled a couple of extra 3/16" holes in the plate to allow air through, though it does take longer to warm up than I'd like (especially when the weather is cool).

Check out the tech tips at https://www.stewartcomponents.com/in...formation_id=6

I did the same on my small block to get some more coolant flow at startup. The thermostat sits a few inches off the block & that first opening takes a bit longer. Thanks for the reminder. I'll keep it as a possibility if problems persist.