I have an 86 Ford F150 that had a cracked block. We replaced the block, it has a new water pump, thermostat , all new belts, and we did the firing order. After a few days of running great it has now started overheating again and today it died on the highway from overheating. Any suggestions?????

 

its not unheard of for thermostats to be bad right out of the box. Are both radiator hoses hard(have coolant running thru them)

Fan clutch?

Did you flush the coolant system? A lot of people dont realize sand from the block casting slowly falls out and gets cycled around with your coolant wearing out your hoses and waterpump bearing. It also will create sludge as well as old coolant. This will clog the system and create poor flow.

Remember to use distilled water, not tap water. To flush the system, remove the thermostat and plug a garden hose into one of the heater hoses(napa sells a flush kit) and run the water until the green tint goes away. start the truck and let it run. Drain the radiator and block. Fill radiator with distilled water, start truck and pour an additional 2 gallons into radiator. Run for 5 minutes, drain block and radiator. Fill radiator with 2 gallons of distilled water, run again and then drain block and radiator. Add you straight mix of antifreeze, then dilute with distilled water to reach optimal boiling/freezing points.

 

You might possibly have a cracked head now from the over heating thus blowing exahust fumes back into the system causing it to over heat. Do you have milky oil? Does the plugs when pulled out look like the are burning correctly? Good luck and what size motor are you dealing with (4.9 IL6)

 

You don't mention what engine is in your F-150 but you ought to pressure test the cooling system.
this will show any leaks or cracks that might have been overlooked.

You have the classic symptoms of a partially clogged radiator and a collapsing lower radiator hose.

Is there a spring inside the lower hose to keep it from getting sucked flat by the waterpump at sustained high rpm's?
When you had it all apart did you flush the radiator?

The only other thing I can think of is a reversed head gasket when the engine was re-assembled.
But you had an overheating problem to begin with and now you still have an overheating problem so I would check the radiator for restricted flow and look at the lower hose first.

Just my 2c

 

My truck is not quite overheating but getting close to it a lot of the time. we replaced the thermostat 4 times this spring ,it has a new radiator, a new water pump was put on it last year, and we installed and electric cooling fan along with the original mechanical fan. also, the mechanical fan is not a clutched fan. It turns all the time the engine is running. The truck also has the original fan shroud on it. After we replaced the radiator and put the electric fan it runs a lot cooler than it did before but still hotter that it use too. when you run the a/c is when it almost overheats if I sit at a stoplight too long or the truck sits still to long. once the engine gets hot it does not want to cool down . I have to turn the a/c off and rev the engine a little bit above idle with the electric fan on to make it cool down. sometimes when I am towing my trailer it will run hot even without the a/c on. I can't imagine that the engine needs all that fan power to cool it down . The only clue I have is that the engine is worn out and has some blow bye on the piston rings. Is it possible that the blow bye in the crank case is causing it to heat up? or could the flow of water be restricted by sludge or corrosion in the block? Also I can run the a/c fine the first part off the day but towards the hottest part of the day (3-5 pm) it heats up and doesn't want to cool back down. I am sure that since the truck came from the factor with a/c I should be able to run it on a hot day just fine but something is wrong and I cannot figure out what the problem is!

 

Try using a hose to push water thru the condensor fins up front and backwards thru ythe radiator and see if dirty water just pours out. My 94 would start trying to over heat with the ac on and the condensor and radiator fins were clogged with dirt.

 

I can't imagine this is it but I noticed the heads gaskets that come for a stock replacement head could use to have some of the holes in the gasket widened so that more water can flow through the system keeping it cooler. I have been building a motor (351w) and noticed the head gaskets come in such a way that you might need to modify them depending on the block.

my $0.02

 

If your A/C is on the throttle positioner should increase the revs automatically.

Check the solenoid at the front of the drivers side of the carb for voltage with the air conditioning on.
If there IS power just replace the TP solenoid.

 

it has a new radiator in it but I will try to clean out the condensor fins

 

it doesn't have the stock carb on it . The reason I have to rev it up is to make the motor cool down. when at a stop light I put it in neutral and hole the motor at a higher speed which turns the fan and water pump faster which cools it down faster.

 

I am going to try a new mr. gasket 160 degree thermostat in it tomorrow and see how it goes. this thermostat is also a high flow thermostat and it says that it helps with overheating.

 

You should try and adapt the throttle positioning solenoid to your new carb.

Which carburetor do you have now?
I know it isn't hard to do with the 0-80457s that I'm using.
I just had to elongate one hole in the bracket.

160* is too cool for a street driven vehicle to run optimally.

 

I have the edlebrock 650 . The previous owner put it on . the 160 is the coolest one, we are trying it because we have tried all the others and there is really nothing else in the cooling system that could be causing to overheat . considering that it has a new radiator, water pump, electric fan on top of the mechanical fan, we have flushed the cooling system twice and it still wants to overheat. as far as I know, there is no indications that there is anything wrong with the heads . so I have no idea what is wrong with it. I would appreciate anybodys input on this matter as I am fresh out of ideas.

 

Surely a sludged up block could cause hot spots and overheating.

If it has a solid mounted fan it is not stock. An '86 HO should have a clutch fan.
Perhaps the one that's on it does not fit the shroud closely enough?

Edelbrock sells the 8059 solenoid and bracket for this application; http://www.edelbrock.com/automotive_.../8000/8059.pdf

Shouldn't matter with an electric auxiliary fan mounted (but this is obviously a bandaid that is still not working)

If the thermostats you've installed haven't worked a lower temp one won't help.
The thing is overheating, even a 195* is wide open by then.
Wide open is wide open, after that it doesn't matter.

So, the new one will open at 160*, the truck doesn't care if it still can't shed the heat.

Good luck!

 

Does it ever actually boil over? The gauge could be off.