Overheating 1975 F150 custom 2wheeled drive w/460, c6, w/air with 37000 miles, rough farm miles.ffice:office" /><O:p></O:p>
I have just bought this truck.<O:p></O:p>
Installed new thermostat, Drain, acid flush, filled antifreeze, installed new hoses.<O:p></O:p>
Disconnected heater core.<O:p></O:p>
Installed mechanical gauge.<O:p></O:p>
Drove 70mph w/ air on about 30 miles no problems 160F<O:p></O:p>
Drove fine around town 5miles about 40mph w/ air on 160F<O:p></O:p>
Sat at idle 15min 160<O:p></O:p>
Shut off for 20min.<O:p></O:p>
Drove about 5miles w/air on about 55mph gauge 160F <O:p></O:p>
Drove about 5miles more w/air on about 65mph gauge rises 190F <O:p></O:p>
Then 220 for 2miles as I am trying to get home before boil over 55mph shut off ac at this time<O:p></O:p>
Then boil over occurs 235F 2miles from home.<O:p></O:p>
Have receipt that radiator was rodded and vatted 2yrs ago.<O:p></O:p>
But drained fluid looked like weak tomato soup with smell of anti-freeze not green.<O:p></O:p>
Is there away to test water pump on vehicle?<O:p></O:p>
How do I test radiator flow on vehicle, is that even possible?<O:p></O:p>
Of course I can remove and replace both but is there a better way than replace and hope my problem goes away?<O:p></O:p>
I am asking for your experienced advice as I am not a mechanic and seek your wisdom.<O:p></O:p>
Seeking experienced wisdom,<O:p></O:p>
kw<O:p></O:p>

 

Do you have a fan shroud?

 

Fan shroud won't make any difference in this situation, as he overheated while doing 55-65mph. At that speed there is more air coming through the radiator simply from the truck moving than from the pull of the fan. Fan shrouds only help up to about 35mph. After that, the motion of the vehicle creates more airflow.

 

Unless the fan blades are on backwards - and it is pushing air forward instead of pulling it into the engine compartment!
(Don't ask me how I know this.)

 

What does the oil look like? Any sign of water in it? You should get it up to temp with the cap off the radiator and see if there are bubbles or trapped air in the system. If there are bubbles it could mean head gasket time. Are both upper and lower radiator hoses hot? If they're both hot I'd think the pump is OK. Got the tstat in the right way. Could it be bad out of the box? Wouldn't be the first one. Block could still be full of diahrrea. My tired old 460 will only get half way up the gauge sitting with AC on and after a freeway speed driving. Normally it stays pretty cool.

 

yes the shroud is on
fan is pulling air front to rear
oil is good, no sign of water in oil or transmission
burped 3times no bubbles
upper and lower hoses are hot
tstat in with dome to top, spring to engine
sitting in drive is ok
but 65+ overheating intermittently is prob.
thanks for all the input
pressing on
would removing the stat help in my locating problem?
or create more probs?
you stories of experience helps

kw

 

Sounds like your t-stat is junk. not closing when it should to keep your temp UP at idle and then sticking closed once it closes. Just my guess.

try a new thermostat. Buy a STANT SUPERSTAT only, in my opinion. Buy a 195 NOT a 160. There is no reason to use a 160 at all, in fact all you will accomplish is shortening your engines life and decreasing gas mileage.

Also, the PO could have took the rebuilt radiator and put a junk one in the truck before he sold it. NOT LIKELY but possible.

 

Put a Robert shaw or Motorcraft T-stat on (195 degrees) stant t-stats are junk.

 

Sure you can take your tstat out and run it to see if that is your problem. I would not leave it out for any long period of time though, as your engine is most efficient at around 200F +/- and a properly functioning tstat will get it there quicker and keep if in ideal range.

 

Glad to see that you installed a new mechanical water temperature gauge!That takes a lot of the guess work out as you can see real occurences.Easy stuff first:What type of fan are you using?Clutch fan or direct drive belt driven?What shape are the belts in and are they tight?Engine dead and cold:turn the fan by hand in a right hand rotation and see if there is some resistance to turning.Assuming you have a clutch fan.This will at least prove that it has some capability to turn with engine speed and draw air.Later on we can still see if it is pulling when engine is up to temperature.You mentioned that the coolant that was first drained was questionable.Are you satisfied that the flush you performed has pretty well cleaned out the cooling system?Can you look into the coolant fill spout of the radiator and see the top of the tubes?See any trash or deposits around them?What does the external core look like?Any debris or dirt packed in the fins?What does the A/C condenser look like externally?Look for trash/fin damage,etc here also.Make sure the back of the condenser is clean and flows air.Make sure the core at the front and all the way through the radiator is able to flow air.Install a new 195deg thermostat in the engine.Running down the highway at speed @ 160 degrees of water temp. is too cool.Look at a few of these things and post back to let us know what you have found before we move on in diagnosis.Sorry about the long post guys!!

 

Drained radiator.
Flushed with prestone T in hose from top of engine w t-stat in.
Ran hose until flush water from radiator top and bottom was clear
Removed 160F Tstat.
Filled and burped
Took off down road 50mph w/ac on
190F in about 4 miles.
Heading home at 45mph no ac 210F 2miles later 220F
1mile from home 225F
Home at last with less than 230F more than 225F.
Shut off engine
Climbs above 230F steam coming out of overflow in less than 1min.
Start engine drops to 220F in less than 1min.
Stop engine rises to 225F in less than 1min.
Start engine drops to 210F in less than 1min.
Stop engine rises to 215F in less than 1min.
Let sit overnight try again later.
answers :
clutch fan
good belts and tight
turn by hand with some resistance
will look at radiator tubes
external core radiator and ac core looks clean no damage, no bugs, or trash

thanks to all for you input
will press on ....later
need rest.

kw

 

Well,looks like you have eliminated a lot of the list.When you get a chance,look at those inner core tubes.How much trash did you get to flush from the cooling system?Do you have or can you get an infared heat gun?It would be interesting to know the temperature differential between the upper and lower radiator tanks.Ideally,you would like to see the lower tank running 10 to 14 degrees cooler than the upper tank.This would show that the core is flowing and is trying to cool.I think that there is a real possibility of the core at least being partially blocked either by scale or maybe they closed some tubes at repair time.Famous trick about the radiator shops is to do this if the core is not to be replaced.Do you see any signs of the fan leaking viscous oil from the hub?Does the fan assembly seem loose,tight or rough spots when you turn it?Where is your ignition timing set at?See if you can get the tank temperatures when the engine is at normal operating temperature.Post back here when you get a chance.Long post,sorry.

 

I've seen this happen with a cracked exhaust runner.

 

look at those inner core tubes:
Can’t see much but tubes look mostly clean
3rows with 4th row toward front of truck looks like soldered closed hard to tell.

.How much trash did you get to flush from the cooling system?:
Not much has been flushed twice.

Do you have or can you get an infared heat gun?:
Yes sees about 10 degrees diff. top hotter w/o tstat.

Do you see any signs of the fan leaking viscous oil from the hub?
No

Does the fan assembly seem loose,tight or rough spots when you turn it?:
smooth and tight

Where is your ignition timing set at?
Buddy has my gear to check, will get later

Thanks,
will keep on plugging
kw

sorry, but what is exhaust runner?
as stated I am not a mechanic, so please bear with me.

 

Thermostat in system is essential.It provides a restriction of sorts in the coolant flow from the cylinder block that allows the hot coolant to flow at a reduced rate thru the radiator core so that it can cool.10 degrees between the tanks is at the very minimum of differential between the top and bottom tanks,would like to see a greater spread in temperature.Ideal would be 13 degrees.Make a determination about the inner core condition.I keep harping about this,but it sounds as if that cooling system has been abused.There is a test for the water pump jacket pressure,but it is almost as easy to pull the water pump and give it a visual.I still lean towards that radiator.I had a similar problem with mine a few months ago.It was an original radiator(31 yrs. old)had been taken care of and cleaned on a regular basis,and still managed to give up.At the time,I replaced it with a new four row radiator,195 degree regulator,new hoses,and water pump.Post again with your other findings,let us know what shows up.Sorry again for the long post.