I got it dug out. It was actually sitting on the corner of my cleanest junk pile. Outside diameter of the threads is 1"

 

Maybe pull that sender out and look at the length. It MIGHT be all the way against the outside wall of a cylinder and reading THAT instead of just the water in the jacket. The worst part about these engines is the marginal cooling system although it sounds like yours is upgraded enough that it should be plenty. Make sure you have enough FLOW. I've seen the little water pump impeller rust away where there was nothing left but the hub. And maybe run without a thermostat for a little bit and see what that back-of-the-block temp does. It really SHOULD be 195 or less at that point.

 

What's up guys, so I have a similar issue thatbI can't figure out. 87 f150 4.9l new thermostat 195° new, water pump dual electric fans wired to ignition so on at all times. Needle gets up to R and M and sometimes A the past couple of days on a 20 minute drive home. Stopped at the grocery store 2 blocks form my house on my way home. Came out and all the coolant was on the ground. It had boiled out the reservoir tank. Needle was reading R when I got to the grocery store and O when I left. Wasnt steaming but seems a bit too hot for my taste. Boiling is deffinently too hot. What would the issue be to cause it to be running that hot? Any input would be greatly appreciated.

 

Is your radiator cap good? The pressure in the system keeps the coolant from boiling until it reaches a higher temp. May not be overheating. What coolant mix are you running?

 

Autozone 50/50 also the cap is only about a year old. Maybe I should pick up another one just to be safe.

 

When was the last time you topped up the radiator before you lost all the coolant?

 

A few days before it over flowed. Then again after it boiled out the reservoir tank

 

it also boiled out the tank again yesterday when I got to the store. After about 20-30 minutes in the store it didn't want to start. Turned the key and nothing. Turned a few more times and jiggled it a bit and finally got it to crank and start. I did pick up a new cap and some coolant additive. I'll put those in this morning and see how it does on the way home today

 

Did the 87 come with electric fans?
Me thinks not and just about everyone that does the electric fans runs into the same issue after the fan swap.
Does the truck have AC, me also thinks yes.
If you put paper up to the grille does the fan suck it to the grille strong or just kind of holds it?
It should suck it to the grille strong to be able to pull cold air thru the AC condenser & radiator to keep the motor cool.

Oh also got to ask when did this start after the fan or water pump install?
Truck use 1 surp belt, me thinks so, or V belts?

What shape is the radiator in? How old? When up to temp feel a cross the face / tubes and see if they are hot all over the same or if you have warm spots with no flow.

Put the stock fan & shroud back on and lets see what happens.
Dave ----

 

Thanks for the input.. The truck didn't come stock with electric fans. I put thme in about 3 weeks ago. The tune up, water pump, thermostat, was all done about 8 months ago. Had a new radiator when I bought the truck about a year and 2 weeks ago. Its been an issue since I've had it, but only seems to over flow on hot days. I kinda just assumed the electric fans would solve the problem. The fans are pullers and yes can suck the paper up pretty good. Also no hot spot on the radiator that I can feel and both upper and lower radiator hose even Temps but very hot (just checked today after a 20 minute drive home from work). I did add a coolant additive and new radiator cap this morning. It didn't get past the 0 today on the way home. So maybe this will help for now. 🤞 Thank you everyone for the input and keep em coming please.

 

Keep us updated, hope that solved it though. I had a thermostat that would occasionally stick open, or closed and it took me awhile to figure out my cooling issues.

 

So did this start 8 months ago or 3 weeks ago? That should tell you where the issue is.
Then you say "Its been an issue since I've had it," and how long has that been?
I am sure it did not leave the factory over heating so something has to be wrong with the factory cooling system thing is to find what it is.
" I kinda just assumed the electric fans would solve the problem" Throwing parts at it and not even factory parts is not the way to go.

So lets go back before the fan change and it over heating.
When you got the truck was the cooling system full of mudd? If so how did you flush it and was this before the new radiator?
My gut says it was full of mudd and you flushed it till it was clear water coming out. Changed the radiator and it was ok for a little bit till it got hot out.
That is when you did the water pump & stat and then the fans because it still ran hot.

If so I would put money on there is mudd in the bottom of the cooling chambers of the block keeping the coolant from picking up the heat from the block and it keeps getting hotter till it boils over.
How many casting plugs (freeze) have rusted out? Another sign of mudd in the block that flushing will not remove.
Only way I know of to clean this mudd out is to have the block hot tanked, read rebuilt.

Now I have not tried this but you can try and drain and flush the motor again. Pull the 1/4" plugs to drain the block, cap the heater hoses and lower radiator hose and fill the block with a something that eats rust like Evap-O Rust and let it sit for a week. Drain and flush and see if that helps. Don't be shocked if casting plugs (freeze) start leaking after this.
If so pull them all and take a coat hanger and rut around to see if you can break up any mudd sitting on the bottom of the passages.
You can now get a hose in the openings and do a flush that way also to break up the mudd.

I have 1 motor when I got the car was fill of mudd and no flushing, new radiators even a shroud that never came on the car, ect. would keep it from over heating.
I had many casting plugs rust out because of this and just used the rubber plugs till I could pull the motor for a rebuild.
I have yet to pull it but I know it is the mudd in the passages is why it over heats. The car has been sitting for 10 years now because of this and don't think I will ever rebuild it as the car is not worth it.
Dave ----

edit: lower radiator hose have a spring in it?

 

Thanks Dave, I've had the truck for about a year and 2 weeks, it already had the new radiator when I baught it. Previous owner says the radiator was about 2 months old. It looks nice and clean. I have flushed it, no dirt, or dirty water comes out of it. Ill take a look at the plugs and go from there.