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I just traded a 1997 Corolla for a rust free 1981 f100 it's a bit of a project but I am working all the kinks out I put a new thermostat in it because old 1 was stuck open previous owner put a brand new radiator in it but it's not the right radiator it's set up for truck with coolant tank so when themostat opens coolant pours out of hole on radiator can I cap in with something or do I need to add a coolant tank somewhere or do I need whole new radiator ??? Looking for cheap route but also wanna do it right I don't like tow bills lol
Last edited by FirstFord1994; Dec 25, 2017 at 07:44 PM.
Reason: Hit the submit button by accident
The radiator may be correct. Your 1981 F100 had a coolant recovery tank mounted at one time. They all did. I don't know how hard it is to find used ones. New should be available in the aftermarket for way less than a radiator. Really, any tank from any vehicle would work given reasonable volume. No tiny ones from a Honda four cylinder. Check the junk yard. Dorman probably makes one designed to fit your truck. Probably less than $50.
My V8 only has 1 line, it's a hi-cap though. If they are too full some will go to the reservoir or run onto the if it doesn't need one. If you run a 165-180 thermostat it will keep your engine cool, but don't let it get too cool. As coolant passes through the rad it will condense then expand when it gets hot. The system is pressurized so you may just be able to add an overflow line to run to the ground and just keep an eye on your temps, the radiator doesn't need to be completely full to the cap. If you don't have a coolant reservoir than you don't have wiper fluid either, at least that's how it is on my truck.
I got wiper tank and I put a 195 thermostat in because it was what factory called for there is a hose running to the ground from bottom hole on radiator by cap and I can't find a factory tank on dorman or advance Auto website even checked Amazon and eBay
You will be hard-pressed to find an OEM tank. Cheapest thing is to go to a junkyard or buy aftermarket ones like the one above. Sometimes a few NOS parts will get posted on ebay but bids can go pretty high. Back in the day, you ran cooler thermostat in the summer and warmer ones in the winter. EFI has ended the need to do this unless you still own a carbureted vehicle. I would try letting the coolant that runs out when it opens collect in an empty bottle until it stops running out, then check you're temps. If it doesn't run too hot take it for a drive, if it's going to overheat then it will most likely happen while sitting still. If it overheats while driving, turn on the heat in the car and get back home asap.
It's easier to figure out what no to do than what you should do.
It has 2 holes under radiator cap 1 for relief and 1 for tank I can take picture tomorrow if I get home before dark
Your truck sounds like what mine started off as.
Ok here is a picture of what mine started off with.
I say started with as the radiator is not right for the year, it is for a later year like 84 or so.
Any way you can see on the far side the radiator/wiper wash tank, it is a 2 part tank. I don't think you can buy them new after market as I could not find any, so good use it will have to be.
As for the radiator you can just make out the over flow nipple just under the cap. A hose would go from that nipple across the top of the radiator to the over flow tank.
I have never seen a radiator with 2 nipples just under the tank.
I have see down lower on the radiator side tank a larger nipple you put the heater hose on. Heater hoes would go from water pump into heater out of heater to that larger nipple on the radiator tank as the return.
If that is how your radiator is and you have a heater return then yes you could cap it.
Also note if you just filled the radiator then started the motor when the stat opens or when you shut it off it could "puke" as trapped air comes out.
When cold open the radiator top off as needed, leave cap off. Start motor and run till up to normal temp. As said it may puke out a little coolant and that is ok as the stat opens & closes a few times. If a lot comes out top it off but if just a little keep an eye on it till the stat opens/close a few times.
When the level stays the same you can top off if you want or just put the cap on and top up the over flow and call it done.
Dave ----
What's wrong with that one? The washer fluid reservoir is the coolant overflow tank too, the hose hooks onto the rad. Looks like you need to run that line to the radiator and plug the other. You can see it run across the shroud (https://www.npdlink.com/store/produc...272-60243.html) in that picture.
That lower hose is below the radiator cap. It should be capped, it's for some other application. You need your tank hooked to the top port which is above the radiator cap. When the pressure exceeds the spring in the cap, it will then let the fluid flow.
You can run without a tank, just run a hose off the top port down to the ground so when it pukes fluid it will not get all over the engine compartment and make a mess. If you do not run a tank, you must leave a air space in top of the radiator. If you do not leave enough air space, it will puke out of the hose when the engine gets hot and make a air space by itself. If it does that, then on a really hot day it may puke a little more till it gets enough air space for the coolant to expand.
That is the only reason to run a overflow tank, so you can keep the radiator full at all times. When it gets hot it pushes the spring open in the cap, the fluid goes to the tank. When it cools off it sucks the fluid back out of the tank into the radiator.
Back in the day, you ran cooler thermostat in the summer and warmer ones in the winter. EFI has ended the need to do this unless you still own a carbureted vehicle.
I don't know where you heard this but it's not true.
It looks like you have a later model replacement radiator. These were consolidated to fit 1985 - 1996 trucks.
The top nipple should have a rubber hose attached to it that connects to the coolant overflow bottle.
The lower nipple was there for vehicles with EFI. A rubber hose attached to it that connects to a metal bar that runs across the top of the radiator and attaches to another rubber hose that connects to the throttle body heater on EFI vehicles.
I you have a carbureted vehicle, cap it off, and put a hose clamp on it!
