Sorry if this is a dumb question, but I've been wondering about this for a while. When parked, there's a little hole at the bottom of the radiator where fluid drips out, and leaves a small puddle. It looks to be the color of the coolant to me. What is the purpose of that hole? Is this normal?

Thanks!

 

If there was a hole in the radiator the pressure inside when the engine is running would produce a steady stream.
I think the tube in the pic with the drop of coolant is a locating boss cast into the tank for installation alignment.
You might have a tank that has a small crack near the boss or a leaking seal above the boss.
The tank is held on with crimped tabs from the aluminum core.
There is a seal between the tank and the core.
The tabs can weaken with age and the seal can leak.

 

Thanks for the help. So I took off the radiator cap this morning and there's a bit of coolant around the threads and base of the threads on the reservoir tank. Thinking it might be worth it to replace the cap.

Wondering if I should also do a pressure test and try to locate the source of the leak. Is it possible to replace/repair those seals you mentioned, or will I need to replace the radiator?

by the way, my temps today were in the high 190 range, occasionally seeing 200-202 so everything seems normal in that regard.

 

Do you still have the OEM cap and what year is your vehicle?
The OEM caps have a rather small pressure relief spring.
The Stant aftermarket caps have a larger looking spring.
If your cap is right above the drip on the bottom I would replace the cap and see if that does it.
The tank seals probably aren't serviceable, once the aluminum retaining tabs are bent over they won't hold a rebending.
I tried on a '92 Explorer radiator to push the tabs back down, which stopped a seeping seam, they held for a month or so and it started leaking again.

 

I picked up a new motorcraft radiator cap today. It has the same design as the old one, but I think there was an update to it, from what I read - MC RS-527. It feels way tighter putting it on. The old one may have very well been the original, but I've only had this truck for a few months. It's a 2000.

I searched and searched but the leak is very hard to locate. I can't see any evidence of the leak actually happening where the metal meets the plastic (and there's those tabs you're talking about). If anything it seems like it must be leaking at the base where it sits on the rubber grommet that supports it. Possibly the plastic is cracked there, but since it is at the bottom I can't see it?

I'll keep an eye on it for a few days with the new cap. It's crazy how slow the leak is. Just from me cleaning that grommet a bit tonight, I bet it won't drop at all onto the driveway.

 

Yes, there was a problem with the original caps and Ford came out with an improved one. Good move.
These kinds of leaks are hard to find. You need to pressurize the coolant system and see if it holds pressure. IF not it has a leak. If you are sure the hoses are all tight then the radiator might be faulty and needs to be replaced. Usually if it has been leaking for a while and you remove the radiator, you can see where it has been leaking.
good luck.

 

Thanks, even with the new cap it's still leaking in the same spot. As far as I can tell, it has to be the radiator. The hoses are all good and tight - no wet spots at all. Looks like I'll just need to replace the radiator at this point.

Trying to scope out what a good replacement radiator will be now.

Also, looks like the auxiliary coolers (trans, power steering fluid) are all separate? I shouldn't need to disconnect any cooler lines - just upper and lower radiator hose, as well as over flow tank?

 

Do you have an early 2000 Excursion?
Some of the early builds did not come with a trans cooler in the lower tank and have only the smallish aux cooler.
This was not a smart decision on Ford's part.
I think midyear 2000 the radiators were getting the trans cooler again.
I tow a camping trailer and have the radiator tank trans cooler, upgraded the aux cooler to the 5R110 cooler (more than twice the size of stock) and added a 3rd B&M Supercooler.
I think any replacement radiator you find will have the trans cooler, which you don't have to use if you choose.
There should be a 1" coolant hose connection next to the lower radiator hose which is a supply line for the engine oil cooler.

 

very interesting, great info! It is a 2000, not sure if early or mid, I will check tonight. But I'm pretty sure there are no trans cooler lines on the radiator itself.

So I may just go ahead and "upgrade" to the trans cooler on the radiator. Do you know if it will fit right on, or would I need adapters?

btw, trans temps right now are in the mid 150s on my 45min commute. Of course the formula used by my obd adapter might be off, but thought I'd mention that.

I'm also interested in upgrading the aux cooler instead, if it's even better than the radiator and not too expensive. Not sure how much towing with be in my future down the line but more cooling is always better

is is there an upgrade for the aux that will just be plug and play?

 

I think you would need adapters that will go into the radiator tank trans cooler fittings. The lines to the OEM aux cooler (3/8") would need changes, too. Now would be a good time to install the Dorman 918-216 trans cooler ($190 Amazon) used for the 5R110 trans in the 6.0 Excursions. It bolts right in place of the old aux cooler. It has 1/2" lines which lowers line pressures so it will be less likely to trigger the cooler bypass circuit.

 

150 isn't very high but normal if unloaded.
I've seen it as high as 210 unloaded in 120F driving uphill.
The 6.0 cooler is bigger. Ofcourse if you install the 6.0 cooler your fluid will stay even cooler since the 4R100 doesn't have a thermostat.

 

Even though the trans can handle fluid temps in the 210 deg range I would rather have the trans fluid never go over 160 deg or so.
A bypass valve can be added to only allow fluid flow thru the coolers above 180 deg.

 

Too high a temperature isn't good but neither is too low.
Someone added one of those thermostats but I think it wasn't a success and he removed it. Can't remember if it was because it was too small of a diameter or something else.

 

A good quality bypass valve properly installed should work fine.
The design isn't much different that an engine coolant thermostat.
Newer tansmisions now come with them built in.