I've been putting off doing the head gaskets (and I know it needs it) and just keeping the coolant topped off. But this weekend after topping off and a short trip out I came back out to find a puddle of coolant under truck. I topped it off again, started it up, and tried to see where it was coming from (the puddle was under the front of the truck roughly between the corner of the radiator and overflow tank). I saw no leaks while it was running so I shut it off. When I came out a little while later there was another puddle. I think I see where the coolant is coming from - the coolant pipe coming off the corner of the radiator (see attached pic), but why does it seem to leak after I drive the truck? Can anyone help with a diagnosis?

 

It looks like it's coming from that cooler line and the reason it's not leaking while driving, how would you know at 55mph? Also when was your waterpump changed?

 

I see you still have the black plastic plug in yours. Those can easily break.

In the pic, there seems to be a green residue at the seam right below the pipe.

Mine was oozing coolant from the short section of heater hose that goes from the block to the curved metal pipe that another heater hose connects from the curved pipe to the firewall. It sits sort of behind and under the alternator. When I had my alternator off, the cracked hose was obvious. With the alternator on, it is mostly hidden from view. It was enough leakage to form small puddles on top of the water pump.

I ended up eliminating the curved piece of pipe and running new heater hose from the block to the firewall. No more oozing coolant. Check all your hoses and tighten the clamps well.

I am not sure off the top of my head where that metal pipe goes without going out to look at mine.

 

The metal pipe is one side of the engine oil cooler. One of the rubber hoses above is return from valve body heat plate. You are most fortunate to have a copper/brass radiator. You can find a local indy shop that works on tractor and construction equipment radiators. Take yours out, and they will usually acid flush, rod out, and resolder any needed area for like $60 - $80. If leak is around the oil cooler line fitting it may have to be soldered.

I got a salavged unit from the boneyard, put it in, and the oil cooler was plugged! Red light would not go out, while I'm in front of the truck watching for water leaks as it warmed up..... so while it is out, have them check both the coolers.

No stopz leekz pleazzze.

 

I used this in my wifes Volvo, worked GREAT!!!! I highly recommend this stuff, just follow the directions to a "T".
I put it in her cold car, then drove for 30 min, no leaks for 3 weeks now and normal operating temp.
Only use one bottle IF you decide to try it.
Normally I would be right there saying do not use, but this stuff actually works.
I bought mine locally.

K-Seal? Permanent Coolant Leak Radiator Repair - 8 Oz | Land Rover Engine Parts at RoverParts.com

 

May work, as it is an external leak. Might also snug up the connection that threads into the the radiator, oil line screws into that. If problems happen, radiator can be flushed and rodded out cheap, and thermostat is also cheap.

 

Put a pressure tester on it and see what leaks.

 

My old radiator leaked in the exact same place as his, no fix other than re-soldering it, it is leaking around the bung hole on the radiator tank.

 

Yep, and at the same time the rad shop can rod it out, be good to go for the next few years. I guess a very careful person could solder it up while in the truck... but it is easy to pull, once you master the fan clutch removal. Acid flush and rod out is a treat for the old brass and copper radiator. I have seen that connector soldered, and I saw a similar (identical) size on a Rangie that was just threaded.

 

Well when I get around to doing the fan clutch, the radiator will go to a radiator shop for refreshing.