I cant figure out where exactly the leak is coming from... I know it's not the water pump or easily seen hoses attached to it. The leak seems to becoming from the back half of the engine area. When the heater is on it seems to only slightly leak or leak slower. When the AC is on it really seems to flood out. I got under it to try to figure out what or where but its leaking all over the oil pan and transmission area... My thought is it's a hose but there is so much clutter in that engine area i can't see what hose or even where hose...

 

I had an issue with a coolant leak and it turned out to be the heater control valve that's located beside the AC accumulator (on my 1998). Unfortunately I found it too late and the leak caused my accumulator to rust. Ended up having to replace that too. For the life of me, I couldn't find a leak anywhere. All hoses and everything looked to be in great shape.

 

Pooling area

coolant pooling
I found the heater control valve and at first i thought thats what it was from b/c it was a little tiny bit wet ish... but when i got the front end of the truck up and got it leaking again its not there. It's odd like looking at it all the leaking should be on the passenger side of the engine compartment in very noticeable spots but this seems to be the right side and seemingly from behind the engine but in front of the fire wall. The only spot i can clearly see pooling of liquid is on top of the engine... its not making any sense b/c i dont know of any water hoses that would be in that area.

 

Pin hole leak in a hose will spray an almost invisible stream to another area, making it very hard to ID

Warm up engine, that will pressurize cooling system to 14psi
Then shut off the engine
Now move your hand around the hose without touching them, near where you think the leak is


There is an Evaporator drain on the passenger side engine bay, on the firewall, it will leak WATER any time engine is running if you have AC, whether the AC is on or not, but WILL leak more water when AC is on
Not coolant, its water
All vehicles with AC do this

 

Ok, just out of curiosity... do you have to top up the engine coolant? The reason I ask is... the oil inside the AC is very green in colour. You're indicating the Left Front of your engine. The AC compressor is there. As well, there are High Side AC lines that go to the rear of your engine along the Right (passenger) side. You say that when the AC is on, it dumps this liquid. Sounds like you may have an AC leak, my friend.

 

it's not the normal AC been on to long leak. This is like someone didnt turn the sink off all the way leak or like a **** stream of coolant rate. Almost as if the truck is a dog past it's prime and can't hold its bladder anymore. I had the truck run for 30 mins and nothing... then I looked around saw no new spots. Ran it again and poof pissed itself the engine was smoking from it getting on the exhaust. when i look underneath It drips from all over the oil pan and Transmission.

 

I do have to top it off after it leaks all over the place

 

So i am apparently stupid... I found the leak and in the pictures i even circled the leak spot both times. The stupid thermostat was spitting out coolant from the back end that i couldn't see. I was watching the pooling spot and noticed once in a while it would spray out. As usual i was so focused on the problem i wasnt being patient and seeing the solution right in front of me...

 

Good work

Thanks for the update

 

Was gonna start a new thread for this, but since we've already got a top thread about a similar subject I figure I might as well ask here. Sprung a sudden coolant leak during easy city driving. When I pour water into the radiator under zero pressure I see visible streams coming out from what looks like two locations. Here's a gif that should show them decently well (tried to embed, forum wouldn't let me, apologies for any inconvenience): https://imgur.com/a/NUEFFbT

Really worried about that steady stream farther back, but oil isn't frothy or milky, truck passed the glove test about six months ago and hasn't been running any differently since then (no dropoff in performance or anything like that.). What do you guys think is leaking? Let me know if there's any other information I can provide.

Edit: should've said, but 1994 4.0 OHV, manual transmission, 4x4.

 

Can't really tell what that is, a description would have helped

Looks like passenger side alternator braket on a 4.0l

That could be water pump gasket or heater hose spraying out, if engine was running
Or lower intake where it attaches to the passenger head, which was a known issue with the 4.0ls because of the aluminum intake and cast iron head

There is a core plug(freeze plug) on both ends of each head, the one behind alternator bracket could have rusted out

Steady stream, which is hard to see, would be a core plug on the block is rusted out
You can replace it with a rubber expansion plug

 

Oh, sorry, yeah, that's the passenger side alternator bracket. Engine was off. Thanks much! I'll look into this further.

 

Thanks for the posts on V6~4.0L~SOHC engines & TStat housings; good reference info.
Replaced the old leaking FRPlastic TStat Housing with a new Aluminum TStat Housing
in 2019Aug on a 2001 Ford ExSportTrac; no leaks as of 2020Mar after ~5K more miles.
My full write up with pics on that repair:
http://2001fordexplorersporttrac.fandom.com/Coolant_ThermoStat_Housing

 

So what was your solution to that I'm having the exact same problem

 

Replace the ThermoStatHousing;
an Aluminum ThermoStatHousing is recommended
over either OEM or any aftermarket Plastic version.

 

To sterben: DILLARD000'S March 2020 post didn't come up on my computer.
My notes on the subject are below.
Metal replacement t-stat housing: simmonsautosportz.com p/n SA9, ~$140
Standard replacement “How to”: http://bengrosser.com/howto/fordthermostat/
Metal replacement “How to”: https://2001fordexplorersporttrac.fa...moStat_Housing

I trust these links work.

 

Sorry for the above dead link; I changed that wiki page title & screwed up that link.
Forum won't let me correct that older thread entry, so here's the correct link
https://2001fordexplorersporttrac.fa...ant_ThermoStat

 

A coolant pressure tester is massively helpful with this. They are a tad pricey but work great. They let you pressurize a cold engine. So its easier to go feeling around in there for the leak.
build pressure to what's printed on the radiator cap. No more. Because too much pressure and you'll create new leaks. Then watch the guage to see of pressure is dropping. And go around to see where its pissing out. If you cant find anything external. Then you could pull spark plugs to see if it's a headgasket leak and its filling up a cylinder.