Coolant leak has me stumped

[CopyKat]

I pulled the engine out of my truck the other day in hopes to find the coolant leak, and fix the main seals.

I've torn the engine down to the short block and from what I can see there was no leak from any of the gaskets. I thought that the headgasket had blown and I had coolant in the oil. When I dropped the pan there was no coolant in the oil there were a few pieces of ice that was likely from condensation. With the intake off there is one spot that may have been leaking at the back of the intake coolant jacket going from head to head. Again no signs of a major leak. Pulled the heads only to see a bunch of carbon buildup but no signs of burning coolant. I carfully pulled the head gaskets off to see if there are signs of leakage. Nothing. I've got to inspect the heads better and the lower intake.

This has me stumped as I was loosing close to 4 liters of coolant per day. Once the pressure would build up you could see the coolant puddle forming under the truck.

Anyone have this sort of thing happen. I don't want to have to replace the gaskets only to find a crack somewhere or a leaking frost plug once the engine is back in the truck.

BTW its a 1994 Aerostar OHV Engine.

 

[410Fortune]

where did the puddle form?
ever do a compression test?

waterpump, heater core, hoses, thermostat housing all check out?

4 liters a day and you cant find it? = ??????

where under the truck does the puddle form?

 

[CopyKat]

where did the puddle form?
ever do a compression test?

waterpump, heater core, hoses, thermostat housing all check out?

4 liters a day and you cant find it? = ??????

where under the truck does the puddle form?

Comes off the belhousing, driver side. It's hard to tell but I know it's from the back of the block somewhere. It was leaking down the y-pipe. It was hard to tell because the firewall was right there. and you couldn't see anything from underneath other than the coolant dripping on the exhaust.

You would think there would be obvious staining from the coolant but there is nothing. That's why I'm stumped. None of the frost plugs are wet. I've got to check the ones on the back of the heads. It could be those ones. I've got to inspect the heads and intake for cracks. Nothing that is obvious and jumping out at me yet.

 

[410Fortune]

hmmmmmmmI would suspect the intake manifolds from where you describe

Dripping onto the exhaust = no wonder no puddles

4.0L OHV are notorious for needing new gaskets upper and lower intakes due to coolant and air leaks (150K miles +), its very odd you didnt see any issues

I am guessing there is green residue all over the back of the engine above the trans bellhousing but below the intakes?

 

[CopyKat]

I am guessing there is green residue all over the back of the engine above the trans bellhousing but below the intakes?

Not really it's hard to tell. Like I said I was hopeing for an obvious sign of a leak but there is nothing that Jumps out at me.

 

[410Fortune]

is your passenger floor wet?

 

[CopyKat]

I should have capped off the water pump and heater hoses then put some water in the block and put some air pressure to it, before I ripped it apart. :x

Looks like I'll have to do that when I get it back together. This way I know if it's leaking before I put the engine back in the truck. :roll:

Hey this is the first time doing this so I'm still learning. Next time I'll know more and will go through a couple of extra steps before ripping it down.

 

[CopyKat]

is your passenger floor wet?

Nope. It's not the heater core. I don't have carpet so I'll see it right away. floor only gets wet when it rains. I still haven't found that leak on the drivers side.