List of everything that can leak coolant on a 3.5L

[Shovel]

I figured this might be helpful for posterity to just write it out.

Coolant can leak from a Gen 2 or Gen 2.5 V6 from the following places:

• Coolant overflow tank
• Coolant overflow tank hose
• Radiator cap
• The radiator itself
• Upper radiator hose
• Lower radiator hose
• O-ring behind water pump
• Water pump gasket (under timing cover/aluminum monolith bracket)
• Heater core (inside dashboard, difficult to get to)
• Hoses between heater core and firewall (older models.  Newer ones have aluminum head pipes between heater core and firewall, that protrude directly into engine compartment)
• Heater core hoses (rear of engine, center, connect to heater core at firewall)
• Throttle body heater hoses (two small rubber hoses which connect to the throttle body)
• O-rings for coolant bypass pipe (under upper intake manifold)
• ....

I'm not looking at the truck right now so I don't remember what else I missed, what else?   

[PA_JERO]

1. Freeze plugs 8 of them (3 on either side of block and 2 on back of block that you cannot see)
2. Block coolant drain plug. ( driver side towards front of block, kind of behind A/C compressor)
3. Water bypass pipe between the 2 cylinder heads that go from back of head to back of head.
4. (Then the money spot) behind the water pump in the V but in front of the intake 1/4" hoses, 3.5 SOHC and 3.5 DOHC are slightly different, but the hoses still exist.

[IncorpoRatedX]

-Thermostat housing
-depending on the year the year, one of the two heater core pipes has a rubber coupler halfway up it, so it will leak and seem like its the heater core when it's just a hose.


i was going to say the 1/4 hoses but kevin beat me. I can't think of anything else.

[Shovel]

Thanks guys,  I didn't even think about the block drain at all.   

Since cooling problems and leaks come up in discussions pretty often I thought it would be useful to have a definitive list so you could say here's everything to check and if it's not leaking from any of those places, check them again because it can't really leak from anywhere else. 

[PA_JERO]

I dont really want to be captain obvious, but.... Head Gaskets!

Booyah

[Montero_Guy]

Mine was leaking from the o-ring on the radiator drain plug on the passenger side of the radiator.

[jaccox]

Mine was leaking from the o-ring on the radiator drain plug on the passenger side of the radiator.

Same here. kept getting air in the system. Replaced this lil dude and no more leaks/air in the line.

[JohnnyBfromPeoria]

It can also leak from the jug of extra coolant that you carry with you to refill the system from one of the above mentioned leaks you haven't fixed. Just thought I'd mention it because it happened to me, and, well, it did leak out of my Montero.

John B.