coolant leak, can't locate source

[airborn_ranger]

Hillary leaks coolant at about 1 pint/minute after I fill radiator and overflow, engine not running.

Leak seems to come from above water pump.

Upper/Lower rad hoses ok; heater hoses ok.

No coolant in oil; no telltale signs of cracked head exhaust sounds.

No coolant coming out of weep hole on water pump, and shaft does not move in its bore and rotates smoothly.

WTF? Any ideas of leak location, or how to locate it (flourescent die?)

 

[triumphrider-1]

Thermostat housing or housing gasket maybe?

 

[airborn_ranger]

thermo housing

Good idea! I forgot to include that one. It is dry as well. Thanks for the input!

 

[triumphrider-1]

One other thing I could think it might be is leaking aroung the hose/fitting connections. That, or leaking around in the intake plenum, dunno.

Others on here might be able to give you some more/better ideas.

 

[CopyKat]

I've got a similar leak but from the back of the block. I'm leaning towards the coolant transfer ports going into the lower intake. There is a set of the front of the heads and one on the back.

 

[MrE_Powers]

timing chain gasket has water cooling passages on the 3.0 maybe the 4.0 has same.

 

[CopyKat]

timing chain gasket has water cooling passages on the 3.0 maybe the 4.0 has same.

Yes it does. Coolant in the oil would be a sign for that.

 

[BeaterMan]

i feel ya pain, my 85' 2.8l does this aswell and i've determined its where the h2o pump bolts to the engine. no fluid comming outta the weap hole, but all around the pump itself. looks like someone previously had replaced it and did a butcher job sealing it up -2 diff colors of rtv sealing it up. some people

 

[brendank]

I've got a similar leak but from the back of the block. I'm leaning towards the coolant transfer ports going into the lower intake. There is a set of the front of the heads and one on the back.

Is there a frost plug on the back of the block on the 4.0 like there is on the 2.9? I just pulled the transmission and clutch out of a BII w/ 2.9 to replace that plug.

 

[airborn_ranger]

Hillary is parked for the first time in her life...

I can't find the source of the leak, thus it is in the garage. She has never failed me in the decade that I have owned her (1st owner). The coolant leak is a relatively minor thing... I just can't find it. Thanks for all of ya'lls help! I'll let you know what I find. My time problem is that I work two 40-hr/wk jobs, which leaves no time to do anything other than work. On my vacation days, I fix my trucks! Therapy!

 

[snake]

You'll need to pressure test it. You can use a compressor if you are VERY careful. Just take the hose from the coolant recovery tank, and with the rad cap on and tight, shoot 20lbs or less of compressed air into the hose. It should go past the rad cap internally and then hold it tight. Overdoing it will blow the crap out of something expensive so keep it to a minimum. You'll find it then by golley...

 

[airborn_ranger]

snake, thanks for keeping this thread current!..I'll do what you suggest. What do you think about flourescent die to ID the leak location?

 

[calypso93]

I think the dye test is a good idea. Beats using a flashlight and mirror.

 

[sljensen]

Have you pressurized it yet?

Mine was leaking bad on my expl. I couldn't find it until I put pressure to the radiator. It was leaking on the passenger-side corner-front of the intake to head. One tube of alumaseal and I made the last 500 miles to 200K. It is starting to weep again so it looks like I'll have to do the gasket. You are going to have to put some pressure to yours and get a good light and be offensive in your technique and possibly language.
Bye.

 

[JoeCanada]

What you described sounds exactly like a lower intake gasket leak. I had the same problem on mine, it would piss coolant when not running. Found the leak behind the A/C compressor bracket. Took me about 3 hours to do, although I know it would be less if I had to do it again.