Hi all, I am new to the forums but not new to mechanic work. I rebuilt a 3.0 last year for a friend of mine that was loosing coolant slowly and the lifters were ticking. It had 200,000 miles on it so we decided to do an engine overhaul. Pulled the engine and tore it all down and sent it to my machine shop and he did all the machine work which it didn't have to be bored but all the rest of the machine work was done. The only thing I noticed was milky, puffy, residue on the bottom of the intake manifold when I pulled it off. I just thought the intake gaskets were seeping so I didn't really follow up on it. Its been back together for over a year now and runs great but its still loosing coolant. I have pressure tested with no external leaks that I can see and no excessive white smoke at the tail pipe when started up and no evidence of water in the oil. Asking what do you fellows think and what would be your first move on this thing. It's loosing coolant alot more now than it was a few months back and I am just at a loss and i,m fixin to tear it back apart and see what I can find!! Does anybody think the intake maybe cracked or does it possible point to a head problem??

 

I had a '94 4.0l with similar problem, disappearing coolant with no pressure loss on test.

It was the overflow hose, had a small crack where it ran over the top of the rad, coolant only leaked out when engine was hot, hose was being used.
And location caused it to evaporate pretty quickly.

Also if wondering about a possible head gasket leak or just as a test next time you do a pressure test.
Install pressure tester and pump it up to 18psi
Disconnect coil or all spark plug wires
Turn engine over, if there is a head gasket issue then gauge will go up and down on compression and intake strokes of the leaking cylinder.
To find the leaking cylinder, remove 1 spark plug at a time and crank engine, when gauge stops jumping then last plug removed was in the leaking cylinder, reinstall plug to confirm.

You can do this same test without a pressure tester, it is called the Glove test.
Put a latex glove(with rubber band) or balloon over rad cap opening.
Block off overflow hose.
Cooling System is now sealed.
Disconnect coil and crank engine.
If glove bounces then there is a head gasket leak(or cracked head)
Pull 1 spark plug at a time to ID cylinder that is leaking

 

That is some good advise!! After doing some checking today I have found that the coolant is going into the oil. About two weeks ago I checked the oil when he stopped by it it was slightly higher that I remember it being when I changed the oil last time. Now its well above where it was just a couple weeks ago and its chocolate brown looking on the oil stick. Could it still be a cracked head or possibly a cracked intake manifold?? Gonna start pulling it apart tomorrow after work and see what I come up with. Thanks RonD for the info!! That is a good way to check for a coolant leak from the cylinders into the cooling system.

 

A cracked head will usually happen between valve seats, so it would vent to cooling system.
Head/block mating have lots of cooling passages surrounding each cylinder, so when a head gasket fails it usually fails by leaking pressure from cylinder to cooling system.
There are only 2 or 3 oil drains and maybe 1 oil passage in a hydraulic lifter head, so head gasket leaking coolant into oil is not as common.

Intake manifold has coolant flowing thru it and could leak coolant into gallery, where Cam is, which is a direct path to oil pan.
But this should show up on a cooling system pressure test as a leak.

Head gasket cylinder leak might not, the leaking cylinder may have both valves closed at the time of the test, so will hold pressure, that's why moving crank/valves is always a good idea when testing cooling system for leak.

 

I talked to the guy that does my machine work and he said to go ahead and pull the intake manifold and bring him the intake and the gaskets so he can check them out and we will go from there. I pulled the intake this evening and it looked fine to me and the gaskets looked good too. I see myself pulling this one back out and taking the whole engine back to the machine shop eventually. Got to be a crack or something somewhere.

 

intake manifold gasket