I can't find my coolant leak

I have a 98 with the 4.0L.

I just rebuilt most of the engine (except for the mains, they were fine).
New Pistons / rings / rod bearings
New water pump
New radiator.
New Hoses.
Heater core bypassed at the moment
0630 junkyard head pull, cleaned up, cleaned up the valves using a basic lap method. After 500 miles, compression is fine and the engine runs great.
New fel-pro head gasket, and thoroughly cleaned the mating surfaces and checked for warp. All was ok.

Problem is, I cannot for the life of me find my coolant leak. Its a pretty big one, drips off the front diff.

I've sealed, and re-sealed the #11 head bolt using permatex high temp thread sealant.

I'm going to pull the t-stat housing and reapply RTV because i did break the seal once, and put it back, but it was during installation. Its the only thing I can think of. That is 'above the block' where a leak could occur.

I've noticed that from the front of the engine, coolant runs down the joint between the head and the block, from the front to the back of the engine on the distributor side. It also seems to dribble downwards from right under the exhaust manifold, straight down the side of the block.

I wouldn't think the #11 head bolt could leak water all the way around to the distributor side of the engine... I'm just running out of ideas, and antifreeze.

Freez plugs

scottmcneal said:

Freez plugs

Click to expand...

I thought of that, but would that cause the coolant to run along the seal where the head gasket is? I thought those were sort of 'on the side' of the block.

(And no, i don't think the head gasket is leaking, thats just the place where coolant wants to dribble down along.. That seam between the block and head.)

I'll check the freeze plugs anyways, since they may also be leaking, but i'd like to figure out where this visible flow is originating. Theres so much dangerous stuff moving around right where I need to look.

This is not my engine, only some images to point out where i'm seeing coolant.

Im going on the assumption you know for sure the head is strait and true, also that you torqued it down to factory specifications. Assuming all that was done properly id say its probably that little metal pipe that screws into the top left side of the water pump. It is probably not on tight enough and makes a leak similar to the one you are describing

I had a leak like that and it turned out to be a small freeze plug on the drivers side up by the #1 cylinder, almost under the exhaust manifold.

I didn't think to check that stupid pipe. I screwed it in and adjusted it by hand. I'll bet its that, or the thermostat since I goofed with it.

At least its cool this weekend. I was going to reseal the thermostat last night but i lost my black RTV so that didn't happen.