thanks guys but neither quite what i was looking for, i can't really see where the water feeds in and out of the block..
I am new to my XJ and have discovered coolant leaking at the back of the engine somewhere, its very difficult to see as it is right against the bulk head. I am assuming its the dreaded cracked head i have been reading about so much but want to be sure none of the coolant pipes are leaking first...
There should be four rubber hoses attached directly to the engine:
The water pump has a hose coming from the radiator - this is the point where coolant is introduced into the engine block proper. The water pump also has a nipple that has a smaller hose connected to it - this is the coolant supply for the cabin heater (flows out to the heater core.)
Water then flows through either the heater core or the engine block - and makes its way to the thermostat housing (front of cylinder head.) This has both the hose for coolant return to the radiator
and coolant return
from the heater core fitted to it, and that closes both loops.
The heater plumbing itself can vary, and there is usually a heater control valve plumbed into the heater hoses (deleted on later models, ca. 1999 I think.)
The simplest ways I've found to check for coolant leaks without tearing everything to bits:
1) Check all points where a coolant leak is possible for a white residue. This means anywhere the hoses attach to fittings, the hoses proper, the water pump fittings, the thermostat housing, and around the front, rear, and left side of the cylinder head (as mounted.) (The cylinder head does
not have coolant passages on the right side as mounted - the only fluid that passes through there is oil. Either up through the pushrods, or drainback form the cylinder head.)
2) If you do not see any white residue anywhere, start the engine and let it idle. This is probably the quickest way to get the coolant up to operating temperature. Using a bright flashlight (preferably one with a fairly narrow beam as well,) cast about underhood and look for a small plume of steam - the light will cause it to show up better in anything less than full daylight. Once you find the plume, you can follow it down to the source.
Note that it is possible to have a coolant leak from the head gasket without losing compression as well, so be sure to check that junction.
The "cracked head issue" you've heard about is the 1999-2000-(early)2001 #0331 cylinder head castings - we escape the first year by still using the #0630 head (if you don't have distributorless ignition, you don't have the #0331 head.) This is a crack between the #3 and #4 cylinders, and it allows coolant to bleed into the engine oil sump. However, this crack typically does
not result in an external coolant leak.