Chrysler Repair: Water Pump and Heater, head gasket leak, head gaskets

Question
I have a 1994  van with 3.0 in it.  When reving motor it produces a large amount of coolant on the garage floor on right side.  At idle it does not do this but drips of coolant are present on right side.  Heater will only blow cold air unless higher than idle which then leaks fluid.  Uses a lot of coolant.  Temp gauge stays normal as long as I keep putting fluid in.  A mechanic says it's the head gasket and I want a new pump put in. At high rpm's it will drop a quart to half gallon of coolant in a matter of seconds.  

Answer
Hi Mike,
I guess you are asking whether to focus on the water pump or the head gasket as the cause of the leak. The heater is not doing well because the flow of water to it will be reduced or eliminated as you lose fluid from the system.
I find it hard to believe that the loss of fluid is due to a head gasket leak. If you are not getting any excessive white smoke out the tail pipe or a milky look in your engine oil or pressurization quickly in the cooling system (all of which are the possibilities with a head gasket leak) I would look more to the water pump or a hose/intake maniflold type of water leak, rather than a head gasket leak. I would imagine by looking carefully from all sides of the engine you could tell from where the water is coming out. The pump is as you probably know mounted directly to the front of the block behind the timing cover and behind the timing belt. So if/when that leaks it is much more "internal" looking than an exteriorized type of water pump. So why not look and see if it is coming from the front of the engine, fairly lower that where the head gasket level of the engine is located. It would be very desireable to get a handle on this so you don't go more repair than is needed. The water pump alone is a fairly time consuming job, and of course when/if you replace that you also want to put on a new timing belt. But I would want some proof that one of the two head gaskets is leaking, and which one it is, and why it is only leaking to the exterior of the block and apparently not getting coolant in the oil or water in the exhaust, or pressurization of the cooling system as the result of such a headgasket leak before I paid for a removal of either cylinder head. The head gaskets can leak, but there should be some proof of it. You might want to do a compression test on all 6 cylinders and let that also be a factor in your decision. If the readings are all at least 100 psi and within 25% of oneanother, then that too would make me question why the diagnosis of a head gasket leak. There are also water passages to the intake manifold and the heater hose outlet on the back side of the engine that could be the source of the leak.
Maybe you need to talk some more to the mechanic, and even limp it over to another shop for a second opinion. But be sure to keep the water level in the system as full as you can so you don't do damage to a head or the block from overheating it.
Roland