So truck was running fine, 1994 7.3 idi turbo, then one day I look and coolant reservoir low. Fill it. Check next day, reservoir and rad low. Add a gallon to rad and fill reservoir.

So I start it and look for leaks. Dripping off engine cross member at back, looks like dripping from under or behind water pump.

Squeeze rad hoses, seem limp. Let it run till it warms up good, still limp. Shut off, squeeze hose, can hear hiss from rad cap. Take it off and look closer, can see the rubber is slightly eroded and obviously not sealing.

So, obviously gotta order a new rad cap, but what else is likely the issue? Would the low system pressure have caused cavitation and pit a pinhole in water pump?
Or did the low coolant level maybe take out water pump seal?
Never overheated.
Just wondering what I might be prepared for before I start looking to order stuff.

 

You can rent a coolant system pressure tester from most parts stores. Using this would allow you to check closer for leaks with the engine cold. If the coolant is coming from the water pump then it's probably time for a replacement. You can also listen to the water pump with the engine running using a mechanics stethoscope or long screwdriver. If the water pump bearing is on the way out you should be able to easily tell. Good luck!

 

If the water pump is leaking, most of the time you can grab the fan blades and see and feel the play in the pump shaft, any play, it's shot. If the play is in the fan hub, then it's shot.

 

water pump has a small hole in the lower bottom of the shaft housing going out to the fan. when the pump gets old and tired, it starts leaking out of that hole. it is kinda like an early warning sign to change to pump before it fails completely and leaves you stranded on the side of the road.

the bad radiator cap probably let you go longer with the bad pump by not holding all the pressure in causing it to leak worse.

 

Be sure to remove the belt when checking for play, I've had a few that wouldn't show up with the tension of the belt holding them.

And yeah sounds like water pump weep hole, basically when the bearings get play the interal seal leaks and it washes the bearings further hurting them. Whoever designed that weep hole was a smart guy. A lot of hydraulic pumps use this design as well.

 

I have had a similar issue with my 89 f350 but realized after I changed water pump that it’s leaking from somewhere near the vacuum pump not sure where I’m guessing the head somewhere

 

The heads on IDIs will get loose and leak oil (but usually from the backside). Put a clean sheet of cardboard under the truck for 1 night and then look at the oil/coolant stains. My truck had obvious oil drips at the back of the heads due to loose head gaskets (front of the truck to the bottom of the pic). If the head gasket is so loose that you're loosing coolant then it's probably time to at least tighten the head bolts. You should also check the coolant drain plug under the passenger's side exhaust manifold and the block heater. One of these might be leaking.

 

Put new water pump in, seems to be holding coolant perfect now.
I figured with 300,000km on it even if the water pump was fine, a new one wasnt a waste of money.

I cleaned the block with a wire brush on rotary air tool before the gasket and gasket maker and pump went on.
It was an easy job other than removing the fan nut. That ended up being an air chisel job.

 

IF you use a Knocker Wrench on that fan Clutch Nut, it won't cause you near the Grief

 

I'm not sure what a knocker wrench is, but I tried to find one to rent or buy and the only option was spending 120$ so I went this route haha.

 

Now that is a Knocker Wrench

But hey what ever ya gotta do