XJTPD

To start off, I have a 2000 Sport with 215k. Engine was overheated bad about 10 months ago. Head was machined, new valves, etc. New head gasket, intake manifold, radiator, some lines, and much more was done and now it runs amazing. Noticed a small coolant leak by the water pump so I assumed that was leaking. Pulled the pump and noticed this:

Put a new gasket and the pump is already new. Put it all back together and it’s still leaking a tiny bit of coolant from the same area, leading me to believe it is in fact a crack. The leak is minor so I’m fine just driving and replacing the lost coolant as I go, as it is not a lot and the engine temp stays cool all the time. But is there a way I can stop the leak? I’ve done some research into JB Weld and the coolant additives (KSeal, stop leak). I would much rather go the JB Weld route than pour that stuff into my radiator, but any advice on how to fix this issue is greatly appreciated.

robsjeep

Well I agree, the coolant stop leak chemicals are a last resort, they can gum up everything.
JB Weld is marketed to do this type of repair, there maybe other brands that also work, perhaps as good, perhaps better, so research that first.
I have done JB Weld repairs on cast iron machine tool parts, they have held up, but they are at room temp. The engine part you got is likely a good candidate for this kind of fix, it is likely a low stress area.
Key things are to make some sort of Vee groove (with rough surfaces to provide bite for the epoxy) A dremel tool is good for this. Assess how far the crack goes. depending on the crack, and its end point you may wish to drill a crack stop or grind a large radiused end to the crack, but this maynot be possible. Since the crack apprears to be in a low stress area it may very well not continue to grow, so a stopper hole may well NOT be needed specially if it will be difficult or make a much bigger JB Weld fill.

Another option might be a thin flexible sealer in conjunction with the gasket Aviation Brand Form A Gasket for example might work without the need for opening up the crack. Just slather it over the crack. More detailed assesmnet should be made to determine if this is a good fix or not, it cant hurt to try, you can always go back to JB Weld. But JB weld might be the needed solution. It more likely if it works to be a permeant fix.
Consider an acid etch prior to JB Weld to assure all traces of oils are removed and surface is prepped for bonding. Metal paint preps of phosphoric acid base are used for this. This will be best chance of good adhesion of the JB Weld.

ijeeep

I'd Vee notch it, wash with acetone, JB Weld, 24 hours later file and sand flat. For sealant I use Permatex #2 / Versa-Chem #2, the green stuff NOT the brown. Any excess that squeezes out breaks down and goes in suspension.
Silicone sealant that squeezes out doesn't break down. It solidifies. Usually where I don't want it to.

Dave51

Can you wire brush the outside surface to see how far the crack extends? You may want to slap a pin in there.

robsjeep

Note, where possible place the vee notch on the inside, the pressure side for best results. this will allow the cooling system pressure to push the epoxy patch into the vee, rather than out of the vee.