Ok, so here's the deal...

I have a 1996 Dodge Ram 1500 (2WD) with a 5.9 V8. started having a bad water pump gasket leak around 190K miles, so I replaced the pump and was sure to torque to spec. But... there was still a leak...

So, then I changed the thermostat and a new gasket (i figured it could use a new gasket since the pump needed one) which in all honesty, i probably over-torqued... but, there was still a leak!

It only leaks when the engine is almost completely warmed up... as soon as the thermostat opens, the leak stops. The drops come from somewhere above the water pump pulley, because it drips onto the harmonic balancer which spashes it all over the lower radiator hose (which I did consider as the source, new hose with new clamps). I think it could be pooling somewhere too, because if I'm driving and come to a stop, the belt squeaks for a bit until it drys off.

I have checked and double checked all hoses, hose clamps, torque specs on the pump mounting bolts... I HAVE NO IDEA WHERE ELSE TO LOOK!!

Does anyone have any idea of what I could be missing?!?!

 

do a compression test and that should help you pinpoint the leak

 

by pass hose?

leaking when the t- is open when the motor is warm

 

Does the 96 have the same waterpump as the 98? If so check the O-ring for the heater hose return pipe?

 

timing chain cover gasket

 

+1.... ......

 

In that general vacinity you have several place it could be coming from. Your temperature switch is near the t-stat housing you have the bypass hose which is the short slightly bent hose coming from the top of the water pump going directly into the front of the intake manifold. Youve got your heater hose pipe that goes into the pump that yes for the guy that asked does indeed have an o-ring thats supposed to seal it all up. the t-stat housing itself the upper radiator hose going into the thermostat housing neck. the water pump itself and then the lower radiator hose. I believe theres also freeze plugs on the front end of the cylinder heads also the timing cover itself. Although the timing cover if it were leaking fluid it would be going into your oil and more than likely not leak to the outside of the engine.
Your post did not say wether you simply used the provided gaskets to seal your water pump and t-stat housing. Me personally I've always used a nice bead of blue silicone on both sides of my gaskets and have never had a leak from them again. If the thermostat housing has been over torqued to badly it may have affected the flatness of its sealing surface which you can correct by putting some sandpaper of a nice sturdy and dead flat surface and then sanding the bottom of the housing on top of the sand paper but make sure your paper is on a flat and solid surface. Also you did not mention if you had replaced or if you have inspected the upper radiator hose. The factory spring style hose clamps are cheap and loose their ability to put enough clamping force around the hose. For that reason I always replace that style clamp with the appropriate sized screw operated hose clamp. (not to mention that I hate it when my pliars slip off of one of them dang spring clamps and it whacks the finger I'm using from my other hand to help guide it to where I need it to be! Yowsers that smarts!) You said that it leaks when its almost warm but then stops when the t-stat opens which makes me suspicious of either a lack of proper sealant on the t-stat housing, the upper rad. hose not being clamped properly or having a hole in it, or the bypass hose for the same reasons as what I've outlined about the upper radiator hose. When someone has asked me to replace a water pump on one of these engines I have always insisted on a new bypass hose because its such a pain to get to let alone the fact that its mostly covered and out of sight due to the alternator/ A/C bracket. the o-ring that is around the heater pipe coming out of the water pump on the drivers side of the engine... I typically will put a little Blue silicone around that pipe along with a fresh o-ring as just an added measure of protection. If the leak is coming from around the temp sensor you should see a build up of residue around the sensor along with signs of corrosion simply replace it using teflon tape wrapped twice in the proper direction around the threads. The aforementioned freeze plugs at the front end of the cylinder heads would also be a very easy thing to spot so I dont think they would be your issue either!

If you used Blue Silicone on both side of your gaskets they shouldnt be leaking. If you reused your original spring clamps they may not be clamping hard enough and causing you problems just replace them with new screw style clamps. If you reused your old bypass hose It's real easy for it toleak with out being able to identify it due to it being covered up. Make sure your heater pipe isn't leaking at the water pump.

Not much else on that engine shy of having something cracked that will cause this issue! Hope this helps!

 

My timing chain cover leaked coolant outside of the block. Did not get in oil as far as I could tell. I had a leak after I changed my radiator like you're describing. It was the upper radiator hose, leaked bad right as the motor got to operating temp, then stopped after t-stat opened. I got that leak fixed and then the heater core started leaking. Apparently, the new rad put some pressure on all my old stuff.

 

id say bypass hose or timing cover....or possibly a bad intake gasket?

 

+1 on timing cover gasket. I had the same problem, and couldnt find it, until I replaced the timing cover gasket!