Last March I flushed cooling system, great until yesterday I noticed my coolant was about 1/2 gallon (2 quarts) low. Filled it up this morning, actually overfilled it, drove a bit, came home and saw coolant leaking at bottom of water pump area. But - strange thing is the coolant level is still full, and I don't see leak anymore. Water pump was replaced about 7 years ago, but strange that I don't see leak anymore. Any ideas?

 

Well, Mac, if I were you.... Wait! I am you! Aw, just go ahead and replace the thing!

 

If it was leaking I would replace it. Are you certain that it was coming from the weep hole in the water pump?

 

Thanks, Dak! Don't like talking to meself. I'm not certain, but it was coming from water pump area. I drove it about 20 miles yesterday on interstate, checked this morning, and still full and no sign of leaking! Being overfilled wouldn't cause it to leak at water pump area would it? It'd go into the overflow tank I think. I'll try to crawl under tomorrow to check better.

 

Could be the bypass hose on the top of it, I had that issue with my 93 3.9

 

Ah, keil, I think you might have nailed it! Is that the small, about 3/4" hose right on top of pump?

 

It's larger than that. It goes right underneath the alternator/ac bracket. It is only a few inches long and often is neglected.

You can't overfill the cooling system, it is meant to be completely full all the time. As the coolant heats and cools it expands and contracts and the rad cap will allow excess into the overflow or suck coolant back in to the cooling system.

 

That area is sort of a mess for possible coolant leaks. You've got your thermostat housing, Temp sensor, and a mess of hoses. Best way to figure out whats leaking is to do a pressure test but thats not always possible in a DIY kinda thing.

Clean up the area the coolant is if its really bad and then warm the truck up and start squeezing hoses. You should be able to find your leak that way.

 

Thanks a lot guys! I'll check tomorrow if weather holds. Tornado near me today!

 

The other place it can be leaking is at the corners of the plenum (intake manifold) where there are water passages that go thru the manifold gaskets. After 228,xxx miles, the intake gaskets and front and rear plenum seals were pretty well fubar.

My V8 had some pretty bad coolant and oil leaks, I replaced everything--gaskets, thermostat & housing, water pump, all the hoses, and used RTV to seal the water pump bolts. No more leaks--but then there shouldn't be.

If you go through the top end of the engine, be sure to replace all the hose clamps--the one on the bypass hose (the short hose that runs from the top of the water pump to the front of the plenum) had failed and that turned out to be a major source for the coolant leak.

If you do pull off the plenum, replace the o-ring on the distributor, too. Have a look at the oil pressure sender, as well.

I ordered all my gaskets and o-ring from RockAuto. By a wide margin the best deals. I fabricated my own 1/4" aluminum plate valley pan (using the gasket as a template.) But bought my hoses & water pump from the local stores of the major autoparts chains--they were competitive on hoses.