The Stovebolt Site Forums The Shop Area Engine Shop leaky seal between h2o pump and block

are there any common leaks that occur when replacing the gasket between block and H2O pump? I have a 54' Chevy 1/2 ton 261, I took the belt off to replace it and when I did I noticed a small leak coming from underneath the pump, maybe from one of the bolts underneath?, really hard to tell. So anyway, I replaced the gasket ensuring all surfaces were clean, put a hair thin coating of silicone on both sides so it would stay in place put it all back together and the son of a $@#!%& is seeping ever so slightly, maybe a drip every 20 secs or so from underneath still!!!!!!!, does it take a little while for the gasket to swell? Need help!!!and is there a special kind of silicone for engine use? :mad:

Is this a new water pump? If not it probably needs to be replaced, there is a weep hole on the bottom of the pump under the bearing, when it starts leaking it drips from the bottom . just replace the pump, if you clean the gasket surface good and clean, no need for sealer. However a little rtv never hurt anything.

You should NOT be using the clear silicone - go to any auto parts store and get the stuff made for high temperatures. They have "form a gasket" and "gasket sealer" - you want the latter (smaller tube).

Did you put sealant on the H20 pump bolt threads? Since they go right into the water jacket, you need to think about leaks there too. I put a dab of red form-a-gasket on there, and no leaks yet.

(But I must qualify that - I haven't actually filled the engine with water yet... )

-Boyo

I had a similar problem with a new water pump. As per the suggestions of a few stovebolters on this site, I added some Bar's stop leak, it took care of the problem.

Well it was the darn weep holes, a new water pump is on the way! thanks for the tip on the gasket sealer, that water pump was the original over 40 years old. thanks for the help!

The preferred stop leak is the copper seal or aluma seal. Comes in a tube as a dry powder, and won't plug up your heater or radiator. Avoid the bottles of liquid with pellets, I had to replace a radiator in a Nissan after using the Prestone stuff.

Once again, Dr. Fred T is right.

The Aluma-Seal is GREAT. I put some in a radiator I bought from Ebay a few months ago. Radiator was NOS, but had a dent that apparently broke some of the cores and there were leaks EVERYWEHRE. Garage was full of anti-freeze in 2 hrs!

One bottle of Aluma-seal later, the leaks are history. Driven several hundred miles since. No sign of leaks whatsoever.

-ftyler

Do the water pump mounting bolts go into water jackets on a 235/261? My 1954 shop manual and 1954 "Technical News" and technical service bulletins do not suggest sealing the water pump bolts on either a 235 or a 261. I am now putting together a '54 235 engine and while I never sealed the water pump bolts in the past, I would be pleased (and perhaps prudent) to do so now.

Thanks, Tim

No problem , they are blind holes.