Ok, a little over-dramatic title, but none the less I was pretty shocked upon seeing this...

So I removed my water pump and found this inside of it.. Yes the rust is expected, however the weird jelly? Is this common, or at least on an old sitting pump like this. There was more of this in the water pump cavity on the engine of course, so I scraped and wiped it out, I'm going to shine a flashlight down the cooling passage and see if there's more down there.

On a side note now I want to flush out the coolant passages on the block again, any special ways of doing this or should I just run a hose to it and flush with water?

That looks to be some type of cooling system sealer.

Looks like couscous, porridge or mashed potatoes...what does it taste like?

Old jellied coolant. I would be sure to flush!! Don't forget the Heater Core and get a new Thermostat.

Minced garlic?

BTW, don't you just love surprises when pulling water pumps! Here's one of mine:

I flushed (many times) with water with the thermostat houshing and water inlet off (those were also replaced).

YUM! That's DEFINTELY chess pie! What it's doing in your water pump is an interesting question indeed.

Seriously, could that be some "stop leak" treatment?

My dad and I figured it was some type of "pour in fix" for the water pump or cooling system.. It's texture is that of petroleum jelly and it is scentless.. Anyhow a longggg flush is indeed to come. The thrmo and housing don't look bad or have any signs of this gunk on them but I already have a new thrmostat.

When I got the car the heater core was bi-passed and I have yet to get to it, however I'm thinking it might turn out to be another "pleasant surprise"

I like the missing fin Leon, it almost looks like something you would find washed up at a beach..

It's silica, someone was running strait tap water through a leaking cooling system for a while. If you are on "city water" as apposed to "well water" or use alot of water softeners you will find the same stuff in the bottom of your home water heater. It is water soluable and will flush easily.

I had green gel goo in the cooling system of my 1971 when I first bought it. I picked as many of the goo balls out as I could and I flushed the rad with a garden hose but I seriously doubt if I got anywhere close to it all out. On the bright side, I have had no trouble at all with cooling. In fact, even after a hard 30 minute track session in the Texas summer heat the temperature gauge was reading somewhere close to the middle. My 1971 is a track car so I don't have a heater system hooked up. If I did I would take more care to get the system as clean as possible before filling it with coolant. Just my $0.02

I like the missing fin Leon, it almost looks like something you would find washed up at a beach..

Poor neglected cooling systems, wonder what'll pop up next!

One remedy for a leaking rad was to crack an egg in there. Doesn't look like boiled egg though:)