Ford 8N Cracked Block

Please take the time to read before replying Apparently my 8n has a cracked block. I replaced the head gasket where I didn't see any sign of a leak. I put in a new thermo stat and even removed it. I know about the level on these (whatever # that is). It just starts heating up and up and up. My question is where is the most common place for these to crack. It has to be somewhere that builds pressure.

have you done:

compression test?

leakdown test?

cooling system pressurize test?

have you had the pan off with cooling system pressurized.. looking up for drips of green?

So it is overheating? I haven't heard of that as a symptom of a cracked block. Water in the oil? Oil in the water? Are there bubbles in the coolant? You said no sign of a leak - I assume you mean down the outside of the block.

If it is heating I would be more tempted to say you have plugged coolant passages in the engine or you need to have your radiator boiled out.

Sure, they crack, but it isn't so easy to accomplish.

Wifes uncle had a tractor salvage in the 1960's and 1970's He would buy all those for $200.00 or $300.00 and put something called water glass in the radiator (I think, I never seen him do it) run them for a while let them cool down, the stuff set up and the thing would run for years. I've seen it on the shelf at the local parts houses.

Cooling system is clean. Without having to do any testing it is obvious that it is building pressure. I don't see any exterior leaks. I had the head leveled that took 8 thousands and checked for cracks so it shouldn't be overheating.

water glass......AKA......sodium silicate. Hadda little bottle in my chemistry set from Christmas. .......chemical Dell

a cooling system pressure test is not for seeing if there is pressure building inthe cooling system.

you not into testing? no problem.

good luck with the issue.

I DID NOT SAY I wouldn't do testing I just am open for suggestions. I just thought someone had run into a problem like this and had an idea!!

(quoted from post at 19:54:30 06/20/13) I DID NOT SAY I wouldn't do testing I just am open for suggestions. I just thought someone had run into a problem like this and had an idea!!

Click to expand...

have & the radiator was fine, BUT the block was so full of rust that water could hardly, if at all, get between the cylinders!

What temperature does it get to when it's heating up and up and up?
Do you have a temp gauge installed?
You could also use an infrared thermometer to check.
I missed what it is that tells you it's overheating or building pressure.
Cleaning out the block with some vinegar is pretty cheap and easy.
If that would help the trouble you are seeing.
I would second the oil in the water/water in the oil question.
Are either of those present?

LMJ ,Is the coolant circulating through the radiator with the engine running,thermostat removed cap removed and looking in the radiator? Check it out.the impeller could be loose or not turning with the shaft. Or there were a few rebuilt water pumps that had the wrong impeller on them.

Water glass = sodium silicate = stuff that has been used to preserve EGGS for long-term storage so they don't dry out. (WIKI says for up 5 months!) YUM!
Water WIKI glass

These engines run cool with the 160 degree stock thermostat. Actually run better using a 180 degree thermostat.

The large surface area of the pan with the rough sand cast finish and the reinforcing ribs also working as cooling fins really help dissapate the heat. The sand cast finish has more surface area for heat transfer than a smooth sheet metal pan.

The friction modifiers in modern engine oil also reduces the heat from friction compared to the non additive mineral oil used in the 40's.

Classic cracked block will show signs of milky colored oil where the coolant has been forced into the oil. This condition can be checked easily with the dip stick. The pressure in the coolant chamber is greater than than the oil pasages after the engine is stopped. This when the contamination occurs.

A leaky head gasket will show signs of air bubbles in the top surface of the radiator
as evidenced when the cap is removed.
A leaky cylinder cover gasket will make the engine run hot because the air bubbles decrease the thermal film coefficient between the coolant and the radiator tube surface, resulting in a decrease in the heat transfer rate. The higher combustion gas pressure travels to the lower coolant chamber pressure through a passage way between the combustion chamber and coolant hole.

Normally, the block cracks between the top cylinder cover bolt hole and the exhaust valve seat because this is the region of maximum thermal gradient and resulting maximum thermal stress. The coolant then travels into the engine oil pan.

If the engine has over heated and conventional mineral engine oil is used the oil needs to changed because the lubrication properties of the oil has been greatly reduced from elevated temperature. Synthetic motor oil does not have this problem.

Bob,
When I was in the Navy - over in Sardinia - we would get replenished by another ship about every 3 months. I remember getting cases and cases of refigerated eggs - maybe 40 dozen to a case - in waxed/sealed cardboard boxes. We ate them every day and they were fine right up till we got new ones. Who knows how long it took to get them to us from the time they were layed.
As for the sodium silicate; wasn't that the stuff they poured into the oil to wreck them beyond repair during the Cash for Clunkers program?
wrecking engines

yep.. that was the stuff!