Help - Engine Overheating

It sounds like you have it narrowed-down pretty well. I guess the circ pump is about all that is left to check. One time I had a circ pump break a blade off of the metal impeller and the blade was blocking the water passage from the pump into the block.

Of course, on the down side, it could be a blown head gasket or a cracked head (or block). A compression check might help diagnose this.

If you do a compression test on all cylinders, the one with the crack or blown gasket will have lower compression. You would not necessarily have water in the oil.

Chester:

180 degrees is nothing to worry about. 180 is where my '77 runs most of the time. I really do not like it to go below 180 as the engine is less efficient and tighter (tighter means excellerated wear) the colder it runs. Do not get me wrong, excessive heat is worse, but 180 degrees is fine.

The steam you are seeing could be just the result of atmospheric conditions. If the water is cold and/or the air is cool, then steam is normal. One way to elimnate this variable is to run the engine out of water (i.e with Fake-a-lake or similiar) and see if it still steams. Pick a warm day to eliminate cold air causing steam.

When you said blew the impeler, did the blades break off? Mine did it this year,it became hard and brittle and each blade broke off(from not changing it in 8 years). Some were in the pump housing.(I wish I counted them) I took all the hoses off between both pumps looking for the rest. I found three stuck in the exhaust manifolds. And I took the pump off the engine to check behind the pump. There are two holes about the size of a quarter where water goes in the block through the timing chain cover. The circ pump on the enginge can rust with age, I changed mine about 10 years ago because it was leaking, and I could'nt believe it was pushing water because the fins were almost worn away. Also I've heard of the inside breaking loose from the shaft and not spinning, causing the raw pump to fill the engine.

I'm with David 180 degrees is far from hot.
mine is FWC and runs 170 - 180. 155 on the hose.
I would suggest that 170 is the ideal temp and 15 degrees either side is OK.

first make sure you are running at 180 degrees and do not have a incorrect gauge, try one of the noncontact thermometer from sears to make sure the engine is running that hot. Any hotter and you start to melt exhaust hoses. Also when does it run at 180 at idle, high speed, midrange?

Verify that your guages are giving you a good reading by measureing the actual temp of the water. Over time corrosion builds up and that creates resistance. Higher reisistance is what moves that needle to the right. Many people just accept that the guage is reading 10 to 15 degrees high. Turn the ign key to run, disconnect the wire from the temp sending unit, you should get full needle deflection. Then ground it to the block and the needle should fully deflect the opposite direction. Also ensure that someone didn't put teflon tape around the temp sending unit thread to "help seal" the fit. The threads are the ground point on the unit and the teflon often prevents from getting a good ground. The sending units don't fail as often but sometimes they do. You can hunt down the resistance readings for various temps if you really enjoy the journey of trouble shooting.

If you are sure the wires and guage are good, then go the top of this page and click on DIM logo. Go the the FAQ and there is a trouble shooting guide for over heating. You say you verified water flowing at the Raw water pump...., but how much flow? Check out the page. Great info.

With the T stat out the actual engine temp shouldn't get over 110ish. I have also heard from several quality PCM mechanics that 160 to 180 is a good temp as long as it stabilizes.

Sorry for the long post.

You should be able to leave your hand on the exhaust manifolds all day long. It will be warm but not to the extent that you have to remove your hand. If you have to remove your hand after 10-15 seconds then it is too hot. And at 180 degrees you will not be able to leave your hand on them.