Need opinions from the engine guru's.
 

We got a tractor in at work that overheating, the tractor is a Ford 871 with a 172 gas engine. It takes about 30 minutes for it to get the temp gauge into the red, it was the same on both the new and old gauge. Here's a list of what's been done so far.

New rad - old one was pretty beat up and had a small leak
New water pump
New thermostat
Switched from 3 blade to 4 blade fan
Set timing
Head was checked by machine shop for cracks and new head gasket
Air cleaner check for restrictions even though I pointed out a plugged air cleaner would make it rich

The tractor runs great other than the temp issue and we're starting to run out of ideas, I don't think it's a carb issue because the plugs look good and if anything it's a little rich. The engine was rebuilt a few years back by another shop in ohio. We also popped the freeze plugs out of the block and from what we can see it's pretty clean but I'm leaning toward something in the water jackets blocking the flow. Ideas or opinions welcome.

Edit - another theory I threw out was plugged exhaust but I'd have a hard time believing the engine could ever run as good as it does with a plugged muffler.

Does the engine have a vacuum advance????? Is it working right????

Try backing the timing a degree or 2. I had a small block Chevy we had to do that to when we pulled heavy trailers.

There is an additive that claims to drop coolent temp up to 20 degrees. I never tried that stuff......not sure if it will help.

I would try running the tractor without the muffler and air cleaner.....only way to eliminate that possibility.

Let us know what you find.

The engine has weights in the distributor that control the advance, there in good shape and move freely.

did you test the old/new thermostat?

Not sure if they tested the old one but I pulled the new one back out and tested it and it's good.

Not a guru but here's a few things.

Do you see coolant flowing in radiator when t stat opens?

Pressure test radiator cap?

Running lean will cause over heating after a while but I would imagine manifold would be getting red

Do you have a temp gun to measure inlet and outlet temps of radiator to compare to gauge?

Dumb I know but correct rotation water pump and also, fan installed correct way?

Merk is right about timing too. Weights might seem to work but let's get some specs and numbers at certain rpms

Check the lower hose to see if obstructed,or collapsing under running conditions.
a lot of manufactures put a spring inside to prevent collapse.
Ford makes a pusher fan as well as conventional fan, pulling air through the radiator,-- is it installed correctly?
( I've seen that mistake)
check that the water pump is actually circulating the coolant.
( can you see into the radiator to affirm flow?)
Is the system air logged someway??

Some engines are best started and then coolant added so as the pump puts it
into all passages.
Just some ideas to possibly to help.:bigthink:

The fan is on correctly and we can see the water circulating in the rad.

Is it boiling?
put a thermometer in the rad to see if it is indeed too hot.
Have you garden hose flushed the block passages when you had the freeze plugs out? ----and the head?
Is there a noticeable drop in coolant temp comparing the bottom hose to the top hose??

No, it's not boiling over.

No, they didnt flush the block.

I will check for a temp difference between the hoses tomorrow.