philipswanson

I have discovered what I believe to be the biggest weakness in the 4.0. My cylinder head machinist explained it to me and it's not a cracked heads or block.
The scenerio goes like this, a problem in the cooling system causes the engine to overheat. The block is cast iron and the head is aluminum. They have different expansion rates which causes the head gasket to compress more than normal when in a hotter state. The engine cools off and leaves a gap between the head and block. Water rushes down the cylinders and causes catastrophic failure. Water gets in the oil in large quantities and its all over. Moral of the story, keep the cooling system in tip top shape or kiss your engine good-bye. This is what happened to mine according to my machinist who has done hundreds of these. I am looking for a better head gasket to minimize this effect. I think thicker is better to take up some of the expansion and cool down. That's the main problem with these engines IMHO. I am convinced that's what caused mine to fail because everything else inside the motor looks good because I got it quickly after the water intruded.

Phil Swanson

07 Stang

Interesting. What's the warning signs before damaging the engine?

philipswanson

Getting it hot and then water in the oil as explained above.

Phil Swanson

ucinn

Seems like a very good reason to get the metal thermostat housing and replacing that plastic one even if it hasn't broken yet.

jwog666

all i can say is no kidding, overheating an engine causes damage, doesnt matter if it has aluminum heads or not. water will not "rush" into the cylinders. however if the head becomes warped from overheating it will start to consume coolant due to a leaking head gasket. this concern is non unique to 4.0l engines. simple solution is, make sure you dont drive the engine without coolant, the temp gauge is your friend

philipswanson

It DOES matter if it has aluminum heads! Especially when combined with a dissimilar block material such as cast iron with different expansion rates. That's the whole point! Some engines are much more prone to this than others. According to my machinist, the 4.0 SOHC Ford is one of the worst with this problem. He would know, all he does is heads and he does a bunch. He tells me that many 4.0s SOHC Fords as of late are coming in with this issue. Mine was not a thermostat housing issue but a cracked plastic radiator seam.

Phil Swanson

jwog666

if you overheat a sbc with cast heads, you can take out a head gasket as well, the point is, if you are overheating ANY engine you are already doing damage, the aluminum head cast iron block combination has been around for many years, and works very well, as long as some idiot doesnt keep driving it while overheating and cook the engine.

artsvettes73

This is not a unique problem of the 4.0 There are countless numbers of engines built this way. Across all the manufactures. Overheat anyone of them, you will get the same results

ucinn

My Chevy celebrity did the same thing when it cooked. Warped head, blown gasket, water in the oil...it was a pos though anyway.

philipswanson

Yes, any engine can be damaged by high heat but they have different weak points. Yes the cast iron block and aluminum head combination has been around a long time but they don't all have this problem of compressing the head gasket. Again, the Ford SOHC 4.0 is especially prone to head gasket compression. Apparently, more so than many other engines of similar materials used in their construction. I know the 3.8 and the 4.6 seldom have head gasket compression.

I am just passing along information from our head machinist who again has done hundreds of these and thousands of other heads and knows more about head problems than any of us. You can sluff it off or take it seriously and learn something. Your choice.