Cracked Head Symptoms

[Broosedamoose]

Other than overheating, what are symptoms of a cracked head? (2007 4.0L) My engine overheated quite a bit after blowing a head gasket and now I'm wondering if I cracked a head. The truck just has a rough idle and stalls out almost every time I go from drive to reverse. It's not over heating and there are no codes. I'm just trying to figure out why it idles so rough after replacing the head gaskets! It's driving me nuts!

 

[Broosedamoose]

Anyone?

 

[RonD]

There is no way to tell the difference

A blown head gasket or crack in the cylinder part of the head would have the same symptoms, cylinder pressure exiting into the cooling system, causing coolant to be displaced by air(exhaust) and engine over heating because of coolant loss

Cracked heads on the 4.0l SOHC engine is not at all common, on the 4.0l OHV it was, but totally different head castings
The OHV had a thin spot between valve seats, if head metal was over expanded(over heated) then they would crack there

Its possible for any head to crack, 4.0l SOHC does have aluminum heads, which expand more when over heated, which crushes head gaskets faster
But the cracking of the head is just not as common as on the 4.0l OHV cast iron heads

You can do the glove test to see if you still have a cylinder to cooling system leak, and ID which cylinder it is
But if your engine is still blowing coolant out into the over flow tank after startup then you still have a cylinder leak

 

[rubydist]

The probably more likely thing is that the head(s) were warped from the overheating, and the new head gasket is also leaking because it was not squished properly all over.

 

[Uncle Gump]

The symptoms you have don't say head gasket/cracked head.

I would start by double checking your work... plug wires... vacuum leaks... electrical connections. Have you put a scan tool on it and looked at any engine data?

 

[RonD]

Double check coil pack spark plug wires, then check them again, follow each wire to its cylinder

[3 4]
[2 6]
[1 5]

These are the "matched pairs" on the coil pack, the 5 6 4 side often gets mixed up

 

[Broosedamoose]

Okay, so we can say it's definitely not a cracked head. How about the added compression although I know it's minuscule? The heads were milled 30 thousandths. I've checked and rechecked the wires and they are correct. I have no vacuum leaks. Compression is 160-165 in all six cylinders. Fuel pressure is 63 psi. All I can come up with at this point is maybe something went wrong when installing the new head gaskets and one is leaking. But I have no overheating or extra coolant in the reservoir! It's looking like I'm going to have to just live with the issue because there is nothing else to check! Any other ideas?

 

[Dirtman]

Is the idle "rough" because its low? And does the truck run smooth besides the idle and stalling when going into reverse? Aka it runs smooth while driving?

 

[Broosedamoose]

Is the idle "rough" because its low? And does the truck run smooth besides the idle and stalling when going into reverse? Aka it runs smooth while driving?

It idle right at 700-750 in Park, 650-700 in Drive. Other than the rough idle and stalling she runs fine. Still pulls good getting on the highway and runs smooth on the back roads.

 

[RonD]

Idle should go UP "in gear", reads like computer is not kicking up RPMs(opening IAC Valve a bit) when you shift it in to gear
I would expect 50-100rpm increase "in gear"

Same when AC is turned on, but not doubled, AC on in Park should bump up idle same as "in gear"

not that that cures rough running

 

[gaz]

Broosedamoose,

0.030" will raise your compression ratio just about 1 full point. The lower intake manifold requires an adjustment to insure proper flow after a 0.030" mill.

With the increased compression, premium fuel will be a bonus.

My other thought about stalling is torque converter, is it an automatic; if so check your fluid level.

 

[Broosedamoose]

The lower intake manifold requires an adjustment to insure proper flow after a 0.030" mill.

I don't believe I have a lower intake manifold. I'm pretty sure it's all one piece composite that bolts directly to the heads.

I wonder if the IAC is going bad. They usually just die but maybe it's just tired. The truck has 230K miles on it. The tranny fluid is right on the mark.

 

[RonD]

Ford used a true solenoid for IAC Valve, 3rd party brands are stepper/solenoid type so don't always work well with Ford computers
Motorcraft or Hitachi brand are true solenoid type IAC Valves

Yes, IAC Valves can get "sticky" at the spot they are at most of the time, i.e. idle for that engine
Easy to clean them
How-to here: https://www.explorerforum.com/forums/threads/iac-valve-cleaning-thread-w-pics.84220/