2003 FX4 4.0 heads

[bostonshouse]

I am new to the forum and new to Rangers. My 14 year old recently purchased his first car which he will be rebuilding for the next year and a half. It is a 2003 FX4 Level II with the manual transfer case. The previous owner had started a "pre-runner" build which apparently starts with a few cans of black primer over what was a halfway descent factory paint job. The truck is ugly but it ran pretty good. It had a broken and poorly repaired thermostat housing and a bad temp sensor which we replaced. We also did a quick tune up with coil, wires and plugs. It runs well now but has a bit of a lumpy idle and stutters when acceleration from idle but runs really great once over 2k rpm. Yesterday it started leaking water from the exhaust pipe and smoking. It was a ton of water. I will run a test but I am assuming we have a blown head gasket and/or a cracked head. Is that a safe assumption. There is nothing to do with the thermostat housing that would dump water would it? Anyway if it is the heads my plan is to buy new complete heads, studs and gaskets. Here are my questions.

1- I have searched the web and have come across contradicting information on if the heads can be replaced on the 4.0 SOHC with the motor still in the car. Does anyone have any input there?

2- I have been working on cars and motorcycles my whole life but mostly easy classic stuff. Last time I replaced heads it was about an hour of work on a 66 Ford Mustang 302. how big is the effort of changing heads on this beast?

3- Any gotchas or anything else I should do while I am in there?

Thanks in advance for your help.

 

[thcscubajohn]

If your head is cracked then it is safe to assume that the engine was abused. If it was abused to the point of top end failure then it would also be safe to assume that the bottom end is not far behind. If you're going to spend a year and a half on it you might as well pull the engine and do a complete rebuild. It'd be a good learning experience for your kid and he'd be getting a reliable truck. Of course, you can just change the heads and see how long the block lasts if you want.

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[thcscubajohn]

As far as diagnostics see if your oil and coolant are mixed and if coolant is coming out of the exhaust then you definitely have a head problem

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[bostonshouse]

Thanks for your response. I may do a full rebuild but before I commit, I would like to get the heads off and take a look. It runs pretty nice so I am hoping it is a head gasket issue. Can those heads be replaced without removing the motor?

 

[thcscubajohn]

I am not sure I've a 94 so I don't know about clearances on a 2000

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[thcscubajohn]

*2003

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[adsm08]

The driver's side head can be replaced with the engine in the vehicle. The passenger side is a bit more problematic, but technically not impossible. The issue is that if you tear it down that far you def want to do the timing sets. That does require puling the engine.

You will also need the special tool set to set the cam timing when you are done, and both cams need timed any time one of them is disturbed.


I would not rule out the possibility of it being just a head failure. Up to around 2002 the SOHC heads were prone to cracking if overheated. If you had a failed t-stat housing you could have overheated bad enough.