4.0 Cracked Head Replacement Thread w/ Pics!

[Sevensecondsuv]

So the last time I checked the oil it was clean, one tank of gas later and it's a milkshake Actually it had been going through coolant for a while so I knew something was up - I was just waiting until it spread to the oil. Sorry for the crappy pictures, the only working digi camera around here has a broken flash

It took me about 4-5 hours to get to this point:



This is the passenger side head. Look close and you can see a nice crack between the valves in the middle cylinder. The driver's side head is the same way.


Here's the block after I reemed the ridges out of the tops of the cylinder walls, cleaned the pistons off, and surfaced the deck. I also cleaned out the head bolt holes with a tap.



Yep! At least half of these are going to have to be replaced:

 

[Sevensecondsuv]

Now for the new parts:

Rebuilt 93TM castings. One exhaust manifold is new, the other one just needed a good cleaning, coat of manifold paint, and rethread flange bolt holes:






The gasket set (came with graphite head gaskets)


The cleaned and serviced (new filters, o-rings, and pintle caps) fuel injectors:


I also found a set of low mileage rocker arms and pushrods on ebay. The pushrods look perfect. 4 of the rockers were a little worn but I had 4 good ones left on mine so I swapped 'em out:



All that's left now is finish honing the cylinder walls a little and slap it all together. Hopefully it'll be done by tomorrow night. I'm getting sick of the slow, ginormous, gas-swilling F-150 I borrowed from my parents. I don't know how people could daily drive something that large. It's just annoying!

 

[jmg8550]

What did you clean the pistons with? You want to be careful with the metal you are allowing into the engine. And why are you honing the cylinders with the pistons still in the engine? And you are not doing yourself a favor by getting rebuilt heads of the same casting when you can pick up NEW bare castings that are thicker for $150 each. Not picking on you, but I'm am in the process of rebuilding my 4.0L engine. My heads also cracked, I just have a lot of miles on my truck and decided to go all the way. Best of luck to you, hope it turns out well.

 

[Sevensecondsuv]

I'm not worried about the metal. I'll clean and vaccuum it good then change the oil a few times once it's running.

I cleaned the pistons with a wire brush in a drill. I placed the old head gasket on the engine, brought the piston to TDC, and had at it. The headgasket prevented me from touching the deck surface with the wire brush.

I'm just honing the upper portion of the cylinders enough to blend the ridge reeming I did in with the rest of the cylinder wall.

Yes I know I could have got new castings for 150 each and then spent another 200 on valves and springs or paid a machine shop that much to regrind my old valves and set them up in the new head. These were $250 for a fully assembled pair. They are 93 TM castings, which are supposed to be less likely to crack than the 90 TM castings I had before. Besides that, they are completely within factory spec, pressure tested, and carry the same warranty as the new castings. The stock heads are good for well over 200,000 miles if you maintain the cooling system (the previous owner of mine didn't do that which I why I'm currently replacing the heads) which is longer than the bottom end will last. If I was pulling the whole motor and rebuilding it I may have gone for the new heads, but as it is, I just didn't see the point of spending an extra 200-300 bucks.

 

[jmg8550]

Reasonable explanation.

 

[MikeWild]

I ran into a similar issue with the heads on a parts exploder I bought. I could have gotten some after market heads out of China for $250 a side, not to mention the costs involved with machining and replacing pistons and cam. I figured if I went that route I'd have a really decent next to new engine, but it would have cost like 2 G's. Instead I went and picked up another 4.ol from a wrecker for $400, pulled the valve covers and replaced 8 of the rockers and push rods.

 

[Sevensecondsuv]

Well I got 'er all back together. Fired up the first try like it was never taken apart. It runs like a raped ape now! Seriously, I can't remember a time when it's run this smooth and powerful. I took it for a 25 mile drive tonight and checked the oil and coolant when I got home. Both still look perfect! Looks like I solved the problem!

 

[MikeWild]

right on. Must be a nice feeling after putting in all that work to have a really decent engine again!

 

[Xploda]

Tom Morana has heads for the 4.0 and its ported and polished. he said when I called they flow 4 times better than stock or so. I think the flow rate he said was somthin like 500cfm or somthin I might be wrong that looks funny lol. I Just know it sounds worth it, just too bad for them fully set up with everything is like 1700$ time to sell my other explorer and buy these pups lol

 

[JoeCanada]

How many miles were on it when your heads went?

 

[Lifted2x]

Tom Morana has heads for the 4.0 and its ported and polished. he said when I called they flow 4 times better than stock or so. I think the flow rate he said was somthin like 500cfm or somthin I might be wrong that looks funny lol. I Just know it sounds worth it, just too bad for them fully set up with everything is like 1700$ time to sell my other explorer and buy these pups lol

I think that money would be better spent on a 5.0

 

[Sevensecondsuv]

How many miles were on it when your heads went?

Well, it's got 165,000 right now but I've had an indication of cracked heads for a while (loss of coolant). I replaced the heads right after it developed crankcase milkshake.

The 4.0 heads usually only fail once they've been overheated. When I got the truck at 75,000 miles the cooling system was half full of sludge from the PO never doing any maintenance on it. I'm sure that had something to do w/ it.

 

[JoeCanada]

Sounds like the exact same story as mine. Similar mileage, similar poor maintenance history from P.O. and similar indications leading up to failure.

I figure had mine been properly taken care of in it's past life, this probably wouldn't have happened.