03 4.6 cracked block | Ford Explorer Forums - Serious Explorations

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03 4.6 cracked block


Well-Known Member
June 6, 2018
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City, State
Year, Model & Trim Level
2003 Explorer Limited 4x
I have a 2003 4.6 with coolant in the oil and was surprised by the head gasket sealing pattern. The combustion chamber sealing area on the right side block face is shiny where the seal ring should be except there is a crack between Cyl 1 and 2. It does not appear to be transferring coolant or oil so it does not worry me too much.

The left head gasket is the odd one, it appears to have been torqued improperly as the block surface is shiny until you get in between the cylinders then it is dark. There are cleaner spots but still looks like the gasket was pinched in between all cylinders. There are also microcracks in between the cylinders on the gasket itself and between 6and 7 almost connected to each other.

Long story short, any thoughts on the crack and block sealing surface pattern? (Last pic is right head crack, others are the left head sealing surfaces)




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Personally, the crack doesn't bother me as much as warp. I'm not sure what had to happen to get the crack ( serious overheating?), but I suspect that the deck is warped. Clean it an put a straight edge to it. Pretty hard to get a head gasket to hold on a warped block.

You would probably be better off talking to a machine shop as they can give a better idea if that motor should go into the recycle bin (my gut says toss it).

@kydirtscooter Most important thing to me is to know whether the combustion chamber flange on the gaskets extends far enough out over the sleeves to ensure adequate loading on it. If loading is inadequate, combustion pressure will force gases under the flange and through the crack. When that becomes sufficiently high, coolant temp. will go higher, and radiator pressure will go up. I'd worry about the crack if sealing is not done on the sleeves. Important that the cylinder openings on the gaskets are nearly as large as the cylinder bores. It would help to see the new gasket construction.

Happens that I worked for Victor Gasket Co., Div. of Dana Corp. for many years working with and studying head gasket sealing. imp

From the limited view I have the aluminum casting between the cylinders does not appear to be cracked to the water jacket. Looking at the sealing ring and opening of the new head gasket, it appears as though the crush is partially on the sleeve and partially off. I will get a better look tomorrow and post a pic for people to see if for nothing else just to see. Looking for a complete drop in right now, just not comfortable with possibility of not fixing coolant in oil.

Just a final update with pictures of the head gasket sealing area on the deck. I have also included valve train pictures of my abused 4.6 and then a better maintained 4.6 both with the same mileage. I have put 400 mi on new to me engine, runs great!

A few more notes. The original engine had bearings with 9/2002 build stamped into them. These coincided with the vehicle build date with the final build being at the Missouri plant not Kentucky Truck. It looks like there were quite a few coolant in oil failures from cracked blocks in the 4.6 Explorers between gen3 release 2002 MY and early 2003 MY. I found reference to a fair number of people replacing head gaskets, and or having heads redone and new gaskets to still having coolant in oil post attempted repair. I did not find much beyond early 03 MY cracked blocks. My heads and block were within spec on out of flatness spec.

I do know mine was overheated a few times, not sure on severity of it. When I pulled the front cover, the oil and coolant mix were almost up to the top of the pan lip. My fill tube was full of snot and drivers valve cover was absolutely coated with snot. Both valve trains were filled with a large McDonalds cup of sludge. The cam towers were wiped, although oddly enough the other bearings were in OK shape, not enough slop for knocking or oil pressure loss. Oil pump looked fine. I drove over 100 miles home and it ran great go figure.

If you do have similar issues or find coolant in oil for a 02 or early 03 chances are high the block is cracked. I was able to pressure test and after an initial drop it would hold steady a few psi lower and only hot. Cold would hold fine.

If you end up getting a complete engine from a yard or you pull it, keep in mind a few things as the completes are NOT identical between 02/03 and 04/05!
  1. 02 and 03 MY use a throttle cable and cruise control cable. This means your throttle body is different than a fly by wire system I.e. 04 and 05. My engine is from a 04 MY and my old throttle body worked, intake is the same pattern
  2. 02 and 03 egr feed tube, vacuum module and pressure sensors are separate subsystems. The passenger solenoids and vacuum tubes are routed to the front bracket on the pass side. The differential pressure sensor is on the cowl and attaches to two small pipes on the egr feed tube from the manifold. Additionally, the egr valve uses a single vacuum line for the actuator which mounts to the throttle body. Both systems are very different but if you keep your old system components they will fit.
  3. 04 and 05 4.6 drivers heads have a different power steering mounting setup. Very slightly but a no go if you have a 02 and 03 style pump. The two subsets of years have the same pump but the casting on the 02 and 03 do not have a hole for the back pump mount and it HAS to. This is because the front boss on the head does not exist on the 04 and 05 so your pump will only be held on by 2 bolt when it NEEDS 3. Two ways to fix, drill your casting or buy an 04-05 pump. AutoZone catalog is incorrect, they list the 02-05 pumps as one in the same. This is NOT TRUE!
Hope this helps, and good luck!