4.0 Cracked Head??

Never heard of it.

Are you sure the new head is definitely cracked this time, or could it be just a bad head gasket? Just a thought. A bad head gasket would be more likely to allow the loss of coolant from the water jacket into the combustion chamber(s) or outside the engine more likely than a cracked head would. At least it's where I would start looking first after inspecting all other cooling system components. Just my $.02 .

Regards,

GK

If your first one failed from overheating you may also have warped the block, causing gasket failure on your second one,which is losing the coolant and may have cracked/warped the cylinder head. (I'm assuming you know that the best way to crack a cylinder head is to pour cold water into the hot engine when you notice that the coolant is low, but I thought I'd mention it just for completeness :-)).

Dave Milne, Scotland

wot he said. Is there any steam coming out of the exhaust ? As another thought, have you ruled out the water pump leaking ? That would be my first port of call.

Dave Milne, Scotland

Thanks Guys,

I will look into these things. Just to answer your questions, I have seen no external leaks, all looks clean.

From the last time, it has never overheated.

THanks for all ur input. Hopefully it turns out to be something minor.

Any mayo in the oil, John ?

Dave Milne, Scotland

My local mechanic told me that this is a common problem in the Jeep 4.0. That he has seen it and repaired it many times.

After having the head replaced, and obviousely the head gasket, it had been fine, coolant level stayed normal.

There are no signs of coolant in the oil, or leaking externally. The other odd thing is, it does not blow excessive smoke. On a pressure test, the cooling system will hold pressure just fine.

According to my Mechanic, the crack in the head causes the coolant to leak into the cylinder after the vehicle is turned off. Basically i lose about an Overflows worth of coolant over a month or so.

I love my jeep, but i am getting fed up. in 2 1/2 years and 40,000 miles, i should not be going on my third head.

I'll just chime in with the others and agree that cracked heads are definitely not common on the 4.0L engine. I've actually not even heard of that happening myself though that's certainly not to say it can't or doesn't happen.

Jerry

Ditto... I'd be a little wary of a mechanic that calls a cracked head (or even a blown head gasket) on the 4.0L a 'common problem'. Can't recall it ever being discussed on this newsgroup, and certainly none of my 10+ friends/aquaintances here locally with 4.0L TJ's (or even

4.0L YJ's) have ever experienced it.

Dave

I'll just chime in with the others and agree that cracked heads are

Is there a chance the deck of the block is not true? If the block is warped it might be causing it to happen. I have 2 4.0L jeeps...and neither head has cracked (knock on wood).

Sean

Thanks all for the input.

I'll post once i see what's up with it.

message

Ditto what Jerry said. I've been reading this group (though i rarely post) and driving Jeeps with 4.0s since 1998. Cracked heads appear to be very, very rare.

Your mechanic may have been just shooting the breeze.

Regards,

DAve

Jerry Bransford wrote:

Or attempting to make excuses for poor repairs on the first head replacement. Had a Datsun dealer try the same thing on me. First head gasket on a Datsun 2000 started loosing coolant at less than 20K miles. Head mechanic claimed that "this engine is a racing derived engine and is always prone to head gasket problems when driven hard". Datsun racing shop a few miles further away claimed "head mechanic at dealer has his head firmly inserted in a dark and smelly place" and reused the existing head with the mere additional step of simply making sure it [and the engine] were flat and followed the correct torqueing sequence.