The cylinder head on a Jeep 4.0 is all one piece, so there is no #2 cylinder head - it is just "the cylinder head" for all the pistons.


Does he mean that the block is cracked or the cylinder head is cracked? If it is the latter, it is much much easier to fix and would also explain the coolant leaking into the cyl, but it wouldn't really explain the low cylinder pressure

Honestly, get the motor running properly then deal with the cooling system. Really there are only a few pieces to that (water pump, hoses, radiator itself, and fans)

 

Not sure but your probably right.

 

The cylinder head on a Jeep 4.0 is all one piece, so there is no #2 cylinder head - it is just "the cylinder head" for all the pistons.

Does he mean that the block is cracked or the cylinder head is cracked? If it is the latter, it is much much easier to fix and would also explain the coolant leaking into the cyl, but it wouldn't really explain the low cylinder pressure

Honestly, get the motor running properly then deal with the cooling system. Really there are only a few pieces to that (water pump, hoses, radiator itself, and fans)

If it is a cracked (block or head) as we suspect your oil should have water in it and it should look like chocolate milk. If that is the case it's done. Needs a full rebuild.

 

That's what's got me concerned. So if it was one of us do you take the Jasper offer and go from there?

 

At this point I don't think you're going to get a better offer. If you can afford it I would take it in your shoes. Good luck.

 

Ok, thanks guys. I appreciate all the help. I'm going to talk to my mechanic today and find out EXACTLY what is wrong. I'll specifically ask for clarification on whether is has a cracked head or block.

 

The main concern is whether the bearings in the motor have been damaged or the life of them shortened. Basically coolant in the oil could have robbed the bearings of proper lubrication. Short of a total rebuild could be a taking a chance. Run the oil in the coolant concern by your mechanic and see what his thoughts are. We can only surmise he's hands on.

Besides the engine issue what's your vehicle like body and mechanically wise?

 

I spoke with my mechanic and he told me that the original issue was the exhaust valve which had a leak because of cylinder 2.
The current issue is a cracked head which is a defective part. It was on there for literally less than 30 miles. He said there is no coolant in the oil. The coolant was being blown out the exhaust.

I really appreciate all your help!

 

Ok, if he is sure that the block is in good shape and it is just the head that is bad (the head also holds the intake and exhaust valves), then you should be OK to slap a new head on there. If he is confident that it is only the head, I would go that route. Rough googling says a Jasper 4.0 new will be close to $3200

30 miles is not enough to toast any rings or bearings unless you were like towing uphill or something (IMO). A new head is going to be much cheaper and easier to swap in than an entire engine subjectively.

Jasper is a pretty well regarded company. They do research on why engines fail and make engineering changes to help mitigate those weakpoints. I would be surprised if they kept an 0331 head knowing the casting deficiency. The proof is that they are willing to give you 40% off a new motor without really having much info on what happened, thats really good service IMO. Every other company on the planet would have probably told you "tough cookies" and made you pay retail.

As far as "which head is best",

Clearwater cylinder heads has a pretty good reputation for 4.0 Jeep heads because they use a new and improved casting design which is thicker where the 4.0 head is prone to cracking (specifically the 0331 casting). I would STILL prefer to have a head built by a reputible local machine shop because Clearwater Cylinder Heads does not have the most stellar reviews in regards to customer service, but the Jeep forums have generally good things to say about them. They rebuild pretty much all cylinder heads and in general the Jeep 4.0 head is really simple in design. You would want to check what casting you currently have and call them for a quote for a NEW head (ideally not rebuilt).

https://www.cylinder-heads.com/

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A valve issue that's now a cracked head 30 miles later. Coolant being blown out the exhaust without getting in the oil.

I'm sorry but none of the above adds up. It just doesn't and I don't think your getting an honest report.

Get a second opinion.

 

I followed your advice and did get a second opinion. I'm still dealing with everything to get my Jeep running properly. The second mechanic took a look and said that the original job to replace the cylinder head and gaskets was done incorrectly. He said there is a missing bolt in the head which connects the intake and exhaust manifold (which is also installed incorrectly). There is also intermittent lifter noise as well as a broken ear off the intake... He says the break is very clean and that the mechanic who did the head job had to have broken it off. Finally, there is a crack in the exhaust manifold. FML
The fun part is now trying to get reimbursement/error fix from the original mechanic.

 

Can't say I'm surprised. Give it a try but I doubt you'll get anywhere with him. Hard lesson.

 

This could be related but I discovered something about these recently because I have mine tore down. Over time they acquire raised humps on the block deck and once these are there, and if they are not removed, all the new head gaskets in the world are not going to seal it up correctly.

 

Good to know. I'll let my new mechanic know and ask him to look it over.