Replace cylinder head or entire engine?

[Coldstrat]

I have a 1999 4.0 with 103k miles and MT. I have been fighting low oil pressure (changed sensors several times, cleaned out pipe) and loss of coolant issues (not leaking, not noticing any smoke) for months.

I know, at least, a new cylinder head is in my future. My worry is that if I do the cylinder head and the oil pressure issues remain, I only fixed part of the problem, and I should have replaced the entire engine.

Also - numerous oil changes and the oil that is drained looks fine, no indication of coolant in it. That being said, gel does build up on the inside of the oil fill cap (indication of coolant at cylinder head).

So - thoughts on if the cylinder head will fix the low oil pressure issue in addition to the loss of coolant?

Appreciate the advice and discussion.

 

[SkylinesSuck]

Your cylinder head has no direct affect on oil pressure. Replacing it will not help your oil pressure. I wouldn't suspect it needs replaced at this point, but it sounds like your head gasket at least needs it. Take the head to be checked for flatness and cracks while it's off. '99 was still the 0630 casting, right?

Use a mechanical gage to verify oil pressure. If that says it's low as well, might be time for a bottom end rebuild depending on the pressures. What are your figures now?

 

[Christian Y.]

I was in a similar situation (coolant issues top end and a little bit of knock on the bottom end). I opted for a new engine just to start fresh. I daily my TJ and didn't want to have to potentially deal with more issues in the near future.

 

[Coldstrat]

@skyline - I haven't checked the oil pressure via mechanical gage (I would need to buy the tool(s)). After 2 pressure gauges and pipe cleaner attempts, I figure the pressure is what the pressure is. I am having the somewhat classic problem of oil pressure bing good at start up and then dropping when engine is hot. My heel/toe driving has improved dramatically as I keep RPMs up (RPM up = pressure up).

For me the solution isn't as much about dollars as it is about time. I will do the work myself and figure if I can just replace the entire engine over a couple of weekends, that's a quicker solution than going through rebuilds.

 

[macleanflood]

A rebuilt engine is just under 2k from sandjengines.com.

Parts + time - I'd buy the reman and swap it in a weekend and get back to wheelin.

-Mac

 

[bromel]

Your cylinder head has no direct affect on oil pressure. Replacing it will not help your oil pressure. I wouldn't suspect it needs replaced at this point, but it sounds like your head gasket at least needs it. Take the head to be checked for flatness and cracks while it's off. '99 was still the 0630 casting, right?

Use a mechanical gage to verify oil pressure. If that says it's low as well, might be time for a bottom end rebuild depending on the pressures. What are your figures now?

Some late 99s had the 0331 head. I suspect that's what he has, unfortunately. OP, the easiest way to tell is if you have a coil rail (0331 head) or a distributor (0630 head).

 

[Coldstrat]

A rebuilt engine is just under 2k from sandjengines.com.

Parts + time - I'd buy the reman and swap it in a weekend and get back to wheelin.

-Mac

That's exactly what I'm thinking. Thanks for the link on reman engine supplier, I've started to shop around if I go down the entire engine route.

 

[Christian Y.]

I too used SandJ for my reman. It was over a month to get it built and then another week to get delivered west coast. IIRC they are WA based.