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Discussion Starter · #1 ·
2001 TJ, 4.0 liter, 3 speed auto, 145k miles

I have been losing coolant but never had any milkshake or other signs of coolant in oil. Have been using either Mobil 1 5W30 or Mobil Super 5W30 (both high mileage) changed every 5k miles by me.

I changed the oil three weeks ago and sent a sample to Blackstone (first test on this vehicle). Also started doing more research and learned about the 0331 head, etc.

Today, this oil analysis came back and I just confirmed a few small bubbles between the 3 and 4 valves. Also had very small amount of milkshake on the bottom of the filler cap - first time.

My question is whether to put $ into a new head (probably have a local shop do it) or start shopping for a reman complete motor. TJ is a long-term keeper.

TIA,
Tom
 

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If it was me, I'd put a rebuilt block & head since you plan on keeping it.
 

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With only 145,000 I'd put a head on it.

By the way, 145,000 was a lot of miles on a car in the 60's but by todays standards, it hasn't made mid life. I pulled mine at 318,000, and if it were mine, I'd quit using 5w30 and use a little heavier with some ZDDP in it, I used Rotela 15w40
 

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That's a lot of iron. I'd be concerned about the rings and cam as well. I'd do as AZ01TJ suggested.
 

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DIY junkyard head or professionally rebuilt engine. Don't skimp on the replacement engine. Scare up another car to drive for a while and a place to work and make it a project.

Or if luck plays your way buy a wrecked Jeep and do the engine swap.

Engine science has come a long way and a built 4.0 with some porting and timing and profiling, enhanced squish, could be a real nice improvement.

A built Nissan Pathfinder VQ engine could be wicked.

GM Atlas inline 6 could also be awesome.
 

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Discussion Starter · #6 ·
First step will be head replacement - less $ investment and I can do it in my garage.

Reman 0331 ($350) or new heavier casting from Clearwater ($550)?

While the top is open, it there any value in replacing lifters and pushrods? What about rocker arms? I don't want to invest if there is serious block damage but don't want to pass up cheap insurance either.

I'll also replace the radiator and water pump (and finally get to the RMS). Should be a fun few weeks in the garage!

Tom
 

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I've yet to see a Blackstone oil analysis of Mobil-1 from the 4.0 that didn't show excessive iron. That's one reason I have never been a fan of Mobil-1.
 

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My local JY gets about $50 for a head. You can practice on their stuff before you trash yours trying to get it apart. If it looks bad under the valve cover move over to the next one. When you get it back from the machine shop it looks like new. Wrecked cars usually have running engines.

Read about breaking-in lifters. The wear surface on the cam can be damaged.
 

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You can take your other engine parts in with the head and the machine shop will clean them in the dip tank.

If fasteners break off they can extract them or fix the holes.
 

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You are certain it is a bad head and not just a blown head gasket? Did you do a Compression Test of the cylinders to determine a bad head?
 

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I've yet to see a Blackstone oil analysis of Mobil-1 from the 4.0 that didn't show excessive iron. That's one reason I have never been a fan of Mobil-1.
Agreed.
 

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What are your oil pressure readings? My quess probably low. Probably will need new bearings. Hopefully you got to it before bearing de-graded
 

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Were it ME (and obviously it's not), I'd ask a professional and do some math. I plan to keep my Jeep 30 years. What option will get me there?

My .02
 

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Best place to spend my $& groupie.
 
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