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watchamakalit

Advice Needed my MJ is sick

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The situation:

I have been chasing oil leaks on my MJ for a while now fixing one after another.  I have found the source of the worst one.  It is the head gasket.  I have a full shop and mechanically inclined to do just about any work I need to do, head gasket included.  My situation becomes a little more difficult to resolve when I throw in the fact that I have a rolled 98 ZJ sitting in my shop with a good running 4.0HO.  I would also like to avoid as much down time with the MJ as possible due to it being my daily.  So I am seeking your advice on how I should approach the situation.  Below are the options I am down to.  What approach do you think is best?  Funding is there for a full rebuild of the motor if nessecary but would be happy with a minor refreshing job on the internals.  Keep in mind this is my daily so reliability is the goal.  Not looking to build a high octane turbo stroker motor.  Just a good solid truck I can count on to go anywhere I need. 

 

Option 1

 

Replace the head gasket in the MJ and go on down the road.  The problem I have here is the day or 2 of down time while the head is at the machine shop being checked.

 

Option 2

 

Pull the head from the ZJ, send it to the machine shop and checked.  Install it on the MJ when it returns.  Very little down time.

 

Option 3

 

Pull the entire HO motor from the ZJ, disassemble, inspect, clean and reassemble the motor and when completed, install in MJ.  Again very little down time. 

 

 

 

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2. Except where ya gonna put your temp sender? 

 

4. Just put a head gasket in. 

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2. Except where ya gonna put your temp sender? 

 

4. Just put a head gasket in. 

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2. Except where ya gonna put your temp sender? 

 

4. Just put a head gasket in. 

I would use the tstat housing off the ho

 

Are there advantages to the ho short block over the renix?

 

 

 

 

 

My build: https://r.tapatalk.com/shareLink?url=https://comancheclub.com/topic/8033-finally-found-onenow-it-has-a-new-floor/&share_tid=8033&share_fid=53169&share_type=t

 

 

 

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12 hours ago, watchamakalit said:

Replace the head gasket in the MJ and go on down the road.  The problem I have here is the day or 2 of down time while the head is at the machine shop being checked.

Skip the machine shop portion. Pull the head off (carefully, undo each head bolt a few threads at a time in a criss-cross pattern), clean the mating surface up, put on new gasket, stick the head back on, tighten bolts according to FSM, have a beer.

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Skip the machine shop portion. Pull the head off (carefully, undo each head bolt a few threads at a time in a criss-cross pattern), clean the mating surface up, put on new gasket, stick the head back on, tighten bolts according to FSM, have a beer.
What makes you so confident that I don't have a warp or crack in the head causing the leak? There is no sign of the gasket being blown out the side like I would expect from a gasket failure. Just oil seeping from head to block connection.

My build: https://r.tapatalk.com/shareLink?url=https://comancheclub.com/topic/8033-finally-found-onenow-it-has-a-new-floor/&share_tid=8033&share_fid=53169&share_type=t

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39 minutes ago, watchamakalit said:

What makes you so confident that I don't have a warp or crack in the head causing the leak?

This. 

 

Rebuild,  not 'refresh'. 

 

Look to Mellings for oil pump, cam and lifters. Cloyes for timing set. Felpro for gaskets. 

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It's very common for the gasket to leak oil there. 

Heads rarely warp unless overheated badly.

A good Felpro gasket should work just fine.

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Look at the discoloration between cylinders 2 and 3, a new head gasket would not have solved my problem. 

 

dkv31ZC.jpg

 

Also, what someone needs to do is -accurately- cost out a head gasket replacement. 

Include time. 

 

Head gasket.

Head bolts.

Coolant.

Oil and filter.

Cleaning supplies. 

VC gasket. 

Spark plugs and wires.........yes. 

Stat housing gasket and stat. 

 

 

 

 

I'll bet you are damn near $400. 


Not including any ancillaries such as studs, nuts, bolts, hose clamps......etc..........broken or need replaced. 

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Look at the discoloration between cylinders 2 and 3, a new head gasket would not have solved my problem. 

 

dkv31ZC.jpg

 

Also, what someone needs to do is -accurately- cost out a head gasket replacement. 

Include time. 

 

Head gasket.

Head bolts.

Coolant.

Oil and filter.

Cleaning supplies. 

VC gasket. 

Spark plugs and wires.........yes. 

Stat housing gasket and stat. 

 

 

 

 

I'll bet you are damn near $400. 

 

Not including any ancillaries such as studs, nuts, bolts, hose clamps......etc..........broken or need replaced. 

 

I don't think that cost estimate apply to mine. Already have a felpro reusable vc gasket. I am due for an oil change anyways. Just changed plugs wires cap and rotor.

 

So I'm out some coolant and a tstat and gasket and a head gasket and bolts. The head gasket set (includes tstat gasket) can be had for $50 ish. And bolts for the same. So $100 worth of parts and I'm there. I personally don't count my jeep wrench time towards labor. Its just what I do when I can't go fishing. Lol. Besides even a $400 repair bill is still better than a new truck.

 

My build: https://r.tapatalk.com/shareLink?url=https://comancheclub.com/topic/8033-finally-found-onenow-it-has-a-new-floor/&share_tid=8033&share_fid=53169&share_type=t

 

 

 

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53 minutes ago, watchamakalit said:

 

 

 

 

 

I don't think that cost estimate apply to mine. Already have a felpro reusable vc gasket. I am due for an oil change anyways. Just changed plugs wires cap and rotor.

 

So I'm out some coolant and a tstat and gasket and a head gasket and bolts. The head gasket set (includes tstat gasket) can be had for $50 ish. And bolts for the same. So $100 worth of parts and I'm there. I personally don't count my jeep wrench time towards labor. Its just what I do when I can't go fishing. Lol. Besides even a $400 repair bill is still better than a new truck.

 

My build: https://r.tapatalk.com/shareLink?url=https://comancheclub.com/topic/8033-finally-found-onenow-it-has-a-new-floor/&share_tid=8033&share_fid=53169&share_type=t

 

 

 

 

 

You missed the point- entirely. 

 

 

I don't care what you do or how you do it.......not trying to convince you of anything, other than- 

 

A value needs to be placed on the effort, time, parts........one repair vs another........then judge or discern which solution is best.

And which solution is actually a solution in the long term, most people are shortsighted. Save a dime today and spend a dollar tomorrow.  

 

 

I just looked it up.

 

Summit, Felpro head gasket set, 4.0 $110

ARP head bolts, $87

Oil and filter.......no BS here- $40

Coolant- $15

Cleaning supplies and misc sundries- $40

 

$292. 

What is one weekend of time worth?

 


Now, if that does not solve your problem.....? Chuck a weekend and $300 to the trash and start over again. 

 

In the real world, and I don't mind telling, I earn $200 per day, that is what my time is worth to me. 

 

So, two days and $300..........$700 project. 

 

Now, will I spend $700 and not spend at least the $250 for a valve job? No, I won't, so add that into the equation. 

 

 

 

I make general statements for the most part, I don't get personal, it may be your thread but it's not about you. 

There are many others who take what someone says as the Gold Standard of knowledge. Providing the balance. 

 

 

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Best shots I could get of the leak. Its. All the way down the pushrod galley side. I'm not opposed to just a headgasket and bolt change if that takes care of it. Is this the common oil leak you reffer to?c192e50a14f384e953d33ae4bb68528a.jpgc161b3f71621e1fb9bbde7cbd7a9ca71.jpg

My build: https://r.tapatalk.com/shareLink?url=https://comancheclub.com/topic/8033-finally-found-onenow-it-has-a-new-floor/&share_tid=8033&share_fid=53169&share_type=t

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That is a known issue on the Renix and early HO 4.0L engines. My 91 has seeped oil out of there as long as I can remember. There was an updated head gasket released in roughly 1993 that corrected the issue with silicone sealing beads in the gasket along the oil return paths. Any aftermarket head gasket should have this feature built in. Almost every Renix and early HO 4.0 I've seen seeps at least a small amount of oil from that area. Your head isn't warped, it's just a design flaw in the gasket. A new head gasket would fix it, but is it worth it to you to pull the engine apart just for this leak?

 

I want to say there is a TSB out there for this issue. In it, they recommended simply replacing the head gasket with the updated version.

 

It looks scary, but it's not a "bad head gasket" in the conventional sense, and if the leak is not severe you will not hurt anything by ignoring it. You can do a leakdown test and coolant test to confirm if it makes you feel better.

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2 hours ago, Minuit said:

That is a known issue on the Renix and early HO 4.0L engines. My 91 has seeped oil out of there as long as I can remember. There was an updated head gasket released in roughly 1993 that corrected the issue with silicone sealing beads in the gasket along the oil return paths. Any aftermarket head gasket should have this feature built in. Almost every Renix and early HO 4.0 I've seen seeps at least a small amount of oil from that area. Your head isn't warped, it's just a design flaw in the gasket. A new head gasket would fix it, but is it worth it to you to pull the engine apart just for this leak?

 

I want to say there is a TSB out there for this issue. In it, they recommended simply replacing the head gasket with the updated version.

 

It looks scary, but it's not a "bad head gasket" in the conventional sense, and if the leak is not severe you will not hurt anything by ignoring it. You can do a leakdown test and coolant test to confirm if it makes you feel better.

 

I have done a leak down test but not a coolant test.  Every thing seems to be in order with the health of the truck.  I was just always taught that anytime you pull a head you should have it checked.  I suppose the oil seepage isn't terrible but it is really bugging me just because I know its possible to now pee oil everywhere I go.  I am glad to hear that it is a common issue and not a pressing one.  But unfortunately Ill never have a leak free comanche if I don't change it and I really wanna be leak free.....

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It's not uncommon for 4.0L to seep at head gskt. HO more than Renix. Easy fix I pull lower hose to drain coolant (less mess than petcock) undo two nuts for exhaust, unhook fuel lines, loosen rockers and remove push rods (keep in order) set wire harness and ign. wires aside, move A/C compressor aside, remove head bolts starting at ends working inward, pull head intake and exhaust in place, engine hoist is nice but a friend will do (heavy). That's pretty much it. I've done this job on a lift in about three hours on the floor give yourself the better part of a day

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