Manifold gasket failure?

[eaglescout526]

Eagle has developed an issue to where cyl 5 is not firing at idle and while cold. But seems to fire when warm and under higher RPMS.

258ci or 4.2L for anyone about to ask. 
 

89MJ and I have been going back and forth on this since I discovered the issue a couple nights ago. We are now to the point where we think its the manifold gasket that has failed at cylinder 5, I found the bolts at 5E, 5I and 6I loose(I=intake E=Exhaust). Made somewhat of a difference but not noticeable enough to be pleased with such. I can tell its been serviced as it has one of those full modern gaskets like what you would find for a 4.0 vs the original gasket that seals the intake only.

 

Can the gasket get worn out to the point where it will no longer seal correctly at a single cylinder? Trying to confirm a theory. 

 

Otherwise, from what I can tell, 5 has compression and spark. My compression tester set doesnt fit the head and so I cant confirm how good the compression is. Though it would tell me the condition of everything that makes that cylinder run. But I have had nothing but issues with that full gasket style even on my 4cyls. 

 

For your viewing pleasure, here’s what the spark plug looked like on 5 prior to cleaning:

 

I think it looks like this because of the valve cover leaking oil and seeping down the manifold gasket and the intake sucking the oil in and basically creating this mess.

 

[eaglescout526]

Bump because I made this post last night.

[derf]

Could be a head gasket.  That's a lot of carbon buildup.

 

I'm doing the intake and exhaust on the 258 in my CJ.  I did the Fel-Pro gasket set.  The main gasket goes on first, then loosely bolt up the exhaust only bolts. The two top center and the two at either end.  Put the second part of the gasket in place and be sure it goes on the alignment dowels.  Then the intake.  Maybe start the lower bolts first.  Then the upper bolts.  Torque to spec (23 ft-lbs for the CJ) in a circular pattern inside out.

 

I left out the second (intake only) gasket and had a gap.  The other gasket looks to have sealed it up pretty good.

[AZJeff]

When it comes to manifold gaskets, the OEM style are very finicky and marginal to get a good seal, especially with age.

 

Someone on one of the Jeep forums turned me on to the special gaskets made by Remflex.  They are the bomb.

 

 

[hgeranium]

1 hour ago, AZJeff said:

Someone on one of the Jeep forums turned me on to the special gaskets made by Remflex.  They are the bomb.

Agree. I think Eagle_SX4 was the one to tell me the same thing. Really not that much more expensive than the OEM style too.

[eaglescout526]

12 hours ago, derf said:

Could be a head gasket

I’m hoping not. Doing the valve cover alone on the Eagle was bad. 
 

2 hours ago, AZJeff said:

When it comes to manifold gaskets, the OEM style are very finicky and marginal to get a good seal, especially with age.

Unfortunately the gasket has been serviced before and is using the single piece 4.0 gasket which the 258 is not supposed to use. There’s been a lot of questionable service done to the engine such as having platinum spark plugs and the valve cover having a cork gasket sandwich. 

[eaglescout526]

16 hours ago, derf said:

Could be a head gasket.  That's a lot of carbon buildup.

 

I'm doing the intake and exhaust on the 258 in my CJ.  I did the Fel-Pro gasket set.  The main gasket goes on first, then loosely bolt up the exhaust only bolts. The two top center and the two at either end.  Put the second part of the gasket in place and be sure it goes on the alignment dowels.  Then the intake.  Maybe start the lower bolts first.  Then the upper bolts.  Torque to spec (23 ft-lbs for the CJ) in a circular pattern inside out.

 

I left out the second (intake only) gasket and had a gap.  The other gasket looks to have sealed it up pretty good.

 

 

You jinxed me, it is the headgasket. Found some moisture on the dipstick and a little bit of a milk shake. But not too bad, I think its been caught on time.

[derf]

1 hour ago, eaglescout526 said:

 

 

You jinxed me, it is the headgasket. Found some moisture on the dipstick and a little bit of a milk shake. But not too bad, I think its been caught on time.

Sorry about that.  Those heads are heavy and not easy to get to.  They're bad enough in a CJ.  An Eagle won't be fun.  I end up using an engine hoist to get them in and out.

 

Glad you found it though.

[eaglescout526]

11 minutes ago, derf said:

Sorry about that.  Those heads are heavy and not easy to get to.  They're bad enough in a CJ.  An Eagle won't be fun.  I end up using an engine hoist to get them in and out.

 

Glad you found it though.

All good, just one of those coincidences hah. I shouldve anticipated this given its got 140k and probably sat for a few years, similar situation was had on my MJ when I revived her. Hell for all I know, when I put the evaporust in the block, thats probably when it started to fail.

 

I am not looking forward to it, but I am looking forward to seeing a possible AMC headgasket. This car still has the original AMC plug wires.