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Discussion Starter · #1 ·
Okay first, this is an 85 CJ7 with the standard 258 engine. Only mod to the engine is the Mopar MPI kit. So a few months ago while I was on the freeway I started to hear what sounded like a ticking noise coming from the engine. After later inspection I could feel an exhaust leak coming from the manifold. The leak seemed to be coming from the number four exhaust exit on the manifold, right where the manifold meets the engine, next to the lower bold that holds it on. By number four I am counting from the fan end of the engine going back. I can feel the exhaust pulse from this spot. I thought this would be a simple fix, just install a new gasket. So, I take everything apart and discover there is no gasket there!! After inspecting the manifold there are no cracks or any other problems. Cool, inexpensive repair. Install new gasket and reassemble. Start her up and…..same noise and leak!! Now I’m just a tad bit annoyed. Okay, I think about it for a while and decide, okay, maybe the manifold is warped. I now purchase a new exhaust manifold and install it this last weekend. Everything has been reassembled, all bolts torqued down and all hoses reconnected. Start her up and….same damn thing!!! I take it apart and inspect it. There is nothing preventing a good seal at all. I look at the gasket and can clearly see on both sides the impression of the manifold and the impression of the engine. The gasket is sealing fine. I notice that down by the hole in the gasket where the bolt goes through there is black soot build up. There is no soot around where the gasket meets the manifold for the actual exhaust port. Again I can clearly see there is a good seal here. The leak seems to be coming out of the bolt hole for the manifold mounting bolt. Does this make sense? Is this even possible? All I can think is that there is a crack inside the head that is allowing exhaust to go through that bolt hole. Has this ever happened to anyone elseIf this is the case, what are my options to repair this? Can it be repaired?
 

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Remove the manifold and have it faced at a machine shop. It's likely warped and not sealing well when you installed it.
 

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Discussion Starter · #3 ·
Leve, it's a new manifold. The leak really seems to be coming out of where the bolt goes.
 

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Make sure that the bold head surface on the manifold is flat and smooth. Cut a flat washer out of a copper sheet. It should be fairly thick - 1/16" would good. Put it back together with a new bolt. That should take care of it.
 

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If you've had it on, and heated the engine up, then it's no longer new. It could have been warped since you first installed it. I'd bet the face needs to be milled. That should take care of the problem. Run the thoughts by your machinist.
 

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hmmmmmm.....try installing it but leave the suspect bolt out?.....just thinkin out loud but,if u fire it up at nite and it is leaking out that bolt hole, i would think you would see some flame in it?

course i may just be talkin out my a$$ /ubbthreads/images/graemlins/censor.gif ....again /ubbthreads/images/graemlins/grin.gif
 

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I would try Jim's Idea first. Since it will be pretty easy, and you won't have to take anything apart again. If it works, run it.. If it doesn't work you may have to pull the manafold off. Bring it somewhere to be checked, mill if needed. If it is good, the posibility is there that the Head is warped. You can have that milled if it isn't too bad. Also taking it off, you may be able to determin if it is cracked or not.

You did not mention if in all of your install, take apart, install take apart... If you were using a new gasket each time. Make sure you use a new gasket each time. Also spend a few extra $ and get a high quality one. When you install it and you have all the bolts torqued down.. run the motor, get it hot, let it cool, and re-torque. Good luck. I hope Jim's trick works for you.
 

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This may not be a good idea, and some one say if it's not, but why not take some Ultra copper or other good silicone, put a dab on the threads of the bolt for the suspect hole, install everything let it set. fire it up and see if you still have a leak. if not, either leave it and don't forget to clean the hole each time you EVER have the manifold off. too much old silicone in a blind hole will keep a bolt from fully seating.

just thinking out loud though.
 

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It's possible the bolt really isn't seating now due to carbon at the bottom of the hole.
What you think is tight may not be.

Try it without a lockwasher, see if the bolt's head goes all the way down to the surface.
Try it with a slightly longer bolt to make sure it can seat, then use the right one.
Run a tap down the hole if it's not seating. Sometimes a few whacks on a small screwdriver in the hole is needed to shatter the carbon deep in the hole. Blow out the dust.

Have a close look at the bolt itself - has someone replaced it? Do the original bolts have a shoulder just under the head to seal it? May be as simple as using the right bolt.

I'd do the above, if it's seating fine but still leaking - with the right bolt - then I'd use the copper gasket stuff on the threads down deep, and a brass or copper washer under the bolt head. Silicone won't last and will burn, making it difficult to remove later.


But is it really coming out the bolt hole?
Get it in the shade - preferably in a fairly dark area, or even at night.
Have a friend squirt oil down the carb while he revs it up - you want to make smoke.

Then while it's smoking use a strong flashlight and mirror - if needed - to find where the smoke's coming out that area. Hold the light crosswise to the smoke. The strong light will reflect off the smoke, then you simply look for the source.

If you can hear it leaking - ticking, even listening through a heater hose like a stethascope may find the source.
 

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Discussion Starter · #10 ·
Okay, so I tried retorqueing everything down to spec and in the order specified. No luck, still leaks. I tried doing as Jim suggested and made an addtional "gasket" out of copper for the center portion of the manifold. This didn't work either. Lastly, I used a longer bolt for this hole and then somthing bad happened. When I started her up, a small amount of coolant began to leak out of the hole. Now I'm certain that the head is cracked within the hole somewhere. However, once I removed the bolt and replaced it with the original the leak stopped. I'm thinking the longer bolt force the crack open more. I've been driving it for a couple days now and it runs fine, other than the exhaust leak making it sound like a volkswagen. So......what to do.....I bought this CJ back in 1995. It had a remanufactured engine put in it about 30K miles before I bought it. I myself have put between 140,000 and 160,000 miles on it since then. The way I look at it, I got 10 years and well over 100K miles out of this engine. Not too bad. Now, here are my options as I see them right now. My last resort with this head is to try to fill the hole up with JB Weld and see if that will stop the leak. If possible I will try to redrill through this and use a smaller bolt to clamp the maniold in that spot. I don't see that I have much to loose at this point. Anyone see problems with trying this?

Option 2: I can get a rebuilt head for around 200-300. Or maybe even find a 4.0 head in a junkyard. Not sure I want to do this for an engine with this many miles on it, plus it needs a new oil pump and rear main seal.

Option 3: I found one company that will sell a remanufactured engine, freight included both ways for $1400.

Let me know what you all think. Thanks.
 
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Riff...have you done a compression test?
Is the engine running hot?
Are you loosing coolant?
What happens if you leave the bolt out completly as Jim suggested?

I don't think your MPI will work on a 4.0 head

If you really need a 4.2 head, I have one with about 15K miles on it...
 

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If you need a head i have one that i picked up from DDawg16 about a year ago collecting dust in my garage. I live a few hours south of you - San Marcos(So Cal) to be precise. Let me know if you are interested. I think i paid about $60 for it. Let me know if you are interested or in the area.
 

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[ QUOTE ]
Jim suggested and made an addtional "gasket" out of copper for the center portion of the manifold.

[/ QUOTE ]

That's not what I meant. My suggestion was to make a thick copper WASHER for under the head of the bolt. I think that still might work.

But a new head for $60 sounds like your best bet. The JB weld idea doesn't have much chance of working - not worth the effort IMO.
 

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Discussion Starter · #14 ·
Re: HELP!! Weird exhaust manifold leak!

Jim, the "gasket" I made included that. I basically overlaped it across the bolt hole and made a hole smaller than the diameter of the bolt to make sure of a seal. Why would the JB not work? too hot for it to hold?

Ddawg, how much would you want for that head? I haven't done a compression test on it and it is not running hot. Keeps the same temp as usual. The MPI should work on a 4.0 head since the kit was essential the same system off of a 94 wrangler engine.

Gik, do you know how many miles are on the head you have?
 

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Re: HELP!! Weird exhaust manifold leak!

JB is too soft to hold the bolt with any significant amount of torque applied. Heat will also be a problem. JB Weld has its applications, but that's not one of them.
 
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Re: HELP!! Weird exhaust manifold leak!

Riff, I think the one I sold to Glen has less miles on it and it is cleaner (minus the garage dust).....take your pick....Glen, did I really sell that to you for $60? Boy, we did have a lot of beers that day....

Both heads have new valves and valve guides. Valve springs are different...Ford 302 HP springs...it gives you the inner dampner spring just in case the main one breaks.

But first, I would suggest making sure your head is in fact cracked....

Glen....I still have your chain.....and no, the jeep is not done yet....only just sent the tub out to have the firewall painted. Been too busy making babies...yea, Suzy is pregnant again....
 
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