If this has been addressed in the forum, please forgive me, I've searched and though my key words only include coolant, valve, cover... all the results come back with cracked heads, head gaskets, and engine rebuild threads.
My problem, I'm replacing the valve cover on my daughters 1991 Cherokee Sport 4.0L and as I am cleaning the surface of the head I noticed the rear bolt hole on the left side was green. Upon further inspection, it was slowly spewing coolant, running out and down the back side of the engine, slowly but continuously. I screwed in one of the bolts by hand to plug it while I try to figure this out.
Another thing, upon reading through a bunch of the posts I see that there is a dreaded 0331 head in the 2000 and 2001 model year. I noticed that this engine has an 0331 head, did the 1991 engine use that model head? The block serial number (I05MXI6) indicates manufacture date of May 16, 1991, correct? Am I looking at a later model replacement head? I don't see any cracks anywhere I'm just leaking coolant from that one bolt hole. The coolant is as clean as brand new, always has been since she bought it last year. Only about 4k miles on it since she bought it.

Any recommendations about how to remedy this coolant issue. I was thinking nylon tape on the threads of the bolt, maybe some RTV in the hole as I put the bolt in or maybe coat the bolt with RTV after I put the nylon tape on it? Have any of you experienced this before?
Thanks!

As I was inserting this image I just now noticed that it appears that this bolt hole may have been fitted with a helacoil (sp?). Something doesn't look right in that picture. Hmmmm What the heck have I opened up here!!!???

I took a closer look at the suspect - leaky bolt hole on the head and also took a picture of one of the other holes for comparison. I think that this leaky hole has been tampered with in the past. I added a few more photos below.

No taper, looks as if someone used a chisel on this one. You can see where the top thread wraps around at about the 10:00 position and abruptly stops. Above threads the head material is straight up, not tapered... I believe the taper is required to guide the bolts into the thread to avoid cross threading.


Reference hole, tapered around top and appears to be machined, nice and neat leading down to threads.

 

Thinking I05MXI6 might be an '01 made on May 16th.
Would explain the 0331 head.

https://www.autozone.com/repairguide...00c1528008a7c2

 

Thanks Ralph77 but the link you gave me is provides reference to Wrangler codes, i have a Cherokee. Nevertheless, I hear what you are saying. From what I have read on the codes, the first digit provides a number for the year, a 1 means 1991. I don't know what the first digit is for the 2001 jeep Cherokee, I wish I knew. I had a hard time finding out how to decipher the serial number and what it means. You make a good point though. I am also changing the oil filter adapter O-Rings and the adapter I took off the engine does not match any of the ones I saw in the videos I watched on YouTube, nor could I find the proper O-Ring sizes when searching auto part stores stating that I was looking for 1991 engine, nor anywhere online searching 1991 engine. I finally found a video with what appeared to be a similar setup but not exactly the same with O-Ring kit part number listed in the comments. It's for a 1998 so I ended up buying that one and am waiting for it to come in now. All indications are pointing to this being a 2001 engine. Hmmmm, still need to address coolant in my bolt hole.

 

I saw that but betting it still applies.
Just out of curiosity I wonder what exhaust manifold you have on that.

 

Wonder if someone had previously broke a bolt off and tried to drill it out and went too deep into a water jacket then installed a heli-coil or insert (looks more like insert to me) and used a punch to pin it in place? Had you noticed coolant leaking prior? If was holding coolant before and not loosing any I would just use some good high temp thread sealant or Teflon tape and see how it goes. By the way hows you oil pressure looking?

 

That hole has been Heli-coiled. It was probably drilled out after being broken off and the guy drilled it too far breaking into the water jacket. It's not an 0331 head unless it has the coil mounting bolt holes near the spark plug holes or "0331" case into the metal on the manifold side like my picture. Look near the top of the pic. This pic is to show what the markings of the "TUPY" head that replaces the 0331 head are. You can apply a really good sealer to the bolt and hope it seals it under pressure, but the be

st way is to remove the heli-coil (a real PITA!) and install a solid insert with a blind bolt hole in it and seal that. They do make threaded inserts specifically for that purpose, but you'd probably need somebody with machinists skills to do it.

About you oil filter adapter. If it has a T-65 torx socket in it, it's a later one, but if it has anything different in the way to use a tool on it to remove it, it's an early one. You should go to cruiser54.com for more information about your jeep.

 

Ralph77, are you yanking my chain? The exhaust manifold is impossible to see, if there was any identifying markers on the exhaust manifold, the intake completely covers it and the axle/suspension completely blocks it from underneath. From what I can see, poking my flashlight through the holes, nooks, and crannies... the exhaust might be upgraded... they are pipes, not cast iron.
The identification marker on the intake is
33007067
AS II596 with the Chrysler symbol stamped right after this number.

 

Was not leaking coolant before, has always held well, never overheated over the summer months either.
Oil pressure is good.

 

Yeah, I'm thinking the gasket sealed it.

 

Thanks for the reply, I suspected an insert or heli-coil.
My head most definately is stamped with the "0331" identifier on the top and the coil is bolted to the side right behind the AC pump.

 

You can see them enough.

 

Okay, you've got a bastard. You've probably got a 2000 or 2001 engine in it with a distributor instead of the coil rail, right? The exhaust passages in the head are smaller than the early head and it may have an exhaust manifold adapter on it so the header will seal. There's a definite mismatch on the exhaust ports on the bottom where they fit together that requires an adapter to make the seal. It's possible somebody just put an 0331 head on it, but I doubt it.

 

Dave1123,
You right about nailed the head question... what are your thoughts on this oil filter adapter. This is a bastard alright. I think we're about to officially go off topic so I'll ask this last question because the leaky valve cover bolt hole has been solved. My Frankenstein engine is only beginning and it's making it very hard to buy parts. Before I reassemble my valve cover I need to return my 1991 valve cover gasket and buy a 2001 valve cover gasket? I thought it was weird how the gasket didn't fit right, I have a Fel-Pro cork gasket and it's not right, almost but just not right. I've used Fel-Pro valve cover gaskets before, they make better quality than this. Now I know why. How about the valve cover... the one I have is cast aluminum. Didn't they use stamped metal in the later model 2000-2001? The 1991 pictures I've seen on the internet have cast aluminum. I'm so confused.
Here are some pics of the head... you can see the exhaust headers w/ adapter plate and the head stamp 0331. The distributor. And the coil which is actually bolted to the engine block not the head. And then there is the oil filter adapter... where did this come from... pre 1987?




Side note, when installed the oil filter is oriented facing up (12:00 position). Every other adapter I have seen has the filter facing towards the rear (9:00 position).

 

I believe it's from a Wrangler. Early model at that. And yes, the 2000 has a stamped steel valve cover. I use a Victor-Reinz steel and neoprene sandwich gasket that doesn't need sealer. The problem is I bought 3 from Rockauto on a manufacturer close-out and haven't seen them since.

If you have an industrial hydraulics supplier near you, take the bango bolt and o-rings to them and you can get the 3 rings for around 50 cents for all 3.

 

If you think you want to, you should replace that 0331 head. It's a time bomb waiting to happen. They have a habit of cracking. You can get a factory "TUPY" head or a "Clearwater" head. Actually any 4.0 head will fit that block if you pull the locator dowel pins out of the block or use a head with the holes for them.