2.5L head bolt

[gogmorgo]

So I didn't think I would get to this right away, but I can't stand not knowing. I'm looking at changing the head gasket in a '91 2.5L. Total milkshake in the oil after ten minutes driving at most. 

Yeah, that bad. 

Considering I have zero knowledge of the engine's history, I'm kinda anticipating finding worse than just a bad head gasket, but I've got to start somewhere. I've got a gasket set on the way, but none of my usual parts sources have listings for a bolt set, and given the lack of history and known problems, I'm not excited about reusing them. One of the parts guys we use at work has a set coming for a "2.5L '96 Wrangler", whatever that is, which seems to be the way to go per some brief research, 2.5L TJ. I haven't really been able to find too much though. Some people are also saying to just take the 4.0 bolt set and not use all of them, but there were length differences between them and the TJ set, according to my parts guy at least. 

Anyone been here before?

[mnkyboy]

Up till about 86 they used 7/16" head bolts, after that the 2.5l got 1/2" head bolts.

 

Any 1/2" bolt set for an, MJ,XJ,YJ,TJ, or 96 up Dakota will work, i believe on 96 and up 2.5ls the number of bolts with studs on them increased, but otherwise they should be the same.

[Jeep Driver]

The direct answer to your question-

 

84-85 engines had 7/16 bolts, every year thereafter had 1/2" bolts. Just order a 1/2" set and you'll be fine. 

You could take out a bolt or two and compare against a 4.0 set, can't answer that question, however, a 2.5 set will be cheaper. 

 

 

I want to present something here, if you don't like what I type, just let it be. This isn't just for you but for anyone who may read it. 

 

When I bought my truck it was presented to me as having a rebuilt engine with 5000 miles on it. I have no reason to doubt what the seller sold me, engine looked fresh and ran great. Ran cool during the test drive, oil pressure was between 40 and 60lbs. 

 

I put a little over 105K miles on the engine, probably 110 to 115K total. 

 

After three years I began to battle overheating and a loss of power, numerous reasons for the lack of power but a loss of compression was a given. One sign or tell of what I suspected was that I could clean the engine and within three to four days the passenger side of the block at the head, opposite the lifter galley, would weep oil. No matter, it would weep and remain wet. The other tell was a tremendous amount of blow-by. 

I never had any coolant in the oil, however, I did lose about 1 qt of coolant per month with no explanation for it. 

 

This block and head has long been sold, I took these pics not to document the cause of my problem but to sell these. The real tell was the head gasket itself. 

Loss of compression between cylinders 2 and 3. I suspect some coolant loss also. 

 

The pics still tell the story-

If the builder had decked/planed/resurfaced the block and head this problem would have never existed. 

 

 

 

 

Do I think you can swap your head gasket and get away with it? sure, lots of people do, I've done it. 

That said, there is a reason why you are where you are. 

 

If you buy the ARP bolts, torque in sequence as normal but to 110lbs, torque once and forget about it. 

 

 

 

 

 

 

[Jeep Driver]

4 minutes ago, mnkyboy said:

Up till about 86 they used 7/16" head bolts, after that the 2.5l got 1/2" head bolts.

 

Any 1/2" bolt set for an, MJ,XJ,YJ,TJ, or 96 up Dakota will work, i believe on 96 and up 2.5ls the number of bolts with studs on them increased, but otherwise they should be the same.

FWIW, I replaced my with a '98, same number of bolts, all blocks and heads are interchangeable. 

[87Warrior]

I used these last year when I had my head rebuilt. '86 2.5L.

https://www.amazon.com/gp/aw/d/B000C2AHC2

Had a few extra, but no real downside. I also used a 4.0 manifold stud and bolt set in the head that worked great.

[mnkyboy]

54 minutes ago, Jeep Driver said:

FWIW, I replaced my with a '98, same number of bolts, all blocks and heads are interchangeable. 

I know they are the same, the newer ones just have more bolts with studs to mount things to.

 

IIRC, the earlier engines have two bolts with studs on top and the later ones have 5 or so with them.

[gogmorgo]

Thanks guys. I'm guessing the front driver's side becomes a stud as well? It seems kinda funny to me that it's a bolt while the others on that side are studs. I've also read about that one needing sealant because it goes through a coolant passage?

 

I'm definitely onboard with getting the head surfaced, I'm just not sure if there's a machine shop within 200 miles that will do that for me, but I should know tomorrow. One of the guys I work with has a pretty good handle on that sort of thing (journeyman heavy duty mechanic) so I'll be picking his brain tomorrow for sure. 

 

Thats fresh oil and distilled water. It ran for maybe 15 minutes since the last change. The oil I dumped out of it didn't seem to have much if any coolant in it... but then neither did the cooling system. 

[Jeep Driver]

28 minutes ago, mnkyboy said:

I know they are the same, the newer ones just have more bolts with studs to mount things to.

 

IIRC, the earlier engines have two bolts with studs on top and the later ones have 5 or so with them.

.Sorry, now I understand. 

[Jeep Driver]

The one bolt, the wet bolt, book calls for 80lbs IIRC, I went 90lbs. 

[87Warrior]

I followed my 03 TJ FSM for torque values, 4.0 section as Jeep was using the 2.4 in 03. You will need the proper sealant for the front, driver side head bolt.

You should get the head resurfaced and pressure checked, and the valves measured and lapped. My machinist found two exhaust valves that needed replaced with about 190k miles on the engine.

[mjeff87]

12 hours ago, 87Warrior said:

I used these last year when I had my head rebuilt. '86 2.5L.

https://www.amazon.com/gp/aw/d/B000C2AHC2

Had a few extra, but no real downside. I also used a 4.0 manifold stud and bolt set in the head that worked great.

And you'll notice that they are not hex head, they are 12 point.  You'll need a deep well socket for them (and for the studs I had to drill/ream out the center of the socket so it fit over the shank) when I changed the head gasket on my TJ (2.5L).

 

Jeff

[gogmorgo]

Well this may have just become moot.

[mjeff87]

Well, that sucks.

 

I've got a perfectly good 2.5 sitting in storage that you can have for free, but you're a bit far away.  It's near Pittsburgh, PA.....

 

 

[gogmorgo]

What's the chance of getting it to Chicago area for late October?

Not that I'd be hugely excited about hauling it all the way from there to Los Angeles then 30 hours back up the left coast, but it's an option I'll consider if I can't figure something out before then. But I'm sure I will. 

I'm curious which would've happened first though, the hole in the gasket, or the hole in the piston right next to it? I've buttoned it all back up for now just so I don't loose anything. 

[mjeff87]

I don't have any way to get it anywhere other than where it is now (it's 6+ hours away from me now).......sorry.

[gogmorgo]

Yeah no worries, I totally understand. 

So far not much is showing up even semi-locally. I posted up in a couple groups but the responses mostly have been people making fun of me for wanting to stick with the 2.5. Haven't seen anything on kijiji/Craigslist, or car-part.com either. I'm sure something will surface soon enough. 

[yxmj]

Look on Kijiji Manitoba.....there is an ad for a pre and post 97....$250 for both......would that be of interest to you?

[gogmorgo]

It would be if they weren't 2000km away!

Its pretty crazy to me because there was always a couple in MB. But in AB? Diddley. And there's what, five times the population here?

[yxmj]

Sorry...I thought you were just over the border in Saskabush

[gogmorgo]

Yeah I guess that's sorta my fault... I'm on my third province since joining the club. 

[Eagle]

A friend and cross-town neighbor just blew a piston in his 2.5L Wrangler. He bought a set of new Sealed Power pistons and rings, dropped the pan, and just replaced all the pistons. He didn't even hone the cylinders, just used a ridge reamer to clean away the carbon ridge at the top. You could do the same job, but in your case I think a light hone in the cylinders after cutting the ridge might be in order. Not trying to remove material, just to clean up the bores and leave a very fire tooth pattern to help the new rings seal.

[gogmorgo]

Yeah, that'll likely be the way to go, I just don't really have a good place to do that just now. Pulling the head really made me aware of how much $#!& falls out of trees, dust blowing down the street, etc. Not sure I really want that if I'm pulling the engine so far apart. 

[Eagle]

My friend did his outside in the driveway. Let's face it -- you're not building a NASCAR Grand National. Clean is good, but it doesn't have to be operating room sterile to run. I did one many years ago in my brother's hay field.

[gogmorgo]

So I managed to locate a 2.5L, but it's out of a '90 YJ. I'm not really seeing much info on whether or not block and more importantly head differ between the Renix and HO. I did however encounter references to the engine being detuned in the Wrangler as opposed to the XJ/MJ version... (why?)

Looking at RockAuto, there is only one long block available for the '90 YJ. The same part number is listed under the '91 MJ, but there are also a couple others. This tells me that there is a difference, even if things are interchangeable as previously stated?

[Jeep Driver]

28 minutes ago, gogmorgo said:

So I managed to locate a 2.5L, but it's out of a '90 YJ. I'm not really seeing much info on whether or not block and more importantly head differ between the Renix and HO. I did however encounter references to the engine being detuned in the Wrangler as opposed to the XJ/MJ version... (why?)

Looking at RockAuto, there is only one long block available for the '90 YJ. The same part number is listed under the '91 MJ, but there are also a couple others. This tells me that there is a difference, even if things are interchangeable as previously stated?

They're all exactly the same