Changing Head Gasket - Few Questions

Okay kids, I'm going to be starting in on my head gasket this weekend and had a few general questions for you...

1. What size/pitch are the head bolts. I plan on replacing them becuase I know the valve cover's been off before my ownership and can't guarentee that the head wasn't removed before.

2. What the hell is "Perfect Seal," the sealant called out in the FSM for the head gasket (sealant on the head gasket?!)

3. Size/pitch of the manifold studs, I'm missing a few

4. Suggestions for tests while I'm doing this. I have no clue how to do a leakdown test...care to explain?

5. Suggestions for getting the carbon off the pistions..I'm sure it's coated!

Thanks, you all are the reason is the greatest!

Sequoia

Get the bolts from the dealer, you're probably not going to find them anywhere else. There gonna get for 2 or 3 bucks each, and there's like 14 of them. Instead of perfect seal, go find "right stuff" made by permatex. It come in a black can that looks and operates like cheez-whiz. Best stuff you'll ever use. Also, get the upper end gasket set from the dealer. You'll get a newer style head gasket that looks like 3 shim plates riveted together, with water jacket sealer around the water jacket holes. Also you'll need gasket sealer like copper coat. I used some stuff from the dealer in an aresol can. it's the same type stuff only easier to apply evenly.

Are you going to take your head to a machine shop? Mine was warped and valve seats were pitted. Refer to your own "need head work" thread, as I posted about this there.

Don't worry about the carbon on the pistons, it'll be back soon enough anyway.

Make sure you keep your push rods in order and dont let any junk fall into the lifter galleys.

Other than all that, the FSM is going to be your best friend. Be sure you have a good torque wrench.

Fun stuff!

Dan

1: Get a new set from the stealership. Personally, I wouldn't mess around with hardware store bolts. For that matter, I wouldn't pick up a set that wasn't specifically for my engine. Don't know if anybody like ARP offers a set.

2: No idea. The head gasket I get from my friendly Jeep parts pusher came with the sealants pre-applied. I *THINK* my 94 FSM specifies no additional stuff.

3: No clue.

4: For a leakdown test, you need a pressure gauge to screw into the sparkplug hole. Develop pressure, leave the piston up near TDC and see how fast/far the pressure drops. Check the FSM.

5: I woudn't do anything about that, I'd be concerned about scratching the bores. SeaFoam, GM Top Engine Cleaner, etc.

FWIW, I put on a remanned head from AutoZone last fall. $200 + core.

ChiXJeff

Like the others have said go with factory parts. Also in the Mopar Performance Catalog there is a header attaching package available which you should buy for the intake/exhaust. It includes all the hardware and is cheaper than getting them seperate. On cleaning carbon I would disconnect the head pipe run the motor and spray in a can of Mopar Combustion Chamber cleaner for carbon bulidup.

I will be getting my head surfaced for sure, I'm just trying to get all my ducks in a row before I get started.

Jeff: How's that AutoZone head work for you? That'd be an awfly easy way to do it (maybe I'd even be able to have my Jeep back running as soon as this Monday instead of the next).

Leakdown is just what I thougth it was, just wanted to make sure!

Thanks for the help, I'm sure I'll end up with more questions when I get everything off (or, God forbid, can't get something off!)

So far, so good........ I have to keep tweaking the valve cover bolts down (I have snapped far too many bolts, read: don't know my own strength!)

The way that I looked at it was that I only had the 1 vehicle, and what would it cost me to have the head checked, surfaced (if necessary,) maybe valves, and how long would I have to wait for it. Made the decision pretty easy IMHO as I had the replacement head waiting before I even started the job. BTW, you'll have to get new alignment pins (probably from the dealer again) for the remanned head, they don't come with them. You'll also reuse your push rods, rocker arms and nuts. AZ's heads come with valves, springs and retainers installed.

BTW, hit every bolt you can see with PB-Blaster or your favorite brand of rust-eater for at least a couple of days in advance. If all goes well, you *SHOULD* be able to do it all in 1 day.

I suspect you'll have the most trouble with broken and/or stripped bolts on your exhaust. I've got a complete Borla (LOVE Stainless exhausts!) so it comes apart pretty easily.

I'll have to go looking for the resolution on why your XJ croaked, I seem to have missed it.

Luckily I live in Southern California, bolts don't rust quite as often I agree on that exaust though..all my life I've hated doing anything to exaust!

I over heated it (at least a dozen times since I've owned it in the past five years) one too many times, it finally ate the head gasket, here's the post: The Sad Story and The Continuation)

Ah.........

Unfortunately, as your rig is just plain DIW, you may not have much of a choice. It took AZ better than a month to get mine, and it took a couple of NASTY phone calls to the AZ regional manager to finally get it in gear. The local shop manager finally figured out how to get through the corporate BS.

The older gaskets are a carbon fiber or something. FSM does say not to put anything else on the head. The newer gaskets are a different story, in fact the can of sealer I used says MOPAR right on the can, and the directions tell how to use it. Ryurabbit works at Dodge parts counter, and told me the Dodge neons had a bad rap for blowing head gaskets. After they switched to this newer style gasket, no more problems.

Dan

I know what you mean on Neon's! My girlfriend has one. (In fact, I have to change it's gasket!)

My .02.......

I will not do this in any order and will repeat some so just take it as is:

Do not use Copper Coat or any other stuff on the head gasket unless is specifically called for. Is rare anymore for any headgasket to require anything at all. Is always best to do the dealer for all gaskets and parts. Use brake cleaner spray and paper towels for ease of use to clean all gasketed surfaces.

As for the headbolts, i am not sure i'd necessarily replace them. Really, only torque-to-yield headbolts require replacement. Not sure what your's are. If do need them, only do dealer for the bolts. Sometimes specs are provided to actually measure the bolts to see if stretched too much. If thought to be good, clean the threads and chase them with a die and use a matching tap to clean the holes in the block.

A leak down test will tell you very little at this stage of the game since the head gasket is already known bad.

Maybe knock off the big pieces of carbon if present or excessive on the tops of the pistons, otherwise leave it alone. Not worth the effort.

I have seen really bad mass-rebuilt engines and heads. One issue is that you do not know what the engine/head had been through in it's past life...some have been totally abused. Also, do not know the quality of the replacement parts used. I prefer to take engine parts and heads to a known good shop/machinest. That way you have a better idea of everything to do with the, in your case, head: The actual condition when brought, and the final overall results. By the condition of the head that is determined sometimes may point to other problems with the engine. You have options as to exactly the level of work you may want done to the head, ie., new valves and guides if want to last another 100k miles, or the old ones and go maybe 50k or less. I just like real control of work done to engine systems, have seen such bad and inconsistent work done over the years.

Also make sure to ck all cyl bores while head is off. Ck for ridge at the top and scoring and discoloration of bores just to give you an idea of the wear of that part of the engine.

Oh I'll be looking at them cylindars good! (Actually i'm afriad to, I tend to get ahead of myself and say "Well, as long as I'm in there...")

I do see your point on the head there, and that was a thought of mine, but that idea is out anyway becuase of the lead time and the cost ($350 these days), it was just an idea for a quick turnaround. I will be getting my head worked on.

As for leak down test, I was going to do that after the head gasket job, I know it wouldn't be a very good timing, it would tell me if I have something else brewing (Rings).

Also, FYI, per the FSM you can re-use the head bolts once, it calls for you to paint the heads of the bolts to determine if they've been re-used or not. The reason I am going to replace them is that I cannot be sure that the head hasn't been removed before (I am not the original owner), I know the valve cover has been (by the sealant), so just to err on the side of caution I am going to replace them, yes, I can be anal at times!

Sequoia

Well good........

Now is a good time to be anal!! I am totally anal about real engine work, on mine or other's. If the other's are not willing to pay that price i don't do the work!!

I guess they do not state bolt lengths to ck for stretching in the FSM? Too bad, is easy to ck.

To ck leakdown afterward sounds strange. I guess could tell you things, but to find these out at that stage of the game could almost be counter productive or something. Normally broken rings will leave a groove or score in the cyl bore, but NOT always. I would think instead consider other signs of bore/piston problems: Oil accumulation on sparkplugs, or/and oil loss not from leaking as best determined, power loss, vibration and uneaven engine running, quick oil contamination.

The surfacing of the head it will need will raise compression and efficiency a little. If the bores and such are really marginal this sometimes can be too much for the rest of the engine. Sometimes falls back to a judgement call.... Good luck!!

The Jeep FSM specifies that the head bolts can be used one more time for in-service replacement, after that they are to be replaced. FSM says to mark 'em with a daub of paint when they are re-used, so the next guy who works on it will know they've been used. (I guess that assumes he's also read the FSM.) If in doubt, buy a new set -- it's cheap insurance.

Once the head is off, take a look at the tops of the pistons. If there's heavy carbon build-up, I would carefully chip/scrape it off. Do two pistons at a time, with the pistons at TDC and rags stuffed in the other holes to keep the chips from going where you don't want them. Use a scraper or something with a sharp edge but rounded corners -- the pistons are aluminum, which is softer than steel You don't want to gouge any tracks into the tops of the pistons, you just want to scrape away the heavy accumulations of crud. Work slowly and if you have to tap the scraper, use a wooden, rubber or plastic hammer, not steel. This just softens the impact a bit, to reduce the likelihood of scarring the surface. If you want to hit it with a wire brush in a drill, get one with brass bristles, not steel.

Update:

So I've got the head and manifolds off, and here's what I've found.

1: The cylinders look decent, not a great cross hatch on them, but not nasty scores. They're smooth to the touch and by the feel of it don't have a huge ridge at top, I haven't mic'd them.
2: My exaust manifold is not cracked! I don't know how I managed not to have a cracked manifold, but it's perfect.
3: Three of my exaust ports had evidence of coolant, a white residue.
4: Everything else seems to look good.

There is one question though...Why did they cover up water ports next to the cylinders? I've got a bunch of crud on the head gasket from where water was hitting it.



Sequoia

Re: Update:

GSequoia said:

There is one question though...Why did they cover up water ports next to the cylinders? I've got a bunch of crud on the head gasket from where water was hitting it.

Sequoia

Click to expand...

Coolant dwell time and for even cooling of the cylinder head. Most of the flow comes at the back of the head forward with the smaller holes on the side. This should give a even as possible cooling of the head.

Ahhh..okay, I've always wondered why there were holes in the head, holes in the block, but none in the gasket (I've come across this in more than just the 4 litre).

Sequoia

IT's not uncommon to see various passages for coolant blocked on head gaskets intentionally by design.

Remember that engine blocks (and heads) are sand cast, meaning that sand is used to form the mold into which the molten cast iron is poured. Once the iron is cooled, the sand must be removed from all the various INTERNAL as well as external passages.

One of the ways the designers make this sand removal easier is to create openings in the "deck" of the block that serve only to allow the water jacket around the cylinders to be cleaned of sand.

If all those passages were then left open to cooling water circulation, the head would actually develop "cold spots" which could contribute to spark knock, carbon accumulation, and high emissions. To compensate for that, the designers create restrictions or blockages in the head gasket.

That's why head gaskets don't always completely match the pattern of openings in the block/head.

Make sense?

Sounds great that you say there is not a ridge at the tops of the bores. If no ridge and fairly consistent honemarks down the bores then is not necessary to mic the bores...sounds like they are okay. Very good.

Did you find obvious head gasket problems, ie., broken or/and corroded areas indicating where the coolant loss was? Is good to have confirmation of a bad gasket so as to assure the problem is not a cracked head or cyl bore. I will assume you are still bringing the head to a competent machine shop for at least a pressure ck and a surfacing?

White residue is not normally the evidence of coolant in cyls, but a 'washed' combustion chamber and piston top. The white residue is more of a burned oil indication if excessive, or normal conditions if light coating.

So what made you think the exh man was cracked? Different sounds? Did you find broken or missing man bolts?

Well, on the manifold, the cracked sound. But I know that these manifolds are common to crack so I just got myself ready to find a crack (didn't want to have a surprise!). But a lot of the bolts in that manifold were loose, two were missing.

As for the head gasket, it looked a little bit touchy in areas, not too terrible, but not too good either. And that head is going to a shop, just have to wrap it up and put it in the girlfriend's car.

Didn't know about the residue being oil...that's noted now

Sequoia