Head Gasket

I'll try to make a long story short: Buddy told me a few days ago his radiator (97 4.0 xj) had exploded and he overheated. He called me about an hour ago and said he had replaced the rad and tried to drive home; made it 30mi and started billowing white smoke...........got towed home.

I'm going to replace the head gasket for him this weekend (have never done so), I'm mechanically competent (have re-geared 5 axles and helped rebuild a T-18) and can obviously follow directions but any tips or things to look for or replace while I'm at it?

Thanks

1) Its a bitch.
2) Start early
3) Get good QUALITY gaskets
4) Torque everything to spec.
5) Its a bitch
6) Get all your fluids: PS, Coolant, Oil, etc...
7) Have fun

I would replace the manifold gasket as well. Drain the oil, coolant, and PS fluid first. Swivel sockets and extensions will help you with the manifold bolts. Put the manifolds on the head before you install it and use a cherry picker to drop it in. Besides that nothing too bad. Maybe replace the belt.

oh and search...

Make sure the head hasn't warped or you'll have to do it twice.

I strongly agree that if you're going to go to all that work, you should take the head into a machine shop and have it checked (flatness, magnaflux, etc.). Cheap insurance.

Make sure the head screws don't have paint dabs on them - if they do, get new ones. If they don't, paint them when you're done.

Use PTFE/Teflon pipe dope or RTV sealant on the #11 - driver's side front - screw threads.

Replace the thermostat housing screws, as they tend to be corroded. Use CRES, brass, or bronze - if you have to get carbon steel (SAE grades,) coat the threads and shank with RTV on installation.

Get replacement screws for the manifolds - I like silicon bronze for these, but you have to find a specialty shop for them (like Fastenal.) If you can only get carbon steel, get SAE5 screws - they lose less strength due to the heat-cycling. Use LocTite #272 or nothing on these screws! You'll als find it helpful to have a 9/16" "flex" socket (inbuilt universal joint on shorty socket) to reach the lower rear screws. New studs can be cut from 3/8"-16 threaded rod, but you'll want to get 3/8"-16 nuts to go with them (OEM are 3/8"-24, but the head end of the stud is 3/8"-16)

Use RTV copper (a thin, even layer) on both sides of the manifold gasket. This will not only help to hold the thing in place while you're torquing, but help to prevent burn-through if a screw works loose (check screw torque annually.)

USE NO SEALER on the head gasket! Period.

Scotch-Brite wheels work wonders for stripping old gasket residue, use them. Flush with carburettor cleaner after you're done. This will also strip carbon deposits from the tops of the pistons (use medium for that, fine for gsaket crud.)

Concur with servicing the manifolds on the bench - it is much easier that way! If you're fairly large (like meself) you can R&I the head as an assembly using muscle power - or else you'll want to get a crane hoist. The head casting is good for 60-70#, and add the goodies (usually, I'll drop the head, manifolds, and fuel rail in as an assembly. Somewhere under 100#, I'm sure - but the reach makes it difficult.)

Have the head checked at a machine shop. You shouldn't have a crack - and a good machine shop will have a straightedge to check the head with. Spec is .003"/6" longwise max warpage, .001"/1" max warpage crosswise. Check between the straightedge and the head deck in various locations.

While you're there, check the manifold surfaces - I think that spec is .003"/6" there as well. Check both sides.

You yourself can check the head and manifolds if you're on good relations with your machinist - I had a good enough working relationship with mine that I could take the parts in, borrow his straightedge, and drop off a six or two in return. Fifteen minutes and I'm out and done, and it didn't disturb his day at all (too bad he went back into engineering and got out of machining.) If you plan on overhauling engines more than infrequently, you can buy a ground straightedge from various MRO sources or engine supply houses - Goodson (www.goodson.com) or MSC Direct (www.mscdirect.com) come readily to mind.

Coolant should be drained before you start. Accessory fluids need not be drained - those parts can be tied aside with wire. Change the oil after you've buttoned it all up - you're going to knock crud loose, and most of that will drain out with the old oil. If you have a dry sump and knock it all loose, you'll want to change the filter after you've run the engine for a couple of hours.

Don't think I've missed anything...

Thanks for the quick replies; tons of great info. I called him and had him search out local machine shops, but that and parts quality is up to him, I'm just providing labor. Unfortunately he's damn near broke and that's why we're trying to do it this weekend, so he can get back to work. No worries there with be plenty of adult beverages.
-Randy

Fel-Pro gaskets are good, and they're easy to find.

I prefer Victor-Reinz, but they're not at easy to find.

5-90 said:

Fel-Pro gaskets are good, and they're easy to find.

I prefer Victor-Reinz, but they're not at easy to find.

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Much appreciated sir. We're going to the parts store tomorrow morning to grab the gaskets, RTV, lock-tite and hopefully they'll have some feeler gauges to check the head. He informed me that he let his 'idiot' friend borrow the xj and when the rad exploded said 'idiot' continued to drive until the motor shut off..................Can't wait to see how this goes.
-Randy

shmoken875 said:

Much appreciated sir. We're going to the parts store tomorrow morning to grab the gaskets, RTV, lock-tite and hopefully they'll have some feeler gauges to check the head. He informed me that he let his 'idiot' friend borrow the xj and when the rad exploded said 'idiot' continued to drive until the motor shut off..................Can't wait to see how this goes.
-Randy

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Well, you may get lucky. An aluminum head would be damned near guaranteed to warp after treatment like that, if not crack outright. Iron heads can put up with an amazing amount of abuse, contrariwise, so you might not need to do any work. Granted, this is for an inline six - the length of the head can complicate things (it's a shade over two feet long.)

Feeler gages - if the machinist doesn't have them, find yourself a new machinist. While we're on the subject - why for don't you have a set? They're cheap enough...

The rest of the gig is pretty straightforward, just pay attention to what the manual tells you and what you've been told here (since most of this advice will have come from people who didn't do the job in a shop - they did it in their driveway... Doing a job under suboptimal conditions makes you not want to have to do it again, so you learn the little tips that are like "taking out insurance.")

5-90 said:

Well, you may get lucky. An aluminum head would be damned near guaranteed to warp after treatment like that, if not crack outright. Iron heads can put up with an amazing amount of abuse, contrariwise, so you might not need to do any work. Granted, this is for an inline six - the length of the head can complicate things (it's a shade over two feet long.)

Feeler gages - if the machinist doesn't have them, find yourself a new machinist. While we're on the subject - why for don't you have a set? They're cheap enough...

The rest of the gig is pretty straightforward, just pay attention to what the manual tells you and what you've been told here (since most of this advice will have come from people who didn't do the job in a shop - they did it in their driveway... Doing a job under suboptimal conditions makes you not want to have to do it again, so you learn the little tips that are like "taking out insurance.")

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Well that makes me breathe a little easier, first thing I told him was not to get his hopes up.

By the time we get the head off tomorrow I don't think anybody in town will be open to look at it. I was actually referring to getting the gauges from the store for myself, not sure why I don't have any yet, I have calipers, a micrometer, dial indicator and magnetic base but no feeler gauges, soon enough though.

And yes many thanks again to all that posted up tips, I went and read the procedure in my manual, I like to go into a project as informed as possible.

If it got hot enough to shut down I would be checking that head for cracks iron or otherwise. Check valve seats & all around the inside of each cylinder dome. I would hate to see you do all that work & end up having to pull it apart again. When you put the manifolds on the head make sure you line up the 2 dowels on the intake to the head. If these don't line up the manifold is aluminum the dowel can wedge in the manifold creating a nasty vacuum leak which will cause the idle to be very high RPM (ask me how I know). Also make sure you don't have any broken manifold bolts as it is easier to drill them out on the bench. Good Luck.

Weeeelllllllllllll it wasn't the head gasket. #2 piston was missing a chunk out of it.

Will a OBD1 4.0HO (91-95?) swap in relatively easy? Found one local for $400 w/84k

sounds like his "friend" didn't tell him just how hot it really got!

the long block (block and head) is a direct fit. you just have to use all the accesories off the 97.

x99j said:

sounds like his "friend" didn't tell him just how hot it really got!

the long block (block and head) is a direct fit. you just have to use all the accesories off the 97.

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What about electrical connections to the harness? Thats the main issue; I've searched and most people say just run the 97+ head on the older block, but seeing the trauma that this thing's been through I'm not sure I would want to do that. I'm mechanically inclined but an electrical retard.

you should not have any elec issues if you use the accessories off the 97 motor. by accessories i mean intake, throttle body, all the 97 sensors, 97 fly wheel, 97 oil pressure switch, 97 coolant temp switch, 97 exhaust manifold. you are going to have to dress the salvage motor with everything from the 97 motor (except for the blown head and block) mike

here is a guy in this forum that put a 99 motor in an older cherokee. page 6 is the one you want, it is the engine swap page. mike
p.s. he dressed the 99 motor with the older 91 parts and then went high performance on some parts.
Link page 6:
http://www.naxja.org/forum/showthread.php?t=940576&page=6