Finally got around to finishing pulling the head on my 1990 trooper. Thanks to all those who helped me out, I couldn't have done it without the forum!

A little background first: I pulled the head because I knew I had head/head gaskets problems. First indication was stumbling at idle, accompanied by white smoke out the exhaust. No overheating involved, these symtoms first appeared after a cold start! Not realizing what the problem was at first, I shut the engine down for a few hours before trying to restart. When I tried to restart the engine would not turn over at all...it had hydrolocked!! At this point everything came together and I realized what was going on. I was worried I had really screwed up the engine at this point, but I pulled the plugs out and cranked the engine over to blow out the coolant. After putting the plugs in it started right up and idled fine, with no apparent problems. I revved up to 2500 for a few seconds and everything seemed fine, no vibrations or strange noises. So hopefully the hrdrolock didn't damage anything?<img src="/forums/images/graemlins/confused.gif" alt="" /> By the way, the engine has 156,000 on it and has never had the head off. So after pulling the head, here are some pics of what I saw:
PIC 1
PIC 2
PIC 3
PIC 4
PIC 5

The head gasket is in place in the first pic, and the broken part you see sticking up over the piston is part of the gasket. It should be more clear in the next pic. The remaing 3 pics are all of piston #4 itself. So, the head gasket obviously failed, but exactly why I don't know. By the way, all these pics are of cylinder #4, since that is where all the problems are...the other cylinders look fine.

What I am really concerned with are the 2 little chunks that the head gasket apparently bit out of the piston somehow. Hopefully they are fairly clear on the images. They are right underneath where the head gasket failed, and based on their shape look as if they were caused by the broken head gasket impacting the piston crown? Looking at the cylinder wall in #4 piston there is no apprent scoring, no sign that loose metal caused any damage to the wall. Rotating the engine over by hand everything turns smoothly, no strange noises. I looked at the head itself and couln't see any cracks, but intend to magniflux it to make sure. The undersides of the valves look fine.

So my question is what is the implication of the piston damage? Is it severe enough that I need to replace the piston? <img src="/forums/images/graemlins/confused.gif" alt="" /> Or is it mild enough that I can just throw on a new head gasket and continue to drive without worry? What should I do? I know no one can say for sure, just looking for some advice since I have no clue. As always, thanks for any help!! <img src="/forums/images/graemlins/cheers.gif" alt="" />

EDIT by Mod: If you would like to resize those pictures, you can put them back into this thread. But they are just a bit big as they are.

If it were me, I would just run it as-is. I would have worried that the damag mushroomed the piston enough to contact the cylinder wall, but I see no scoring (especially in the darkend space on the cylinder wall above the first ring land).

As for cause of failure, who knows. All it takes is for that sealing ring to crack, or the head to loosen (or a combo of both) and it blowtorches it away to the next nearest location (in your case, the cooling jacket).

Don't forget to chase and clean out the holes for the head bolts before you put it back together.

Good Luck,
Michael

That gasket is EXACTLY what mine looked like. Looks like you also had some oil seepage out that back corner to the outside of the engine? Mine did also.

Make absolutely sure that the dreaded "pin syndrome" ain't at work here.

You _are_ gonna have the head re-worked, yes ? It should be at least vacuum checked for leaks (cracks, valve sealing) and for flatness before re-installing.

From what I can see in the pics, you can probly get away with that piston, I'm with Michael on that.

Dejavu, mine looked identical to your's when it went at 156k miles also . There was no damage to any of the pistons, but it let go on number 4 in the same spot. Since you've got the head off, make sure to have it checked (as mentioned) for cracks and such. And if you have any broken exhaust studs, now would be a great time to take care of it . I had one broken one, so I decided to replace all 7 (2-3-2). Unfortunately the 1st stud broke off on me, but I was able to get them all out and replaced. Shouldn't be a problem for another 150k miles. Good luck on your rebuild. Mine just rolled over 171k miles. Take care.

- Jim

Lemmee ask this:
Was the rearmost exh manifold stud
broke off on either of these two
cases? Mine was, not sure if it was
a contributing factor, or a symptom.

I replaced the studs, I think I used
Dorman product, but don't remember the
size. The nuts I used were from VW ...
I think they're the ones they used on
the 4cyl 2Gen VW. They were much easier
to get than the Isuzu ones! I think
they are some copper alloy...

Good Luck!

Thanks everyone! I really appreciate the input. Glad to hear you think I can get by with the piston damage...I was definitely worried about that.

"Pin syndrome" Troopersphere? Can you fill me in on what that means? I will defenitely give the head a thorough exam before/if it goes back on, meaning take it to a shop and have them perform whatever diagnostics they can. Both my manifolds are still in place...I haven't had a chance to take them off yet, since the trooper is at my parents house about 3 hours from where I live. I don't recall seeing any problems with the rear exhaust manifold stud, but I will take another look at it next time I go home. I do have a rocker arm bolt that broke off in the head during removal, but so far that is the only stud/bolt I have managed to break...still not quite sure about the best way to deal with that.

Speaking of cylinder heads, are they pretty dependable unless they over heat? If mine checks out fine I am wondering if I should put it back on or bite the bullet and get an AMC? I have been running cool ever since I put a new radiator in 4 years ago...and even before that the engine never had a major overheat/boilover. It was getting to the point though where I could tell it was running hotter than it should, thus the new radiator.

"Pin syndrome" Troopersphere? Can you fill me in on what that means?

It is the possibility of the dowel pins being too tall after you mill the block and/or head. This could prevent the head gasket from being properly compressed and therefore, cause a failure.

I know that TS is going to disagree with me, but it is a definate friendly disagreement. I don't think that the dowel pin is the source of much of a problem with shaved heads/blocks. I say that because a) I have heard very few people even mention it and b) I've run both a milled head and block without issue.

That said, it is a full possibility and one that is easy to prevent. Heck, I filed mine down when I put in the last head gasket. <img src="/forums/images/graemlins/smile.gif" alt="" />

Michael

both my Trooper and Impulse had the same studs snapped. expansion rates of the adjoined metals make it not uncommon for aluminum head motors to bust these studs. an easy preventative measure is to elongate the 4 outer most holes in your manifold/header in order to allow some extra room for movement.

I too have recently been through this. My problem turned out to be a cracked head, as well as the head gasket. There is also a possibility of the "pin syndrom", which was discussed.

Read the link from a couple weeks ago.

LINK

I think I'll be getting a new AMC head pretty soon.

Hope this helps a bit, and adds a bit to the discussion.

Ken

What Michael said! and, I'm not gonna disagree with him! There have only been a few stories that seem to confirm the existence of the pin problem. But, there's no way to know for sure if any of these type of gasket failures are NOT due to it. Just a look at where the gaskets failed, and the location of the pin...

The fix is easy, so it's worth checking before you put it back together.



Well, yeah, cuz overheating is a sure way to crack them.

Why would they overheat though ?

Poor maintenance/condition of the cooling system. I'm sure this was a contributing factor in my failure. I'm guilty.

Head gasket failure causing loss of coolant, air bubbles trapped in the head causing localized overheating of the head.

I think head gasket failure is just a fact of life we have to live with as long as there are aluminum heads on iron blocks. It's gonna happen eventually, no matter how well you maintain the engine.



Personally (MHO) if I decided not to replace the head, I would have it completely rebuilt, and the cost of that would probably reach, if not exceed, the cost of the AMC.

There were 5 generations of head castings, and you can tell which you have by looking at the back of the head. It is rumored that the 1's and 2's weren't as good as the later ones, with the 5 being the one to use if you had a choice.

Check out the search feature, most if not all this can be found in past posts!

Good Luck!