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Re: your blown head gasket, it's most common to see that between cyl 3 & 4 but, there ya go! You'll have to at minimum get the head surfaced. These do have issues with burnt exhaust valves so I'd highly recommend, at minimum, you pull all the valves out of the head and check for valve burning/seat recession. The intake valves will probably look really good and may only need a slight lapping-in with fine valve compound. Depending on what you see on the exhaust side, maybe the same. Or it may need the valves ground. Have the head pressure-checked as well.

For best results, use an Isuzu OE head gasket. They are less prone to blowing out. El-Cheapo gaskets will likely blow out the fire rings within a few thousand miles. Jerry Lemond (JLEMOND on this site) can provide one of those.

If you get a chance, post a pic of the firewall side of the head. We need to see the casting number. Lower numbers are more prone to cracking, especially after an overheat.

Change all of the cooling system hoses or I guarantee, one day they'll blow out. Then it's Goodbye, Head! Check the radiator for proper flow and install a new, 180-degree thermostat with "jiggle" air-bleeding valve. Put the rig on ramps, or jackstands, or point up a hill, to bleed air out of the system. Entrapped air that doesn't "burp" out will cause overheating.

Nice, low-miles Trooper! Very clean.

HTH & G'luck with the repairs.............ed
 
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Yeah, #2 casting wasn't the greatest (#3 and #4 are better), usually the cracks aren't external but found in the combustion chamber of the cyl head, or in the ports. What you see on the outside is probably just sand-casting "flash".

Better go over that head with a fine-tooth-comb. You might consider getting a new casting, because they are an improved design with better water flow, stronger, more reinforced metal and much less prone to cracking. That being said, if your head passes all the visual crack tests and pressure-tetsing, too, it might be OK.

But you've got to consider the machine shop cost of all that testing, then surfacing the head and doing a valve job. They ain't as cheap as they used to be, for sure! I had a rude awakening last time I did a valve job, I could have spent a bit more and bought a new head. Fortunately the head worked out and she ran for a long time.

You might consider getting a "jerry cam" while you've got it all apart. This special-grind cam from Jerry Lemond (JLEMOND here at the Planet) will really wake up the engine's mid-range and top-end. A worthwhile investment. You can P.M. Jerry if you're interested in that.

The ZuZu 4-cyl bottom ends are very stout, with one Achilles Heel: the crankshaft thrust bearing rings. They are 2-piece, so if they get a lot of wear they can fall out. Then the crank thrusts against the block and wears both parts out, to a non-repairable state. Not Good!

Might not be a bad idea to take a real close look at the thrust bearing rings and consider replacing them. Can't hurt, that's for sure.

Sounds like a good course of action with the block, carry on! :thumbright:

Oh, and a few eBay heads (check with Jerry, he sells 'em too):

https://www.ebay.com/itm/Isuzu-2-6-SOHC ... 0005.m1851

https://www.ebay.com/itm/NEW-ISUZU-2-6- ... Swd~RZOtsT

https://www.ebay.com/itm/Isuzu-2-6-SOHC ... 0005.m1851
 
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If you go with the newer-style pistons, it'd probably be better to also go with the newer-style head with smaller combustion chamber. I'm wondering, though, if a mix of old-style flat-top pistons and the smaller combustion chamber might give a beneficial boost in compression ratio.

Maybe Jerry Lemond can chime in on recommendations for a mix-n-match...........ed

p.s. I reached into my archives and found a blurb from Jerry saying that the small-chamber head on an older 2.6 was a "very worthwhile upgrade".

His son's 2.6 automatic Trooper has the cyl head upgrade, and he found it ran well with timing set at 6 degrees BTDC. Depending on the particular quality of regular gas used, on occasion it might ping a bit, but a tank of mid-grade settled it right down.

IMHO the deep-dished pistons are gonna reduce compression ratio over flat-tops. From what I understand, the real reason for this change was emissions. So it would seem there's no clearance issues when putting the small-chamber head on a flat-top-piston lower. Coupled with a "Jerry Cam" and freer-flowing exhaust, it should give a significant boost in performance.
 

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takemehome4LOroads said:
Thanks for the idea Ed. I've read many of your helpful replies on other threads and I shudder to remind you I live in CaLiFoRNia. Do you think that combo of early pistons+late head+Jerry cam would cause issues for the Smog test? I wonder if anyone else in CA is running that config.
Oh, No, not Commiefornia! My deepest condolences!! :shock: :twisted:

The most significant effect of higher compression (besides more power!) is an increase in NOx emissions. The Jerry Cam isn't so radical a grind, and I can't imagine it'll have much effect on smog.

You'll definitely want to run a CARB-approved new catalytic converter along with your cat-back free-flowing exhaust. A new cat should make 'er run nice n' clean, I'd think. Make sure all your other emissions devices (sensors, EGR, etc) are working properly, too.

Might not be a bad idea to ask ZuZu Guru Jerry Lemond what he thinks about that.
 
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takemehome4LOroads said:
Quick update: Painted with freeze plugs installed
NOICE! :thumbleft:
 

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That's a really good deal on that new head.

Have Fun!
 

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That looks like carbon buildup to me. Have you tried to attack it with a small screwdriver or other suitable scraping tool? I bet it crumbles away.

Since you're borderline-fail, anything that blocks the normal amount of recirculated exhaust gasses might throw the emissions test off.

Let us know what you find........ed
 

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takemehome4LOroads said:
I'm still having trouble passing smog due to high NOx at 25 mph. I think I've found the issue to be that my timing is too advanced due to the harmonic balancer having slipped.

With the timing marks aligned, the HB mark should read 0*BTDC, is that correct? Here's how mine looks:

It looks to be reading 6*BTDC when the mark is aligned, so whatever I set the timing to it's actually 6 degrees advanced from that.

Edit: Wait, I think I have that backwards. It would actually be retarded by 6 degrees. If I set timing to 12*BTDC based on the mark, the engine is actually firing at 6*BDTC. Well there goes that theory!
Yes, timing would be retarded. But you really don't know what the exact value is, because lining up the cam timing mark is a quite inaccurate way to positively determine TDC. I'm assuming that the belt is properly aligned with the crankshaft internal timing mark on the engine block cover (under the lower timing cover).

Your best solution for that dilemma is to replace the harmonic balancer, since it obviously has slipped.

I'm wondering how old is the catalytic converter? Because most postings in which they were unable to pass emissions testing, the problem was solved with a new cat.

I found a site with comprehensive instructions on how to test for a failed cat. I'm gonna bookmark this one because it's one of the best I've seen:

https://axleaddict.com/auto-repair/How- ... -Converter

I found a P/N at Rockauto for a replacement harmonic dampener, Dayco PB1400N. This was the only one they had in stock, around $121 plus shipping. These are a-plenty on eBay, Amazon, etc etc for around $140+.

There's also listed a Dorman 594-805 and Summit Racing has 'em for $102.99 with a shipping delay:

https://www.summitracing.com/parts/rnb- ... eid=srese2

The Dorman website has a lot of good info including OEM part numbers:

https://www.dormanproducts.com/p-106329-594-806.aspx

There's one on eBay, too: https://www.ebay.com/itm/New-Harmonic-B ... 4542697650

Jerry Lemond is a good resource, I'm sure he can get these too. From what I've heard, he's feeling a bit better, and that's a good thing!

HTH.........ed
 

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Man, that is just ridiculous that you have to smog a 31-yr-old vehicle! And failing by 33 Parts Per Million!!! Unreal!

It looks like the NOx output is really sensitive to engine timing, maybe once you get the damper on there and get the timing "tweaked" in it'll do better. BTW when you're replacing the damper, it wouldn't be a bad idea to pull the lower timing belt cover and confirm that the belt timing marks are still aligned. Murphy Never Sleeps!

Here's a few good tips for passing smog tests that I didn't think of, like inflating your tires to the high-end, makes the engine work less!

https://axleaddict.com/auto-repair/Tric ... -Smog-Test

https://www.smogtips.com/eight_things.cfm

On the EGR, if you manually pull a vacuum on the EGR valve and it moves, does the engine idle poorly? If so, at least you know you're getting flow thru the valve and it's having some effect.

The shop manual also says you can depress the EGR valve diaphragm to get the valve to move, but watch out, use gloves as it'll likely be Hot! Don't ask me how I know this!! :wink:

The manual says that with the engine warmed and vehicle stopped, you should be able to get the EGR valve to lift at 1/4-1/2 throttle. So if it's not doing this, maybe there is a problem with the back pressure transducer.

I can post some EGR troubleshooting pages out of the shop manual if you need them.

Good Luck!.......ed
 

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Looks sharp! Is the automatic pretty snappy with the Jerry Cam?

Sounds like you'll have the EGR problem whipped.

Sooner or later you'll have touched everything on the rig and shouldn't have to fix it anymore!!! :mrgreen:
 

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I'll second the recommendation for an aftermarket trans cooler. It might also be a good idea post-flush to refill with synthetic transmission fluid. The 4-cyl Aisan auto trans is a lot more durable than the lousy 4L30E behind the V6 models. So hopefully it ain't hurt. How's the transmission fluid look now? If it smells burnt, definitely gotta get it flushed and do some upgrades.

On the engine cooling issue, partially-plugged radiator is a possibility. It might work ok on the "flats" but up in the hot hills it's not gonna cut it. A good radiator shop could recore it for you, maybe even add a 3rd core for better cooling. If you could find a high-capacity aluminum radiator, that might even be better for heat transfer.

Check your fan clutch to make sure the fan is blowing hard when the engine is hot. That could cause overheating trouble as well.

And make sure you have a 180F thermostat, it's a bit on the low side but that's what the factory put in there.

BTW you may benefit from one of the "watter wetter" products that reduce surface tension in the coolant, for better heat transfer. IDK which one is better but these guys claim to (or it might just be a pitch for Redline products):

https://romanceuniversity.org/water-wet ... -additive/

I just checked at Rockauto and they have the Liland Global 1130AA all-aluminum radiator back in stock:

https://www.rockauto.com/en/moreinfo.ph ... 40&jsn=404

https://www.rockauto.com/en/catalog/isu ... iator,2172

Very reasonably-priced at $135.79. They've been out-of-stock forever, good to see an alternative available.

Nice trip, though, the Trooper took to those trails with aplomb!

Cheers..........ed
 

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Hard to day without comprehensive radiator testing. And yeah, I'd expect a custom 3-core radiator would be more than the alum one at Rockauto. At least if an aluminum radiator cracks, you can get it welded!

All these rads nowadays with plastic tanks, once they leak at the Tank-to-Core O-ring, it's all over. Or splitting a tank, even worse.

If you still have a good local radiator shop, it might not be a bad idea to stop in and talk to them. No doubt they'd have good input on the merits of brass vs aluminum rads, number of cores, etc.

Getting hard to find a radiator shop anymore, all of the good ones around my area closed down years ago. To much of an environmental hazard, I reckon. Plus all the $$$ associated with dealing with that.
 

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hessmess said:
I like that aluminum radiator, I believe they dissipate heat faster but I have never needed one myself. I have a 3.4 V6 standard trans and it has a two core and works great. I traveled thru Wyoming last year at 75 MPH and 95 degrees and never had an issue. But that auto trans will create more heat anyway. I think I would go with an auxiliary trans cooler first and see how that does, certainly won't hurt. I did that on an old F150 I had years ago, what a difference.
Yeah, that's an angle I didn't think about, the fact that you're removing a lot of heat from the existing radiator, if the auto trans cooling is handled separately. That could make all the difference in the world, and maybe not require another radiator, since now it'll be completely dedicated to cooling the engine.

I can relate with the 3.4, I have an aftermarket brass 2-core, and years ago I towed a ski boat (around 2,000 lb towing weight) out of Oregon and up I-5 North across the Columbia River, toward Seattle area. It was well over 80 deg and was towing in 5th at 70+ and she didn't miss a beat. I only had to downshift on a couple of the really long, steeper grades. And that's with the stock exhaust, not the performance 2-1/2" that's on there now.

The temp gauge was rock solid. Could have easily done over 80 but that's pretty sketchy towing a boat, and not good for your driving record (or pocketbook) if nailed by the WSP!

Since it sounds like the cooling on the 4-cyl rig is "on the ragged edge" only in hot, extreme conditions, the aftermarket cooler should take quite a bit of heat load off the rad, and the extra cooling now available from the rad, for the engine, should do the trick I bet.
 

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If it's not a ton of metal, I'd imagine it's wear product. A normal occurrence.

I was looking at various aftermarket coolers, and Mishimoto was a favorite at Amazon. They do make quality products.

Here's a heavy-duty fan-cooled unit at a fairly reasonable price:

https://www.amazon.com/Mishimoto-MMOC-F ... ve&sr=1-43

You could combine this with a Derale temperature control valve, and also a Derale thermostatic switch.

The temp control valve always lets 10% go thru the cooler, to prevent air locks and other flow issues. It bypasses the other 90% of flow away from the cooler, until temp is above 180, after that all flow is routed thru the cooler. Thus solving any cold-running transmission issues.

Here's the thermostatic control switch, which turns the fan on at 180F and off at 165F.

https://www.amazon.com/Derale-15721-8AN ... B000A8MWL2

Here's a whole bunch of Derale stuff, they offer the fluid control valves in a number of configurations:

https://www.amazon.com/s?k=derale+fluid ... e-asc-rank

On the transmission, there are various schools of thought; one that says it may be dangerous to the trans's health to change all fluids at once. You can do it gradually by sucking 2-3 quarts out of the dipstick tube with a small transfer pump, then adding the same amount of new fluid.

This will mix over time, and the cleaning action of the new oil will be more gradual. It takes more fluid this way, because you end up pulling some of the new oil out every time you do the drain/refill cycle. But you're reducing the risk you may have when giving the trans a complete shot of new fluid, which would have its way with all the old deposits in the transmission.

Or, you can just flush the heck out of it. I've never heard of an Aisin Warner having huge problems, like the V6 4L30E does.

A cool trick is to disconnect both transmission cooler lines from the radiator; then figure out which is the supply side and which is the return. It'd be obvious very fast if you were to start the engine and observe fluid out of one or the other line!

Attach longer, temporary hoses to the lines, and you can route the discharge to a suitable container; then fill another container with clean ATF and let the transmission return line suck the new fluid back in.

The advantage of this type of flushing is that you're gonna renew the fluid in the torque converter, as well. IDK if the torque converter on these has a drain plug, otherwise the only way to get new oil thru the converter is to use the system to flush the new through.

Maybe Buster will weigh in, he has Light Years more experience with automatics than I have! :mrgreen:

HTH............ed
 
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