Hi all, I just bought an old 24v HJ61 that has supposedly 200k kms on the clock. I say supposedly as the speedometer looks like it had been disconnected and wound back perhaps, I pulled the dash to fix a gauge when I first got it and the speedometer connecting cable popped right out!. Is there any way to tell without pulling the head if it has been rebuilt with alfin pistons? I have searched the forum and have gleaned that the EA rebuild kits have pistons stamped with "2A" underneath, I will drop the pan and see if I can see any markings when I get home from work (I work offshore). Any other clues that you guys might have would be appreciated. I'm worried about the pistons dropping rings after I breathe a little more life in to it with more boost/ fuel. Getting real excited, bought a pyro, boost gauge off flea bay and now saving for the upgraded valve body for the a440f. I would hate to have those pistons come apart and tear it up! thanks for your help in advance...
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The non alfin pistons seem to go at around 300,000 - 350,000 kms. Keep an eye on your compression - especially in cylinder 5 and 6. If these drop, you may have to do an overhaul. If you get them early enough, the rest of the engine should be in good shape for whatever level of rebuild you want to do....
Sorry, i have no info on identifying pistons without holding them in your hand and eyeballing the ring lands.
Sorry, i have no info on identifying pistons without holding them in your hand and eyeballing the ring lands.
I have a set of Alfin pistons also with the 2A stamp but not from EA. I still believe that they all (aftermarket) come from the same manufacturer.
Good luck checking them out, and don’t forget that there is the strengthening baffle between sump and block, and if you disturb this when you drop the sump, then you will have to drop the oil pump feed and transfer pipes to reseat and seal the plate. They would also both need gaskets if disturbed. Also, if you manage to remove the sump with the baffle undisturbed, then it's a bit of a bitch to look up under the piston, but possible. It’s going to be messy either way.
Some more piston info at this posting, sorry I don’t know how to paste a link.
12HT Pistons . Are they or are they ought.
Discussion in 'Diesel Tech / 24 volts' started by Gengis, Aug 26, 2014.
George
Good luck checking them out, and don’t forget that there is the strengthening baffle between sump and block, and if you disturb this when you drop the sump, then you will have to drop the oil pump feed and transfer pipes to reseat and seal the plate. They would also both need gaskets if disturbed. Also, if you manage to remove the sump with the baffle undisturbed, then it's a bit of a bitch to look up under the piston, but possible. It’s going to be messy either way.
Some more piston info at this posting, sorry I don’t know how to paste a link.
12HT Pistons . Are they or are they ought.
Discussion in 'Diesel Tech / 24 volts' started by Gengis, Aug 26, 2014.
George
Great advice above do a compression test to determine engine condition. I found number five low on compression from shattered rings with very little cylinder damage I was lucky and got it early and rebuilt with the standard EA kit. If anyone goes to the trouble of fitting alfin pistons might as well do the whole thing with bearings, gaskets etc and make it last another 500,000 mile with good service.
I made my compression tester out of aluminum rod turned down one end to have a piece of flat bar with three holes drilled to suit and a 1/4 hole drilled through the guts. with a fitting tapped to suit a borrowed gauge.
I made my compression tester out of aluminum rod turned down one end to have a piece of flat bar with three holes drilled to suit and a 1/4 hole drilled through the guts. with a fitting tapped to suit a borrowed gauge.
That's about where you will see the "2A" if you go that route. All the best and keep us informed.
I am wondering if it possible/reasonable to drop pistons out the bottom of a 12ht for inspection by just removing the pan and bearings. My 12ht has 388,000 Kms on it and I am concerned that it may be a ticking time bomb. I have only owned it for the past 14,000 kms so I have no idea if it has had pistons replaced. Last check it had good compression, but seems that could change quickly if a compression ring broke.
negative on that even if you removed the pistons you couldn't put them back in since a piston ring compressor wont work in such a confined space.
There is no certain way of seeing if your pistons have the alfin inserts without pulling the pistons. The 12h-t im rebuilding has previously been rebuilt in japan and it already had alfin pistons installed. My pistons however do not have the markings the pistons in the above posts have. you can check my signature for the 12ht rebuild.
I would. It certainly cant hurt. The problem is its always a snow ball affect. If you pull the head and the pistons it would be silly not to check the mains and the cam shaft. Read my thread on the 87 in my signature.
you could always buy my long block and swap it in 
Vossie
#thecrazycruiserman
question, are 12HT's prone to grenading once they have that kind of mileage? ive just put a 12HT in my 45 and i have no idea what its mileage is, but if i had to guess i would say +250,000kms.
but if looked after, should they not be as long lived as any other toyota diesel? my fathers hilux 3L has 530,000kms with oem pistons, my moms 1KD prado has 448,000kms with oem pistons, my fathers old 1HZ 75 series LC had 700,000kms oem and the 1hz 80 series LC i grew up was over 1,200,000 kms last time i saw the current owner....
what im saying is, is there a specific reason why these engines fail at a certain mileage or is it just bc people push them too hard?
what im saying is, is there a specific reason why these engines fail at a certain mileage or is it just bc people push them too hard?
I guess a good place to begin the debate is, do the 1HZ, the 3L and the 1KD pistons have Alfin inserts???
Is seems the broken rings and ring lands cause the majority of 12HT mishaps, so 250000 on a "not to well maintained and often pushed" non alfin pistoned engine seems about right??
I guess a good place to begin the debate is, do the 1HZ, the 3L and the 1KD pistons have Alfin inserts???
Is seems the broken rings and ring lands cause the majority of 12HT mishaps, so 250000 on a "not to well maintained and often pushed" non alfin pistoned engine seems about right??
Its one of those things that you could argue tell the cows come home and this guy will say "mine died at 250K" and the other fella will say "I put 600k on mine". I've met guys who flat out deny that non reinforced pistons are a concern at all. However, no one would put aluminum crank shafts in their engine, or use aluminum connecting rods or an aluminum cam shaft. Its just too soft a material. It is a weak point of the engine and many other engines that are non reinforced. Other than that issue the 12ht is really an amazing engine. I talked with an old fella recently with a 2lt he turbo'd that the ring lands were hammered out so far he just put another ring in to take up the extra space. He drove to my house in that truck! Might be an option for those who are extra frugal.
GTSSportCoupe
2LTE abuser
Generally normally aspirated diesels can get along just fine without reinforced ring lands in the pistons. If someone turbo charges them, the increase pressure and heat is what will begin to cause problems with these pistons. The 2H is a classic example of this.
Most Toyota turbo/supercharged engines came with upgraded pistons compared to their normally aspirated cousins. Most that I've seen are semi-forged/hypereutectic, have reinforced ring lands and are ceramic coated on top. Then again, most I've seen are newer than the 12HT....
I am surprised the 12HT pistons are a cause of concern with that engine, as the rest of the motor is so well designed....
Most Toyota turbo/supercharged engines came with upgraded pistons compared to their normally aspirated cousins. Most that I've seen are semi-forged/hypereutectic, have reinforced ring lands and are ceramic coated on top. Then again, most I've seen are newer than the 12HT....
I am surprised the 12HT pistons are a cause of concern with that engine, as the rest of the motor is so well designed....
Vossie
#thecrazycruiserman
sorry for being dumb, but what is it in the engine that is not reinforced?
my understanding was that alfin inserts were an upgrade to ring land on the piston to reinforce and increase robustness. but surely that doesnt mean that not having them will result in catastrophic failure.
sorry for sounding paranoid, but i just put in my 12HT and theres no way on earth i will have the time/money any time in the next year to open it up, and its my daily driver. so all this talk of grenading 12HT's has me a bit worried.
No Vossie, not catastrophic, just a slow,,, silent.............. Sorry, my soutie sense of humour . Lets just say that alfin pistons stand up to fiddeling and tweaking and bad maintanence better than the origionals, and not many of us are aware of what our engines went through before we got them.
Just follow the Douglas Adams advice, and, Dont Panic
Just follow the Douglas Adams advice, and, Dont Panic
The ring lands ware out causing the rings to break for some reason on cylinders 5 and 6. A compression test will tell you if you have broken rings or not but don't sweat it as these engines are very strong and wont explode they just start running on five cylinders with some blue smoke until the cylinder heats up and start firing again.
can someone tell me what these numbers mean ?
+1 on the slow decline. I would imagine that the ring lands would have to be pretty bad before the rings broke. My first indication was hard and white smoky cold starts. I'm in a colder climate though and you may not get as much of an sign as I did. My compression went way down to half normal with a ring land expansion in one cylinder of about a millimetre. It ran perfectly once it warmed up. Just check your compression once a year or so... and start with #5 then #6.
Reviving an old thread. I was just searching around to see if anyone has posted pics of the damage that is common in the stock 12HT. I have rebuilt 5 and all have had this damage. Its been most severe in piston 1 and 2 in the ones I have done, and its always most prominent on the intake side (also where the injector is). I think the condition is accelerated by neglected injectors. Sticky and leaky injectors wash the cylinder wall.
Rebuilding one now. Piston 1 and 2 below. This engine ran OK. Sounded a little off to me but I dont think most people would have noticed.
Rebuilding one now. Piston 1 and 2 below. This engine ran OK. Sounded a little off to me but I dont think most people would have noticed.
