12HT Rebuild thread and questions (1 Viewer)

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Vossie

#thecrazycruiserman
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Hi all.

so ive had the 12HT in my 45 for a year now and am loving it. but i have noticed a few issues:

1. she starts solid, but while cold blows a white/blue smoke until warm.
2. even when warm, for the first 30min, she smokes under throttle.
3. once running for a while, she stops smoking as badly, other than thick black smoke when i rev her up to 2000rpm.
4. blowback. with the oil cap off, theres a noticeable blow back at idle.

so, i want to rebuild her, and this will be the thread to chronicle it. but i have some questions to ask before i pull the trigger on any spares.

the 12HT is effectively the same as a 2H as far as the bottom end goes, right?

can you use pistons, rings and bearings from a 2H, or are the 12HT pistons and rings specific.

i know the story on getting the alfin pistons, but what should i do if i cannot get these?

is it possible to just change the rings and nothing else?

the reason i ask is money is always a big issue for me. i live in Zimbabwe where not only is it tought to find anything, but importing is almost impossible and down right expensive.

so what are my options?
 
can you use pistons, rings and bearings from a 2H, or are the 12HT pistons and rings specific.

Pretty sure they are unique to the 12HT. I would find some way to get an Engine Australia rebuild kit. $1200AUD?
With ring only replacement , who knows. Better chance of it working if the cylinder had a light hone.
This is the engine from the Coaster, right? Its probably had an adventurous life.
What viscosity oil are you using? I would use anything less than 20/50.
 
Pretty sure they are unique to the 12HT. I would find some way to get an Engine Australia rebuild kit. $1200AUD?
With ring only replacement , who knows. Better chance of it working if the cylinder had a light hone.
This is the engine from the Coaster, right? Its probably had an adventurous life.
What viscosity oil are you using? I would use anything less than 20/50.

you would or wouldnt use anything less than 20/50? im currently using Castrol GTX diesel, which is a 15w40

ok, but i did a bit of searching on toyodiy, and found this
ToyoDIY.com

according to that page, the part numbers for 2H and 12HT pistons, bearings and rings are the same. so now im confused...
 
you would or wouldnt use anything less than 20/50? im currently using Castrol GTX diesel, which is a 15w40

ok, but i did a bit of searching on toyodiy, and found this
ToyoDIY.com

according to that page, the part numbers for 2H and 12HT pistons, bearings and rings are the same. so now im confused...

20/50 is the recommended oil by Toyota Australia for the older 4 and 6 cyl diesels and I imagined Zimbabwe temps would be similar.
I would give it a go and see what happens. 20/50 is all I have ever used, except once where I used 20/60.
I always thought the turbo pistons would be different.
 
20/50 is the recommended oil by Toyota Australia for the older 4 and 6 cyl diesels and I imagined Zimbabwe temps would be similar.
I would give it a go and see what happens. 20/50 is all I have ever used, except once where I used 20/60.
I always thought the turbo pistons would be different.
will look into the oil story, see what i can find.

so, according to that page, does it seem to you that you that 2H and 12HT parts are the same?
 
The 2H is an indirect injection engine, and the 12HT is direct injection. These are fundamental differences. 2H has pre-combustion chamber in the cylinder head, and 12HT has the combustion chamber (bowl) in the piston. The 2H has flat top pistons, 12HT has bowls in the pistons. Totally different.
 
The 2H is an indirect injection engine, and the 12HT is direct injection. These are fundamental differences. 2H has pre-combustion chamber in the cylinder head, and 12HT has the combustion chamber (bowl) in the piston. The 2H has flat top pistons, 12HT has bowls in the pistons. Totally different.

sure, i get that. i just dont know why the part numbers are the same?
 
sure, i get that. i just dont know why the part numbers are the same?

For an 89 HJ61 12HT this is what I get for piston part numbers in Toyodiy:

13101 PISTON SUB-ASSY, W/PIN
13101-68020-01 STD, MARK 1 6 $259.03
13101-68020-02 STD, MARK 2 6 $259.03
13101-68020-03 STD, MARK 3 6 $259.03
13103-68020 O/S 0.50 6 $259.03

For an 89 HJ60 2H this is what I get:

13101 PISTON SUB-ASSY, W/PIN
13101-68011-01 STD, MARK 1 6 $263.49
13101-68011-02 STD, MARK 2 6 $263.49
13101-68011-03 STD, MARK 3 6 $263.49
13103-68011 O/S 0.50 6 $259.03

Not sure what you were seeing. I also recommend checking part numbers through Megazip, as they tend to show more replacement part numbers than Toyodiy (there might be updated versions of these parts).
 
For an 89 HJ61 12HT this is what I get for piston part numbers in Toyodiy:

13101 PISTON SUB-ASSY, W/PIN
13101-68020-01 STD, MARK 1 6 $259.03
13101-68020-02 STD, MARK 2 6 $259.03
13101-68020-03 STD, MARK 3 6 $259.03
13103-68020 O/S 0.50 6 $259.03

For an 89 HJ60 2H this is what I get:

13101 PISTON SUB-ASSY, W/PIN
13101-68011-01 STD, MARK 1 6 $263.49
13101-68011-02 STD, MARK 2 6 $263.49
13101-68011-03 STD, MARK 3 6 $263.49
13103-68011 O/S 0.50 6 $259.03

Not sure what you were seeing. I also recommend checking part numbers through Megazip, as they tend to show more replacement part numbers than Toyodiy (there might be updated versions of these parts).

ok, i was looking at 1985 12HT as found in the HJ61.

297E8F0C-04A9-45D0-80E9-814FB5C82B40.png


ok, so we know pistons should be different due to the cups, but what about rings?
 
i just dont know why the part numbers are the same?

If you find a part number and do a search it will give you a big list of models that use that part, but when you click on that model its not there.

The rings are unique to the 12HT @$360USD a set for OEM from megazip. Or $1060USD for an Engines Australia full rebuild kit. + shipping.
Can you get things sent to South Africa and cross the border to get it?
 
If you find a part number and do a search it will give you a big list of models that use that part, but when you click on that model its not there.

The rings are unique to the 12HT @$360USD a set for OEM from megazip. Or $1060USD for an Engines Australia full rebuild kit. + shipping.
Can you get things sent to South Africa and cross the border to get it?

i could, but i will be hammered on duty. as it is, $1060 is a ton of money for me. i can probably expect to pay in the region of 80% duties on that too
 

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