My 12HT Rebuild Journey... (1 Viewer)

Joined
Dec 13, 2010
Messages
129
Location
Langley BC
Disclaimer… I’m not a certified mechanic but I’m fairly “handy”, have a lot of tools and I have rebuilt a few 4cyl gas engines before….

Background, I purchased this 12HT back in 2014 and swapped it into my Hj60. The engine came from a 1988 JDM HJ61 and had approximately 270,000KM’s on it when I got it. I put another 50,000KM’s on it before I started having issues….

Part One:

I had noticed that the engine temps were creeping up over a period of a couple months then eventually noticed that I was losing water.
Didn’t really know where it was going. Oil still looked good and it really wasn’t pushing white out of the exhaust.
Shortly after that, the temp gauge spiked and I noticed it was low a lot of water.

I suspected the head gasket was blown from me slowly turning up the boost and giving’r

I parked it and debated what to do for almost 6 months…
I eventually did a compression and leak down test but it was inconclusive. I ended up ordering an OE Gasket Kit and was just going to re-gasket it.
I pulled the engine and tore it apart. I did not see anything catastrophic. Yes, things were obviously warn but no tell tale signs.

I measured the bore and the crank end play. Things were out to be out of tolerance (to be expected) but nothing extreme.

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Joined
Dec 13, 2010
Messages
129
Location
Langley BC
Part Two:

As it turns out, I had a very small head gasket leak between the water jacket passage and the cyl No 1.

I discussed things with my Land Cruiser friends and they all said, “well, since you gone this far…. may as well get it machined and install new parts.”
The hard part was finding a local machine shop familiar with Toyota Diesel engines….

On a recommendation, I used Alec's Automotive Machining in Burnaby, BC , Canada. (They do diesel engines and have done a few 12HT’s)
They said they would do all the measuring and machining but I would have to source all the parts since they know that would be cumbersome and time consuming and do the final assembly.

I ended up disassembling the entire engine myself. I took the disassembled Head and Block to the machine shop. They checked everything and we discussed options.
Everything looked okay just some tired and worn parts as to be expected..

The hot tanked and Magnafluxed the block and head.

Crank was good so they just polished it. The bearings had some unusual wear but it did not transpose onto the crank.
Head was good so they cleaned it up. They did a simple valve grind and installed new seals.

We decided to go 20thou (0.50mm) over and I ordered/paid for all the parts from Engines Australia. They were easy to deal with as well. (Thanks Engines Australia)

The one other issue (which we knew about) was piston protrusion. As noted on the piston box, this needs to be checked. The machine shop had to mock one up, measure and then send all 6 to be machined a bit. I could not find any concrete data/specs on what the protrusion should be so the machine shop went by experience.

I had an issue sourcing O/S thrust washers. My kit came with stock washers but we needed more.
Finding O/S washers was hard and I had to pay a premium of them… good luck on this part!

The machine shop installed the pistons, rings, bearings... installed the crank and bolted the head on for me... and that was it.

I was to do everything else/final assembly.

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Joined
Dec 13, 2010
Messages
129
Location
Langley BC
Part Three

I got the engine back home. I painted the block + some parts. Cleaned and slowly and methodically installed all the remaining parts.
I Installed new Water pump, Thermostat and had the injectors rebuilt.
I left the Turbo and Injection Pump alone. They seemed to be okay + I can deal with that later if I have issues.

Words of wisdom….

The hardest thing for me to do was carefully taking everything off the engine. I didn’t want to break any bolts,housing & casings. I followed the FSA very closely.
Cleaning 310,000KM’s of grim is nasty! Dealing with the original gaskets was a pain.
Invest is a parts cleaner or a large bin and solvent (diesel works as well)
Invest in a high quality gasket scraper. I hear the Loc-Tite gasket remove works but I could not find any in my area.
Invest in a high quality, low scale torque wrench.
Label EVERYTHING as soon as it comes off. Put it in baggies and bins right away!

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Joined
Dec 13, 2010
Messages
129
Location
Langley BC
Part Four

I won’t lie, the start up was nerve racking and I felt a little ill. I think my biggest concerns was if it was timed right.
Took a bit a purge the injection system. We cranked it a bit to get the oil pressure up... then finally tried to start it. It immediately sprung to life!

Now that is all done it wasn’t as hard of a job as I thought it would be. There are a few key things you have to pay attention on plus be slow and methodical.
It seems to be running great. Just some minor house keeping items to deal with… mostly small coolest leaks. I needed up getting new hose clamps.
I’m at stock boost and it seems to go as good as it did before when I was running more boost.

Here is a video of the swap and reinstalling the rebuilt engine back in and starting it up for the first time.

Hope you enjoy the write up…. If I can do I, so can you!

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Joined
Jul 22, 2003
Messages
18,604
Location
Perth Western Australia
Great write up.
But I suspect your engine had far higher klms than 270000. Mine was like new at 314000 and it had been used for towing horses around to equestrian events.
Anyway, you have a lot of klms in front of you. Good effort on the rebuild. Slow and methodical is the key.
 
Joined
Dec 13, 2010
Messages
129
Location
Langley BC
Thank you!

The engine had 320,000Km's on it and if it was for the head gasket issue I think it would have survived another 100,000KM's with no issues. It was still making good power and not smoking. Since it was all apart and I planned to keep it for a while I decided to just spend to money and have it refreshed.

I also don't know how the previous owner treated the engine. Being in Canada the winters can be a bit hard on them with no block heater.
 
Joined
May 15, 2005
Messages
9,163
Location
Ladysmith
Well done. After all this Covid crap be nice to see it finished and running. My engine is pushing the
400,000 km mark and I’m running a GTurbo now. So like you I’m thinking of a pre-emptive rebuild
before failure of anything. But I will contact you at that time for some tips. I also have a box of
Coleman stoves.
 
Joined
Jul 2, 2021
Messages
13
Location
Brisbane
Hi all, awesome post and just was I was looking for haha. Seems it all went very well for you and i'm glad it's firing well, it'll love you for it i'm sure!

I'm looking to replace pistons in my 12ht 390k with suspected blow by. It's the mechanics today for a compression test and will see what the results are. I would love to rebuild myself, (very handy with the tools and have done all other work to date) but don't want to take on something I can't complete. Any idea on the level of work, skillset, tools, processes involved and if a home garage job would be out of the question? Do you have access to a clean workshop, full tools etc? I'm trying to save dollars but also really enjoy getting stuck in myself.

I know a full rebuild is best but my idea is preemtive check and replace of pistons and rings, not a full rebuild and give a general once over as the engine runs well otherwise. I've been looking at Engines Australia as well so i'll hit them up as i'm chasing the Alfin inserts, seems the only option anyway. If i'm just replacing pistons, can this be done with the engine in situ or does it have to be pulled to remove pistons and rods etc?

FYI i'm getting injectors serviced, turbo overhauled and i'll fit an intercooler so trying to make sure other things are good first.

My main concern is the fear of worn cylinders from busted rings and seems the only way to check is to strip and replace anyway, correct?

Cheers for any help.
 
Joined
Sep 30, 2014
Messages
537
Honestly it’s not that difficult to do yourself. Take lots of photos along the way, have the factory service manual and you’ll need a couple of specialist tools but you’ll save a lot of labour costs. Plus if you’ve stripped most of it down and got stuck there are shops/members on here who can help you through the tricky parts for a relatively small cost.
 
Joined
Dec 13, 2010
Messages
129
Location
Langley BC
Glad you like my thread. I was in the same dilemma.

With 390KM's of wear, I think your bores will be out of round and in-between sizes where even if you installed stock size pistons, I'm not sure how long it will last before you will get blowby again. Your thrust end play will be out of tolerance as well.

Even if you just decide to install new piston and rings, you would want to replace the bearings as well... if you are going that far, I'd pull the engine and do it right and replace all the gaskets/seals and install new parts like I did.

I did everything in a single car garage and in my driveway. Picked dry/good days to pull and install.
You will need a engine hoist and a engine stand. I'd make sure your engine stand is beefy. 1500lbs is about right especially when you start reefing on things.

Tools:
- Extra large breaker bar,
- Metric sockets and wrenches,
- High quality gear puller. Don't get a cheap one. Pulling the crank gear was a chore. Took me all evening to get that one gear off and I broke the puller 3 times. I ended up modifying the puller to be stronger.
- Torque wrench (Small/Medium size (10-75ftlbs) and a extra large (+350ftlbs) for the crank pulley,
- Good gasket scraper (I used a "push/pull" Snap-on one)
- Large rubber bin to wash parts. (Diesel works good)

Take pictures and label everything in baggies and bins.
Talk to the engine shop before you do anything. Set some expectations for both of you.
FSM is your friend. The one found online pretty much listed everything I needed. Re-read every step before do it.

Not a hard engine to put back together. The hardest parts are cleaning old gaskets and timing.

The only real issue I had was installing the oil pan. It's a two step process. You need to make sure you have enough gasket compound and everything is ready to go!
(I ran out 3/4 of the way through! doh!)

I hope that helps?

Mike
 
Joined
Jul 2, 2021
Messages
13
Location
Brisbane
Glad you like my thread. I was in the same dilemma.

With 390KM's of wear, I think your bores will be out of round and in-between sizes where even if you installed stock size pistons, I'm not sure how long it will last before you will get blowby again. Your thrust end play will be out of tolerance as well.

Even if you just decide to install new piston and rings, you would want to replace the bearings as well... if you are going that far, I'd pull the engine and do it right and replace all the gaskets/seals and install new parts like I did.

I did everything in a single car garage and in my driveway. Picked dry/good days to pull and install.
You will need a engine hoist and a engine stand. I'd make sure your engine stand is beefy. 1500lbs is about right especially when you start reefing on things.

Tools:
- Extra large breaker bar,
- Metric sockets and wrenches,
- High quality gear puller. Don't get a cheap one. Pulling the crank gear was a chore. Took me all evening to get that one gear off and I broke the puller 3 times. I ended up modifying the puller to be stronger.
- Torque wrench (Small/Medium size (10-75ftlbs) and a extra large (+350ftlbs) for the crank pulley,
- Good gasket scraper (I used a "push/pull" Snap-on one)
- Large rubber bin to wash parts. (Diesel works good)

Take pictures and label everything in baggies and bins.
Talk to the engine shop before you do anything. Set some expectations for both of you.
FSM is your friend. The one found online pretty much listed everything I needed. Re-read every step before do it.

Not a hard engine to put back together. The hardest parts are cleaning old gaskets and timing.

The only real issue I had was installing the oil pan. It's a two step process. You need to make sure you have enough gasket compound and everything is ready to go!
(I ran out 3/4 of the way through! doh!)

I hope that helps?

Mike
Thanks everyone and especially Mike for the very thorough breakdown of expectations and info, especially the point of out of round bores!
As mentioned, i'd love to do this process but making the call to do it right and do it once seems key.
I've just got it in to MTQ engines here in Brisbane for the injector servicing and had a compression test with all cylinders running well so at this stage i'll be leaving it be and reassess in the future. FYI results are:
1=380, 2=360, 3=360, 4=390, 5=380, 6=400
The workshop called to let me know and after letting them know i'm only keen for genuine parts and ideally overhauling the exact injectors and ensuring they don't just swap out or replace with inferior parts, they've assured me they'll be swapped with already reconditioned genuine parts.
I haven't had it dyno'd pre injectors but i'll update once it's running but moreso once i've installed the new PDI HJ61 intercooler and GTurbo Grunter.

Thanks again for the advice, it's all helped me to understand the full process and i'm sure i'll be referring to this when the full rebuild occurs.
Cheers
 

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