1988 HJ61 12ht Rebuild (1 Viewer)

[maddog632]

Hey everyone,
I am going to be rebuilding my 12ht soon and was wondering if anyone can give me some pointers of what to expect.
I have heard Alfin pistons are a must.
I am also going to be fitting a intercooler when the motor goes back in the car and want to know whether to go front or top mount.
Also upgrades to turbo.
Thanks.

 

[Silveredition]

Engines Aus rebuild kit, front mount intercooler, GTurbo and a HD clutch (if manual)...
I am going to purchase a HPD intercooler as I tried the diy EBay one, but it wasn’t right, so I sold it..

 

[maddog632]

Did you do the work yourself?

 

[Silveredition]

I haven’t done any of it yet - but that is the plan... it will be intercooler before rebuild (unless something silly happens). It (1988 hj61 5 speed manual) has only done 586000kms, so will hopefully be a long way into the future....

 

[maddog632]

Oh ok. I read the other day that the 12ht had a problem with the top piston ring wearing out its seat. The post said it could happen as young as 350000 even sooner if it is a jap import (which mine is). I might just be freaking out haha. Last thing I want is for it to die on me.
I've never had to look at mine mechanically just the normal servicing. But recently its losing power and not running right.
I'm looking at getting it checked out by HPD or another diesel shop in Adelaide.

 

[Silveredition]

All of my info above was due to me freaking out thinking I had to do a rebuild immediately to prevent the top ring snapping and going through the engine before it went at 350000kms...(I was at about 500000 when I read about it...)
Get it checked out, and rebuild if you want / if necessary - otherwise just drive it!!!

 

[maddog632]

Ok thanks heaps mate. I’ll let you know how I go.

 

[Freewheel]

My top ring land went at 325,000 km on piston #5. The other pistons and every thing else were in really good condition at that mileage so a proper rebuild was pretty easy. New valve guides, and everything machined nicely to do first oversize pistons.
The items important to me were Alfin pistons, an OEM Toyota head gasket and a careful replacement of all the frost plugs, including the weird one on the water cooling plate on the side of the block.

Easy to check to see whether your rings are eating into the pistons. Compression check!

Interestingly- in my truck, a wet test only raised the compression by 40 PSI, so a wet test is not necessarily a good indication of determining whether its a valve or ring land problem. We figured it was a valve issue, and didn't verify it was the ring lands until the engine was apart.
Do number 5 first- it seems to be the one that anecdotal evidence says fails most often- but check all of them anyway, cause it can happen to any of them.

The other obvious clue that you may have a ring land issue is a lot of white smoke on startup, and you're able to verify that your glow system is working fine.

 

[maddog632]

Thanks Freewheel.
I’m going to be doing a compression test sometime this week. But I have a feeling it’s not good.