Seeking Advice on KZJ70 (1KZ-TE) Head Replacement: Should I Stick With It?

[rubensan]

Hi everyone,

I could really use some advice. I’m currently in the process of replacing the cylinder head on my KZJ70 with a non-OEM head. Upon opening the engine, I discovered that this isn’t the first time it’s been worked on—the head that cracked wasn’t the original one either.

The engine is the original 1KZ-TE, with 300k km, maintenance every 10k but the previous owner seems to have tried to push some extra power on it.

Along with the replacement, I’m also having the engine block resurfaced to ensure the head gasket seals properly and prevent any future leaks. I’m committed to getting the job done right, but some people have been warning me that, because the engine has already been opened before, I’m likely to encounter more problems down the road.

I’m relatively new to 4x4s, and this is my first one. I really love this model, but I’m starting to wonder if I’m setting myself up for ongoing headaches with this engine. If replacing the head compromises the reliability of this otherwise well-regarded engine, I’d rather cut my losses now and look for another model or 4x4.

The truth is, I paid a lot for this KZJ70, and in hindsight, I might not have made the wisest decision with this purchase. But here I am, trying to make the best of the situation.

So, my main question is: Does replacing the head (especially with a non-original part) significantly reduce the reliability of this engine? Or should I keep going with the repairs and stick with it? I’d really appreciate any advice from those with more experience!

Thanks in advance for any guidance!

 

[Shayne]

An oversize exhaust starting direct from the turbo is my theory as to why i never worried about a blown head and my kzj90 has been well tested doing 90+ mph towing a trailer all day long .

 

[Gr8Yota]

I had the head replaced on my KZJ70. But I had an OE head. When this was done an intercooler was made and fitted on advice of Maarten at All-American whom I regard a Toyota guru. there was never another issue with the engine.

 

[Tel Boy]

Relax, don't panic. Your truck is a great vehicle which will reward you well if taken care of, which it sounds like you are doing. It's not the most comfortable or quietest on the road but when it gets off road it really comes alive, you won't find much better.

I have a KZJ70, but with the mechanical 1KZ-T. Many people have written about cracking heads on these and other Toyotas and I have done a lot of reading online to find out what to do about this known problem. Some knowledgeable people believe that all indirect injection diesels are prone to cracking heads when they have turbos fitted. It doesn't happen to everybody, not to me, for example (yet!) and I have thrashed the truck mercilessly in long drags in very soft sand in the Sahara and have pushed it hard when towing. The answer is to take real care of the cooling system and watch the temps.

Good advice from Shayne and Gr8Yota above. I have an intercooler fitted, there's plenty of room in front of the rad. I would love to fit a 3" dump pipe also but haven't got round to that yet, though I have bought the turbo flange. Best thing is to ignore the useless OEM temp gauge and fit a decent aftermarket one and fit an EGT gauge also. And pay attention to them.

There are some really useful threads on this site and on Mud. Have a trawl around. Here are a couple to start you off

Cooling the 1KZ-TE motor:

Evenin' All. As many of you will know, I use my 1998 KZJ95 UK-spec Colorado for towing a double horse trailer. When I bought it, I expected the 3.0 litre 1KZ-TE turbo diesel to be well up to the job of pulling around two tons with four or five occupants plus equipment. The reality has been...

www.landcruiserclub.net

Tuning and Understanding your Toyota Viscous Fan Clutch

Landcruiser or Hilux overheating? Your factory fan clutch is probably under-filled and incorrectly set from factory. Fix this first and you may save a lot of time chasing issues. (4 Runner or Tacom…

neuralfibre.com

Anyway, the bottom line is you have now got a brilliant truck and putting a new head on the engine is NOT a mistake, it's the start of a wonderful relationship. Have fun.

 

[extraease]

Hi everyone,

I could really use some advice. I’m currently in the process of replacing the cylinder head on my KZJ70 with a non-OEM head. Upon opening the engine, I discovered that this isn’t the first time it’s been worked on—the head that cracked wasn’t the original one either.

The engine is the original 1KZ-TE, with 300k km, maintenance every 10k but the previous owner seems to have tried to push some extra power on it.

Along with the replacement, I’m also having the engine block resurfaced to ensure the head gasket seals properly and prevent any future leaks. I’m committed to getting the job done right, but some people have been warning me that, because the engine has already been opened before, I’m likely to encounter more problems down the road.

I’m relatively new to 4x4s, and this is my first one. I really love this model, but I’m starting to wonder if I’m setting myself up for ongoing headaches with this engine. If replacing the head compromises the reliability of this otherwise well-regarded engine, I’d rather cut my losses now and look for another model or 4x4.

The truth is, I paid a lot for this KZJ70, and in hindsight, I might not have made the wisest decision with this purchase. But here I am, trying to make the best of the situation.

So, my main question is: Does replacing the head (especially with a non-original part) significantly reduce the reliability of this engine? Or should I keep going with the repairs and stick with it? I’d really appreciate any advice from those with more experience!

Thanks in advance for any guidance!

I replaced the the head on my 1996 kzj 70 about 8 years ago with a non oem head and all has been good. I also replaced the radiator and water pump as I suspect the engine overheated and the radiator was original. I suspect that may have cracked the head.
At the time the mechanic checked the engine. The big end and piston rings bores ect. were fine. It is a farm vehicle, pulls a sheep trailer and has worked well since. It is great to drive has not cost me much to maintain otherwise. It of course has a bit of rust which needs to be dealt with but nothing too problematic. I get it serviced once a year and ask the mechanic to spend some time checking it out for any problems. This allows me to plan, order parts ect. for any issues well in advance. It is a twenty eight year old vehicle that has worked hard and needs the appropriate maintenance.
Best of luck, whatever you choose to do.

 

[Aeroelastic]

The KZ-TE is a robust and strong engine comparing to other manufacturers - in Toyota world, it's not on top of the list as you have other far more legendary diesel like the 1HDT or 1HZ. And I would say aftermarket head isn't necessarily not good, it's down keeping the kz te cooling system on a tip top condition. You can have a search in the 90 series forum area and there are alot of discussions about this. One thread by Bob Murphy is probably the one to read if you haven't. As pointed out by Tel Boy above https://www.landcruiserclub.net/community/threads/cooling-the-1kz-te-motor.130304/
And Shayne is also spot on about getting bigger exhaust- keep EGT down.
From online forums etc. A lot of people put the aftermarket AMC head in when they replace the kz te head. It's a Spainish company I think, and they have strengthen the coolant galleries within the head where the Toyota OE seems to crack - not enough thickness due to needing to incorporate the pre combustion chamber within the head - indirect injection. The AMC head has a lot of good reviews. And in the UK, Roughtrax carries them. You can buy them fully assembled or only Barehead and reuse your Cam shaft and valves but will need someone knows what they are doing to swap over. https://www.roughtrax4x4.com/toyota-4x4-parts/engine-parts/cylinder-head.htm

The block of the kz te are pretty strong. Especially if you said the truck has been well maintained.