1KZTE - What's the first sign head is toast?

[OM617YOTA]

~174k km's on mine. Using a couple tablespoons of coolant per week and can hear bubbles moving through the heater core. The bubbles seem to get particularly bad after a sustained high speed run. Darned if I can find any external leaks. I don't see bubbles in the radiator when running, it's not milkshaking the oil.

Been running a diesel fuel additive with potassium in it, so UOA may not show anything meaningful. Maybe an exhaust sniffer in the radiator outlet.

Current plan is to keep driving it, keep topping up coolant, and wait till it's bad enough to be definitive.

Any other ideas?

What's the current best head and gasket kit for a 1KZTE? Not looking for power, just reliability. Don't have to worry about this again.

 

[TheBussman]

you can do a block test, but a negative result does not for sure mean that it's good. A lot of times they will pass when testing in park but only leak under load. oil analysis is one of my favorite ways to test for slight leaks. what year is your 1kz? The early ones have more issues i think?

 

[OM617YOTA]

you can do a block test, but a negative result does not for sure mean that it's good. A lot of times they will pass when testing in park but only leak under load. oil analysis is one of my favorite ways to test for slight leaks. what year is your 1kz? The early ones have more issues i think?

Thanks for the input.

Not familiar with a block test, what is that? Mine's a '96, worst candidate. I was kind of hoping it had already been done before coming over from Japan.

 

[TheBussman]

Thanks for the input.

Not familiar with a block test, what is that? Mine's a '96, worst candidate. I was kind of hoping it had already been done before coming over from Japan.

it's tool with a blue chemical in it that connects to your radiator filler, if the fluid changes color it confirms exhaust gas present. 1/2 of the slightly failed heads/gaskets I use it on pass though.

 

[BiffS]

Easiest thing to do is put a radiator pressure tester on and check the pressures. A normal pressure will be 5-7 PSI if lukewarm or even somewhat hot. IF it shoots over 13PSI or more when you rev it: bad headgasket, and 95% chance bad head. We've done tonnes of these in Hiaces and they've all been cracked. Most of the time they go 17-25 PSI right away, indicating the combustion pressure in the head.

We've also had a couple cracked blocks around the back side of #3 and #4 cylinder too. Have. good look and dye/ pressure test the block and watch for that.

 

[Dougal]

If it's a 1996 then just order a new head. It was only in the 2000's that they stopped cracking.

 

[OM617YOTA]

Thank you both.

Easiest thing to do is put a radiator pressure tester on and check the pressures. A normal pressure will be 5-7 PSI if lukewarm or even somewhat hot. IF it shoots over 13PSI or more when you rev it: bad headgasket, and 95% chance bad head. We've done tonnes of these in Hiaces and they've all been cracked. Most of the time they go 17-25 PSI right away, indicating the combustion pressure in the head.

We've also had a couple cracked blocks around the back side of #3 and #4 cylinder too. Have. good look and dye/ pressure test the block and watch for that.

I don't think it's building any more pressure in the cooling system than it should, but time to get a tester.

If it's a 1996 then just order a new head. It was only in the 2000's that they stopped cracking.

I got it at ~134k km, any chance it was done in Japan before it came over?

Any recommendations on best head and gasket set?

 

[BiffS]

I have two Hiaces with under 100k km in the shop right now with cracked heads.it doesn't take a lot, unfortunately..we've done 4 this year alone.

Reach out to my partner at Hiyota Parts and he can get you what you need, tariffs prepaid.

 

[OM617YOTA]

Thank you.

Is doing the head generally a one-time thing? Do it right once and good for the rest of the life of the vehicle?

 

[BiffS]

Thank you.

Is doing the head generally a one-time thing? Do it right once and good for the rest of the life of the vehicle?

Typically for an owner who maintains it.

So the cooling fan upgrade to 10 blade. Clutch fan upgrade, EGR delete, good exhaust and you're set.

 

[OM617YOTA]

Typically for an owner who maintains it.

So the cooling fan upgrade to 10 blade. Clutch fan upgrade, EGR delete, good exhaust and you're set.

That's really good news.

I've never had it overheat or even get warm, even in the warmest temps we get here. Are those upgrades really necessary? Although I've also recently learned that the factory temp gauge is intentionally inaccurate, so maybe I actually have no clue how warm it's gotten. Adding my own accurate temp gauge is definitely on the list.

EGR is already gone and I added a manual boost controller to bump up boost, and didn't add any more fuel. Just a couple more PSI dropped EGTs significantly. No clue why it's tuned so hot from the factory. Maybe that bought me more time, maybe that made the head fail sooner.

 

[Dougal]

Thank you.

Is doing the head generally a one-time thing? Do it right once and good for the rest of the life of the vehicle?

Here in NZ we are full of used JDM imports. All the 2LT and 1KZ owners I knew who replaced a head never had to do it again. I think the head design improved but also they didn't keep them another 15 years.

IMO the other upgrades aren't needed unless you're running them hard all the time. If you're running them hard you have the wrong engine anyway.

 

[OM617YOTA]

Here in NZ we are full of used JDM imports. All the 2LT and 1KZ owners I knew who replaced a head never had to do it again. I think the head design improved but also they didn't keep them another 15 years.

Great. New vehicles are utter garbage and I do plan to keep this another 15 years, so maybe we'll see.

IMO the other upgrades aren't needed unless you're running them hard all the time.

Got it, I'll get a proper temperature gauge installed and go from there. I do expect it to run reliably and keep the AC blowing cold when commuting at 40c ambient temps.

If you're running them hard you have the wrong engine anyway.

Agreed there, not a hard use engine. This is my daily driver commuter, it will get the occasional crawl up a logging road and light(600kg) towing, but I have a truck for real truck type things.

Thanks folks. I'll keep an eye on this and reach out to Hiyota Parts.