1KZ-TE Overheating (1 Viewer)

[dawsonmarch]

Good day gents,

My mechanical prowess has been humbled by a hot 1KZ for over a year now, I need some IH8MUD wisdom

Here's the deal
Symptoms

• 1994 Hilux Surf 1KZ-TE non intercooled, little over a year ago I replaced the cracked cylinder head.
• Pre Turbo EGTs happily climb over 700 C on long hillclimbs. When I let off the gas temps spike further to 900ish for ~10 seconds. Not super confident that the sensor is telling the truth, but it is decent quality and displays consistent behaviour, although the behaviour is consistently weird. Temp Probably is real, but could be fake
• coolant eeeaasily will go over 105 C on long hillclimbs chugging along at 60-80 km/hr. I stop at this point to cool her.
• Engine starts 2nd crank every time, no evidence of low compression. Doesn't roll coal, no evidence of running rich.
• Fuel economy is decent, ~ 11L/ 100km

Cooling maintenance done:

1. Refurbished OEM radiator. Looks brand new.
2. New aftermarket cylinder head/ head gasket / studs
3. EXT Tranny cooler
4. New OEM coolant pump
5. New OEM thermostat
6. EGR delete
7. Intake gunk cleaned
8. Resistor mod
9. Boost T running max boost before Fuel cut
10. Injectors rebuilt by professional diesel shop
11. Viscous hub rebuilt
12. new glow plugs

I've got a couple desperate ideas to try, but I'm struggling to come up with a reason for why it is overheating so bad that doesn't seem highly improbable. I know the engine is notorious for running hot, but I also know guys with Bone stock 1kzs that pass me on those hills towing trailers, so I think something has to be fundamentally wrong here.

Any input is greatly appreciated.

 

[veiloctane]

even though it's a new OEM thermostat. Is it a possibility it could be bad have you tested it with boiling water?
how about the radiator cap? it's easy to miss the small things.

Does pressure test the radiator and cooling system?

How's the air flow? do you have a winch or a large bull bar blocking airflow?
do you know the AFR fuel ratio? are you too lean or too rich on fuel?

are you making lots of smoke? what color is it under full load?

 

[dawsonmarch]

even though it's a new OEM thermostat. Is it a possibility it could be bad have you tested it with boiling water?
how about the radiator cap? it's easy to miss the small things.

Does pressure test the radiator and cooling system?

How's the air flow? do you have a winch or a large bull bar blocking airflow?
do you know the AFR fuel ratio? are you too lean or too rich on fuel?

are you making lots of smoke? what color is it under full load?

Haven't tested the thermostat, that was my next item. It doesn't explain the EGTs but its probably my main suspicion for the coolant temps. I'll check the rad cap, although the coolant in overflow tank maintains fairly constant level and no air pockets form in the coolant system so I think it would be fine. I have not pressure tested the coolant system, but theres no leaks so.

Airflow through the rad should be ok, there was nothing aftermarket restricting it until I installed an external tranny cooler that sits in front, however it was overheating before I installed the cooler and I didn't notice much difference in coolant temps after installing it.

I don't know the AFR, I might try turning the fuel down a bit on the injection pump in case it is running rich, however I've never seen smoke (aside from a puff on startup) even under full load (although I'll get someone else to drive by giving her the beans to check)

Thanks mate

 

[-MaTTi-]

Cracked cylinder head. My condolences.

 

[veiloctane]

Cracked cylinder head. My condolences.

that is a possibility, he needs to do some testing to be 100% sure
leakdown test
compression test
block tester


good luck!

 

[dawsonmarch]

Cracked cylinder head. My condolences.

that is a possibility, he needs to do some testing to be 100% sure
leakdown test
compression test
block tester


good luck!

Tbh I wouldn't be surprised based on the bull**** I went through with the company I bought it from, although there aren't really any dead giveaway symptoms of a cracked head it seems to me. The coolant looks good, no contamination, doesn't bubble or lose fluid. Not too sure what else to look for, and not sure why a cracked head would cause high EGTs, or coolant overheating in my case (I thought the reason engines with cracked heads would overheat is because the engine consumes coolant). Although the engine does have a fair amount of blowby, just barely not enough to knock the oil cap off if I unscrew it. I'll run a compression test and see what it give me.

Rant : I was a broke student and wanted to save a grand to not buy an OEM cylinder head, but I figured going with a trusted local JDM shop that deals heavily in Hiluxes would be a good bet, and the head still cost 1000$ so it still wasn't a cheapy chinese head. Well, it shouldn't have been. 1st head came, had metal shavings all over it. They told me clean it up and chuck it on. I did, and the truck didn't start. Took me a while to learn the lesson that you can't trust parts just because they were brand new, because the reason the engine wouldn't start is because the cylinder head had leaky valve seats and couldn't make the compression to fire. I told them this and they barely believed me, telling me that the valves "didn't need to seal 100% because things move so fast in there". ****ing tools. Second head came, big scratch in the head mating surface, shavings everywhere again, and leaky valve seats. THIRD head came and the ****ing camshaft would barely turn, turns out it was because the camshaft was warped. Every step of the way these ***** blamed me, saying that it was perfect when it left their shop and insinuating that I keep destroying their heads. In the end I took all 3 heads to a machine shop and had them mix and match parts to get a good head, although I am stuck with the cheap chinese cast head that I'm sure they used and claimed to be high quality. Icing on the cake, I sent them the 2 garbage heads back and they accused me of using an angle grinder on the valve bucket shims, which had some micro scratches that couldn't even be felt with your fingers, which of course came to me in that condition, and they received in the same condition. Angle grinders don't scratch. They cut. **** those guys. Never again, buy nice or pay twice.

 

[veiloctane]

Could be just a poor head gasket job.

 

[-MaTTi-]

I found that the intake channels (or exhaust?, I don’t remember) was smaller in my chinese 1KZ head. It lasted only few months/7000 km before I changed it again, OEM that time.

 

[4runnermods]

Check the vacuum lines too.

 

[bj70bc]

head gasket seems likely, check the overflow for slow but constant bubbles

 

[Drennooo]

Cracked cylinder head is possible. Super common fault here.
Not all OEM thermostats for the 1kz are the same. Here in Aussie we commonly run 71Celsius thermostats. Still a 1kz toyota thermostat but not the official ones for the 1kz models sold here(as far as Im aware anyway). I think the official ones might be 82 or 88 or something. These make a pretty big difference. I can dig out the toyota part number if you like.

You said you rebuilt the viscous hub. How much oil did you use?

When you go to climb a steep hill and you plant your foot does the car bog right down? How many kms on engine?

 

[Jdub94]

Tbh I wouldn't be surprised based on the bulls*** I went through with the company I bought it from, although there aren't really any dead giveaway symptoms of a cracked head it seems to me. The coolant looks good, no contamination, doesn't bubble or lose fluid. Not too sure what else to look for, and not sure why a cracked head would cause high EGTs, or coolant overheating in my case (I thought the reason engines with cracked heads would overheat is because the engine consumes coolant). Although the engine does have a fair amount of blowby, just barely not enough to knock the oil cap off if I unscrew it. I'll run a compression test and see what it give me.

Rant : I was a broke student and wanted to save a grand to not buy an OEM cylinder head, but I figured going with a trusted local JDM shop that deals heavily in Hiluxes would be a good bet, and the head still cost 1000$ so it still wasn't a cheapy chinese head. Well, it shouldn't have been. 1st head came, had metal shavings all over it. They told me clean it up and chuck it on. I did, and the truck didn't start. Took me a while to learn the lesson that you can't trust parts just because they were brand new, because the reason the engine wouldn't start is because the cylinder head had leaky valve seats and couldn't make the compression to fire. I told them this and they barely believed me, telling me that the valves "didn't need to seal 100% because things move so fast in there". f***ing tools. Second head came, big scratch in the head mating surface, shavings everywhere again, and leaky valve seats. THIRD head came and the f***ing camshaft would barely turn, turns out it was because the camshaft was warped. Every step of the way these ***** blamed me, saying that it was perfect when it left their shop and insinuating that I keep destroying their heads. In the end I took all 3 heads to a machine shop and had them mix and match parts to get a good head, although I am stuck with the cheap chinese cast head that I'm sure they used and claimed to be high quality. Icing on the cake, I sent them the 2 garbage heads back and they accused me of using an angle grinder on the valve bucket shims, which had some micro scratches that couldn't even be felt with your fingers, which of course came to me in that condition, and they received in the same condition. Angle grinders don't scratch. They cut. f*** those guys. Never again, buy nice or pay twice.

Any luck on finding your culprit?

 

[dawsonmarch]

I found that the intake channels (or exhaust?, I don’t remember) was smaller in my chinese 1KZ head. It lasted only few months/7000 km before I changed it again, OEM that time.

Hmm I don't have my oem cylinder head anymore but I think I would have checked that when I did the job (i hope). No bubbles and cooling system holds pressure so seems like its still kicking. Been about 7000 kms, and I'm about to do a 4000km road trip so we'll see how she goes lol

 

[dawsonmarch]

Any luck on finding your culprit?

Not really. I turned down the fuel with the screw a little bit and it seems to have helped EGTs and maybe coolant temps a little bit. Now it can handle pretty much everything I've come across without breaching 100C except for one massive hill on a highway near my house. A couple kilometres long of decently steep grade, I have to chug up quite slow and heaters blasting and it will hold around 100C, but if I leaned on the gas at all it would shoot up. Usually take a break halfway up that hill.

My only remaining theories are that because I have quite a bit of blow by (enough to rattle the oil cap a lot when unscrewed, but not fall off with the threads down. If I flip it so it's resting upside down on it's flat side it will fall off) maybe the engine has poor efficiency and has to work really hard without putting out a ton of power, leading to overheating. Or maybe my auto trans is s*** and very inefficient. Or maybe when I got my rad re-cored it's not as good as stock, which I doubt because its a pretty good job. I'm pretty confident the head isn't cracked (yet) because it held pressure on a coolant system test, and no bubbling or coolant consumption whatsoever.

At this point I've done literally everything in the coolant system except for upgrading the rad. For now I'll live with it, but I think that upgrading may be the only real fix.

 

[Jdub94]

Not really. I turned down the fuel with the screw a little bit and it seems to have helped EGTs and maybe coolant temps a little bit. Now it can handle pretty much everything I've come across without breaching 100C except for one massive hill on a highway near my house. A couple kilometres long of decently steep grade, I have to chug up quite slow and heaters blasting and it will hold around 100C, but if I leaned on the gas at all it would shoot up. Usually take a break halfway up that hill.

My only remaining theories are that because I have quite a bit of blow by (enough to rattle the oil cap a lot when unscrewed, but not fall off with the threads down. If I flip it so it's resting upside down on it's flat side it will fall off) maybe the engine has poor efficiency and has to work really hard without putting out a ton of power, leading to overheating. Or maybe my auto trans is s*** and very inefficient. Or maybe when I got my rad re-cored it's not as good as stock, which I doubt because its a pretty good job. I'm pretty confident the head isn't cracked (yet) because it held pressure on a coolant system test, and no bubbling or coolant consumption whatsoever.

At this point I've done literally everything in the coolant system except for upgrading the rad. For now I'll live with it, but I think that upgrading may be the only real fix.

Gotcha. Thanks for the reply. I think I run pretty rich, as well, but I think it has something to do with the injectors getting old. I get some rough starts if it sits awhile before clearing up after about 5 seconds and sometimes lets out a nice diesel puff. Doing intake manifold gaskets, egr delete, and gonne go ahead and swap glow plugs and injectors out for safe measure. Gonna try to clean up intake manifold as best I can, and hopefully valves aren't too bad but we'll see. I ran some HotShots treatment through the fuel and that definitely knocked out some crap already, but I can only imagine there's more.

I also have blowby but I got quoted $7500 USD for a rebuild and I'm just not ready to spend that kind of money, so hoping this stuff will keep me goin for a good while before anything major is needed.

 

[dawsonmarch]

Gotcha. Thanks for the reply. I think I run pretty rich, as well, but I think it has something to do with the injectors getting old. I get some rough starts if it sits awhile before clearing up after about 5 seconds and sometimes lets out a nice diesel puff. Doing intake manifold gaskets, egr delete, and gonne go ahead and swap glow plugs and injectors out for safe measure. Gonna try to clean up intake manifold as best I can, and hopefully valves aren't too bad but we'll see. I ran some HotShots treatment through the fuel and that definitely knocked out some crap already, but I can only imagine there's more.

I also have blowby but I got quoted $7500 USD for a rebuild and I'm just not ready to spend that kind of money, so hoping this stuff will keep me goin for a good while before anything major is needed.

I get a diesel puff every startup but goes 2nd crank and idles nicely. Injector rebuild/replace is always a good call, I did mine for peace of mind. From what I've been told these old diesels all get a fair amount of blow and its not really an issue. I'm gonna keep rocking it until it becomes one. $7500 is pretty high though, I bet if you sourced your own parts and did it yourself you could keep it under $2K

 

[Jdub94]

I get a diesel puff every startup but goes 2nd crank and idles nicely. Injector rebuild/replace is always a good call, I did mine for peace of mind. From what I've been told these old diesels all get a fair amount of blow and its not really an issue. I'm gonna keep rocking it until it becomes one. $7500 is pretty high though, I bet if you sourced your own parts and did it yourself you could keep it under $2K

Well... injector replacements might wait. I was under the impression that it would be $300 for the whole OEM set, but that's just for one injector! I see a few Chinese brands where it's $200 for a set of 4 but obviously that makes me nervous

 

[lowcountryfungi]

Well... injector replacements might wait. I was under the impression that it would be $300 for the whole OEM set, but that's just for one injector! I see a few Chinese brands where it's $200 for a set of 4 but obviously that makes me nervous

It's best to have your OEM injectors rebuilt than buy aftermarket, should be $100-150/injector to be rebuilt but they will be good as new.

 

[lowcountryfungi]

I get a diesel puff every startup but goes 2nd crank and idles nicely. Injector rebuild/replace is always a good call, I did mine for peace of mind. From what I've been told these old diesels all get a fair amount of blow and its not really an issue. I'm gonna keep rocking it until it becomes one. $7500 is pretty high though, I bet if you sourced your own parts and did it yourself you could keep it under $2K

Have you replaced your radiator cap yet? Those fail and can cause your coolant to creep up in temps. Also like someone else mentioned could be a bad head gasket install.

 

[Jdub94]

It's best to have your OEM injectors rebuilt than buy aftermarket, should be $100-150/injector to be rebuilt but they will be good as new.

Good to know! I had seen some folks talk about this but wasn't sure what the cost is