Cooling the 1KZ-TE motor:

[johnkzn185]

Yea I have no egr, upgraded radiator from a later model Prado, upgraded to 10 blade fan from another model hilux, blocked off the lower bypass and moved thermostat to the top hose. Also run a rather large trans cooler.
Thing ran like a dream temperature wise. I could smash it all day in summer up and down the sand dunes and soft beaches. Tow my track car (~2.5 tonne) on a 1440km round trip sitting on the 100 kp/h speed limit all the way there and back and temp sat stable, would maybe get to 90 degrees pushing up a hill.

When I had a 71 degree stat up top the damn thing wouldn't even get to 80 degrees, too cold for a diesel I was told, so I put a 82 degree one in.

I know my cooling system works well. Am not too happy that now my engine is on the shed floor though! haha

 

[Shayne]

Just chanced upon this while searching for an air intake temperature sensor with a matching plug to fit my intercooler . The following paragraph relates to forced induction but made me wonder if the AIT sensor might be a hidden gremlin in overheating issues .

Pressurizing the air is directly proportional to the AIT’s meaning the more boost you run, the higher the AIT’s are going to climb. To be fair though, the more boost your run the more air will be found in a given volume. What to look out for is that under higher boost situations you will get AIT’s that will get +50 over ambient and higher temperatures, which at that point the air is so warm that it becomes easier to ignite in the motor, and you may have to pull timing to avoid detonation in the motor. Also richening up the mixture with fuel can help cool the cylinder temps as well to avoid pre-ignitions conditions and help with higher EGT’s.

http://www.enginebasics.com/EFI%20Tuning/Air%20Intake%20Temp%20Tuning.html

 

[johnkzn185]

that's based on EFI petrol fueled cars.

 

[Shayne]

Yes but the EGR valve we all remove or blank is designed to reduce oxygen levels in the fuel air mix or so i believe . I would assume more oxygen means a bigger bang = more heat ?

Does the intake temp sensor also measure oxygen levels and tell the ECU to adjust fuel in order to keep combustion temperatures within the safe zone ? and if it does could a failure at that sensor result in overheat issues ?

I think Beau swapped his engine when he suffered a low mileage cracked head , its likely far to late now but it would be interesting to know the state of his EGR at the time , and if the engine was dumped at the back of a shed somewhere curiosity would have me pulling the sensor to have it tested .

 

[Rich Sims]

Unfortunatley thats the nature of the beast, more power more heat. But its how these engine get rid of the heat is the issue. These engine were designed 25 years ago and used in landcruisers, and even the first ones with 130bhp no electronics or EGR valves still overheated.

 

[Beau]

Yes but the EGR valve we all remove or blank is designed to reduce oxygen levels in the fuel air mix or so i believe . I would assume more oxygen means a bigger bang = more heat ?

Does the intake temp sensor also measure oxygen levels and tell the ECU to adjust fuel in order to keep combustion temperatures within the safe zone ? and if it does could a failure at that sensor result in overheat issues ?

I think Beau swapped his engine when he suffered a low mileage cracked head , its likely far to late now but it would be interesting to know the state of his EGR at the time , and if the engine was dumped at the back of a shed somewhere curiosity would have me pulling the sensor to have it tested .

In theory I've actually been through two engines already (On my third). First time was a cracked head which I didn't replace but a Jap specialist replaced. As it was still relatively new I didn't have the expertise to do the job myself!! But seeing as the engine only had about 70,000 miles when this occurred I would say the EGR system wasn't badly caked and either was the Intake. I was changing the oil every 3000 miles so it probably done the engine well..... The engine that went in was a low millage import engine (Without inter cooler unfortunately) and that took me up to about 160,000 miles without a problem, but had a slight oil leak and was down on power which is when I then rebuilt another low millage engine myself and did the swap.

I had the pleasure of inspecting this engine that did 160,000 miles which was standard other than tweaking the fuel for about the last 20,000 miles. EGR system was caked heavily. Intake had thick layers of hard carbon and suit everywhere. I would put this down entirely to the EGR system. They are one of the worse inventions on a engine in terms of engine durability and longevity. I blocked the EGR on the rebuilt engine so hopefully everything will stay super clean!

Shayne, if I was in the UK right now I would help you out with that sensor you want, I may actually have one, I'm not too sure....

"By feeding the lower oxygen exhaust gas into the intake, diesel EGR systems lower combustion temperature, reducing emissions of NOx. This makes combustion less efficient, compromising economy and power. The normally "dry" intake system of a diesel engine is now subject to fouling from soot, unburned fuel and oil in the EGR bleed, which has little effect on airflow, however, when combined with oil vapor from a PCV system, can cause buildup of sticky tar in the intake manifold and valves. It can also cause problems with components such as swirl flaps, where fitted. Diesel EGR also increases soot production, though this was masked in the US by the simultaneous introduction of diesel particulate filters.[SUP][9][/SUP] EGR systems can also add abrasive contaminants and increase engine oil acidity, which in turn can reduce engine longevity."

The more I look into this the more confused I get haha

 

[johnkzn185]

Yep, i removed the egr system on mine when i bought it, it had done about 205,000 kms. Never inspected the inlet manifold or anything. Engine now has about 248,000 kms on it and after pulling it down, my god! the cacked up crap in the inlet manifold and head from that bloody egr setup. discusting. The egr will be staying off.

 

[Ben]

Does the 1KZ-T have an ERG or is it just the 1KZ-TE?

 

[Shayne]

Here's another question - what activates gas re-circulation ? I'm thinking if its a purely mechanical process the exhaust is deliberately restrictive because the egr pipe is effectively a second exhaust about an inch in diameter that comes into play when certain pressures are reached . Pressure means heat and if your egr is blocked you have in effect narrowed your exhaust manifold .

Another interesting link which suggests the turbo is the weakest link when egr is blocked , i've yet to hear of a turbo failure on our engines so what's next in line to fail if the turbo is bulletproof ?

http://www.dogandlemon.com/articles/ownership-issues/general-egr-problems

 

[johnkzn185]

it's controlled by the ECU. the EGR has a vacuum operated diaphragm setup (similar to a wastegate) that when the ECU send the signal to a VSV it will make the diaphragm open or close.

 

[Sag]

Does the 1KZ-T have an ERG or is it just the 1KZ-TE?

Was just going to ask the same question.

 

[Rich Sims]

My 1kzt didnt on my kzj70. M reg

 

[Beau]

I don't think the 1KZT had the EGR systems but I'm not 100% sure. The EGR system was mainly implemented for emission control and laws in order to sell in certain countries across the world.

As above, it's operate under exhaust pressure that opens a valve that allows a certain amount of exhaust gases to recirculate back into the intake. If you look at your engine facing forward, it's at the left back side of the engine. You'll see a little diaphragm valve thing there with vacuum hoses connected to it. I'm not sure if the ECU has anything to do with it? I removed mine by blanking both inlet and outlet at the back of the head and it doesn't throw any error code so I'm assuming there is no ECU control.

Shayne, the reason I imagine people suggest turbo's failing through the use of the EGR system is that the EGR is putting more heat through the turbo system which creates more wear. I've not actually heard of a 1KZT turbo failure before in person so I don't think they're a fragile piece on these engines. And the weakest part on these engines as discussed is most likely the Head Gasket/Head due to excess heat. Bottom end seems pretty bullet proof. It's a shame really, it's a top notch engine, it just requires a bit of surgery and tweaking to improve it's durability. On the plus side, at least Toyota learnt there lesson and built a pretty bullet proof 1KD (Minus the early Injector seal issue haha)

 

[Shayne]

What's next in line was a Rhetorical question lol . I guess what i'm suggesting is the egr system on these motors might have been designed with a dual function , to my uneducated eyes it does look very much like a post turbo pressure release valve ? I know bugger all about it things like this just make me curious

 

[johnkzn185]

The EGR is ECU controlled. If you looked where the vacuum hoses went they would go to a VSV that it open/closed by the ECU.
Some people when trying a EGR delete just put a ball bearing into the vacuum line before the big valve so it cant see it's signal to open.

It does not serve as a post turbo pressure release. The EGR's purpose is what Beau posted eralier..

"By feeding the lower oxygen exhaust gas into the intake, diesel EGR systems lower combustion temperature, reducing emissions of NOx. This makes combustion less efficient, compromising economy and power. The normally "dry" intake system of a diesel engine is now subject to fouling from soot, unburned fuel and oil in the EGR bleed, which has little effect on airflow, however, when combined with oil vapor from a PCV system, can cause buildup of sticky tar in the intake manifold and valves. It can also cause problems with components such as swirl flaps, where fitted. Diesel EGR also increases soot production, though this was masked in the US by the simultaneous introduction of diesel particulate filters.[SUP][9][/SUP] EGR systems can also add abrasive contaminants and increase engine oil acidity, which in turn can reduce engine longevity."

 

[driver115]

The previous owner purchased the 3.0TD in 2004, 82000 miles and used it for towing a caravan - there followed a cylinder head replacement in 2005, at 90000 miles - after I purchased it from him at 119000 in 2010, one of the first preventative jobs to do was radiator replacement more so for the autobox /oil cooler problem.However, the previous owner had decided not to fit a thermostat ( and assumed at the time that this was the "unofficial" fix for when using the Colorado for towing as the head replacement had been done by his local Toyota dealer for the princely sum of £2000 ?), I had a new thermostat duly fitted, and as I do not tow have thus far experienced no cooling problems - its a pity that owners and enthusiasts have spent so much of their own cash and time with no apparent recourse back to Toyota ?

 

[mallster70]

hey guys, all this talk about gas flow and EGR valves etc etc etc, what can we take from this thread?

we know this engine is not the best designed in terms of the cooling layout within the engine. we know that the EGR valve can/maybe increases head temps.

did new engines, being driven away from the dealership have cooling issues? i would say no. its only after the putting on the many , many miles on the clock that these trucks are capable of, that we find out that these cooling issues exsist.

the question i have already asked in this thread previously was, is it down to the collective failure/under peformance of components which is causing the issue?

is it down to the void in front of the rad filling with crap in that blind spot between the air con condensor?...is it the over reliance on a near twenty year old thermostat which by all accounts at 88 deg probably opens a little too late?....is it down to the magical dissaperance of the silicone oil in the fan coupling?

like i said, we know the engines basic layout isnt good, but is it the case when these important cooling components start to work at 90% or less, is it the poor design which shows them up. and then when they fail, the temp gauge works far too slow to tell you damage is occuring.

i have gone for a 76 deg stat, blown out the rad really well and changed/replaced the silicone oil for a heavier weight in the fan. i monitored cooling fluid temps whilst towing near three tonnes over 60 mile trips. temps moving between 87 and 91 deg was normal under varying loads, only going up to 93 deg when faced with a two mile 20% gradient climb in third gear. no holding back, the truck worked hard and held a steady 50mph. A49 goers will know Dinmore Hill outside Hereford.

im no expert but just did a few bits suggested by you guys. my point is...is it the collective failure? we seem to all be looking for just the one reason.

cheers..

 

[Shayne]

i will be getting a new rad and a new fan before the Romania trip and would like to know more about the lower temp stat , where to get it , where it goes and is it just a simple swap ?

 

[Beau]

i will be getting a new rad and a new fan before the Romania trip and would like to know more about the lower temp stat , where to get it , where it goes and is it just a simple swap ?

If you want a better than standard rad, get a 3 core rad made up! Regarding the temp stat, you can pick it up from Toyota, you'll just need the part number! Simon on the forum can probably help you out with that plus he'll give you a discount too! It's a direct swap with the original one. If you locate the left side of the rad at the bottom, you'll see that hose leads to the thermostat inlet housing. Undo the housing and then the stat will be inside that. It's pretty simple. I'm not quite sure how much space there is to work with though....

In reply to Mallster, I agree with you to some extent. Like I said earlier on in this threat, my first head went at 70,000 miles and the cruiser had never been pushed or abused. I was babying it. On the other hand, I've seen people from africa with over half a million miles on the clock with the standard engine including head. I really can't explain certain things! Take a look at prado point, some of them really push these engines and haven't had any problems. Some on the other hand just have bad luck.

I think it's multiple design flaws that lead to this failure occurring and it all boils down to the top end getting too hot.

 

[Shayne]

I honestly don't think a better rad is nessesary Beau , I know now my truck is more powerful than a 1kd and the temperature gauge only climbs at 80mph . The rad doesn't even need replacing but it does need pulling and cleaning . In nearly 3 years of ownership I can only recall once pouring a mug of water into the coolant to bring it up to the full mark .

But this thread has made me think - why wait until there is a problem when the whole system can be made new for a couple of hundred quid when a failure in any part of it could prove catastrophic .

Might look at modifying the cowl somehow while I'm at it , would be nice if I could just slide it out to hose the rad next time I sink off-road .

on a side note I don't think the air con rad is a hindrance to cooling because it never gets hot , I view mine as a guard more than anything else .

Thanks for the tips on the stat I'm sure it will be pretty obvious when I pull the rad but there's nothing worse than starting a job then realising half way through you should have ordered something else .