Modifying the troublesome slow Thermostat

Hello! I am new here    Just bought a 1998 Toyota HiAce Super Custom G 3.0 L Diesel Auto (3 speed w O/D) KZH100 with 180,000km on the clock. I assume it has the 1KZ-TE engine.

It seems the temperature gauge on these is pretty much useless - a 'dead zone' on the middle of the gauge prevents the temperature gauge from moving up until the system reaches ~110C at which point it can be too late... To avoid blowing the head on the motor I'd like to either modify the thermostat to be more responsive, as per the modification listed in the Toyota Surf forum (sorry I apparently can't post links yet, as I am new here).

Does anyone know if the resistor mod can be performed on a 1998 Super Custom? I assume it will be the same as the one used in the Toyota Surf?? Has anyone done this mod on their Super Custom?

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Some background -

I should have done some better research before buying the van but it seems that the 1KZ-TE engine inside my van can be prone to developing a cracked head... I had a bit of a scare as I got my van home (bought and collected it from interstate) and found that there was a good 3 litres of coolant missing...    I feared a cracked head, but everything seems to be running well after a coolant flush and top up... Pressure tested the cooling system and it seems good, but there may be a slight coolant leak in the rear heating heater core (coolant smell in rear heater aircon) need to work out where that is. I had (stupidly) assumed it was a variation on the 2.8 L diesel used in the Australian HiAce (which do an insane number of kms).

Anyhow... The engine drives great, the turbo really adds some extra grunt and the the moonroof / sunroofs are awesome as we plan on turning this into a camper van    I assume that if I don't let the engine overheat I shouldn't end up with a cracked head and should hopefully be able to get it to 300,000km...?????

Hi Brierly89,

welcome from a fellow SC owner in Adelaide. I own a 1994 3.0L diesel SC van with the 1KZ-TE engine. I also bought the van for use as a camper.

When I bought my SC van, the first thing I did was to change the coolant and flush the system. After I had done that, the coolant levels kept dropping. The leak was traced back to the drain plug from the main radiator. I replaced the drain plug and the problem ceased.

I recently drained the coolant and replaced it. The same problem with the drain plug arose, so it was simply replaced.

Recently also had a problem with the water pump leaking, so I had that replaced along with the timing belt as that was due for replacement.

In regards to the temperature gauge issue, I had in mind to replace the sensor as it may have some residue on it preventing it from giving a proper reading. However I was unable to remove the old one .

I ended up buying an aftermarket sensor that I bolted onto the housing near where the coolant runs into the engine from the radiator.

Website is here   http://enginewatchdog.com/tm2.html

During the cooler months the temperature sits on about 76C unless I go up a major hill like Belair Road or the SE Freeway. During the warmer months, the temp sits on around 80C on the flat. Going up a hill does cause it to rise significantly and approach 100C. I have set the alarm to 95C. Not sure whether that is too low, but I want to prevent a cracked head at all costs.

When the alarm goes off, I pull over, evict the passenger (called an evacuation ), pull up the seat and let the engine cool down with it running, for about 5 minutes or so. I usually leave it until the temp has dropped below 80C. With 37C forecast on Christmas Eve, I think an evacuation is definitely likely on the way to my parent's place   .

I think that the main problem of overheating is the lack of airflow onto the radiators in a van compared to that of a conventional car with a bonnet. My Toyota 4runner never overheated in 13 years of ownership.

Sorry about the long-winded posting, but I hope it is of some help.

By the way, Merry Christmas to all    

Werner

Hi Wener,

Thanks of the reply! Good to hear of someone else in Adelaide with a Super Custom I live in the Adelaide Hills so there are plenty of hills to drive up... I wonder if this is going to be an issue owning one of these... I came across the ENGINE WATCHDOG TM2 and thought of it as an alternative to the modified thermostat gauge. Is it easy to install? Looks like it just reads the outside housing - could be a good solution.

I really appreciate the info! It's good to know what sort of temperatures to expect... I am a little nervous about the fact that yours reaches 100C going up Belair Road or the SE Freeway... Yikes!

Hi Brierly,

my van's engine only heads towards 100C in the hotter weather. During winter, the temp may reach up to 90C.

The engine watchdog TM2 was easy to install, just remove a bolt where you want to put the sensor, place the sensor in place and put the bolt back in place.

There's a few SC owners around Adelaide. Saw one a few weeks ago in the local shopping centre.

regards,

Werner

Hey man that's good to hear. Although today it's 37C and I plan on driving the van up the SE freeway and doing some missioning around the hills! I'll take her easy.

Awesome I'll definitely get a TM1 or TM2 - could save my ass... or my vans ass....

I wonder if fitting a larger exhaust will help alleviate the problem? I've heard they can help lower fuel consumption too.

How have you set yours up as a camper? I'm planning on removing all but the middle double seat and building a bed frame with a sliding part of the frame to make room for the seats when not spun backwards. I imagine most of the time I'll have all the seats out 👍 Sorry... a bit off topic there...

Oh and I actually saw another Super Custom parked in a driveway on my way down to the rego office today =)

I think it would be good to place a second (digital) temperature gauge + sensor next to the original one.
But where are you connecting it? If you are doing that in the tubing to the radiator, it is okay until your thermostat is not opening fully (so not working correctly).

Next to that, I don't see you guys talking about the viscous fan coupling. That is very important.
Do you hear the fan kicking in?
And you can modify it to kick in earlier. There are some threads on Hilux / 4Runner forums about that.

You could also put in a thermostat which opens earlier, but that may give you issues in the colder days. The engine needs to get to full working temperature in winter as well.

I'm not sure if 100 degrees Celcius is directly an issue, but you don't want to go over that.

The radiator should get enough air, but that also depends on how the visco fan is working.

Hi Hiace4wd. Thanks for the info. The vicious fan: is that the one above the main radiator? I don't hear it 'kick in', but I do recall seeing it spinning while I had the 'hood' open to bleed the coolant. How do I know what to listen for? Maybe I should go for a drive with the 'hood' open?

Hmm. I'll have to go hunting for that info! Getting it to come on earlier would be good.

Regarding the sensor I was thinking of getting a TM1 or TM2 (as linked above - sorry I can't paste links yet) which reads the metal temp instead of coolant temp - simply for ease of install. I was thinking of mounting the sensor to here (not my engine in the pic, mine is a little grubbier!):



Is that a bad spot? Am I better off getting a digital read out of the coolant temp instead? That would be beyond me and require the skills of my mechanic I believe.

Hi Brierly,

I think I put my sensor where that rusty bolt above the radiator cap is. I've never really heard any fan kick in as the fan is spinning all the time anyway. The temperature seems to pause a bit at around the 90C mark, so I guess that might be when the thermostat opens(?). I did speak to a mechanic about lowering the thermostat opening temp, but he said it was better not to.

Btw, the alarm came on briefly at the sharp bend on Belair Road last night but went off again before we got to Windy Point LO, so I just kept going and it stayed around the 93-94C mark and it stayed there until we got to the top when it cooled down.

Re the camper, I removed the centre seat and left in the rear (to enable me to take my parents for a drive when we're not camping). I put in a drawer I had made for a Subaru, then Toyota 4runner. I put a flat piece of timber over the top of the drawer, slide the rear seat as far forward as it will go, tilt it down as far as it will go and put a mattress over the top of that. I fill out any voids under the mattress with pillows and old bedsheets. Reasonably comfortable. I think there may be some photos of my setup on this forum, probably in the "show us yours" section. May show up on a search.

regards,

Werner

Hi Werner,

Thanks for the info. I think that spot you are talking about is where the block has it's ground wire run to the chassis. I guess if yours is working well it's okay to put it there. =) I may opt for a water temp season, still deciding.

I already have to spend a good bit on some repairs so am going to add the sensor later. I have been noticing the temp needle sits just above half when going up hills, but on hotter days it starts to climb... I've only had it up to 2/3, but assume that isn't a good thing! Haven't lost a drop of coolant or had any other issues, but I just need to be careful for now.

Found those photos of your camper setup, cheers for pointing me in that direction.



Still tossing up between