Cooling the 1KZ-TE in the Hiace Super Custom

LH119V wrote:

Tremendous post and hugely detailed. I just came here looking for some coolant details but will pour through this when I've got a bit more time.

Just a small thing I've noticed is that it seems the thermostat on the 3L and 1KZ engines operate at quite different temps: https://www.hiacesoutheast.com/store/cooling-system. Interesting

Yes, I can understand this - is the 3L higher?
The thermostat on the outlet works properly, so that will be set to the correct temperature required.
The mid mounted thermostat fad was always dodgy: to reduce the issues they simply lowered the opening temperature.
Of course the Hiace van layout doesn't help the margin of max heat.

But whenever I blame Toyota of following this disastrous fad, I think back to Porsches 996 and 997 engines, which I suspect on average cost Porsche 2 engines for each 911, because apparently even Porsche was too inflexible to simply fix the design flaw.
Their Boxsters were detuned and so survived much better, which is what I think helped save most 1kz engines (heads), a big conservative diesel will always last longer

Incredible write up and referenced frequently.

Do these steps and parts still stand? Any new discoveries or developments in the process?

nagrom7 wrote:

Incredible write up and referenced frequently.

Do these steps and parts still stand? Any new discoveries or developments in the process?

Hi!

Thanks! Yes, it's been working very well.
The landrover engineers who invented the system (to cure the similarly afflicted K-Series engine) knew what they were doing!

The trick is in the gentle 'thermostatic mixer shower' treat of perfect temperature coolant that the engine receives. I.e. robbed of the usual (let the coolant out when it's too hot' exit thermostat method, they invented the even better 'circulate all the time, via the mixer' system.

Probably more economical too as

1. Higher temperatures are now possible, as the temperature is very stable
2. The water pump is always pumping a free system - no restrictions.

@GPW

Where did your source your 35-32-35 T fitting? I've been all over the internet and haven't been able to find one.

I'm trying to avoid having one fabricated as that's usually much more expensive than off the shelf.

Hi!

I bought mine on eBay here, searching for aluminium swaged T seems to turn some up, apologies I can't find the original order.

https://www.ebay.co.uk/itm/193045080350?var=493237424785&hash=item2cf262291e:g:4xoAAOSwWNNdryiC&amdata=enc%3AAQAHAAAA4FOT31zBp2aafuJk2PAcoEL87GbhTChX0rqYdYOV32hVkPXHKQUx33b%2B4LgtfUQqTMSKcRtnVtxoZ4O7t8IUN%2B4fw1DJiasa6II1OyQztuKROLTXDKhKRJGyg1xvflEVEJyA0z62lmIRmR8Lh05wMXPt52xHYJHst46OwREnRM2xH6ZFJSwv4mK2pQrzwj%2FPu%2FtqI3vcRgCSGRmqrWuTnamyWJsoCFupOgWCMQdbnQepQGmaWDZ4zMZG9L52AkoZ9M7PZT23bbFmGYB3m04pxUeA4g7j%2BlH4Iekl6UleFdTI%7Ctkp%3ABk9SR6jJ3aHZYA

and

https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p3671980.m570.l1313&_nkw=Aluminium+T+Piece+Pipe+Connector+-+3+Way+Alloy+Joiner+for+Silicone+%26+Rubber+Hose&_sacat=0

It's the custom intercooler and cooling market, but you can also use a shim if you need to, i.e. if you can find only a 32mm equal Tee, ir a 35mm equal Tee, then you may have to use short pipe to fill the gap, or bore size adapters.

I did spend quite a long time looking, but probably just to run down availability + price.

With supply chains as they are, not always easy. Incidentally, the silicone parts - when I bought them I turned up, expecting a big bin of the parts, and they said 'Oh we haven't make it yet, can you turn up tomorrow?', which reveales that you can probably make them yourself, I suspect there is a youtube video. They really are just wrapped bandages of reinforcing, laid up with heat proof silicone, so if you are really stuck, consider asking for (or making!) a custom pipe with the correct length and ends.

Cheers!

Yeah, I've been searching all the turbo and coolant fittings with every term under the sun. Still haven't found an exact match. Looks like the UK has a much better market for these types of things, unfortunately shipping is too much.

Also I'd like to avoid all the couplers and reducers that would be required to use something that's not 100% correct.

I'm just going to have one fabricated. I've ordered the tubing, and will cut and prep everything myself so the welder just has to stick them together. Shouldn't take them more than 15 minutes.

I didn't find any in the UK this time, but back then, yes!
Making your own seems to be a good idea, find a TIG welder place and they'll do a nice job.

Maybe make it from swaged connectors, as you'll want the swaged ends to stop the pipes wanting to pop off

Yeah, I'm going to have them roll a bead on each of the ends.

@ GPW

Is this what you mean by a swept bend that fills an 18cm square?  

Ganbatte wrote:

@ GPW

Is this what you mean by a swept bend that fills an 18cm square?  

Hi! Yes, except the actual radius is not so important (just so the fluid can flow freely, so nothing sharp).
The key is to make sure the tube ends some 18-20cm away from where it started, so that it clears the crank pulley, before the 45 degree connector to the thermostat is attached.

I.e.

So if you rolled it so one end was upright, it would be 18-20cm off the floor.

Ah, ok. Thank you for the clarification. By 'swept bend' I though you meant constant radius like I pictured, which I'm having a hard time finding off the shelf.

So a 90 degree bend with 18cm legs. Much easier to find!

Just a heads up to anyone else considering this mod, your radiator fittings may not be the same size as those listed in GPW's write up. My van is a 1996 KZH-106W MRPGT (1KZ, 4WD, dual radiators) and the vertical radiator inlet and outlet are 38mm while GPW's are 35mm. No harm as I haven't purchased my silicone hoses yet. Luckily I decided to take some measurements and caught the difference.

@GPW does your van have 2 radiators, or is that just on the 4WD versions?

Hello.

I have a 4WD variant and it only has a single radiator, the upright one.

I wrote a long piece on cooling on my 'show us yours' page. I need to update this as I have the heater matrix back and have done a load of other fettling.

As far as I can tell it's the auto 4WD variants that have the upright radiators and another one that sits horizontally as part of the A/C ‘sandwich’. On mine the horizontal sandwich is just A/C. Possibly the reason for the second radiator on auto variants is due to the auto trans cooler that’s built into the main upright radiator, I think.

If I had an auto I’d very strongly consider installing a separate auto cooler, like most vehicles now have. I think cooling the trans into the engine radiator has many potential flaws. First among these is probably poor cooling but also modes of failure are likely to introduce ATF into the coolant (bad but not catastrophic) and possibly also coolant into the trans (also bad and probably catastrophic).

The only positive of the OEM setup is probably elevated speed of warm up to operating temperature but that wouldn’t warrant the arrangement as is in my opinion.

The 1-KZ have a lower thermostat temp than the 3L.

HTH!

Ok, so here is the 4WD version of this modification.  For reference my van is a 1996 KZH106W.  

4WD vans have a different front cross member and, naturally, a front axle.  Both are very much in the way making it far too tight of a fit to route the bypass between the vacuum pump and crank pulley as GPW did with his 2WD van.  After a lot of head scratching my solution was to relocate the coolant overflow reservoir and run the bypass down along the outside of the fan shroud, passing below the font axle, and then up into the bypass inlet of the thermostat.  

In order to do this I needed a few things:

- Additional 32mm 90 degree silicone elbow
- Additional 32mm aluminum straight coupler
- 32mm silicone heater hose for the bypass rather than standard radiator hose (much thinner walled and better bending radius)
- Modification of the T pipe to angle the bypass branch slightly forward and inward
- A piece of the bottom radiator hose (I cut and mixed pieces of the top and bottom hose to position the bypass T at an angle that didn't place loads on the fitting connections)
- A longer tube for the overflow reservoir

Here is the T pipe.  I fabricated all the components and then had a local shop weld it together for me.  You can see the way the 32mm bypass branch angles forwards towards the radiator and slightly inwards towards the engine.






Here it is installed, viewed from above.  The bypass hose passes through the space that the coolant overflow reservoir used to occupy.  In the center of the second picture you can see where I put a p-clip on the front differential cover to secure the hose at the bottom of the fan shroud.  The thinner walled and more flexible silicone hose allowed me to make bends that would have placed a lot of stress on the fittings using thicker radiator hose.  The plastic end caps on our old radiators can become brittle as they age, so I wanted to avoid placing unnecessary load on the radiator inlet.





From the bottom of the bypass tube I connected the aluminum 90 degree elbow to make the run below and behind the axle, then into the 90 degree silicone elbow, then the 45 degree silicone elbow (via the 32mm aluminum straight coupler), and finally into the bypass inlet on the thermostat.  I may add an additional p clip or brace the hose in some other way where it passes by the axle, but it seems ok for now.



I've put about 600 miles on it now and it works very well.  I have an aftermarket water temp gauge installed with the sensor in the outlet from the head right next to the OEM sender.  Once fully warm water temperature stabilizes at 185F and never goes lower.  There are no big swings in temperature associated with the thermostat opening and closing.  I was able to get the temperature as high as 205F climbing steep grades, maintaining 12 psi boost and 1200F egt for several minutes at a time.  Keep in mind this is all in below freezing temperatures.  I'll have to wait till summer to see how it does in hot weather.

regarding the overflow reservoir, it currently lives in the front passenger foot well.  I ran the tube into the cabin via the plastic wiring harness conduit that enters just below and in front of the front passenger seat, but this location is only temporary.  I modified the access panel above the transmission bell housing to make some additional space for a catch can, and eventually an air/water intercooler.  At some point I'll get around to fabricating a bracket for the reservoir and it can go back there as well.

Anyone know where I can order a new radiator for my hiace? Mine has a bad hole and overheating. Thanks

Hello Wesley1997hiace and welcome to the forum.

I had a similar issue on my ~’92 and I chose to get the OE, and likely original, radiator re-cored. You can read about the experience in my ‘show us yours’ section. The cooling thread is about half way down the first page and is just after the pictures of the rear drums.

It seems that the US does have more parts availability for things like radiators and also more specialist and aftermarket suppliers for Toyotas in general, than here. The Timmy the Toolman YT vids often show aftermarket parts and the companies he suggests would be my first port of call for a replacement if going away from OE.

There’s also a fairly long first post on the ‘suy’ page for parts etc. It might also help you with resources.

The radiator is a fairly tight fit in a Hiace. I think they can be removed below in 2WD but have to be lifted out in 4WD models. Quite a lot of stuff has to come out to lift out the radiator but it’s not that hard. Removing enough stuff will also make getting the replacement / re-cored back in without damage. It might also be wise to do any ‘front-of-engine’ servicing (timing belt and water pump) at the same time. What about fan??

Finally if the radiator has a bad hole it’s likely that the whole of the cooling system might benefit from a decent flush. My post might also help there.

HTH!!

Also, I have a manual but I think the autos have an internal transcooler in the upright radiator. If I had this I’d fit an external transcooler instead.

Some models seemingly have an additional flat radiator, I think. On my van this is just part of the A/C. The model variants are fairly well described in the EPC (see the post at the top of my ‘suy’ section).

More food for thought...