Cooling the 1KZ-TE motor:

[BobMurphy]

Are you sure that your description of the flow on the KZ-TE is correct? (I don't know the answer but it would be worth confirming while theorising over the problem and possible solutions)

Hmmmmm. No, I don't know for certain that my diagrams are correct, but:

1. The water Pump is a centrifugal pump that turns clockwise from the front. The vanes propel the coolant towards their outer tips, creating a low pressure area in the centre (i.e. suction).
The 'snail shell' design of the pump housing means that the pressurised coolant only has one exit - to the N/S of the block.

2. The question is - when the thermostat opens, which way does the coolant flow ??
Towards the front of the block, just a few inches away, is the suction side of the water pump and the connecting gallery looks quite large. Above it is a large hole allowing the coolant to pass between the block and the head.

I can't see the hot water flooding out of the lower radiator hose and the cooled water dropping down into the head and block without there being some restriction to the flow between the last link to the cylinder head and the suction side of the pump. Maybe there is something in the pump housing that I'm not seeing that causes this to happen.

The proof would be to remove the thermostat and see whether the bottom radiator hose gets hotter than the top hose.
If this was to happen it would still look wrong to me as the coldest part of the motor (bottom of the block) would still be controlling the coolant flow to the hottest part - the head.

When I bought my car the paint had been blistered off the bonnet (I haven't fixed that yet) It just proves that heat rises.
Normally, hot coolant is fed to the top of a radiator as it will stay up there, being less-dense than colder fluid, meaning that it decends through the matrix in a controlled manner, being cooled as it goes. If hot coolant was put in at the bottom it would try to rise to the top and a thermo-syphon would be set up in the radiator, meaning the hot stuff would reach the top and go back into the motor before it had cooled properly.

I'd love to be proved wrong as having the thermostat in the cold water flow makes no sense to me, so maybe it does go out the lower hose after all

Bob.

 

[Nuclear Chicken]

All a bit of a conundrum. Looks like what I said earlier about Toyo cocking up big time was off the mark. anyway, your conclusion about the pump type is 100%. The thing is, most manufacturers of anything involving pumps generally want the pumped fluid on the delivery side of the pump, i.e. under pressure, as much as possible for several reasons not least of which is reducing the risk of cavitation where gas bubbles form at areas of extremely low and violent pressure and these bubbles can cause physical damage. The fact is, there is a point at which in the engine system the positive discharge pressure of the pump gradually turns into a suction pressure point, where there is neither positve nor suction and this is the neutral point. Ideally and in theory this is as close to to the fluid entry point as possible. I'm still leaning towards the fact that the pump may not have enough grunt for the job in hand for at least part of the problem. However, as Bob rightly says, if the thermostat doesn't see enough hot water soon enough it won't react and the thing can overheat, period. But, cooling systems are simple enough in principle, and, if the thermostat opens against the hot water the pump should have enough grunt to get the water round the system regardless of where the thermostat is. Sounds also a bit like the thermostat is not ideally located in these motors as Bob's logic suggests. Is there any possibility that there is short circuiting occuring, by which I mean that the water is literally being circulating within all or a part of the engine but with little or none getting to the radiator? Under small loads there may be enough but when the load and the produced heat increase, this 'leakage' may not be enough and hence the overheat. Is is possible to 'plumb' these engines improperly (after a rebuild etc etc for example) or is it just a major Toyo cock-up in that there is some form of short circuiting by design? The theoretical solution is to add resistance in the short circuit and force water when you want it to go but in reality this may be trickier to achieve. Just a final thought is there any possibility at all that the thermostat is trying to open against the flow of water, i.e. that the pump is almost forcing it closed again? In other words, is the 'stat back to front?

 

[BobMurphy]

My diagrams are based on my supposition about how the coolant flows around the head and block and may therefore be wholly wrong

For instance, I have assumed that fluid passing the thermostat goes from the rear of the block to the front in this direction . . .

And then appears in the centre of the water pump housing, here . . . .

What I haven't done is poke something along the passage to see if the two are actually connected (mainly because I didn't remove the thermostat when I changed the water pump, or remove the water pump when I changed the thermostat ).


It may be that the two openings are not connected and fluid passing the thermostat actually has to go up into the head (yellow) and the water pump only sucks fluid from the head (red) like this . . .

If this is true, it would mean that when the thermostat opens, water is encouraged to flow into the bottom hose of the radiator, meaning the flow is the opposite of what I expect (akin to getting water to flow uphill, which doesn't sound right to me).

Has anyone got a Toyota Workshop Manual that shows the coolant flow ??? I would love to see what Toyota intended to happen


If the thermostat was inserted the other way around, its 'business end' would be permanently in the cold fluid at the bottom of the radiator and would never open (quite apart from the fact that I don't think it would fit in the cover). I can't see that being right.


More thoughts please folks


Bob.

 

[BobMurphy]

Well, an interesting development . . . .

There I was, happily working away in the garden when my younger daughter drove up.

"Mums been trying to phone you, a horse has been injured up at the stables and she's wondering if you'll take it to 'The Bush' (Edinburgh University Large Animal Teaching Hospital at Roslin)".

Great, nothing I like better than towing an injured horse around Edinburgh at 17:00hrs on a weekday .

so, up to the stables (8 miles) with the empty Horse Trailer (a little over a ton) - Coolant was fine and there was a hint of warmth in the bottom hose.

Got the horse loaded and took it up into the Pentland hills to Roslin. That's a fair climb, but the temp gauge stayed normal and when we arrived the overflow bottle was normal and the bottom hose was almost warm. I had the cabin heater on and had left the sump guard off temporarily as I want to do an oil change.

The horse (14 year-old Thoroughbred cross Clydesdale) was put on the weighbridge - 614 Kilos. So, with the trailer and all the usual stuff one has to have in the trailer when towing livestock an all-up trailer weight of around 1.7 tons - and it was fine.

The horse is to be kept in for a week, so the trailer was empty on the return. I turned the cabin heater off and kept it at a steady 60 on the M8. If anything, it ran cooler, with the temp needle just a little lower than normal. I guess having the cabin heater off raises the temp in the block and the thermostat then opens.

This morning, after its had all night to cool down, everything if fine. The radiator is brim full and the coolant in the overflow bottle has dropped slightly. I expected there to be some air in the system so was anticipating that.

All looking good then. Maybe the 76 deg thermostat was the right choice - or was it using gasket cement with the genuine Toyota gasket

I have to take one of our horses to Roslin next Tuesday for a check-up and then I'm launching a 4-berth sailing cruiser for a neighbour (about 2.5 tons on the road) on Saturday 16th. I'll report back on progress.


Bob.

 

[Nuclear Chicken]

 

[Cabman]

 

[BlackWidow]

Very interesting read,

Here is the bummer though I have changed the thermostat on mine and has made no difference, but I have the very same symptoms. I can not remember the raiting though so will take it back out and check.

Like you I am confused as to why the thermostat is on the cold side of the rad and you are correct with the coolant flow (or at least for all other engines that I have worked on). It start at the coldest part of the engine (the bottom) and works its way up colecting heat from the engine as it goes. On all other engine the top is where you would expect to find the thermostat so when the coolants reaches the thermostats tempreture it opens allowing the coolant to flow through from the bottom thus regulating the temp eficiantly.

However having said all that mine has been fine up until recently (179000 miles) so Mr. T must of got it correct and that there is somthing wrong with ours/mine.

I think that I will go see my local Toyota techy and see if there is a solution both from this country and South Affrica.

Is yours now ok?

Steve.

 

[BobMurphy]

Is yours now ok?
Steve.

It seems to be OK now.

However, as we have posted elsewhere, the viscous hub on the cooling fan may well be the culprit as it runs out of silicone oil and stops cutting in when it detects the radiator getting hot.

My one problem with that theory is that the thermostat would have to be open for the radiator to get hot enough for the viscous fan to wake-up.

GAH ! . . Will it ever work



Bob.

 

[johnkzn185]

hello from down under. sorry to bring up an old thread, but i wanted to know how your 1kzte cooling is going bob?
have you had any more issues?

i have a 1kzte in a kzn185 surf, and though i've only had 1 overheat on a soft sandy beach so far (havn't had the car long and it's 1 to many times for my liking!). i wish to upgrade my cooling system to work the bestit can as i do a lot of slow beach/off road activities.
i have read through your thread and am thinking of doing a thermostat relocation on mine. i did it on a diahatsu HD-E engine with good results useing a toyota carolla remote thermostat housing (same one as i wish to use on my 1kzte).
though from research i will have to block off the bypass hole in the block where the original thermostat was for this to work. i was thinking of gutting the old thermostat and useing it with the rearsection extended to permantly block the bypass hole.

do you see any problems that might occur if i do this modification? i mean the only reason for the bypass port behind the thermostat is to heat the engine quicker, but if the thermostat is working correctly the engine has to come to temp before the thermostat will open. maybe just a little slower.

 

[BobMurphy]

hello from down under. sorry to bring up an old thread, but i wanted to know how your 1kzte cooling is going bob?

John,

Since I carried out the work on the motor (Thermostat, Radiator, Radiator cap, Water Pump, New fan on the pump, Viscous Fan top-up) I haven't had any further problems.

I do a lot of horse-towing and the temp gauge doesn't go above half-way. Running on the level the gauge is slightly below the half-way mark, which is what one would expect with a 76 deg thermostat. The level in the coolant overflow bottle is normal, as in it gets to a bit over half-way when hot, then drops back to the low mark when cold.

I couldn't swear that the viscous fan is working though. I haven't noticed the fan roar when the motor is hot and suspect that the shaft is sticking and the bi-metallic strip isn't able to turn it - all that Scottish road salt again .

However . . We have had a cool wet Summer with temperatures around 16 deg C so the system hasn't been stressed.

I still think that the problem with these motors is that sudden changes in load (i.e. going up a hill) cause the top of the motor to get very hot before the bottom has noticed and opens the thermostat. It will be very interesting to see how one performs with the thermostat re-located to the top (it would have to be a higher-rated one, of course, around 88 deg C seems the norm).

As for the by-pass valve at the back of the standard thermostat . . If you are putting a new 'stat at the top, I would trim the main valve off the standard thermostat and leave it in situ. The core will then continue to open & close - working the by-pass valve - whilst not affecting the flow through the radiator much. The main spring bears on the back of the valve so maybe some large holes drilled in the valve plate would suffice.

Let us know how you get on with your modification - particularly if you are adding an accurate temp gauge to the set-up as well.

Bob.

 

[johnkzn185]

hi bob,
thanks for the reply.

yea i intend to put a aftermarket temp guage with the sender mounted into the top oulet pipe off the head.

so you think it's worth keeping the bypass system working? the reason i wish to delete this system is to get all flow through the radiator. who know's if the rear block-off plate on the thermostat is closeing this port 100% when the engine is up to temp. if there is still a certain amount of recirculation this is what could be causeing the drama's when the engine is under load. yeah it can get cold down here in winter (i'm on the south east coast of WA), but i doubt we really need the engine to pre heat that quick when a working thermostat will make the coolant heat to temp before flow is allowed.

i was going to be playing with this on the w-end, but my new radiator turned up damaged so now i have to wait 1-2 weeks for another one. i will let you know of my progress.

thanks.

 

[wobbly]

I would def check the working of the viscuous fan as well, quite a long running thread from a guy with a petrol auto with constant overheating, replaced everything, finally turned out to be the viscuous fan wasnt viscuous anymore.

Will try and find it so you can see the symptoms.

Pete

 

[BobMurphy]

So you think it's worth keeping the bypass system working?

Just fear of the unknown really - I don't pretend to be an all-knowing expert on these engines and I don't know what would happen if the by-pass valve was permanently blocked.

On the face of it you would get the bulk of circulation through the radiator - but only when the thermostat at the top has opened. Prior to that there might be some circulation through the turbo and the cabin heater but the water pump isn't going to be doing much (will it complain or cavitate ??).

Personally, I would do one radical change at a time and see how it goes, starting with the thermostat at the top and the original one perforated to allow constant water flow. Changing the lower 'stat for some blocking mechanism can be done later without affecting anything else.

Bob.

 

[roy90]

hi guys,
i too had an overheating issue recently (2months ago) i have the jeep 8 months and all was great, used it towing my offroader and horseboxes and no problems. then i put a set of 33" tyres and heavy steel wheels on and the very next day cruising up the motorway the temp guage started to creep, no leaks or boiling as i kept a sharp eye on it over the following 2-3weeks but it would regularly creep until i put the internal heater on and eased off the power! i cured the problem by replacing the thermo with a 76degree one, new top and bottom rad pipes, new water pump, new rad and full coolant flush. all is tickity boo now, even pushing on up hills she doesnt go past half way!
Can anyone teel me how to definately test the viscous fan? when it was at its overheating i waited untill it was properly hot and swithched it off and straight away tried to turn the fan and it would spin free enough. i also tried stuffing in a rooled up paper slowly when running and it would slowly bring it to a stop....??

 

[AndyCook]

the only time i have heard the fan engage and its "roar" is on steep and long climbs in Pyrenees and Alps, and once in Scotland on the Belach na Ba on road over to Applecross - which is steep and long.

 

[ModelMakerMan]

Fit an electric fan and a thermo switch. Youll get a little more power from the engine as it doesn’t have the drag of the fan any more, you can tell if its definitely working and in my experience its much more reliable.

 

[wobbly]

Ok, so its from the other place, but it does highlight the viscuous fan issue:

http://www.tlocuk.co.uk/forums/viewtopi ... sc&start=0

Pete

 

[Bounder]

Just a word of warning, don't trust the stock temp gauge, Toyota fit a resistor to stop it moving around, when it starts to move the coolant is already very hot.

 

[Roger Fairclough]

Just picked up on this thread.

From the Toyota manual for the 1KZ-T engine.

Starting from the top of the rad., water drops down, exits into the water pump via. the thermostat and is then past into the block via. the oil heater/cooler. Then into the head and out and into the top of the rad. The cabin heater comes off the head and back into the block. The turbo charger is cooled from the block.

The thermostat opening temperatures are between 80-84 deg.C. Valve lift is 8mm. min. This is a relatively low temp. which goes with it's position on the engine inlet position.

On my KZJ-70, I have replaced the standard thermostat with a slightly higher rated one. Can't remember the opening temps. but probably another 4-5 deg. C. The viscous fan has been junked, replaced by a 16" Kenlowe, mounted in front of the rad. The fan is controlled by a therm switch mounted in the top engine outlet pipe.

In normal driving, the fan does not come on. Even town driving does not activate it. Temp gauge remains stable at the normal mark. Engine attains normal temp. in approx. 2 km.

Engine has done 153,000 miles, approx 130,000 miles in the condition described. It doesn't use water or oil.

Roger

 

[BobMurphy]

In normal driving, the fan does not come on. Even town driving does not activate it. Temp gauge remains stable at the normal mark. Engine attains normal temp. in approx. 2 km.

I had a Kenlowe Fan on my Series III Landrover. It had a rheostat that allowed me to set the temp at which it was triggered - do you have the same ??

Have you experimented with the settings ?? The standard temp gauge is notoriously inaccurate / slow to respond and it would be interesting to know what the temp at the top of the block really is when in town traffic on a hot day.

Of course, it has to be balanced with the thermostat - there is no point in blowing air through the radiator if the thermostat hasn't opened - regardless of the temp at the top of the motor.

I am curious about your use of a higher-temp thermostat as that is contrary to what some of us have done (assuming its still at the bottom of the block). I would expect the temp gauge to be showing a slightly higher than normal reading - so why isn't it doing that ?? Back to the heavily 'resisted' gauge I suspect.

Interesting

Bob.