Just got a toyota stat which is marked at 88 deg
Now I dont know if this is the temp when its fully open or that things start to happen - but let me recount this
Used multimeter with temp probe, resolution of +-3 deg
A pan of boiling water with stove full on
When pan boiling fully its reading 104 deg (with stove on full - so maybe there is radiant heat also)
If thermo lowered into water takes around 40 secs to fully open and same time to close when removed
Now when thermo in water around 70 deg and put on the hot stove nothing happens until 100 deg
When the pan is removed the thermo is sealed shut at 91 deg
Even allowing for +- 3 deg innacuracy - I wonder what people make of this?
Thinking the 40 sec delay may influence things I removed fom stove at 100 deg (just as starting to open) - it did not however continue to fully open but stopped less than half way
So I will be trying a non original stat out of interest
Yes, I do have much better things to do - but after reading all the cooling probs just thought I would try it - certainly wont be fitting it yet!
(The one on the van opens at around 72 deg when probe strapped to thermo housing on engine)
Though a toyota box the stat has the word kuzeh stamped on it
So am I missing something? Please enlighten me if I am
Chris
- (#8854) chris turner, 4 Jun 03 17:54
First, are you sure it's an 88c stat? What does the cd say about that part no? Sometimes markings are confusing.
Your meter/ thermocouple has an error of about 4c. (remember that resolution and accuracy aren't the same thing) Assuming you're neither atop Everest or in the base of the Grand Canyon, water boils at 100c.
re. the time constant, the thermostat's temp. is that at which it STARTS to open.
Heat slowly, watch for the valve JUST coming off it's stop- hard to see, and then take 4c off that number!
- (#8855) david miller, 5 Jun 03 1:02
"Yes, I do have much better things to do "
Wrong Chris. Can there be anything better to do than adding to the invaluable store of knowledge contained in these archives? (Don't answer that)
Thanks for posting these findings. Some time ago,I too did a little bit of testing with thermostats but, not to the accuracy which you have. My thoughts are that these thermostats are not the most accurate of instruments and that there are many factors which influence their individual performance. The "stove top" test is a fairly good one I think to test if the stat is even opening at all but, in practice, perhaps the cooling effect of the jiggle valve flow, the under vehicle cooling air etc, are all affecting the operation of the stat in it's somewhat strange location on these engines. My conclusions were that it was important to have the increased valve diameter of the Toyota Stat(30mm), coupled with extra 3mm bypass holes in the stat flange and an accurate gauge(Durite), to tell you what is going on. In practice it seems to have worked well for me over the past 12/18 months. Also in my opinion, to minimise cooling problems,it is essential to check/overhaul the suction/return hoses to the overflow/make up reservoir, and to fit the later Toyota rad/filler cap with it's improved valve arrangement. I do think that there is an element of carelessness by a few owners in that it is not straightforward to check the levels on these engines and, those owners find that the standard Toyota temp gauge warns them, too late, that the coolant level has gone unchecked for far too long.
The word "Kuzeh" sounds a bit strange but, when I get into the workshop I will check my fairly large collection of boxes and stats to see if it appears on any of them. Perhaps a contributor who is fluent in Japanese might enlighten us.
- (#8856) John Davis, 5 Jun 03 1:28
I think Kuzeh means Ceramic.
Its more often associated with Persian pottery. Hope that helps.
Dave Bright
- (#8857) dave Bright, 5 Jun 03 1:47
Thanks for the comments
I got an aftermarket stat from the motor factors to compare
It responds quicker than the toyota stat and also opens earlier and closes later - the flow diameter is slightly smaller but it opens much further that the OE stat
I have no way of measuring flow rate but would hazard an amatuer guess that it is greater on the non toyota one - in fact in the 'short term' I would 'guess' it may be a better stat for the engine
The toyota stats engineering quality looks superior (much more heavy duty) so I would assume it would last longer - someone suggested that stats require a number of operations to settle down - though I wouldnt know.
I thought the triple stepped built in rubber seal (toyota)to be unecessary (esp. as stats have bleed holes anyway - seems a contradiction in design) and infact feel this rubber seal is sticking - though the lube properties of anti freeze and use should settle this down
Which one to fit? Maybe a case of swings and roundabouts but in the saucepan the non original is the favourite.
As it will be a while before I fit it, I will experiment with more cooking and see how I feel on the day
I am certainly convinced that neither of them begins to open at 88 deg so I'll see if further cooking has a bedding in effect
Dave- with the cd being a 97 version the part numbers all seem to have changed (I would be lost without it though)
Chris
- (#9004) chris turner, 5 Jun 03 17:40
Hi Chris
25mm diameter to 30mm diameter doesn’t sound like much, but when you calculate the area, then multiply by the lift, the smaller thermostat is 45% smaller than the Toyota one.
The aftermarket stat I recently fitted to my 4x4 auto caused problems as it was sticking on the receiving plate inside the engine block. This led to some mighty odd temperature readings, so my advise here would be use a Toyota stat with a temperature rating of 82°C not 88°C
dave Bright
- (#9005) dave Bright, 6 Jun 03 1:23
... but remember that Chris has a Hiace, not a townie...
- (#9006) david miller, 6 Jun 03 1:51
Its the same stat fitted to all (I think) the 2.4 toyota deisels and a camry model (though mine 2.8)
The aftermarket stat had probably double the lift in the pan
It also has the flow 'offset' but I assume when doing the job it will be clear why - if not maybe have the offset to the block -
As either stat may see the engine less cooled (current one opening about 72 deg though I dont know what lift)- maybe it will take me past my recent 20.07mpg record!if I dont dissapear in a cloud of steam first!
Life was much simpler when I had shorter legs and a pedal car!
Chris
- (#9007) Chris turner, 6 Jun 03 8:48
Well just for the record, fitted the toyota stat
The one I took off was original fitment also.
With all three in the pan the old stat opened well before the others and was the last to close on cooling.
It also opened wider than the original.
The aftermarket stat is in the middle though it opens and closes with greater speed than the toyotas
The new toyota stat sees running temp up about 4 deg.
97-8deg when labouring up hill on a warm day and 91-4 generally
Based on what I saw in the pan I figure that this new stat will allow less temperature flucuation and faster warm up - and hope in turn this may help mpg. (a week or two will see)
Worth considering that a pan of water is not necessarilly going to duplicate how a stat performs on the engine (ie
no antifreeze lubing its operation and an absence of 0.9 psi pressure)
I also learned that when the probe was held to the side of a pan with boiling water using a tea towel the reading was around 7 deg lower than in the pan.
This tells me that my set up with the probe mounted to the side of the block is never going to be as accurate as a probe in the cooling system - but it will give me an idea as to how the system is functioning
For anyone doing the stat on a hiace with 3L engine - its very easy and quick - only lose less than a pint of coolant, though the top hose does require some massaging when refilling as its increased height over the rest of the system means quite a bit of air gets trapped in it
I know people have fitted duralite temp guages -
Am I right in assuming that this was because the original guages themselves were no good and that the original sensor in the cooling system functions OK?
Just wondered if replacing the sensor would allow the guage to function with more accuracy?
Chris
- (#9078) Chris Turner, 10 Jun 03 17:59
Dave Mason is the Guru on this- if you can stand the gauge not being right at the bottom when cold, adding a resistor in the right place can make it more sensitive at operating temp. It's on AceAnswers.
- (#9079) david miller, 11 Jun 03 0:52
Chris,
"Am I right in assuming that this was because the original guages themselves were no good and that the original sensor in the cooling system functions OK?"
I,m not sure that they are "no good" but, I feel that Toyota might have fitted gauges which give peace of mind throughout average performance, ie, the needle sits in the middle through a fairly wide range of temperature fluctuations. Whether this feature WAS built into the gauge, or is just a figment of my imagination, I am not sure. The "Townace", as a Japanese home market vehicle, was not, I feel, as it's name implies,intended to be the motorway vehicle which it is here and it seems that the Toyota gauge only starts to tell you that you are entering the "bannana head" syndrome, minutes before it happens. There was much discussion on the gauge/stat etc and I followed David Miller's advice/experiments and fitted the Durite gauge and a Toyota stat, modified for the summer months, with three 3mm holes in the flange. I also fitted the Durite sensor. I have had no problems at all and the gauge readings are similar to those which you quote for your vehicle. It is always nice to see the Durite gauge needle, rising and falling, throughout various operating conditions, something which never happened with the old gauge. I do change back, in the winter to another stat, ie,the Toyota 30mm opening one, but, modified with only one 3mm bypass hole.
- (#9080) John Davis, 11 Jun 03 2:18
Chris
If you can hang fire for a week or so, Dave Mason who edits AceAnswers, will be marketing a combined "gauge adjuster" which makes an effective use of the full range on the existing gauge, overcomes the "flat" spot and incorporates an audible adjustable alarm. I've been assisting with trialling the device and have to say I'm very impressed with the product. It's easy to fit and gives an early heads-up of any overheating problem. A cheaper and more function-rich alternative to a Durite Gauge.
- (#9081) Ian Dunse, 11 Jun 03 3:01
Thanks for the responses
Must admit on some earlier vehicles I've owned I have drilled extra holes in stats when I have been worried over cooling issues. However I wonder if I was just making up for faulty readings/clogged rads etc.
>nice to see the Durite gauge needle, rising and falling< too right John! Essential I would say.
As I'm on a bit of a mpg mission (do alot of shortish journeys) at the moment a fast warm up time is good and drilling the stat would defeat the object for the type of journeys the bus is currently doing.
>If you can hang fire for a week or so< when it comes to wielding a spanner this is my speciality Ian!
Look forward to hearing more about the 'guage adjuster'
The adjustable alarm sound just the ticket especially for older vehicles
Nostalgia maybe - but is'nt it a shame that manufacturers have done away with the barrage of monitoring instruments on vehicles?
These instrument pods etc. used to give a good idea of how the engine operated as well as providing early warnings, aiding diagnostics and of course confidence.
Progress!
Thanks again
Chris
- (#9082) Chris Turner, 11 Jun 03 6:48
Yes I can provide the accessory which Ian describes. See Ace Answers, Temperature gauge, Temperature gauge audible alarm.
The quantity being produced is still very limited. If you're interested by all means email me and if I can't accept your order immediately then I'll at least put you in the queue.
- (#9137) Dave Mason, 12 Jun 03 7:03
Chris asked about the Toyota gauge and sensor.
My conclusion is that the sensor is fine. It's a thermistor (resistance reduces drastically with rising temperature) fixed into the head under the inlet manifold, about no. 3 cylinder. Little evidence of problems there.
On the other hand the gauge appears to have been cleverly designed by Toyota to conceal moderate variations in what the sensor is telling it. Giving Toyota the benefit of the doubt, on a new car this may be so as not to worry the driver about unimportant temperature variations. Or it may be to conceal manufacturing variations in the sensitivity of the sensor or the gauge itself. However with our old cars we need a more honest indication of temperature variations, if not of the exact temperature.
I am interested that Chris found, as I understand it, that his old Toyota stat operated about 4 deg cooler than his new one. I believe that I have a very old Toyota stat in my car and it does seem to run cooler than any other - going by the apparent sensor resistances. It reminds me of an inconclusive debate in "Temperature observations/thermostats" about whether we have should be choosing between two thermostat types. I wonder if replacing a Toyota stat does indeed make the engine run hotter - unless you drill holes in it!
- (#9138) Dave Mason, 13 Jun 03 6:42
Also the original Toyota stat had a screw thread incorporated so as to allow adjustment of the opening. The new one does not. Perhaps another factor in the difference in temp.
- (#9139) Ian Dunse, 13 Jun 03 6:50
Dave M - old ground I know but the 2 toyota identical stats
Old stat actually opened almost 20 deg before the new one also with increased lift
The 4 deg increase refers to the average running temp with the new stat
Now when you consider the above figures you have to assume other variables are at work - also 'guess' that when in the cooling system the stat may open before it would in a pan ie:pressure in system, fine vibration, and antifreeze content
Operating temp (90+ probe below the stat)is now achieved in about 2 miles whereas with the old stat it was almost 5 miles
This is great for short runs (just hope the hoses don't blow off etc. when I give it a proper long run!)
Must stress that the on engine readings are just a probe (linked to multimeter)strapped firmly to side of a pre-stat metal water junction with cable ties. The tip insulated from heat loss with silicone sealant - so the actual coolant temp will be different (quite a bit higher perhaps)
Dave B - the non original stat that was fouling on your vehicle - wondered if it was offset like the one I bought but never ran - ie
non original stats may need to be fitted with the offset twisted so it does'nt foul? Otherwise why the offset?
Ian - manually adjustable thermostats! This almost sounds like prototype or research and development territory. However, good concept as it could be adjusted on a service schedule rather than replaced - surely they would,nt rely on the vehicles temp guage though!
Chris
- (#9140) Chris Turner, 13 Jun 03 17:43
Well, got fed up of the toyota stat - granted its been warmer weather recently but seeing 107 deg briefly and seeing 100c regularly on motorway cruising put me off.
(These figures are not directly comparable to the above postings as I have moved the sensor - wedged it into a gap down the side of the engine temp sensor threads, covered with silicone and secured with cable tie. New position reads roughly 4 deg higher but probably more accurate)
The toyota stat was sticking on warm up I believe - ie
now its off its still as sticky as when new - also the toyota stat was very, very slow to respond to temp changes on the van.
I decided to fit the 3 quid wonder with the offset.
Toyota stat doesnt appear offset at all but sticking a 1/2 inch ext. bar into the thermostat housing showed me why the aftermarket stat was offset and allowed me to line it up properly. (also had me wondering why the toyota onw was'nt offset)
The new stat responds very quickly to temp increases and allows the engine to run a few degrees cooler over all - basically it clearly works well for a living while the toyota stat was I think impressively engineered but very lazy.
Remember that mine is a '3L' engined hiace -
Plenty of testimony on site that the toyota brand is best for townaces
People have cited 110c as headwarp time. Assume this is for alloy heads - what might be a dangerous temp for an iron head and block?
- (#9618) chris turner, 10 Jul 03 17:14
Please IGNORE the last couple of postings made by me in this thread. Seems my prob is more serious than stats. Soot in the coolant and operating temps around 100c+ (got the old stat back in now also).
Mechanic confirms excessively pressured hoses
So... maybe the old saying 'if it works, dont fix it' has some value here. ie
It was fine till I changed the stat - then again if I had'nt, then I would'nt have noticed the soot building up.
Been quoted 300 uk pounds to sort head gasket (assuming block/head not cracked) or I can try the 'car go' liquid glass treatment (highlighted in an older thread)
Thanks to Dave Bright for highlighting the meaning of coolant discolouration in a recent seperate cooling thread - you enabled me to catch a problem before it gets catastrophic
Just at the moment - I long for a 'bread and butter' car again.
Chris
- (#9774) chris turner, 17 Jul 03 9:28