(Home) Thermostat access/coolant loss surprise

Hi all, could anyone please clear up the confusion I'm having as to the location of the thermostat,(have a 2C-T) engine, 1990, 2WD Masterace.
The reason I'm asking is that from reading all the posts regarding this subject, some are talking about loosening & removing alternator & belt, to get to two bolts housing the thermostat. Others mention that it is above the A/C pump, from looking at my engine, I'd be going for above the A/C pump - can anyone point me in the right direction, as my expansion tank keeps topping up(I've a new stat. from Toyota) & would like to fit it soonest. I've already changed the rad. cap(again from Toyota) to no avail, still topping up.

Thanks for any help,

Regards, Tony.

- (#6617) Tony Lloyd-Jones, 5 Jan 03

Tony take the kerbside front wheel off - lift the rubber flap above the top wishbone and you will see (armed with a torch) the stat aluminium casting - and yes its awkward - get a quarter drive socket its 10 or 11 mm from memory and an extension - awkward but possible - get a new flat rubber ring to seal it too #
kind regards jim
ps theres a lot of difference in aftermarket stats - so it pays to experiment

- (#6618) J ADGO, 5 Jan 03

I commented previously on my modified thermostat, ie, standard Toyota stat, 82c opening temp, with 30mm valve diameter, but modified with three x 3mm bypass holes in the stat flange ie, copying David's experiments. This worked perfectly, even in the highest summer temperatures with a "head" temperature, signalled by a Durite gauge, never exceeding 85/90c. This has proved to be much too cool for winter so I fitted a standard, undrilled Toyota 30mm stat,but even in the recent cold weather, with ice on the screen, a "head " temperature of 100C is signalled, at all speeds after initial warm up. As the supplementary fans, on the horizontal rad (4WD Auto) are sensed to cut in at 105C, I feel that the head, or water jacket temperature, is far too high. A single 3mm hole in this new stat, reduces the head temperature to only 95c so I intend to put a second 2 or 3 mm hole in the flange to reduce the head temperature to around 80/85.
Could ayone who has a viscous fan, Toyota 82c opening stat with the 30mm valve aperture, and a Durite gauge, kindly advise on what temperatures they are seeing displayed? Also, could anyone advise on what head, or water jacket temperature, is ideal for the 2cT engine? A very low coolant temperature is not recommended, nor, in the case of the 2Ct engine,I think, is a very high temperature.
Someone previously questioned Toyota's wisdom in mounting the stat on the cool, return side of the system. I am beginning to think that, on these engines, the stat NEVER opens in the winter and, coolant circulation is too sluggish. Also, a stat opening temperature of 82c is too high and, although the stat sensor is on the water jacket side of the system, the cool, bottom hose, ensures that the valve stays closed. Did we ever find out if there was a special stat for these engines when used in Japan?
Any comments much appreciated.


- (#6619) John Davis, 5 Jan 03

Tony. Yes, I saw that reference to the alternator but, I think that the alternator got cofused with the air con compressor. The thermostat is under the injection pump and above the air con compressor.ie, where the bottom, or return hose, enters the block. I have not tried Jim's method of location but is sounds good. The stat housing IS awkward to remove and re-fit but, as I have been taking stats in and out, sometimes twice a day, this is how I do it. I can drain down, to a suitable level, via the front rad drain cock. With a 2WD you will have to find that elusive radiator drain cock, just forward. and slightly above, the front axle.
A better way is to have a large bowl, under the bottom hose location,lift up and remove the expansion tank, and disconnect the low level warning plug/socket. Slacken the bottom hose clip, draw the hose back and allow a controlled flow (If you are re-using the coolant)into the bowl. It's not a direct flow but, a large bowl will catch most of it. You will need a 10mm socket with, at least, a 4/5 inch extension. There are two 10 mm bolts holding the stat housing. Re-fitting is more awkward but, if you are able to obtain a length of 10mm studding (or a couple of long bolts)it helps greatly if the studding, or long bolts with their heads cut off, are first entered, finger tight, into the tapped holes (in the block) and the stat housing can then be slid into its location and, one at a time, the housing bolts are fitted as each long bolt, or stud, is removed. It is VERY difficult to get the stat housing, and it's bolts, lined up correctly and Jim's tip of removing the n/side wheel might be the answer.

- (#6620) John Davis, 5 Jan 03

Hi Tony. You say "as my expansion tank keeps topping up". This could be due to the short tube within the expansion tank being damaged, fitted so as to connect to the overflow outlet (the cap is on the wrong way round) or missing. This is worth a look at before stripping thermostat down.The pipe HAS to be airtight to allow the coolant to syphon back to the radiator cap during the cooling down period.
Happy New Year All....Ray

- (#6621) Ray Ambler, 5 Jan 03

A big thanks to Ray, John & Jim for your speedy replies, turns out I was looking in the right place after all. But now I don't know whether to fit it, drill holes in it(if so how many 3mm holes) or go for the expansion tank pipe thing, as mentioned by Ray.
Ray could you please elaborate a bit more with your pipe theory, I thought that the pipe was just purely an overflow, confused now as the bottom of mine sits in the coolant all the time, should it be set higher, etc? How can the cap be the wrong way round?
Any light that you can spread on the subject would be great, as I would like to eliminate your idea before I replace the old thermostat.
Thanks again for all your help.

Regards,

Tony.

- (#6622) Tony Lloyd-Jones, 5 Jan 03

With regard to the expansion bottle. The cap serves as a sort of T piece. The top has the inlet tube coming in from the rad filler neck and the other side is the overflow. The pipe going down on the inside creates the vacuum in the bottle unless the level gets too low. This arrangement allows water to be forced over from the cooling system when the coolant is hot and to be sucked back as it cools down, hence the need for headroom in the bottle. Obviously you need to maintain tight connections for all this to happen otherwise no vacuum. Therefore, what Ray is saying is check all the hose connections onto the cap are tight. If any have swollen or split, replace them.

As for the thermostat - the extra holes drilled into the stat allow coolant to pass before the temp reaches 82, when the stat actually opens. This is all well and good but at this time of year it takes a very long time before the coolant gets up to normal temperature and you are likely to freeze your ass off as a result. It depends on personal preferences and driving conditions/journeys but I put a standard stat in during the winter and replace with the modified one as temperatures pick up.

- (#6623) Ian Dunse, 6 Jan 03

the end of the hose inside the expansion tank must be immersed- as the engine cools the cooling systen forms a vacuum, pulling coolant up the pipe back into the engine. Any air leak in that pipe (or indeed at the rad cap) will result in the system slowly emptying itself through the expansion tank.

Re stats, toyota list the same p/no for all 2C vehicles, and nearly everything else too.

Concensus is that water flow stagnated in the region around the stat in the bottom of the block as the engine warms. This allows too much of a differential between stat and head, allowing large swings in temp. this is compounded by the great proportion of flow "lost" to the heater matrices ( the return flow from the heaters is dumped in to the block just at the back of the stat, so paradoxically, running the heater may increase running temp)

A bleed in the stat, whether a hole or the press mmod to the bridge, result in more flow through the rad at any temperature. There is as Jim said a lot of variance in stats.
My long considered opinion is that the Toyota stat allows more absolute flow at high temps (bigger diameter than aftermarket), although it still runs out of puff at high extremes. It's control is better than the cheapies.
But if you have a Dremel and ten minutes, you can mod the aftermarket one to have the same valve opening (diameter) as the OEM.
One 3mm hole is probably the best addition to this, increasing flow a bit without inhibiting warmup.
If you can do it, the press mod is even better than a hole because it doesn't allow bypass when the engine's cold, it just increases valve lift at all opening temperatures, and decreases the running temp at the same time. Simply, the "bridge" that straddles the stat (side with no springs) acts as a base for the little pin in the middle that forces the stat open. But when cold, there's quite a clearance between the two. It's possible to put the unit in a vice or similar, and bend the bridge down a little, reducing the gap. Reduce the clearance, and reduce the opening temperature! (but as long as a clearance remains, there is no bypass/ leakage with a cold engine.)

- (#6624) david miller, 6 Jan 03

Hi Guys, thanks again to you all for speedy replies on this matter. A big thank you to Ray Ambler for pointing me in the right direction. Had a look inside my expansion tank today, low & behold - NO PIPE inside it, must have fallen off the last time I flushed out my cooling system, didn't notice at the time, Doh!
Just goes to show what a wealth of varied experience people have that contribute to this web site. Will keep the new oem themostat for summer use now, & fit with a few holes drilled in it - (got a dremmel for xmas!)
Keep up the good work everyone.

Regards,

Tony.

- (#6625) Tony Lloyd-Jones, 6 Jan 03

Well done Tony, it's nice to find a simple solution to what might have been something more serious and damaging to the pocket.
Ref the thermostat, my OEM unit, with three x 3mm holes was perfect for summer use. Currently I am using an OEM unit with one 3mm bypass hole and my Durite gauge indicates around 90c after initial warm up. As I seem to have collected quite a few stats, my next experiment will be the adjustment which David mentions or, ideally, a suitable stat with, say, a 70/80 opening temperature.

- (#6626) John Davis, 6 Jan 03

John, thanks for your input, will do the same in the summer with mine. Did a test on my new oem stat. today with interesting results.
OEM stat. should open at 82oC, as stamped on the flange, but tested mine & didn't even begin to open until 90oC & not opening fully until 95-98oC. I then let the stat. cool down naturally & repeated the test twice more, got the same results every time.
Has anyone else ever tested their stat. & had similar results? Would be why people have cooling problems in the summer if the stats. are nearly at boiling point before they open fully. Can anyone comment?

Regards, Tony.

- (#6680) Tony Lloyd-Jones, 7 Jan 03

I've tested a number, both Toyota and aftermarket, and they've all been OK. Totally different responses in the car, but all OK in the saucepan. Be aware that the first mm or so of opening is hard to spot, to say the least...

- (#6681) david miller, 7 Jan 03

Thanks David, did get the same results 3 times, but was using an anologue thermometer & not digital,was wondering whether it would act differently when fitted though.

Tony.

- (#6682) Tony Lloyd-Jones, 7 Jan 03

seems to, it depends on the speed of response how much overshoot etc you will get. I reckon the OEM stat opens faster and farther, ultimitely flowing more. BUT it seems to open later...
Are you measuring your running temp. with a Durite? and is the sensor in the standard location? You can see approaching 10c difference between the standard location and the filler/ outlet elbow...

- (#6683) david miller, 8 Jan 03

The stats are nearly at boiling point before they open fully. Can anyone comment?

Pure water will boil at 100 C at sea level, depending on air pressure. Antifreeze not only reduces the freezing point but also increases the boiling point. Add to this the fact that the cooling system is under pressure, and the boiling point is raised further. I don’t know by how much though, but if the red section of the standard townie gauge is 130 C, the boiling point will be quite a lot higher than 100 C.

Once the stat is fitted to the car, the stat housing acts like a heat sink, and conducts a small amount of heat away. Hence if you measure the temp of the cooling fluid, the stat would appear to open at a higher temperature than indicated on the stat.

- (#6684) dave Bright, 8 Jan 03

Don't think it's relevant, Dave. Tony's refering to boiling point as 100c, which is indeed quite a bit higher than the stat's rated opening temp (as per stat and manual)
The stat's housing has VERY little effect on the opening temperature of the stat. The wax capsule is on the hot face, and even has a large disc affixed to it to increase rate of heat transfer to it. It's actually quite well isolated from the block...

- (#6685) david miller, 8 Jan 03

Thanks Dave & Dave! Tend to agree with both of you, anti-freeze does increase boiling point of water & the pressure will also come into play. Also agree that stat. housing doesn't really act as a heat-sink,as such.
Anyway, have replaced my missing pipe now, will give it a few days, check level again, hopefully all will be well. Thanks to everyone who commented, think I've started something here........

Tony.

- (#6686) Tony Lloyd-Jones, 8 Jan 03

Tony, I am glad you have managed to sort your problem, it just shows how usefull these pages can be. The point I was trying to make admittedly badly, is that the thermostat is restricting the cooling not the heating of the engine.

My hypothesis is that the cooling system of any car has to be able to dissipate more than the maximum heat likely to be produced by the engine. I.e. driving a fully loaded car in the hottest weather. At this time the thermostat would be open, more often than closed. This same cooling system also has to allow for the opposite extreme. I.e. driver only during very cold weather. At this time the thermostat would be closed, more often than open. If there was no thermostat, the engine would be over cooled. The job of the thermostat then is to restrict the cooling of the cooling system, to allow the engine to run at an economical and constant temperature, no matter what the engine load or external air temperature might be.

The saucepan test is good for checking the thermostat actually opens, but if you want to check the operational temperature of the thermostat though, you have to allow the saucepan to cool, and check the closing temperature as well.

- (#6687) dave Bright, 9 Jan 03

A radiator cap applying an additional pressure of 0.9bar or 13psi will make a total pressure of 1.9bar or 27.7psi. (The atmosphere is 1.0bar or 14.7psi)

At that pressure http://www.connel.net/freeware/steam.shtml (Situation 2) indicates that pure water and steam will co-exist at about 119 deg C which is therefore the minimum boiling point if the coolant contains antifreeze which increases the boiling point.

- (#6716) Dave Mason, 9 Jan 03