In case anyone is interested, here are the results of my ten day Scottish tour, following the various mods to the cooling system, ie, a new viscous coupling, Toyota thermostat, modified with three 3mm "by-pass" holes and Durite gauge/sender etc. The Masterace ran perfectly over the 1200 miles (I expected nothing less, of course), it returned an average of 33.3 MPG, a figure better than expected due, mainly,to a lot of motorway driving, only two people in the vehicle, and a speed rarely exceeding 65 mph. A lot of hills, and much work by the auto gearbox with an average running (head)temperature of approx 85c with 95c showing on some of the longer hills and, nearing 95/100 on the "Rest and be thankful" summit through the Argyll forest with, at this temperature, a quick test showing a "stiff" drive through the viscous coupling. Absolutely no indications of overheating and, unlike the original, sluggish, rarely moving temperature gauge, much re-assurance from the very sensitive and accurate, Durite temperature/sender arrangement. Unlike the "old" Toyota gauge, the Durite shows, quite rapidly, coolant temperature falls on hilly descents at low throttle openings, indicating, I think, that coolant flow, through the radiator and thermostat, is satisfactory. Perhaps, when I've plucked up courage, I'll do some tests at 70mph on the motorway next week, on my way to London. I might even be REALLY daring and go up to 80mph. I'll let you know the results.

- (#5503) John Davis, 15 Sep 02

Well, the motorway test was fine. Fairly frequent and sustained speeds of 70/75, on a fairly hot day (approx 21c) with some long crawls through London traffic and those long hills on the M25 down to Dover. The Durite gauge never went above 95/98 and showed the temperature falls, very accurately, during the descents.
I think that the thermostat mods (on David's advice), together with the new v/coupling, were about right, ie, 3 x 3mm bypass holes in the Toyota, 30mm opening unit. I will evaluate it further, as the weather gets colder, and may replace the thermostat, for winter use, with an unmodified one, to obtain a quicker warm up for the heating system

- (#5706) John Davis, 30 Sep 02

can you supply a diagram of the mods to the thermostat and possibly explain the procedure

- (#5707) ron coe, 1 Oct 02

The procedure is to drill "by-pass" holes in the thermostat flange,ie, the plate which takes the rubber seal ring, therebye ensuring that water is circulating, irrespective of the closed situation of the thermostat valve when the coolant temperature is below the thermostat's opening temperature (82c ?) There will be one hole already drilled and this takes the "jiggle" valve, the purpose of this is to ensure that, even if the thermostat should fail in the closed position, some water will circulate and the jiggle valve keeps that hole free of debris. Too many holes will make the engine run too cool but, 3 x 3mm holes seems to be about right for the cooling system on our type of vehicle. It might run too cool for the winter, hence my intention to evaluate the average running temperature in colder weather. I may then have to fit a thermostat with no by-pass holes but I now feel that this is unlikely to be required.

- (#5708) John Davis, 1 Oct 02

i am taking the liberty of posting this extract from another web based motoring discussion group. the writer is, i believe, a retired engine designer for one of the major diesel engine manufacturers. it might be helpful to us and explains explain another vunerable aspect of our cooling systems.

"however this is a good time to issue a reminder that it is extremely important to use the correct antifreeze, especially in engines where aluminium is used for major parts like the block and/or head.

the pressure pulses (vibration) in an engine, especially a diesel engine, can cause cavitation erosion. this is the forming of minute gas bubbles on the surface of the metal which then implode and wear the metal away.

cavitation was responsible for the cylinder block to erode around the liners in my niece's peugeot 106 diesel. this let the coolant leak into the sump and repairing the engine cost her about £1500, far more than the cost of using the proper antifreeze at the proper concentration!

we ought to drop the term "antifreeze" as this suggests something that is needed only in the winter. it is really "coolant conditioner" and it is vital to use the correct grade, to keep it in all year round, and to replace it at the specified intervals. "



- (#5725) John Davis, 8 Oct 02

As the unnamed contributor that John has quoted says we shouldn't call it anti freeze, indeed the trade now refer to it as coolant, after all, if it lowers the freezing point, then it will raise the boiling point as well, just like adding salt to water, it freezes lower & boils higher (helps the veg to cook quicker). The trade also uses 3 types of coolant now, the traditional 'blue' product, which is ethylene glycol based, but there are two new ones, they are red & green & must be used in the correct vehicles, they are biodegradeable & eco friendly, however the Townie is fine on 'blue' ethylene glycol stuff, I would think a 50-50 mix with distilled water would be a good idea, use distilled & this should help with silt & limescale build up as well. HTH Rob.

- (#5772) Rob Drinkwater, 8 Oct 02

I am in Jamaica and i have problem with my clutch fan in my 1994 1800cc townie i have change 3 so far i am thinking of installing an electric fan.what do you guys think. I also have a 1999 2000ce no problem from this one yet

- (#6117) D.Wright, 16 Nov 02

"Too many holes will make the engine run too cool"

Ref my posting earlier in the year, the three x 3mm holes in the thermostat flange, during the warm weather, was, I think, an ideal modification and I had no overheating problems whatever. We have not yet had any really cold weather but,one or two early morning have been a bit "parky" and I am finding that the coolant temperature takes a long time to get to even around 60c and, on fairly short runs, this may not be good for the engine, especially when the weather gets really cold.ie, re lube oil temp etc. Also, heater warm up time is a consideration.
For the winter months I intend to blank off those three holes (or fit another thermostat and have a "summer" and "winter" one) as I feel that Toyota must have designed the engine to work best at a certain temperature, and that my "full flow" modifications might not be desireable during the winter. As the standard thermostat has an opening temp of around 82/83, perhaps this is the optimum engine operating temperature.
- (#6228) John Davis, 1 Dec 02

John,
please don't take offence but I have been following this thread with interest, as I am having trouble understanding the benefits of extra holes in the thermostat.

As I understand it, the viscous fan operates from the temperature of the engine, not the cooling system. I accept that extra holes in the thermostat will reduce the overall temperature of the engine initially, but it will also reduce the need for the fan to en-gauge, because the engine will take longer to reach its desired temperature.

It will also reduce the coolant pressure within the engine, and raise the temperature of the radiator. That means that when the thermostat does eventually open, the coolant entering the engine is warmer, and there is less pressure to expel the hot coolant and draw in the cold coolant.

Even so, once the engine is at its temperature, Little else has changed. If a fault develops, its still going to overheat, and the standard temperature gauge will still work the same. ie by the time you realise that the gauge is in the red, its already to late. Surely the resistor mod, or an additional more accurate temp gauge would give better warning that things are going wrong?

When I was in Japan about twelve years ago in early September, it was as hot as hell and very humid. I asked my interpreter what the extremes were. He told me that in summer the temp is usually above 40 degrees C and in winter usually below -6 degrees C. I would have thought that baring faults, our relatively milder climate would allow the cooling system to function quite adequately. Perhaps if our summers were that hot and we had the air con on more, it may improve the general airflow through the horizontal radiator. Or if our winters were much colder the natural airflow, such as it is, would have a better cooling affect ?

- (#6229) dave Bright, 2 Dec 02

Dave, to respond:
no.1, the townace was designed as urban transport. Tooling down the motorway as we do is not in it's design brief. This stresses the already marginal cooling system (ram flow accounts for little of the rad's cooling air).
no.2, regarding the thermostat mod, what we are doing is actually decreasing the control afforded by the stat, by allowing some water to bypass. The system is fully pumped, yet the pump has to overcome the loss caused by two heater cores. The thermostat (even when fully open) restricts the flow somewhat. Our mod increases the area of the stat's opening at all times and therefore the volume of flow through the rad. Remember that a thermostat isn't an on/off valve, it slowly opens over the full operating range of the engine.

Also, the viscous fan senses the temperature of the air having passed through the rad already, not the engine's temp.

All things being equal, more flow of hot water through the rad, and more cold air through the rad, make the engine run cooler. We see temperatures routinely in the townie that would have the average vehicle's gauge pegged in the red. Anything to reduce that will decrease the strain on the hoses, rad cap, and ultimitely head and gasket.
I presume you have a 4x4 auto, as you refer to horizontal rad- it's fans cut in at (IIRC) 107c...

- (#6274) david miller, 2 Dec 02

"please don't take offence"
Dave, take offence? Not at all. I only wish there were more contributors who used good manners, coupled to good arguments, as you have done.

"by the time you realise that the gauge is in the red"

My mods included the excellent Durite gauge and, with my "cooling paranoia" it is the gauge I watch most. I do feel that any "odd" temperature rise would be noticed.

"the viscous fan operates from the temperature of the engine, not the cooling system"

David has kindly mentioned this. It is a common fallacy re the coupling being operated by the coolant temperature, but, the fan coupling only "slips" or "drives" as a result of the temperature of the air passing over the radiator and operating the thermostatic coil/valve assy.

Ref your comment on the coolant pressure etc and that too much flow (with the modified thermostat) will reduce the system's ability to expel the hot coolant and draw in the cold coolant. I not sure that I do understand this comment but, if you mean "expelling and drawing back" cold coolant from the expansion tank, I would suggest that this does not matter. This feature is, really, just to overcome the nuisance of water increasing in volume as it heats up. Also, as you might know, even an unmodified thermostat has it's "jiggle" valve and, coolant flow is never completely restricted.

The resistor mod? Yes, I agree, a sonic or visual indicator of an impending temperature rise, must be all to the good and would be a very worthwhile addition. However, when I first had my vehicle, I was uncomfortable with the "feel" of the engine/cooling system, especially with a temperature gauge which registered "all or nothing" and, after a short while I confirmed that head gasket problems were starting. With a head skim, new gasket & bolts, coupled with a detailed check on the entire cooling system, ie, rads out, everything flushed etc, I have had no problems at all. The extra mods, ie, Durite gauge, new viscous coupling (I think the old one was OK anyway but, I am paranoid about the cooling system,) new, modified thermostat and a coolant level check almost twice a day, have added to the reassurance and, I think, I have proved their worth over the last 12,000 miles, some of those miles being over the Scottish highlands in the heat of summer.
I do see your point questioning "the benefit of the extra holes in the thermostat" but, can only say, in my case I am sure that this was a good move. It has given me the proof (see my earlier post) that the coolant flow, now that ambient temperatures are getting lower, that these mods are not neccessarily good for winter motoring. That's why, tomorrow, I will be fitting a standard, unmodified thermostat and, changing back, probably about April 2003, to the "full flow " thermostat.
Anyway, thanks Dave (and Dave M) for your most useful
comments/arguments, oh that more owners would take the trouble to air their views and opinions in such a constructive way..

- (#6275) John Davis, 2 Dec 02

Thanks Dave M and John.
I know see the error of my logic.

My confusion stems from information, and probably more my interpretation, of the viscous coupling being linked to the temperature from of engine. I wrongly assumed that this was by way of conduction through the block etc. It makes sense that the airflow from the radiator also causes it to heat, therefore the 3 hole mod suddenly makes a whole lot of sense.

The point I was making in reference to my comment on the coolant pressure, was that although the jiggle valve allows some coolant to pass through a closed thermostat, if excessive amounts pass through it, the temperature of the radiator will increase. Therefore when the thermostat opens, there is less pressure within the Engine section of the cooling system to expel the hot water through the thermostat and in to the radiator, and by this action draw cooler water from the radiator to the engine. I had taken no account of the fact that the coolant is in-fact pumped by the engine. That was extremely dim of me.

Another assumption is that the Japanese never had this overheating problem. I am beginning to think that perhaps they did. Maybe this is why they never exported new ones?

- (#6276) dave Bright, 2 Dec 02

If it adds more weight to the argument, I too tried the adding of extra holes to the thermostat. This was back in early September and prior to a long haul to Cornwall and back and it is only recently that I replaced it with a new stat without the modifications. I have to admit that I was horrified at first to realise how long it took for the temp guage to crawl up to the usual halfway mark (in fact it sat just below it) with the extra holes in it. I had visions of increased fuel consumption, but no, there was no difference. On the plus side, I felt more at ease with the temp gauge showing me that the coolant was slightly cooler than normal despite a long haul and an overworked engine.

The inference is that there is a restricted flow to the coolant and the extra holes help. With a new stat in place, the temp gauge is back up to halfway and sometimes just past and although the worries of overheating may be back, at least my toes get warmed a lot quicker on the colder mornings. The ideal solution of course would be a stat that opens a lot further than the current spec allows but then we are stuck with the design of the 2C engine and the space within the void around the thermostat housing.

As for Toyota exporting new Townaces, it's a lot more complicated than that. Cultures, marketing and costs all have an impact on the design for different markets. As most countries become more "internationalised" maybe we will see fewer differences between home and foreign markets. A shame in some ways - McDonalds have a lot to answer for!

- (#6277) Ian Dunse, 3 Dec 02

Greetings from Moscow.
Just a little report on starting in cold weather. I decided to post on this thread since the subject of cold weather was touched upon. I found out that my 1990 td 4 wheel drive has absolutley no problem starting in -20 weather. It starts just like it does on a nice summer day. I am alittle confused about the holes in the viscous coupling and the whole overheating problem. I do not drive over 110 kilometers per hour due to poor roads and speed limits. That always keeps me right at or a little under 3000 rpm's. The guy that owned the townie before me made 10 hour non stop trips with no overheating problems at all. This could be tied to staying under 3000 rpm's. Has anyone had overheating problems driving below 3000 rpm? To my knowledge, from reading this web site, most overheating problems occour on the moterway at speeds that push the vehicle over 3000 rpm's.

Mervin

- (#6278) mervin, 3 Dec 02

Mervin,
I agree with your theories re RPM. David (Miller) recently reminded us that the Town/Masterace series ARE an urban vehicle and I feel that the constant, high speed, high rev motorway type of journey is not what they are designed for. Although I have, probably, access to better roads than you, it is very rare that my engine gets to 3000 rpm. My motoring is fairly sedate and my Masterace seems to give it's best ride at around 60 mph, with an engine rpm of around 2700. I do think that the dramatic problems we sometimes see posted here are a result of, possibly, lack of maintenance and a bit of neglect, with some owners who really should be driving a V6 Galaxy.

- (#6279) John Davis, 3 Dec 02