Thermostats - careful which brand you buy!

[murcod]

I noticed something interesting yesterday- a year or so back I replaced the factory thermostat with a Tridon one trying to make the Feroza warm up quicker on cold mornings. In short it made stuff all difference.

Anyway, I decided to remove the thermostat completely last week to see how much difference it makes on hot days (aircon on with the temp above 36 degrees I can have overheating issues when caught at traffic lights.) I discovered it runs a lot better with Saturday being 37 degrees and I didn't have a problem! I let it idle for yonks with the aircon on - it cooled down no problems; I caned it up long steep hills and it didn't have a problem either.

Then I examined the two thermostats ie. the Tridon I had just removed and the factory original that I still had. The Tridon has an opening size only around 2/3rd's the size of the factory thermostat, plus the opening is a lot more restricted because of the design of it....

So I've refitted the factory thermostat and will keep an eye on what happens- from now on I'll be buying genuine thermostats. BTW the factory thermostat is constructed from steel ~twice the thickness and has a proper rubber seal on the section that opens/ closes.

I tested both of them in a saucepan and the difference in the openings is obvious once they open up. The rear section of the Tridon (which appears to seal off some coolant path in the block?) also extended a lot further than the factory thermostat. Possibly that could be limiting the maximum opening size once it's installed too?

[Sweeney]

I had a similar problem with my Daihatsu F60.
When I bought it. I replaced all the radiator hoses and the thermostat (Tridon brand) ready for a long trip. Then I started having overheating problems. The radiator was getting raggered and the head gasket started leaking a little of coolant out the side. The radiator was recored and a new head gasket later, still having overheating problems.
I noticed the temp gauge was doing strange things (going up then going down???). I so stalled a mechnical temp gauge (a good idea for hotter parts of Aust) and it was doing the same thing. Hmmm....
I bought a Dayco brand thermostat and problem solved! The old thermostat was opening at 90°C instead of 82°C and closing fully (more like slamming shut) at 82-85°C causing the up-down syndrome.

The DG and DL diesel engines in the F50/F55 and F60/F65 use the same thermostat as Toyota B series diesel.

[murcod]

Dayco actually make one to suit the Feroza - part number is DT46E. Going by the pic on their website it looks to have a similar size opening to the factory original thermostat.



Out of interest the Tridon one and the Daihatsu orig both opened at the same time when heated in the saucepan. I don't what temp that was as I don't have a thermometer that goes that high! The Daihatsu has 78 written on it and the Tridon 77 degrees.

I remember the thermostat listed in the Tridon catalogue was actually the wrong size I ended up returning it and getting the one to suit an Applause (which fitted....)

[murcod]

Here is a pic of the three thermostats side by side (yes, I ended up buying a Dayco...)

Note the difference in the opening size. Also note the Tridon doesn't have a rubber seal like the factory original and the Dayco.

Out of interest the gasket listed in the Dayco catalogue is incorrect- get the rubber one listed for the Applause. The Tridon catalogue also lists the incorrect size thermostat- once again get the Applause one.

The Dayco is a DTE46 thermostat and DTG34 gasket (Tridon part number for the gasket is TTG34 and thermostat TT328-170.) Most auto places will have the thermostat in stock, but the gasket will most likely need to be ordered.