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The mkiv Supra Owners Club

Heating


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The TRD and other colder opening thermostats are TOTALLY AND UTTERLY unsuitable for road cars on stock management systems. The ecu will probably not be fully off the cold start map, the oil will never get hot enough to boil out water and other contaminants, it'll drink fuel, and as you have seen the heater won't work efficiently. Forget air locks, that's not your issue, put a standard Toyota sourced thermostat back in!!

 

 

A rad cap that opens at a higher coolant pressure will stop the coolant boiling until a higher temp above 100 degrees Celcius is reached. You should not need this additional headroom, the stock rad is efficient enough to cover even quite highly modified engines, and stock ones run under high load in Death Valley. The UK won't be an issue.... Allowing the coolant system to potentially achieve a higher internal pressure is just asking for leaks on old engines and cooling components. again, stock is fine and definitely preferable. Unless of course you have one of the many aftermarket radiators that are actually far less efficient than stock, have a front mount intercooler with the stock water radiator duct removed, blah blah. Then the cooling system will be operating way below stock efficiency, and you may need kludges to stop boiling.

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I have a whifbitz rad and for some reason only the cap that comes with it fits on it so I'm stuck there.

 

The stat I will change just incase it helps but I'm not running stock ecu.

Chris you didn't give me a solution buddy lol.

 

It's amazing how many different people have different ideas on what it could be.

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It's amazing how many different people have different ideas on what it could be.

 

There are various things that can cause the symptoms you describe, and peoples experiences differ. I've dealt with similar symptoms on two different Supras (a UK TT auto and a j-spec NA5), and both were caused by suspected airlocks, from having replaced the heater matrix. Both were cured with the hosepipe method.

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There will be other pressure caps that fit your rad. Commonly after market rads for Jap cars use the cap off the MKIII supra stock rads. Take the cap that fits to a decent motor factors or ask Paul what is used. If the engine doesn't reach a high enough running temperature it's 99% certain to be too cool a thermostat, or a faulty thermostat. Old thinking on race engies was to run them cool to allow more timing adavance. Modern thinking tends to be the opposite, run them damned hot to minimize heat exchanger size and drag, and keep oil temps high, and viscosity low, to reduce drag. There is no real case to run a road car engine as low as the TRD stat controls it, but plenty of reasons NOT to run that cool.

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Stock stat is 82 degrees, i'd fit one of those first.

 

How old is the rad cap, is it stock ?

 

If the rest of the cooling system is working correctly then it should self bleed, no

need for jacking the front end up or parking on hills.

 

Has the control arm fell off, you'll find it in the passenger foot well, also does the

expansion tank have any coolant in it

 

Is it bad that I cannot find that in my passenger floor well? Part of my aircon has been removed.

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Right, So First off i Purchased a standard Stat, Think it was an 82 Degree one. Took the top rad pipe off, bottom rad pipe off, Stat housing off and the top feed pipe from the top rad pip into the engine off.

 

Also disconnected two pipes from the back of the engine just off to the passenger side, heating matrix pipes.

 

Heating matrix. I put a hose pipe in the pipe that goes from the drivers lower side of the engine to the heater matrix, switched the ignition on, fans to full, heat to full and turned on the water hot at a decent pressure. Not to hard so i didnt break anything. Flushed it till it was clear water that came out. Very rusty water. Once it was clear i switched it all off.

 

I flushed the radiator and the engine block as well as the overflow tank so there was no rusty water anywhere in the cooling system, all running clear.

 

I then placed the normal thermostat in, re connected everything back up, Got my distilled water as not to let it rust again, mixed it 50/50 with some AL39, army coolant, apparently very good. Jacked up the front of the car a fair bit placed 5ltrs of 50/50 mix in, started her up and then a further 2-3 ltrs till it was full. let it warm up a bit and topped off the coolant as more and more bubbles came up. Then revved the engine a bit and held it for approx ten mins at about 3k revs to get all the bubbles out.

 

Left it running for a while on idle as i cleared up. Lowered the car, put the bonnet back on and climbed it to a Very warm car.

 

O know there may be a few things i didnt need to do but its working so i dont care. This was very easy to do and only cost me 26 euros for the stat and distilled water.

 

thanks guys for all your advice on this. Much appreciated.

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