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The mkiv Supra Owners Club

Coolant - expansion tank low but rad full?


hadyn

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One thing I've noticed with the Toyota rads is that the plastic end tanks turn green when they're about to let go - they start out a solid black colour. If yours is starting to turn green it's time to think about a new rad.

 

Cheers,

 

Brian.

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11 quid ish with the VAT supro :)

 

And when you say end tanks TDR are you talking about the bottom of the rad which joins to the pipe going into the rad? Or the black things either side of the rad core visible from the top of the engine bay?

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11 quid ish with the VAT supro :)

 

And when you say end tanks TDR are you talking about the bottom of the rad which joins to the pipe going into the rad? Or the black things either side of the rad core visible from the top of the engine bay?

 

The top and bottom of the rad Hadyn, one has coolant feed hose attached, the other the coolant return hose.

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One thing I've noticed with the Toyota rads is that the plastic end tanks turn green when they're about to let go - they start out a solid black colour. If yours is starting to turn green it's time to think about a new rad.

 

Cheers,

 

Brian.

 

Yep, mine was a dark green colour.

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Right just been upto my local Toyota to pick the new rad cap up. Checked the coolant in the tank when I got back and bizzarely it has returned to the F level where I topped it up 2days ago??? Whats going on here then??

 

The new cap feels a lot 'stiffer' than the old one but that could be my imagination. Will fit it as soon as the supe has cooled down.

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just a quick q, to top up the coolant do i just add it to the plastic bottle with Full and Low on it, right at the front of the engine bay? sorry really noob question.

 

Let your rad cool off then fill rad right to the top......wack your rad cap on and now fill the coolant reservoir up to the max as well

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The MKIV cooing system will not loose any fluid if all componants are in good condition. Mine has been at the max mark, when cold, since I did a coolant change in the summer, not moved one mm.

 

The expansion tank is exactlythat, allows for expansion. A healthy rad cap will let of some fluid in the system into the expansion bottle , which is drawn back in the the cooling system when the engine cools.

 

A poor cap will let off cooolant at a lower pressure so the expansion bottle fills and often overflows. Evidence of overflow is very hard to find. The first evidence is usually a gradual lowering of the coolant in the expansion bottle over time. Eventually once the volume of the fluid in the expansion bottle is lost, air can be drawn into the system as it cools down. This is often not noticed as checks are carried out when the fluid is hot and the expansion bottle is full and all appears to be well.

 

A cap is not expensive and is the first thing that should be checked/replaced. Many are probably original factory caps and are may be nearing the end of servicable life. It a good idea to keep a spare in the garage.

 

If your cap is OK and the level fluctuates I would suspect air in the system.

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If there is air in the system you will hear it bubbling through the heater matrix as the engine warms up. If the rad cap doesn't fix it check the two hoses that run from the back of the engine into the heater matrix for leaks. A pinhole in one of them will drip onto the bellhousing and is almost impossible to see. I had to replace mine earlier this year. BTW is it just me, or does everyone hate those ridiculous spring loaded hose clips toyota use all over the engine.

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  • 1 month later...
Out of interest where is the L and F markings on yours mate? On the tube or the bottle? Just wondering if mine actually has them and I'm just not looking in the right place :)

 

Low is about 1" from the bottom

 

High is about 2 1/4" higher (this is about 3.5"-4" from the top)

 

You don't need to fill it up, as always check the level when it's cold.

 

On mine the markings are on the right side of the tank.

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ever thaught of evaporation , you are going to loose a bit through the heat of the engine .

i keep an eye on mine each time i clean the car , if its low just top up , been advised to use the red toyota stuff

 

As long as its red Pete it will be ok to use! the colour just destinguishes the properties in the coolant, does'nt have to be toyota based either so long as its red ;)

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