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The mkiv Supra Owners Club

rising water temp


Bossco

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My water temp has been rising from 92 degrees to 115 degrees when the car is on full boost. When I bled out some air and topped up the coolant the temp dropped to 108 degrees. After another air bleed it came down to 102 degrees.

 

Is this just down to trapped air or could it be something else? I've got out all the air I can with the car jacked up but Im wondering what safe temps are and what the temp should be.

 

Cheers

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I do have an FMIC and it's not loosing any water. My rad cap is only a few months old and is a stock Toyota cap.

I was thinking the rad it's self might be shot but I dont have a clue to be honest.

I dont think it's the thermostat as the temp is measured from a defi sensor in the top rad pipe.

Edited by Bossco (see edit history)
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At this stage John I'm not sure how much going single would help with my water temps lol.

 

Bit of an update so help is still needed.

 

At 70 mph my water temp is reading fine at around the 95 degree mark. It's only when the car gets to 80mph or above that the temp starts to rise. The only gauge that rises is my defi, which takes the temp from the top rad hose. The temp gauge next to the rev counter doesnt rise above the 45% mark. Even on full boost.

 

After searching I've found a few possible causes but I've not been able to find anyones symptoms which match mine.

 

I cant find any leeks from anywhere and dont think there is anymore air left to come out. The coolant is not being boiled and I've got no other symptoms of HG failure. It also doesnt show any symptomes of heater matrix failure.

 

Other than the water pump, thermostat or radiator could it be caused by anything else? I am going to put my under tray back on after reading the search results, though I'm not convinced it will help that much.

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At 70 mph my water temp is reading fine at around the 95 degree mark. It's only when the car gets to 80mph or above that the temp starts to rise. The only gauge that rises is my defi, which takes the temp from the top rad hose. The temp gauge next to the rev counter doesnt rise above the 45% mark. Even on full boost.

 

This sounds similar to a problem i'm having with mine (although my temp rise is registering on the stock temp gauge), I noticed the temperature rising while I was sat doing 80/90 on the motorway, I pulled off at the services and as I began to slow the temperature dropped back down again, I then continued on the journey at 70/75 and it was fine all the way there and back.

 

I think my thermostat is either stuck part open or not opening fully, as the engine temp is fine at lower speeds/ lower engine revs, and fine with short bursts of speed i.e overtaking, but on long sustained runs over 80mph it looks like there's not enough coolant flow around the engine and so it begins to slowly overheat.

 

I've bought a replacement Thermostat now and I'll be changing it at the weekend, hopefully that will cure it.

Edited by jim_supra (see edit history)
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Fingers crossed it does cure it Jim. I dont think my thermostat is at fault though as the stock temp gauge doesnt rise above half way, even at full boost. I think I will replace the thermostat anyway as a matter of course. I just wish I knew what to replace to get it sorted rather that using process of elimination.

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I have a similar problem wioth the aristo the defis show a rise but the stock temp guage stays still. If it is exactly the same as mine its normally under boost that the rise happens.

Could it possibly be turbo related/ heatsoak?

Either way i know i need a new rad as mine is a bit tired but i will be interested to see if the thermostat is causing issues too

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Fingers crossed it does cure it Jim. I dont think my thermostat is at fault though as the stock temp gauge doesnt rise above half way, even at full boost.

 

It won't until the very last minute mate. You have exactly the same symptoms I had.

 

Running it for long enough will lead to HG failure though, I've got the T-shirt.

 

Mines hasn't missed a beat, since changing the stat.

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Oh really? :)

I've just been looking around online and I've seen some for £65 which I thought was a bit ridiculous to be honest but if it fixes my problem I'd have paid it.

 

Did you get yours from Toyota. I'f there only around £20 I'll get it changed straight away.

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Yeah Mate from Steve Manley. That included the rubber 'O' ring as well, You may be pricing the TRD ones or something.

 

Hopefully it's a cheap fix for you. Just don't drive the car unless you need to.I blew the head gasket on the way to the garage to have the stat changed:Pling:

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Cheers James.

 

I dont fancy forking out for a head gasket replacement thats for sure. I'm hoping it will be ok. As in previous posts if I stay around 70 mph my water temp is spot on and seems to be flowing well.

 

I'll post up if a new stat sorts it.

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I ordered the thermostat this morning so it should turn up on Tuesday. Fingers crossed it sorts it and I dont ask you to change my water pump. I can see another most excelent adventure coming our way. (Insert tasty air guitar lick here)

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