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Dangerously Overheating!!!


Fitz
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I'll run you guys through the story. The Supra was off the road for about 2 months and was stationary for the whole period.

 

I took it for its MOT which it passed and had it taxed. However, yesterday I was driving along and glanced at the coolant temperature gauge and it was almost on the red mark (careless of me to drive without checking all the levels after 2 months) but luckily there was a garage ahead so I pulled in and bought 2L of coolant/anti-freeze and topped up the rad (after it had cooled) and the expansion tank. I let it run for a bit to make sure all was well and it seemed fine.

 

Today I went out with a few friends and coming home about 2 mins away I look at the temp gauge again and it is WAY past the red line. I've never seen it that far before, it was off the scale so I pulled up outside and switched the engine off. I opened the bonnet catch and steam is poring out and I can hear the expansion tank bubbling away (although its now empty) and everything seems dangerously hot. Is it possible to have a leak?

 

How did 2L of coolant vanish in 24 hours? Also, now one of my HID lights isn't coming on perhaps as the ballast is located not too far from the rad cap so could perhaps have had some effect when it overheated?

 

Any help or words of wisdom would be greatly appreciated. (Sorry for any mistakes, I'm typing this on my iPhone)

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Hi Fitz, how's it going mate? Might also be worth topping everything up and the just leaving the car running outside for 15 -20 mins to see if any patches appear, and keep an eye on everything in the engine bay too. Needs to get nice and hot though - also check the temp gauge to see if it starts at zero or is it sticking as has been suggested.

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Look for clues of leaks: coloured crusty deposits on parts of the engine bay, or patches on the ground where you park up. Does the area around the rad cap look clean? If not maybe the rad cap isn't holding pressure any more and the coolant is boiling off from there.

 

If you're losing coolant, there's 3 possibilities:

1) there's a leak in the system where liquid coolant is coming out. -- look for tell-tale coloured leak stains. Garages can do pressure tests of the cooling system to find hard-to-spot leaks.

2) the coolant is boiling off. -- I think this would only occur from the rad cap

3) head gasket failure -- the coolant is leaking into the engine oil (or outside, but I covered that in point 1) -- look for "mayonnaise" on the dipstick or around the oil filler cap.

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Just checked the passenger footwell, bone dry. No obvious signs of leakage apart from where the expansion bottle top had come off and cleaned its guts out.

 

ScottC gave me a ring and also suggested the rad cap could be buggered which looks feasible.

 

Hopefully that rules out the matrix. Also the oil dipstick is clean, no white residue or build up noticeable.

 

Take a look at the rad cap attached.

ImageUploadedByTapatalk1330271682.139609.jpg

ImageUploadedByTapatalk1330271704.814481.jpg

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Also, just to add. Ive just topped the coolant up again and left it running for about 20 mins. No signs of leakage.

 

I moved the car from where I parked it yesterday into an actual parking bay and when I got out to to check if anything had changed upon throttle usage the overflow to the expansion bottle had smoke/steam coming out of it. Now I'm no expert but that doesn't sound right. So when I took the top off the expansion bottle there was more smoke/steam inside.

 

Any ideas guys?

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Will do. I had a new OEM water pump installed about 18 months ago as the old one was fubard and used to pee coolant out everywhere.

 

Can't remember if the thermostat was changed at the same time or not. I'll get onto the rad cap initially and I may still have my stock one lying about.

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A thermostat that's stuck will either cause the car to overheat (if it's stuck closed) or cause it run permanently cold (stuck open), but wouldn't on its own cause loss of coolant. I guess it's possible that a stuck-closed thermostat could have caused the rad cap seal to fail (this is what they're designed to do, like a safety valve on a pressure cooker), thus boiling off coolant from the rad cap. If the rad cap had failed, I would still expect to see crusty red (or whatever colour coolant you use) crud where coolant has boiled off though.

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Have a check behind the water pump housing for leaks. There is a 20mm core plug that fails in the rear housing behind the pump. Had it happen twice and there has been a few others on here with the same problem. Sadly if its that, the only way to get to it is by removal of the water pump, which means, crank pulley, cam belt covers, cambelt just to get the pump off. Hope its just your rad cap.

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