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Radiator Overflow Hissing


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#1 lewBlew

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Posted 27 March 2014 - 09:55 AM

Hello.

 

Standard 998 A+

 

Any idea why if the engine is hot the radiator cap opens up a little and lets some water through the overflow pipe and onto my subframe, until it's cooled down? When I turn the engine off I can hear it hissing!

 

There's not enough water to see it dripping as such, but the end of the overflow pipe is moist and the subframe is a little bit wet. All in all the level in the rad only goes down by about maybe 1/4 cup a fortnight.

 

New radiator & new cap (all standard spec & from Mini Spares) hasn't made any difference. It's done this for over a year. It's weird!



#2 cal844

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Posted 27 March 2014 - 10:04 AM

Take the car to a garage and have the system tested! Could be the head gasket has gone?!


Edited by cal844, 27 March 2014 - 10:04 AM.


#3 woodley miniman

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Posted 27 March 2014 - 10:08 AM

I agree with cal844. Get the system pressure tested. Also, have you checked the thermostat??? It might not be working correctly. When you replaced the rad, did you flush the system???

#4 lewBlew

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Posted 27 March 2014 - 10:44 AM

Car runs fine, doesn't overheat, doesn't use too much petrol, passed emissions test with flying colours in January. Can it be HG? I drove it to Belgium in October and it was doing this. Didn't miss a beat. I will see if I can get it pressure tested.

 

Haven't checked thermostat, but again the car warms up lovely, doesn't overheat etc.

 

Didn't flush the system as no access to a hose... Coolant was pretty clear when it was changed this year. It was last flushed end of 2012 when I changed the coolant the last time and was no problem then either.

 

So confusing!



#5 woodley miniman

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Posted 27 March 2014 - 09:49 PM

If the head gasket has gone/going your probably find "creaming" in the engine. This is caused by the oil and water mixing. Just a thought.

#6 Carlos W

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Posted 27 March 2014 - 11:07 PM

If the head gasket has gone/going your probably find "creaming" in the engine. This is caused by the oil and water mixing. Just a thought.


This doesn't appear to be particularly common in minis!

To the OP, do you know what pressure rating the cap is?

#7 Alex_B

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Posted 28 March 2014 - 08:53 AM

I would say the rad cap pressure is too low and is bleeding off pressure through the overflow

#8 lewBlew

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Posted 28 March 2014 - 10:10 AM

It's this one:

 

http://www.minispare...ck to catalogue






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