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Old 13th February 2019, 11:40   #21
Simon W
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Update - Residual Pressure Test

TC - I redid the test late last night (i.e. ran the engine for 30 mins).

I've just taken the tank cap off and there was a very slight hiss (engine completely cold).
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Old 14th February 2019, 17:14   #22
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Update - Residual Pressure Test
TC - I redid the test late last night (i.e. ran the engine for 30 mins).
I've just taken the tank cap off and there was a very slight hiss (engine completely cold).

A very faint sigh can be normal, but a sound like a pop bottle hiss would be concering. Can you repeat this test, but revving the engine to 3000 for 30 secconds every five minutes or so? Of course you musn't release the cap for 6-8 hours or till next day.



Quote:
On mine, there's a definite point where something suddenly changes and the coolant gushes out of the expansion tank at an alarming rate. It'll flood the complete tank rim very fast - much faster than I can turn the engine off.

I'd suggest you do the textbook bleed/top up and then repeat this test. The coolant shouldn't become pressurised in this manner unless it's overheating/airlocked/pumped (exhaust).


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Old 14th February 2019, 18:38   #23
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A very faint sigh can be normal, but a sound like a pop bottle hiss would be concering. Can you repeat this test, but revving the engine to 3000 for 30 secconds every five minutes or so? Of course you musn't release the cap for 6-8 hours or till next day.

TC
It's more of a sigh than a bottle hiss. Anyway, I've just done the above test (engine to 3000rpm etc.) so I'll take the cap off tomorrow and see what it does this time.


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Originally Posted by T-Cut View Post
I'd suggest you do the textbook bleed/top up and then repeat this test. The coolant shouldn't become pressurised in this manner unless it's overheating/airlocked/pumped (exhaust).
TC
Ok, I'll do a bleed/top up after seeing (hearing) what happens when I take the cap off tomorrow.

NB. If I turn the engine fan off (via Demist button) or switch the engine off I can hear some faint gurgling going on behind the centre console.
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Old 14th February 2019, 21:36   #24
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- - - - I can hear some faint gurgling going on behind the centre console.

Gurgling means air bubbles. Bleeding and topup essential.



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Old 15th February 2019, 16:01   #25
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Gurgling means air bubbles. Bleeding and topup essential.

TC
Ok TC - will do (bogged down with headlining removal at the moment - the usual nightmare with trim fixings etc. )

BTW, no hiss at all from the tank cap this morning.
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Old 17th February 2019, 00:23   #26
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(...)Pedro - if you put the 400ml of coolant back in so that the level is on the MAX line (measured at cold), then run the engine up to hot and wait (with the car standing still), is there a point when it suddenly starts gushing out of the expansion tank? Or does it only do it when you're driving the car out on the road?

On mine, there's a definite point where something suddenly changes and the coolant gushes out of the expansion tank at an alarming rate. It'll flood the complete tank rim very fast - much faster than I can turn the engine off. (...)
On mine, it only happens when I rev it up for some time ( I would say 5/7 secs.) after the engine is warm.
I also did a test idling until the coolant reaches 87/90º and nothing happens.

I'm suspecting the problem could be the cap or the O-rings. I will give a try and see what happens with the new one

I agree with T-cut, in your case Simon, that gurgling you mention definitely means air locked in the cooling system. Mine doesn't have that noise.
If I was you I would try bleeding the system and see if it can solve the problem.

Anyway I will report the situation in mine as soon as the cap arrives.
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