Flowing water noise?

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hogesar
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Flowing water noise?

Post by hogesar »

First time I've noticed it - started up today and it's like I can hear the coolant running through? Is that normal?
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Re: Flowing water noise?

Post by Conan »

Impossible to tell from your description but it’s normally air in the system that can give a noise.
Keep your eye on the fluid level
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Re: Flowing water noise?

Post by RX8765 »

I've noticed a trickling water sound several times before. Coolant has always been at the correct level and coolant temperature has always been fine.

I assumed it was the air conditioning system but I really have no idea.

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Re: Flowing water noise?

Post by hogesar »

Well the air con isnt on but yeah, I started it cold, let it sit for a couple minutes, came out and sat inside the car and could hear the gushing of water. Panic immediately set in but looking underneath and on top - no leaks.

It increased with revs too. It's now been sat and just started again and I can def still hear it! Swear I couldnt before..
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Re: Flowing water noise?

Post by qwakers »

theres air in it. thats the only reason youll be able to hear the flow.
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Re: Flowing water noise?

Post by dac69er »

when i drained and replaced my coolant i had a slight noise every now and then. it was a little bit of air that was trapped in the system.

i just popped the coolant pipe off that goes into the top of the throttle body a few times and it seemed to do the trick.

if it has come from nowhere you most likely have a leak.
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Re: Flowing water noise?

Post by AndyBrad »

I have the same on mine, its the air con!
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Re: Flowing water noise?

Post by hogesar »

Ah. I presume from when I had the pipe off to the throttle body when taking the manifold on top off. easiest way to get the air out of these? I'll try taking the pipe off from the top of the throttle body..
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Re: Flowing water noise?

Post by warpc0il »

The only legitimate (not a problem) source of running water sound would be the condensate drain from the ac, and even then only in unusual conditions.

Water/coolant flowing through a closed system shouldn't make a noise unless there's also air where there shouldn't be.

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Re: Flowing water noise?

Post by SeriousSam »

To correct a couple of the statements above, it's more likely the heater matrix than the air con (although they are the same box, they use different coolant loops). If the heater matrix is clogged or has an airlock it will make a sound like running water, and if you blip the throttle you'll probably hear a brief increase in that sound. Might be worth checking whether your heater blows hot air, and if not, it's time to flush the matrix.
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Re: Flowing water noise?

Post by ChrisHolmes »

If you top it up at all, unless its just a 1/2 litre or so then use FL22 as that is what the system is filled with.
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Re: Flowing water noise?

Post by warpc0il »

IIRC the coolant always flows through the heater matrix, even when the heater is "off" or set to cold.
The temperature control determines how much of the incoming air is routed through the matrix.

This is different to many cars where the air always flows through the heater matix and the coolant flow is managed by the heater control.

The advantages of our system are;
- much faster response to changes in set air temperature, as the matrix is always hot.
- the engine doesn't get hit with a chuck of cooled coolant, as it would if the flow was changed.
- there's no coolant flow valve that can leak

However, it does mean that any issue that related to un-bled air in the coolant won't sound any different regardless of what you do with the heater control, since you're only switching the cabin airflow not the coolant routing.
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Re: Flowing water noise?

Post by hogesar »

Thanks Warp, interesting and good to know.

However it does somewhat conflict I think, with what ive done prior to your information. I've bled previous cars such as an mg tf by opening the coolant bottle, maxing the heat and the fans for a bit and that's about it. So I've done the same and I couldnt hear the noise anymore? Coincidence, or maybe the noise will still be there tomorrow.
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Re: Flowing water noise?

Post by ChrisHolmes »

Fingers crossed its now gone.
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Re: Flowing water noise?

Post by warpc0il »

hogesar wrote:
Tue Mar 05, 2019 9:12 pm
Thanks Warp, interesting and good to know.

However it does somewhat conflict I think, with what ive done prior to your information. I've bled previous cars such as an mg tf by opening the coolant bottle, maxing the heat and the fans for a bit and that's about it. So I've done the same and I couldnt hear the noise anymore? Coincidence, or maybe the noise will still be there tomorrow.
If I'm right then it doesn't stop your process working, it just means that you didn't have to "max the heat and the fans for a bit" and it still would have worked. :)
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Re: Flowing water noise?

Post by hogesar »

Good news because it appears to be fixed! Now on to my next, potentially more serious issue which i'll post separately..
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Re: Flowing water noise?

Post by SeriousSam »

Dave, you are indeed correct about the way the heating system works. If you have the filters out and the glovebox open with the fans on, you can actually hear the sound of rushing air change as you alter the temperature. Increasing the temperature will drag more air through the heater core, which sounds distinct from air being drawn across the air con evaporator or in from outside. Give it a try some time, it's 5 minutes you'll never get back but i reckon you'll appreciate it ;)
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Re: Flowing water noise?

Post by AndyBrad »

i can only hear mine through the top air vents very very occasionally
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Re: Flowing water noise?

Post by hogesar »

Ok so I appear to be losing coolant. But I cant visibly see a leak, which is obviously not a great diagnosis to begin with.

Anywhere to look?
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Re: Flowing water noise?

Post by hogesar »

I should say, anywhere to look that's not obvious or easy to see from the engine bay!
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Re: Flowing water noise?

Post by warpc0il »

Check the cabin carpet, especially in the passenger footwell, as this is easy to miss.
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Re: Flowing water noise?

Post by Eddie_r32 »

Have you been topping it up much since the flowing water sound disappeared it could just be air locks being bled out which will drop coolant level
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Re: Flowing water noise?

Post by warpc0il »

Never top-up above the level mark on the expansion tank, which is only half-way up, otherwise it will just eject the excess and you'll be left wondering where it went.

And never trust the coolant level light - it lies.
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Re: Flowing water noise?

Post by hogesar »

Hmm...maybe theres more air locks than I thought. I'll look at it when cold tomorrow morning and top up if necessary but it took a half litre this morning and 250ml the other day.
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Re: Flowing water noise?

Post by hogesar »

No dampness pass side floor.