5th Gen - Mysterious coolant loss from expansion bottle?

arif_manji · Post by **arif_manji** » Mon Nov 26, 2012 9:57 am

Hi Guys,

I'm having a very weird issue with coolant disappearing from the expansion bottle. The weird part is that it looses it after a drive when the car is not running. For example, i topped it up to the top yesterday and drove from Peterborough to Bedford (approx 40 miles) and when I reached I checked and found it hadn't lost any at all. However, in the morning I checked it again without starting it and it had lost a quarter of it.

So how is the expansion bottle loosing coolant when the car isn't running overnight? I've checked for cracks or leaks on the bottle and its all fine.

Current Situation / What I've checked:
- Changed the radiator cap - old one didn't look so great, yet still an issue!
- The complete coolant was replace when service 1k ago (original Honda coolant) and was bleeded fine
- Oil is clean on cap and dipstick (still clear after change 1k ago)
- The heater works fine and is very hot
- Car tempreture is fine and doesn't overheat
- Haven't found any leaks on the floor or in engine bay
- Radiator looks healthly and cannot find a leak, looks dry from all angles
- I took the cap of the radiator while it was cold and the coolant was showing full

Has anyone had this problem or can share any light on this? I'm confused!

mercutio · Post by **mercutio** » Mon Nov 26, 2012 10:21 am

its an expansion bottle if you check it right after you stop you wont see any difference its only when its cooled right down that the rad will vacuum the liquid back into the rad so i would look for a leak somewhere else

Post by **vanzep** » Mon Nov 26, 2012 10:23 am

the coolant does expand a bit in volume when its hot so it will be less volume when it cools down and thats the point in having an expansion tank but you may have a problem with excessive pressure in the system
does the top radiator hose swell up?
this is the problem i have at the moment after fitting new water pump and radiator
so im away to check the operation of the cooling fan, rebleed the system and fit a new rad cap- your probably best to do the same.
if that doesnt work then its time to get the headgasket checked

Post by **Merlin** » Mon Nov 26, 2012 10:48 am

Where are you filling the bottle to?

arif_manji · Post by **arif_manji** » Mon Nov 26, 2012 11:15 am

mercutio wrote:its an expansion bottle if you check it right after you stop you wont see any difference its only when its cooled right down that the rad will vacuum the liquid back into the rad so i would look for a leak somewhere else

vanzep wrote:the coolant does expand a bit in volume when its hot so it will be less volume when it cools down and thats the point in having an expansion tank but you may have a problem with excessive pressure in the system
does the top radiator hose swell up?
this is the problem i have at the moment after fitting new water pump and radiator
so im away to check the operation of the cooling fan, rebleed the system and fit a new rad cap- your probably best to do the same.
if that doesnt work then its time to get the headgasket checked

Merlin wrote:Where are you filling the bottle to?

I've physically checked for a leak around the radiator, engine bay and the under the car to see if there is a puddle, but nothing at all. It heats up fine and drives spot on. I could bleed the system again and see how it gets on, new cap is on too. Surely if the headgasket was on its way, it should start to smoke, overheat and a mixture of water and oil on the dip stick and cap?

I'm now filling the expansion bottle right to the top as I get worried about it disappearing on my travels to work as there would be no place to stop and top up. I'm not too sure if the top radiator hose swells up, I've seen one that does? If it does, what does that mean?

I'm going to now leave it sat on MAX and see if it goes down any further, but I suspect it will. Will keep a bottle of water from work with me in the car incase.

Post by **Merlin** » Mon Nov 26, 2012 11:29 am

I used to think the notch near the top of the bottle represented the max/min lines, whereas the real max/min is much further down the bottle. Filling it near the top may cause too much pressure and the excess water gets squeezed out. Could that be what is happening?

arif_manji · Post by **arif_manji** » Mon Nov 26, 2012 11:33 am

Merlin wrote:I used to think the notch near the top of the bottle represented the max/min lines, whereas the real max/min is much further down the bottle. Filling it near the top may cause too much pressure and the excess water gets squeezed out. Could that be what is happening?

I'm assuming this could be it, I'm gonna keep it on MAX and not top up untill it goes down below LOW.

Supermarine Blues · Post by **Supermarine Blues** » Mon Nov 26, 2012 12:02 pm

Don't let it get too low; you'll suck in air.

You'll need a coolant sniffer test for HGF. But it could be a tiny coolant leak in a hose, a weepy water pump bearing, or anything at all really.

GLWTSearch...

arif_manji · Post by **arif_manji** » Mon Nov 26, 2012 12:09 pm

Supermarine Blues wrote:Don't let it get too low; you'll suck in air.

You'll need a coolant sniffer test for HGF. But it could be a tiny coolant leak in a hose, a weepy water pump bearing, or anything at all really.

GLWTSearch...

I had the cambelt changed 1k ago and they guy who did it checked the water pump and said it span fine and didn't need replaceing? I'll keep an eye on the coolant - I'm just hoping it isn't gonna be an expensive fix. Should I get a presure test done?

mercutio · Post by **mercutio** » Mon Nov 26, 2012 12:16 pm

just see how it goes you may have overfilled it causing it to force excess out of the drains