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 Posted: Tue Jan 10, 2012 10:17 am |
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Joined: Dec 09, 2010
Posts: 141
Trade Rating: 0
Location: bradford
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As the title,,,,,
Ive been losing coolant and found its coming from the expansion tank. The tank is not cracked, its coming from under the cap. I renewed the cap and its still doing it.
It does not matter how long i leave the car the system still holds a lot of pressure. I can leave it for a whole day and it still lets off a massive hiss and woush when i take the cap off to check the level.
Any ideas as i can only think of head gasket.
Thanks
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| why wont you work??????????????????? ARGH F**k it!!!!! | |
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Posted: Tue Jan 10, 2012 10:25 am |
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Joined: Feb 07, 2010
Posts: 13077
Trade Rating: +65
Location: England
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Has it been properly bled?
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Posted: Tue Jan 10, 2012 10:44 am |
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Joined: Dec 09, 2010
Posts: 141
Trade Rating: 0
Location: bradford
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erm i guess not but ive only been topping it up and not done a full change.
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| why wont you work??????????????????? ARGH F**k it!!!!! | |
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Posted: Tue Jan 10, 2012 12:01 pm |
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Joined: Aug 01, 2011
Posts: 390
Trade Rating: 0
Location: Bath UK
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In a way it's good because if the system is holding pressure for so long then there aren't any leaks in the system
Like Lee says then most likely you have an air pocket trapped somewhere. Cast your memory back and did it ever run very low on coolant?
What happens is the trapped air heats up and expands and that puts the coolant level up and over pressurises so much that coolant pushes past the expansion cap but as the air cools again you find yourself having to top it up and the cycle starts all over again
Read up on how to bleed the system, do it as per the book and that might be the end of your problem (do it now before the cylinder head does go)
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Posted: Tue Jan 10, 2012 12:47 pm |
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Joined: Feb 08, 2010
Posts: 901
Trade Rating: +1
Location: Istanbul / Turkey
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Link for correct bleding ?
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| 2005 206 RC RED
Bilstein B14 Coilover / Brembo 4 Pot Front 330x28 - Rear 325x8 / Quaife ATB Limited Slip Diff / Janspeed Catback
Lot's of CNC machined customs pars.  | |
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Posted: Tue Jan 10, 2012 1:25 pm |
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Joined: Dec 09, 2010
Posts: 141
Trade Rating: 0
Location: bradford
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say what?
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| why wont you work??????????????????? ARGH F**k it!!!!! | |
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Posted: Tue Jan 10, 2012 1:34 pm |
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Joined: Feb 07, 2010
Posts: 13077
Trade Rating: +65
Location: England
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Posted: Tue Jan 10, 2012 1:36 pm |
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Joined: Jan 05, 2012
Posts: 53
Trade Rating: 0
Location: Oxford
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bleeding is easy find the lowest bleeding point in the cooling system, this could be the thermostat housing, unscrew the nipple untill it comes through with just pure fluid then cap it, then move up the system the next one could be the heater matrix hose. make sure you keep the headder tank topped up the whole time or the process will be pointless, it's best to bleed it when the car is up to temp and with the heaters turned up full that's how i've always done it. if the problem still persists i'd guess head gasket, if you want to be sure about this and you have breakdown cover wait untill its doing it oneday and call the relavant company out and they'll do a check and tell you if it's the head or not
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| "if someone has put it together then I will take it apart" it might never work again but at least I will have an understanding of how it worked and might be able to buy another
The voices in my head may not be real, but they have some good ideas!! | |
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Posted: Tue Jan 10, 2012 3:01 pm |
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Joined: Nov 16, 2010
Posts: 206
Trade Rating: 0
Location: wiltshire
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I always thought air bubbles rose to the top so why bother bleeding the system from the thermostat housing (if that were possible) anyway. Go for the heater matrix hose every time as air bubbles rise to the top.
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| An Ex '03 1.4 GLX driver, German technology all the way now. | |
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Posted: Tue Jan 10, 2012 3:10 pm |
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Joined: Jan 05, 2012
Posts: 53
Trade Rating: 0
Location: Oxford
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i don't question it it's just how we were trained at college so it's what i've always done if the bleed point is there why not use it  the landrover only had one bleed point + the headder tank so i see where you are coming from from a logical point of view but my 306 had at least 2 bleed points, maybe 3? and where does logic ever come into french builds?
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| "if someone has put it together then I will take it apart" it might never work again but at least I will have an understanding of how it worked and might be able to buy another
The voices in my head may not be real, but they have some good ideas!! | |
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Posted: Tue Jan 10, 2012 3:42 pm |
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Joined: Feb 08, 2010
Posts: 10151
Trade Rating: +12
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| gixxerkev wrote: |
| I always thought air bubbles rose to the top so why bother bleeding the system from the thermostat housing (if that were possible) anyway. Go for the heater matrix hose every time as air bubbles rise to the top. |
there is 3 bleeding point on 206
radiator, thermostat and bulk head
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Posted: Thu Jan 12, 2012 1:28 pm |
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Joined: Jan 12, 2012
Posts: 12
Trade Rating: 0
Location: M32 8NA
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If its still doing it after bleeding, run the engine with the radiator cap off. Let engine run a minute, rev the engine a bit and look for bubbles emerging. If its a small constant flow it cud well be headgasket on the way out.
This is exactly what my punto was doing and how i noticed it before it had fully gone
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Posted: Fri Jan 13, 2012 11:57 am |
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Joined: Aug 01, 2011
Posts: 390
Trade Rating: 0
Location: Bath UK
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If the system is still pressurised after a whole day of leaving it then the system is air tight and there are no leaks so it's not likely the head gasket is leaking otherwise the pressure would leak away
Regarding bleeding then air rises to the top of a straight up and down static fluid vessel but when there are horizontal runs and the water is being forced in one direction only then it's easy to develop air pockets at high points in the system. Some coolant systems are easy to bleed and others are a pig, that is why there are many bleed points. It's why every radiator in your house has a bleed valve, air would like to rise to the top and back to the header tank but if it can't get out then it's stuck there
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Posted: Sat Jan 14, 2012 11:20 am |
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Joined: Jan 12, 2012
Posts: 12
Trade Rating: 0
Location: M32 8NA
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| Deckchair5 wrote: |
If the system is still pressurised after a whole day of leaving it then the system is air tight and there are no leaks so it's not likely the head gasket is leaking otherwise the pressure would leak away
Regarding bleeding then air rises to the top of a straight up and down static fluid vessel but when there are horizontal runs and the water is being forced in one direction only then it's easy to develop air pockets at high points in the system. Some coolant systems are easy to bleed and others are a pig, that is why there are many bleed points. It's why every radiator in your house has a bleed valve, air would like to rise to the top and back to the header tank but if it can't get out then it's stuck there |
Not necessarily going to lose pressure if head gasket has gone. The force from the combustion cylinder to force the combustion into the coolant is a massive amount more than the pressure built up in the coolant tank. The damage in head gasket won't be big enough for it to flow through from coolant to cylinder from just that amount of pressure.
If you understand that 
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Posted: Sun Jan 15, 2012 2:20 am |
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Joined: Aug 01, 2011
Posts: 390
Trade Rating: 0
Location: Bath UK
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If there is a leak, no matter how small, then with say 14psi in the coolant system and zero in the cylinders with the engine off, the system pressure would drop quickly. It's exactly that, the coolant pressure that is monitored when investigating a suspect cylinder head gasket leak It doesn't have to flow, even a pin hole would be enough for it to drop pressure.
The fact it witholds pressure even a day later shows it is an air tight system
coolant pressure and compression testing
If the oil wasn't clean, oil level rising with mayo in the filler cap, bubbles in the header tank or boiling over or white smoke out the exhuast then the next step would be a cylinder leak down test
Head gasket gone
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