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Discussion Starter · #1 ·
Hi Guys,

I'm hoping someone can point me in the right direction here. I've read the many recent threads regarding this issue and am still stuck. Its a 1.2 16V 2000 Corsa B-X12XE I think. (chain driven).

The coolant level has been dropping after long journeys and needs to be topped up every few days/week or so. I noticed it when the car started to get rather hot and the level had dipped below the expansion tank. I've ran the engine with the cap off in an attempt to bleed out any trapped air today.

So I've checked the headgasket (spark plugs/mayo/exhaust/pressure in rad pipes on start-up) and I'm 99% sure its not that.

There are no visible leaks so I suspected they are occurring under pressure. All the pipes seem dry and tight. And there are no leaks underneath even with the engine running for 10 mins. I have used a dose of radweld which made no difference either.

I don't think there is any coolant loss into the oil as theirs no significant mayo and the dipstick seems clean/no change in level.

Finally, I checked the waterpump area today by removing the wheel arch panel and although some of the pulleys seem rusted I could not see any leaks.

With the coolant topped up the engine seems to manage its temperature fairly well.

The only thing that I can see is there is lots of grime and grease all over the top of the gear box area (under the battery/clutch cable area). But again, not many pipes there and no visible leaks. Also the coolant tank doesn't seem to be leaking and the cap is fine as it hisses slightly upon opening.

I would appreciate any suggestions as to where to go next...

Cheers
 

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You seem to have checked most things already!

It is possible that the water-pump is leaking into the oil, this probably would NOT produce 'mayo' on the dipstick, but you would expect to see beads of water on it if it has been doing this for a while.

When you say that the coolant cap 'hisses', does it do this continuously or only for a few seconds? If it is continuous, it possibly needs a new cap.

Have you had a look in the footwell? There is a chance that the heater matrix is leaking.

Regards.
 

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Discussion Starter · #3 ·
I haven't noticed obvious beads of water on the dipstick (but I will recheck this later - I don't have the car at home at the moment).
If it is the waterpump leaking into the oil - would a waterpump replacement with new gasket fix the issue?

The cap only does it for a few seconds as I open it - I think its fine.

And again, I'll check the footwell when I have the car back but I haven't noticed any wetness there.

Thanks
 

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I haven't noticed obvious beads of water on the dipstick (but I will recheck this later - I don't have the car at home at the moment).
If it is the waterpump leaking into the oil - would a waterpump replacement with new gasket fix the issue?

The cap only does it for a few seconds as I open it - I think its fine.

And again, I'll check the footwell when I have the car back but I haven't noticed any wetness there.

Thanks
No - it's the timing cover gasket which forms a seal behind the waterpump that is a common problem. But that may not be the issue on yours is there's no sign of oil emulsion.

Given that it's a smallish leak you may find that it only opens under pressure and then emits only a small amount of steam, so you never see liquid coolant dripping. The waterpump can still leak, in which case you could replace the pump and whilst you're at it check the state of the seal behind it just for good measure.

But it could be a small leak anywhere in the system. In that situation I'd try one dose of Radweld - (repeated doses can clog up the system, but a single dose is fine) - when I've had a small leak I can't trace it has often been a permanent fix.
 

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Discussion Starter · #5 ·
Now that I've got the car back, I've had a proper look. I forgot to mention I had already tried Radweld.

It seems that the black gunk on the gearbox housing under the battery is due to coolant spray and dirt sticking to it. I have been losing quite a lot of coolant at times but its not always consistent.

The leak is coming from the heater control valve (I have the A/C model). If I open the coolant cap it now drips quite a lot (I guess I am removing the vacuum that is preventing drips). It also then stops dripping when I start the engine.

I don't understand how this valve works...but I guess it controls water to the heater matrix when I turn the controls to hot? It has a thin narrow vacuum pipe attached to it I think. I can get a replacement valve for £20 and intend to service the cooling system at the same time but could the issue be due to a failure in the vacuum pipe? Any suggestions/explanations would be much appreciated.

I was surprised the Haynes manual doesn't ever mention this valve.

Thanks for all your advice...
 

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I'm not sure what you are referring to as a 'vacuum pipe'? But, yes the heater valve does control coolant flow to the heater matrix.
Pressure in the system is generated by the coolant heating and expanding within a sealed system, the actual pressure is regulated by a relief valve in the coolant tank cap.

As the system cools down when the engine is stopped a very slight vacuum may develop in the system and, as you say this may prevent leaking when the engine is cold, however, if there was anything like a half decent vacuum in the system, atmospheric pressure would crush the radiator core and probably the heater matrix as well. To prevent a vacuum in the system, there is also a valve in the filler cap which allows air into the system as a vacuum develops upon cooling down.

Regards.
 

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Discussion Starter · #7 ·
Just a quick update to the situation...

I've replaced the heater valve and coolant and the major leaking has stopped in that area but there is still some coolant loss.

This is from the waterpump area as I saw stains on the sump when I was draining the coolant. As there is no oil emulsion I am going to go ahead and change the waterpump and auxillary belt and check seals behind at the same time.
 
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