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Discussion Starter · #1 ·
Hi all, new member here.

I have a Captiva 2.4 petrol (LPG conversion) 2007 model. I have a coolant loss/leak that I am struggling to locate. The RAC has pressure tested it and can't find any leaks, it runs smooth and no loss of power. The oil is at the normal level, coolant isn't contaminated, heaters blowing hot and so I'm asking for some advice on what to do now.

I suspect an external leak as it runs well, but I'm guessing at the moment. What would you advise me to do next, any common issues?

It is using around 2l of coolant per week, or half a pint in 40 miles.

Thank you!
Edited by: GreenFingers
 

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Is it only when being driven/running?

Has the water pump been replaced,
advisable at this age, but happily no cam belt, as i think yours is chain? ( but check!)

(It might be worth going to your chevrolet dealer as they can ask chevrolet for known faults) try the australian Holdem Captiva forum as they have more petrol models over there.

Edited by: cruzetype
 

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The fluid must be going somewhere, one possibility is a slight leak on the head gasket between a bore and a waterway, and not into an oil way, if only slight theRAC pressure test on the water systemmay not have been of sufficient pressure to show a drop,also if they pressurise the water side it is more difficult to pass water molecules through a slight leak as apposed to gas molecules passing the other way from a bore to water. Also if only aslight leak and only on one bore the pressure loss may not noticeably effect performance or smoothness but be sufficient to over pressurise the coolant systemand force coolant out of the overflow pipe probably at high revs with a hot engine. Try getting all four bores pressure tested with the block hot and keep an eye on the header tank. This is one possibility to check but I hope it is not the case.
 

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How did the RAC pressure test it? Depending on the typeof equipment sometimes a pressure test is applied to the pressure bottle screw cap thread (for convenience) which because is a good seal on the test equipmentdoesnt show up anything. However, well worth checking that the seal in your pressure bottle screw cap is sound. If it is failing/splitting it just might seepthe smallest amount once warmed up and under pressure. Could be something as simple and inexpensive as a new cap and sealon the pressure bottle!
 

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Discussion Starter · #6 ·
I really appreciate all the replies.

The RAC did use a screw on pressure tester and run the engine warm with it on.

I will reply to you this evening with some better answers, from the above suggestions.

First off, I will pick up coolant cap a before going in the deep end. What ever it is, it needs to be fixed.

Thanks.
 

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If I remember correctly, the heater matrix is a common issue...
 

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If you suspect the system is being pressurised from the cylinders when running, would it not be possible to tape a plastic bag on to the radiator cap overflow pipe, thus proving where the water is going?



And before someone says that you should not block that outlet, a plastic bag will burst before any damage done. Edited by: jegrugby
 

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Greenfingers, I dont know how easy it will be to get new cap & seal the correct size (hopefully Chevy will have used standard item
but I am not betting!). Ifdifficult to source, then a temporary seal can be made from standard PTFE plumbing tape. Pull off long length and twist it into a sort of cord that you can insert into cap groove recess.Be generous as it compresses down well. I have done this as temporary seal previously while I was waiting for correct part.

Aussie Ed
 
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