My daughters Renault Twingo is giving her problems…no surprise I hear you say ….well anyway

The car had a new head gasket a year or so ago and has been fine up till two weeks ago when it ran out of coolant…no heater was the clue I think. Anyway AA came out filled it up but couldn’t find a fault but said to keep an eye out. Since then she’s needed to add a couple of litres.. Anyway Tues morning it wouldn’t start and so she took it to our local garage who diagnosed a coil problem and fitted a new pack. Don’t know if this could be related? At the same time I got them to test the coolant system which apparently passed with flying colours……

So if the pressure test was ok why is it losing coolant?

It could be leaking anywhere in the system. Checked the bottom of the radiator where the frame joins the core.

Thanx. I don’t know anything about cars and thought that a pressure test would show if it had a leak !

pressure test only shows static test in one condition. Dynamically in any of the other conditions it may be leaking.

Assuming like most drivers the coolant is only checked when something goes wrong then it could have been leaking since the head gasket change. Check around the head gasket for staining where it has been leaking and tighten the hose clips especially the radiator ones.

So it’s losing coolant at a rate of 1 litre/week? A pressure test should register a leak of that magnitude.

Somewhat odd – did it really run out of coolant for the AA call or just v low? Did the engine overheat or was the only symptom the loss of heating inside the car?

Taulpaul I think the car “told” her by warning light /engine management system…hadn’t gone completely just too low. And yes about a litre a week. Wouldn’t the garage have spotted such leaks if I had asked them to check the system?

Wouldn’t the garage have spotted such leaks if I had asked them to check the system?

You would hope so. I would suggest trying a different garage.

a leak like that externally should be obvious.

how ever – it may be falling onto the block and evaporating instantly OR leaking between gallery and piston when engines hot and being sent out the exhaust.

Check inside the oil filler cap for a creamy foam and a nasty smell, which is oil emulsified with water mixing in.

Pressure test would only show a leak if it was leaking when they did the pressure test. Could be the head gasket again, if it is then it could either be leaking into the oil (look for the tell tale “mayonnaise” under the oil filler cap or on the dipstick) or into the cylinder where it’ll evaporate without a trace (unless you take the head off and can see the damaged head gasket and evaporated coolant).

Alternatively it could be the water pump, if that’s not spinning, the fluid boils, steam/spray comes out of the filler cap*, the level drops, but there’s no ‘leak’.

*how close is the cap to the coil?

The coolant that was lost must have had to go somewhere, it should be sealed system and use very little coolant, providing there is no issues and your daughter is not doing millions of miles a week…

Renault Twingo would say to me a fairly small engine and therefore probably a reasonably small cooling system and if she has added 2 litres that is probably around 1/3 to 1/2 of the cooling system capacity. When the AA refilled did they fully bleed the system as if not this may explain the reason your daughter has needed to add some more coolant as there may have been an airlock which has made its way to the expansion tank, however an airlock would probably have meant reduced or poor heater quality, usually the first thing a woman notices.

If the garage has checked and said the cooling system is fine then I see no reason to disbelieve them at the moment. Keep an eye for any puddles on the floor or excess steam from the exhaust. You can tell if its steam as it will dissipate in the air quickly whereas smoke will hang around for longer.

I would suggest that the faulty coil has nothing to do with the head gasket, they’re not connected in any real way (apart from the mechanic would have probably needed to remove to do the head gasket) and the ignition system and coolant systems are about as separate as you can get.

To summarise, keep an eye on the coolant level, engine oil level (this might go up if the coolant is making its way to the sump) and see if you’re getting constant steam from the exhaust (you will get some as the ambient temp drops and the engine warms up).

HTH

Another thing, take the coolant cap off (when the engine is cold!!!) and smell it, you may notice a smell of petrol (hydrocarbons) which could point to another head gasket failure… One of the only ways hydrocarbons can get into the cooling system.

thanx S Wobbler sounds like a plan I’ll do that.

The other thing to do is smell the exhaust – if it smells a bit ‘sweet’ there could be coolant getting in the cylinders.

I assume she’s adding anti-freeze/pre-mixed coolant rather than just water? Don’t want a sharp frost to catch her out by freezing the system…