VW Polo 9n3 TDi coolant going down, but no visible leak

[Portland Bill]

Hi everyone,

It's been a while since I owned my own car, and I recently bought a high mileage Polo, just to get me through a few months of being at home from work.

There's a small issue with it, which is starting to get on my nerves now, but the coolant keeps going down, but can I hell find any signs of leakages around the engine bay.

When the low indicator is going off when I turn off the ignition, I'll top the coolant up to the max line. Approx 3-4 days later, it'll be low again.

I've checked the oil, which is as it should be, so no signs of it getting into the engine block, but I've tried cardboard under the engine bay while the engine is running, and I've had a bright working light all around the engine bay, and I just can't see anything.

It's the pink stuff too, so I figured it would be fairly easy to spot.

Can you guys suggest anything to help?

Appreciate it!

K

[anonymous-user]

Firstly, congratulations on the top lurking - 1 post in 63 months!

I had a radiator in my old tdi Skoda replaced in the summer after experiencing similar symptoms, it was weeping from the bottom corners and was hard to see as there isn't much room down there. I had to get my phone down on a 'selfie stick' and take some photos to see.

Re: being easy to spot being the pink stuff, if it's a small leak or two like mine was, it was small enough to evaporate without leaving a drip or puddle at first (it did when it got worse), but large enough to need topping up weekly.

[Portland Bill]

Lol, that sounds about right to be fair. It's been about 6 years since I last owned my own car, so it will have been for my last one that I registered in here.

Anyway, good shout, I'll see what I can do about having a look in there. Maybe get it up on some ramps so I can get underneath it properly.

[GreenV8S]

I suppose you can't completely rule out an internal leak but it's pretty unlikely. An external leak will either drip or evaporate. If it's evaporating, and assuming you have filled it with coolant mix and not just water, it will eventually leave a coloured stain which you will be able to see if you look in the right place. Unfortunately the right place might not be accessible or visible to you. You could try a cold pressure test to see if you can persuade it to drip, which will make it easier to trace, but be aware that some leaks are temperature sensitive and it may not leak when cold.

[Mignon]

Ideally you want a coolant system pressure tester kit. £40 or so on Ebay. You can rig one up with a spare expansion tank cap with a shrader valve from an old inner tube bolted into it. Pump the system up to 14 psi and have a good look round. Take the spark plugs out and spin the engine over and see if any water comes out. If so it's the head gasket that's gone. Try it with the engine both cold and hot. Some leaks happen when it's cold and some only after thermal expansion of the parts.

[Portland Bill]

Am I not right in thinking that if the head gasket had failed, the engine oil would be showing signs of water mixture?

[Mignon]

Portland Bill said:

Am I not right in thinking that if the head gasket had failed, the engine oil would be showing signs of water mixture?

Hmmm, maybe. A small leak would just burn the water off in the cylinder.

[Penelope Stopit]

Portland Bill said:

Am I not right in thinking that if the head gasket had failed, the engine oil would be showing signs of water mixture?

I had a leaking head gasket that didn't affect the engines performance, the leak was out of sight at the back of the engine, when I pulled the engine out I could see where the coolant had been running down the block but the leak never showed up on the ground. As mentioned above, the coolant was evaporating away

[GreenV8S]

Portland Bill said:

Am I not right in thinking that if the head gasket had failed, the engine oil would be showing signs of water mixture?

Depends where it has failed. It usually seals the chamber, crank case, oil and water ways from each other and from the outside world so a failure could connect any of those to each other.