Coolant levels slowly dropping? Also ID this part/sound please!

[miniyazz]

First things first, what's the ? part on the pic below? There's a clicking noise that seems to come from that sort of area (might not be from the part though) - see video here (17MB warning sorry)

Secondly, I've had to top up with coolant a couple of times over the last few months which obviously indicates a coolant leak somewhere. No oil in the coolant and no mayo in the oil level check or filler. No obvious leaks from any of the hoses in the engine bay - some miscellaneous fluid under the car since I parked it up yesterday but it's been raining and there were other damp patches around - and I got the coolant temperature up to 108°C (OBD info) with no apparent bubbling so my informal pressure test seemed satisfactory.

Thoughts anyone?

 

[miniyazz]

Cool, thanks. Do you mean on the pipes? Or just wherever I can see on the underside of the car/the soundproofing?

 

[miniyazz]

Thanks for the info. Should I be overly concerned about head gasket at this point? My feeling was that it's unlikely given normal coolant and normal oil.. but it's obviously a concern I have

 

[miniyazz]

Mk4 Golf (V6, BDF engine), just under 140k.

I'm not sure when or if the water pump has been replaced. It doesn't look like it's mentioned in the service intervals as something that needs doing at a certain mileage/age - does it normally need replacing? Obviously people tend to do it at the same time as the cam belt but this has a chain so no changes.

Will do the above, thanks.

 

[miniyazz]

Alright guys, quick update:

Rate of coolant loss much increased (had to put in a few litres after a trip to Scotland, no overheating or anything - and chucked in a can of radweld while I was up there too 'cause I was bored) so finally got stuck in yesterday.

Piccies:





Took off the front and it quickly became apparent that something was not right around that plug thing (presumably a temperature sensor?).
The clip thing in the bottom pic looked a little rubbish but I presumed the problem was slightly further up with the seal around the sensor, so plugged it back in firmly with a liberal dosing of silicone paste stuff.

Now fingers crossed it solves the problem

Only had a couple of 'spare parts' after putting it back together, too

 

[miniyazz]

How would I go about finding that out? (or whether it's worth worrying about!)

 

[miniyazz]

I was considering replacing it but unsurprisingly I didn't have the right part, and it was a Sunday. I've just put it in the other way round so maybe it'll straighten itself out, haha.

It's also conceivable that the reason it's a bit warped is because I may have pulled on the sensor to pull it out before noticing there was a clip on it, but I didn't think I put that much force on it!

 

[miniyazz]

That could be useful, I'll have to look out for it. My Bentley doesn't seem to know about it (says I have to remove two hoses) but it's unfortunately for the US models so there are one or two small discrepancies.

9L coolant this engine holds