Mysterious coolant leak

[vtwinpilot]

Okay, I sourced a coolant system pressure tester (from Stant) and tested it. The results? It didn't leak. It lost *maybe* 1 or 2 psi over 2-3 mins, but from what I read, that's pretty normal. I mean, who's to say some of that leakage isn't due to the tester, or in the adapter I had to use screwed onto the top of the expansion tank.

But beyond that, after pressurizing it up to 22 psi, I looked everywhere. Everywhere. Nothing. I listened to, hoping to hear something. Zilch.

Further to that, I've not had a leak in the last 2-3 weeks. I haven't had to add a single drop of coolant. It baffles me. For about a month, it leaked coolant like mad, losing a cupful here or there. Now? Nothing.

The *only* thing I can think of that I've actually touched - and that would make a difference - is the expansion tank cap. Perhaps it wasn't tight enough before? Or was overtight and deformed the rubber gasket in there? I have half a mind to just replace the cap straight away in order to be able to cross it off the list. It's original, and the car's an '06, so perhaps the cap is failing slowly but surely, and this is the sign. Dunno.

Thoughts?

[Critical Bill]

I have same problem with my 06 V70 I haven't done pressure test yet but I added dye and could't find any leak.
I replaced reservoir with new cap , new water pump fitted a year ago and still loosing a 50 ml every week

[petey]

Was the engine hot when you carried out the pressure test?
Hairline cracks and the like will only show up then?

But a degas bottle cap is a cheap bit of security and well worth doing for the sake of it; I don’t normally go for “change things at random and see what happens” but it’s a fairly easy clean-hands that’s worth trying.

[Clan]

Originally Posted by Critical Bill

I have same problem with my 06 V70 I haven't done pressure test yet but I added dye and could't find any leak.
I replaced reservoir with new cap , new water pump fitted a year ago and still loosing a 50 ml every week

The most likely place is the bottom corners of the radiator , the coolant evaporates before it drips on the floor but leaves a stain .

Regarding the water pump , if it was a non volvo you fitted , it would be very wise to change it again using a genuine volvo pump .

[Critical Bill]

Originally Posted by Clan

The most likely place is the bottom corners of the radiator , the coolant evaporates before it drips on the floor but leaves a stain.

Thank you Clan . I will check that
I was thinking to replace radiator but I can't find Valeo one anywhere for sale

Originally Posted by Clan

Regarding the water pump , if it was a non volvo you fitted , it would be very wise to change it again using a genuine volvo pump .

Water pump and timing belt was replaced by volvo dealer for £660

[vtwinpilot]

Originally Posted by petey

But a degas bottle cap is a cheap bit of security and well worth doing for the sake of it; I don’t normally go for “change things at random and see what happens” but it’s a fairly easy clean-hands that’s worth trying.

Yup, I was of the same mind, so $7 later, I bought and just put on a new expansion tank cap. We'll see what happens. Fwiw, it's been 3-4 weeks now that I haven't had to add any coolant. I hate inconsistent symptoms!

[vtwinpilot]

Originally Posted by petey

But a degas bottle cap is a cheap bit of security and well worth doing for the sake of it; I don’t normally go for “change things at random and see what happens” but it’s a fairly easy clean-hands that’s worth trying.

Yup, I was of the same mind, so $7 later, I bought and just put on a new expansion tank cap. We'll see what happens. Fwiw, it's been 3-4 weeks now that I haven't had to add any coolant. I hate inconsistent symptoms!