S60R with mysterious water leak

[Gimby]

I had the engine completely rebuilt with new Top-Hat liners, rings, shells, seals etc, together with fully balance crank with SMF and head check and refurbished turbo.
The engine was periodically run up to temperature over a year whilst other work was undertaken on the project car. The oil was always liquid gold.

Big day came around and did a mini shake down run of approximately 14-18 miles on route to MOT. All was well and car was gently driven to allow rings to bed in, not exceeding 3,500 revs. Sailed through the MOT but on route home of 1.5 to 2 miles I got the water coolant light appear. Checked the levels and the header tank was well below minimum.
My first thoughts were possibly a split hose or a poorly tightened one. Due to work commitments I refilled the header tank and travelled the 1.5-2 miles there and same distance back. Again, the header tank was below minimum when close to home. Same thing happened the following day. Subsequently, lifted the car, removed belly tray and looked for water whilst running the car with refilled header tank up to temperature. No leakage anywhere and header tank remained full.
I checked the oil filler and dipstick and to my utter horror, it was coffee latte milkshake.

Observations:
1) Absolutely coolant in to oil only. No contaminated coolant.
2) No visible white smoke
3) Leakage only appears to happen when under load (driving – even gently)
4) Engine running as normal
5) Approx 9 – 10 litres of contaminated oil removed. Car has only covered 31 miles since MOT and internal leakage of half the header tank at 2.5 – 3 miles seems a major issue.

Fault finding;
1) Compression test. Slightly low on no.1 cylinder. Need time for rings to bed in though.
2) Sump removed, coolant system pressurised to about 35 psi and no visible leakage detected.
3) Head removed and gasket and surfaces clean. No signs of blown head gasket which was initial assumption.
4) Oil cooler removed and test ok.
5) Turbo removed and tested ok.
6) PCV water pipe tested and appears ok.
7) Head waterways are being tested but unlikely as it was and know good head.

(Bear in mind, all above tests on cold engine so I guess lack of thermal expansion could be masking results)

I don’t know where else to look and the engine specialists who have undertaken this work many times before are similarly baffled.
I have discounted the water pump and oil pump as I cannot conceive a near juncture of water and oil meeting.
I run a bore scope down the water jackets and no visible signs of cracks. I did note however that there is what appears to be a pre-formed casting hole at the back – exhaust side of No.1 cylinder, close to No.2 cylinder. I assume it’s a location lug for the lower engine crank cradle. Will check further.

Given that we have tested all external bits where coolant and water could meet, I am left with the conclusion the coolant is escaping from the block to the sump given the uni-direction of coolant to oil, possible via the liners but they look good or via that lug mentioned above and between the block and crank cradle.

I would rather not just reassemble the engine and run K-Seal in the coolant, or perhaps go belt and braces and use jb-weld to seal the water jacket apexes to ensure no liner issues and similarly the aforementioned lug hole, plus run K-Seal.
Has anyone experienced anything like this? Your thoughts most welcomed apart from finding the nearest cliff.
Thanks in advance.

[abscate]

I don’t have deep knowledge on this but the R engine has thin walls between the cooling jacket and cylinders , it sounds like a crack there

Is there any “ steam cleaning “ evident in any of the cylinders? Is there any smell of coolant from the silencer?

That’s a horrible feeling after a lot of expensive work

[jonesg]

What about a smoke test of the coolant system to find the obscured leak. Smoke indicates better.