Coolant Loss

[JamesIS220]

I have a 2006 IS 220D with 184,000 miles covered and over the last month the coolant has been dropping from max to minimum in 150 miles driven. I have covered 9,000 of those miles.

I have looked at hoses in engine bay and haven't spotted anything obvious. Is there any hoses that are well known to start failing? Tank to hose join is crusty/stained but always seems dry.

Head gasket, I don't think so as no signs yet and starts great, good idle, no misfiring or steam from exhaust and no mixing of oil/coolant and still good engine performance. Temp just below centre as always. 

Last week went straight through the MOT and did emissions test and it didn't register? Did the test twice while revving it! Examiner very complimentary saying no play in bushes/bearings and has been looked after and you know when taken for an MOT will pass.

Many thanks. James

[johnatg]

It might be something simple - try replacing the cooling system pressure cap with a new one.

But if that doesn't work:

If there are no external signs of leaks from the engine (eg pink deposits) I'm afraid that the head gasket is the likely suspect. You won't necessarily notice anything yet - the leak could be quite slight between a water channel and a combustion chamber - that can even help combustion. But that's all temporary - sooner or later it will (probably) blow big time.

You could get a cooling system pressure test done - even that may not show anything.

 

[STANSKI]

Experiencing same problem - on 07 IS220d, only 107k, MOT on Sunday - here in NI, hope it passes.

Cannot find info on changing head gasket - strange omission on this forum site - or is it me?

[daisellex]

Head gasket gone. 

[jumbojake]

I had a slow leak, turned out to be a seam on the radiator, but really hard to see ... when I was giving it a service, with the engine bay plastic removed, I could just see the pink crystals growing  ... right above the top hose

[Farqui]

Phew, well done finding the cause of the issue and good to hear that not as catastrophic as some thought.

[STANSKI]

Excellent spotting of the leaky radiator.  I am still investigating and am sourcing an egr cooler.  Definitely not a leak in my scenario - just over pressurising.