Head Gasket Failure

It never rains, but it pours.  After just a week of driving about with the gear box behaving nicely, the engine coolant started pressurising.  Even after allowing the engine to cool or having left it several days unused, the coolant expansion tank remained pressurised unless the cap was removed.  There was no contamination of oil or coolant, and the oil loss was not greater than normal (about a pint for every 1,000 miles), but it seemed to be losing just a little coolant.

Even if external leaks could be found, it seemed certain that the coolant loss was associated with the pressurisation.  So, the head had to come off for inspection and the gasket for replacement.  The head was found to have a small area of gas erosion where is sits against the gasket’s sealing ring on the third cylinder, allowing gas to escape into the water way between the second and third cylinders.  A little rust coloured stain on the block deck in that area confirmed it.  The deck was all thoroughly cleaned.

The head was taken to a local engineering company for pressure testing, and after passing that, refurbishment with a couple of new valves, a regrind of the other valves, re-cutting of all the seats, the honing out and insertion of bronze phosphor sleeves in the valve guides and a light skim.  The head appears to have been hot metal sprayed with aluminium before the head and gasket faces were machined, looking brand new.  The hot metal spray allows the head to be built up so that skimming doesn’t reduce its thickness.  The valve guides were found to be pretty badly worn, especially the exhaust valves, so I’m hoping that the burning oil visible in the exhaust at idle and on the over-run will now be stopped and that it will no longer use any oil.

The pistons were de-coked using EGR valve cleaner aerosol, which dissolved the coke fairly swiftly.   They weren’t bad, but it made sense to do it anyway, and it looks like that spray might be effective at cleaning valves and pistons without a strip down.  Once the head was ready, it was refitted with the new gasket and secured with new head bolts.  The rest was built back up with new gaskets and seals.

The injectors had been carefully scraped clean on strip down and left soaking in neat diesel fuel system cleaner (the additive you add to a tank of fuel) to make sure their nozzles were spotless.  The glow plugs were also cleaned up carefully to get all traces of carbon off them.  Unfortunately, on reassembly I checked the glow plugs and found them all to be unserviceable.  I had three used spares in a box, which I think may have come out of this engine when I first bought it, the fourth having broken, so had to refit a failed one temporarily to complete the engine rebuild.  I think it’s impressive that the engine would start instantly, even in winter, with failed plugs.  Anyway, it should start even better now.  The failed plug will be replaced in the next few days.

It’s all a bit of a pain, but these things happen.  Its timing is bizarre, though, immediately after fixing the gear box and also a week or two after Helena paid for the Range Rover’s engine to be done from top to bottom by Turner Engineering.  It’s as if these cars get jealous of each other!

Once completed, the coolant was topped up with a 50% solution of antifreeze and water condensed from the clothes drier – that water should be far cleaner and softer than the local tap water, which is extremely hard and creates a lot of scale.  The car was then moved under its own power to turn it around to get the sump drain at the lowest point, and it was given an oil change.  The engine was left running for a while to circulate the oil and coolant to get rid of airlocks and bleed their systems before rechecking their levels and also to check for leaks.  A few Jubilee clips on the hoses needed replacement and that cured the three coolant leaks I found, and it now seems to run without shedding anything.  The interesting thing is that the exhaust is now running clear and is markedly less pungent, so I’m crossing my fingers that the head rebuild has cured that oil loss that has plagued this engine ever since I bought if, rebuilt its bottom end and installed it in early 2008.

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  1. “It’s as if these cars get jealous of each other!” <– crap the humans are onto us!

  2. Hi Nick,

    I think you’re right mate, it’s jealousy, that and the winged pixies of mechanical misfortune. I’m sure they’re responsible for one part going t#ts up after you’ve repaired or renewed another.

    Glad you’ve got it up and running again.



  3. Really good blog you have here Nick, I have really enjoyed reading about all your different ventures. Keep it up!

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