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I'm considering the purchase of a 2001 VW Golf TDI "mechanic's special", so named because it apparently has a failed head gasket (white smoke). I'm not a mechanic but I'm fairly handy with tools and figure I could probably fix it.

My concern is that head gaskets are not the kinds of things that just fail for no reason, and that this one might be the result of some problem that has done other damage to the engine or other parts of the car. So I'm wondering what the likely causes of head gasket failure might be, and what other damage those might have caused.

Bonus points for indicators of these problems that can be seen without splitting the engine first. :)

Edit: 225,000km (140,000 mi), if that makes a difference.

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up vote 7 down vote accepted

By far the most common cause of failure of the gasket is overheating.

So why would it overheat? Check for coolant leaks in the following

  • engine gaskets
  • water pump
  • radiator
  • pipes

Also check for oil leaks or low oil - these can have knock on overheating effects.

Check your radiator isn't full of sludge - that could be a cause of the problem, or it could get filled with sludge as a result of the gasket failure.

Some gaskets are just badly made or fitted, so check these as well.

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That makes sense. And, from your tone, I get the impression that the overheating isn't likely to have caused enough other damage to be concerned about, provided that I fix the source(s). Do I have that right? – Cheesington Mar 1 '12 at 0:53
That all depends - the longer the gasket survived, the more chance something else happened, but I have had head gaskets fail with no other damage to the engine, just to cooling components or hoses. – Rory Alsop Mar 1 '12 at 7:27
Thanks, that really helps! – Cheesington Mar 2 '12 at 2:47

Be aware that a diesel head gasket is not necessarily a job for an amateur. It is generally not as straight forward as a gasoline engine head gasket.

You may need special tools that many amateurs lack -- a torque wrench, for sure.

Be sure to consult a repair manual for your particular engine. Some VW diesel engines will have multiple head gaskets available, and you have to use the right one for your engine's serial number. The wrong one can result in piston damage if they impact the head. Remember, clearances on a diesel are much tighter than on a gasser!

You may have to replace the head bolts, as well. Some VW diesels use "stretch bolts," that are designed to elongate when torqued properly. These cannot be re-used, and must be replaced.

Be sure to examine the head carefully when you have it off. In fact, many shops will x-ray the head before replacing a gasket. Some VW diesel heads are prone to micro cracks that could be allowing coolant to enter the cylinder, even with a good gasket. These cracks can result from hot-running, just as a blown gasket can.

I wouldn't do this on my only car. It could be laid up for weeks as you go from problem to problem! If it's your "daily driver," pay someone who knows this engine to do it -- they will make sure they have all the possible problem parts on hand.

On the other hand, if you have something else to drive while you dink around on this, it can be a challenging learning experience!

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