HGF diagnosis

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How do I diagnose a head gasket failure?

Head gasket failures usually manifest themselves in one of three ways:

A sudden erruption of steam
An increase of coolant temperature
Loss of power/misfire

If an erruption of steam then...

Problem: Steam is errupting from my car- what is the cause?
Action: stop as soon as is safe and practical. Stop engine, and open the boot. Then as the engine cools, perform the following checks:
Look at the coolant expansion tank. Is there any coolant left? Is it boiling? Is it Green?

If yes, then the steam erruption is likely to be due to a failure of the coolant cap. To confirm, perform the following checks:

Remove the Coolant cap and examine the brass valve. There is a rivet which should be central. If it is not (as in A, the cap on the right), the cap has failed. Replace.
Check the coolant. The level should be above the minimum mark, and the colour green (as pictured in 'B'). There should be no evidence of oil or brown gunge. If the latter, then the head gasket has failed.
Remove oil filer cap and dip stick (C). There should be no evidence of a milky (mayo) residue- just oil. If present, the head gasket has failed.
Check under the car. If a pool of water, remove engine inspection cover and look at the front right corner. If water is seen existing (arrowed, 'D')- the head gasket has clearly failed.

Visual checks for evidence of a HGF

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Thanks to Jon Fredheim for the picture of the failed head gasket (D).

In the event of a head gasket failure, do not attempt to drive the car any further. Arrange transportation to an MG/Rover dealership or specialist for replacement.

If an increase of water temperature or loss of power then...

...stop as soon as is safe and practical. Stop engine, and open the boot. Then as the engine cools, perform the following checks:

Check the coolant. The level should be above the minimum mark, and the colour green (as pictured in 'B'). There should be no evidence of oil or brown gunge. If the latter, then the head gasket has failed.
Remove oil filer cap and dip stick (C). There should be no evidence of a milky (mayo) residue- just oil. If present, the head gasket has failed.
Check under the car. If a pool of water, remove engine inspection cover and look at the front right corner. If water is seen existing (arrowed, 'D')- the head gasket has clearly failed.