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|13th October 2007, 11:06||#1|
Senior - BHPian
How to test for a failed Engine Head Gasket
A head gasket is the coupler between the engine block and cylinder head in an internal combustion engine. Its purpose is to seal the cylinders to ensure maximum compression and avoid leakage of coolant or engine oil into the cylinders as such, it is the most critical sealing application in any engine, and as part of the combustion chamber, it shares the same strength requirements as other combustion chamber components.
Types of Head gaskets
Effects of a failed or "blown" head gasket
The failure of the head gasket will lead to overheating problems, boiling up and pressurisation of the cooling system that can lead to the failure of the radiator, hoses or even the coolant bottle can explode, Oil and water contamination, crack can appear within the cylinder head, poor performance, uneven running and eventual catastrophic engine failure if used for a prolonged period on overheated temperatures.
A damaged head gasket
What are the tell tale signs?
By following this procedure you should be able to identify a failed head gasket:
1. Open the bonnet and with the engine cold check the coolant level and colour. It should be at the normal level and the coolant should be either clear or green coloured, it should still be clean and clear, the interior of the coolant bottle or radiator should also be clean without any signs of a soapy thick creamy deposit. If there is a thick creamy scum then this is a good indication of water and oil contamination and the most common cause is head gasket failure or a cracked cylinder head. If all is as it should be move onto check 2.
2. Take out the oil dipstick, and look at the oil attached to it it should be clear or black, if it is a creamy colour then this indicates that water has mixed with the oil and the most common cause is a failed head gasket or crack in the cylinder head. If the oil is clear or black move onto check 3.
3. Remove the cap to the coolant bottle and start the engine, allow the engine to run up to normal temperature watching that the level remains contant and is rotating as it should, replace the cap to the coolant bottle and leave the engine running, if the vehicle is fitted with an electric cooling fan allow it to cycle on and off on its own and make regular check on the temperature guage, it should sit at normal. Switch the interior heater to hot and turn ON the fan, the heater should blow warm or hot. If after running at normal temperature for 10 mins the guage has stayed at normal, the cooling fan has cycled on and off properly and the interior heater is still blowing hot on demand turn off the engine, goto check 4.
4. Allow the engine to rest for a couple of mins, then with great care and while wearing something to protect you from the heat try sqeezing the top hose from the radiator, if the hose is solid then leave a little longer until you can squeeze it a little then slowly remove the cap to the coolant bottle or radiator. If the gasket or cylinder head has failed there will be a great gushing of boiling water so you must do this carefully. Stand well back and release the pressure slowly, if there is no great gush or just a slight hiss, like opening a soda bottle, it is OK but do not be tempted to dip your finger in it it is still very hot. Now check the oil again and the coolant for clarity if the oil is clear and not creamy coloured and the water is clear and the engine temperature is stable and normal then the likelyhood is that, everything head gasket wise is OK.
The short version (to detect problem)
If the oil is creamy coloured and there are soap like deposits.
If the car over heats for no apparant reason.
If the water is contaminated with oil or a soapy substance.
If the cooling system pressurises abnormally.
Can it be repaired ??
The short answer is yes, but this is not a cheap job, it should be done by an authorised service provider.
The repair will usually involve the purchase of a gasket kit and cylinder head bolts as these are made to stretch and should only be torqued down once.
A replacement head gasket sitting loosely on top of a four cylinder engine block
The cylinder head will need to be sent to a specialist for pressure testing and scanning to take out any warps caused by the excessive temperatures.
If the head has cracked then a replacement head is also required.
|13th October 2007, 19:27||#9|
Senior - BHPian
|14th October 2007, 08:57||#10|
Senior - BHPian
Join Date: Sep 2007
Location: New Delhi
Thanked: 252 Times
Great job Dadu. Will help a lot of hands-on type of people who would otherwise have had to go to the friendly neighbourhood mechanic.
|15th October 2007, 12:24||#12|
Join Date: Apr 2005
Thanked: 24 Times
@dadu - nice article ! Informative, technical and yet simple to understand.
Thanks a lot !
btw, is there any criteria to replace the gasket ( like the oil/fuel filters ), as in after say 50k kms or such ??
|15th October 2007, 12:29||#13|
Senior - BHPian
|15th October 2007, 14:00||#14|
Join Date: Nov 2005
Thanked: 8 Times
This is another reason why we need a temperature gauge in the dash.
Some cars are now giving up provide one for the sake of cost. A overheat-warning light doesn't gradually indicate a problem of overheating.
|15th October 2007, 14:20||#15|
Senior - BHPian
Join Date: May 2006
Location: Greater Chennai
Thanked: 454 Times
Thats a good write up...
The best way and the affirmative view is the mixing of water in the engine oil compartment.
Also..in some vehicles..the engine sound changes .. with increase in temperature.
But I do not agree with your final point #4.
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