Certified Automotive Mobile Mechanic

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Head Gasket replacement

A head gasket replacement is a major and costly repair.  Generally if a head gasket has failed there is another failure which has caused it.  Every time we inspect a vehicle with a failed head gasket we are looking for the root cause of the fault Рthis a lot of the time is from an overheating scenario. A failed water pump, split hose, cracked radiator, stuck thermostat, broken drive belt etc. All of these can cause the vehicle to overheat and damage the head and gasket. Another common scenario is when a timing belt replacement has been missed/ignored and the belt has broken which causes the valves to hit the pistons and bend. This is the same job as the head has to come off for the valve repair.

Today’s vehicle is a great example of another reason for a head gasket replacement – A Daewoo Nubira cylinder head gasket was leaking oil. This was solely due to the head gasket itself leaking. On inspection it was found to be a cheap inferior branded gasket that has been fitted several years before, it had deteriorated and started leaking. Cheap is not always best – quality respected branded parts should be used. This not a job you want to do twice!

On all cylinder head repairs we remove the head and have it overhauled by a professional machine shop. This is necessary to ensure the head is repaired back to specification. They machine/straighten the head, reseat the valves, check valve spring tensions, replace valve stem seals and welsh plugs, de-carbon, acid clean and pressure test the head.

Then it is ready for reassembly. The block is cleaned and the head goes on. Some vehicle require replacing the head bolts, as this one does. As they are one use only “torque to yield” bolts. The bolts must be torqued in sequence to the manufacturer’s specified torqued setting.

Then its reassembly of all the components – inlet and exhaust manifolds, timing belt etc. The time required for this is different for every vehicle, it can be a time consuming and an expensive repair. The final stages before running the engine, new coolant is fitted and the cooling system is pressure tested for leaks.

During the head gasket replacement process its a great time to carry out any other required repairs. Generally its easier to carry out other engine repairs as most items are going to be more accessible with the engine stripped down. This Daewoo received a new water pump, complete timing belt kit, injector seals and spark plugs. Other items that are generally checked/replaced are coolant hoses, thermostat, drive belts, air filter, radiator, engine mounts, spark plug leads, coils, distributer cap, rotor buttons, and of course the oil and oil filter.

Contact us at Certified Automotive if your vehicle needs attention.

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