BMW Z8 Head Gasket Replacement Cost
How Much Does a Head Gasket Replacement Cost?
Head Gasket Replacement Service and Cost
The head gasket is a single, or multiple layer, durable material, that is responsible for maintaining a seal between the engine block and cylinder head. It prevents engine oil, engine coolant, and combustion gases from escaping the engine.
Most engines are constructed of two major components, the engine cylinder block, and engine cylinder head. These two halves must seal to one another, and act as one piece, or the engine will fail. The head gasket is a sealing layer of durable material that is sandwiched between the cylinder head and cylinder block. When tightened down, the cylinder head crushes the head gasket into the cylinder block, causing any imperfections to be sealed by force.
Driveability issues become more apparent and more abundant as head gasket leaks becomes greater. Head gaskets do completely fail all at once, but the majority of cases will offer some hints to failure. When the head gasket begins to fail, The engine may have no symptoms at all. Symptoms only begin to occur when the leak has reached an engine oil passage, engine coolant passage, or the engine cylinder. Once the leak has reached one or more of these critical areas, the engine will react in one of a few ways. The engine may become very difficult to start, and run roughly when idling. There may be engine oil or engine coolant leaking, and the engine may begin to overheat, or run warm. At this point, there may be coolant in the engine oil pan, that looks creamy and lighter in color than the oil. Also, the radiator or engine coolant reservoir may have a gurgling sound, the presence engine oil, or smell of combustion. The engine, in this situation, will have the check engine light on, and the on-board-diagnostics (OBD) trouble codes stored will be in reference to engine misfires, knock sensor, manifold pressure, mass air flow, air/fuel mixture, exhaust and emissions, engine cooling, and catalyst inefficiency. Finally, when the head gasket fails completely, the engine will overheat within minutes of starting, then the engine will stall and fail to restart. While it is still running, the coolant being burned in the engine will produce white exhaust, that smells sweet like engine coolant.
Driving with a failing, or completely failed head gasket is hazardous to the engine, if not impossible. In the early stages of head gasket failure, the engine is already at high risk for failure, especially with the light casting materials used in today's modern engines. Overheating is normally associated with blown head gaskets, but the cylinder head and engine block can fail nearly as easily, and do fail in many cases. Driving the vehicle when a known head gasket issue is present can or will result in head gasket failure, cylinder head failure, engine block failure, or a combination of the three. Blown head gasket, or leaking head gasket should both be taken to a repair facility being towed, or hauled.
Head gaskets can fail at any time, but most technicians would expect the head gasket to last at least 100,000 miles, especially if the engine oil and engine coolant are properly maintained. When considering preventative, or prolonging measures, it is important to understand that the head gasket seals against engine coolant leaks, engine oil leaks, and engine combustion leaks. This puts the gasket into contact with fuel, air, engine oil, engine coolant, and high pressure fire. In order to keep this gasket in good condition, dirty or contaminated fluids should be replaced on schedule, and the engine must run at the proper temperature. This is the best way to help prevent head gasket failure, besides avoiding aggressive driving.
Head Gasket Replacement Repair Information
When diagnosing a check engine light in conjunction with overheating, the servicing technician will connect a professional scan tool or computer to the vehicle via the on-board diagnostics (OBD) port under the dashboard. Reading information stored by the vehicles computer, and comparing that data to actual conditions will lead the technician to components which he may suspect of failure in short order. This may require mechanical and electrical testing, and will typically take about an hour to prove a guaranteed diagnosis and solution. In general, there are a few signs that will immediately cause a technician to diagnose the cylinder head gasket of failure. When engine oil is found in the engine coolant reservoir or radiator, engine coolant is found on the engine oil dipstick, the head gasket is leaking coolant or oil, or a compression test releases air from the engine cooling system, the technician will diagnose the engine with an internal leak. However, keep in mind that the technician cannot determine if the cylinder head has failed without the use of testing equipment, and the machine shop used will determine if the cylinder head is flat and intact. The technician will provide a report from the machine shop, and discuss whether or not the cylinder head must be replaced. If there is no error within the cylinder head, and the location of head gasket failure cannot be determined, the technician may recommend testing the engine block as well. This is a worst-case scenario, and not very common.
Replacing the head gasket and the cylinder head is the some task whether the cylinder head is replaced, or not. The technician must begin by draining all engine fluids, and possibly some accessory systems like the air conditioner or power steering. In some vehicles, the bumper must be removed at this point, with the radiator, air conditioning condenser, and associated fans and hardware attached. The accessories must be removed from the front of the engine, followed by the timing cover, valve cover, timing components, intake manifold, exhaust manifold, and anything obstructing the cylinder head from removal. Lastly, the cylinder head bolts will be removed, in sequence, and the cylinder head can be lifted off, and sent for cleaning, milling, and testing. The engine block-to-head gasket mating surface will be cleaned, and the head gasket will be inspected to identify failure points that will be scrutinized by the technician. Once the components are clean and ready for assembly, the new head gasket is set in place, the cylinder head set on top, and the new cylinder head bolts lubricated, installed, and tightened according to manufacturer specified torque. All other removed components will be installed, and replaced if necessary. The timing components must be installed, and replacement may be recommended. Once the vehicle has been reconstructed, the technician will fill, bleed of air, and test each system to ensure the customer's complaint does not return.
Head gasket additives that claim to stop leaks or reseal the head gasket from the engine coolant passages are dangerous for engines, and can cause overheating when the radiator becomes clogged, or the water pump blades erode from constant particulate contact.
Head gasket replacement means replacement or removal of many components, and the condition of the engine will be well established. If many components are recommended for replacement, or an engine rebuild or replacement is necessary, consider the cost of rebuilding versus replacing. The cost of rebuilding or replacing an engine is influenced by engine type and manufacturer. In many cases, replacement is the more cost effective route, but high performance, or luxury vehicle engines can easily cost over ten thousand dollars. Also, head gasket materials and thickness vary, and the OEM may update their design. Before purchasing parts, the latest part number should be purchased, and the quality should be guaranteed to meet or exceed OEM standards.
This is not recommended as a DIY project. Especially for the beginner or novice, this repair can easily turn into a non-operational vehicle, and a shelf full of car parts. Also, there are many factors to consider while repairing a head gasket. The engine cooling system, engine lubrication system, fuel and air systems, exhaust system, ignition system, engine timing components, and internal engine components must be understood, and properly deconstructed, serviced, and reconstructed. Very experienced DIYers may be able to accomplish this task, but if you have never completed this repair, or if you have questions, get some help before beginning.