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The cylinder head gasket is probably one of the most important sealing components in the engine. One of the telltale signs when this gasket fails is that coolant will mix with the engine oil. When this happens the engine oil will turn to a milky color and a jelly like consistency. Often the more severe the leak the milkier the oil becomes.
Picture of head bolt tightening procedure
Head Bolt Tightening Pattern

One of the biggest causes of repeat repairs when a head gasket is replaced would be the procedure for tightening down the bolts was not followed correctly. Head bolts must be tightened in the correct order and to the proper amount of torque. Tightening sequences and specifications are available in your car service manual that will also include the step by step repair procedure for your model.

Most cylinder heads are tightened in a sequence that starts in the middle and then moves out towards the ends. The bolts are generally tightened in two or three stages. If the final torque is 100 foot-pounds the bolt may first be tightened to 50 foot pounds all away around before the final specification is reached.
 
 
Sometimes when our cars begin to leak fluid we can blame leaking engine gaskets. Often these fluid leaks begin as seepage and developed into a problem that needs to be addressed for the health of the vehicle and the driveway or parking area.
Picture of engine gasket leak
Engine Gasket Leak

For as long as there have been engines there has been a gasket. Over the years the technology has advanced that makes these sealing components more efficient. But every once in a while when they try a new technology sometimes it's actually a step backwards.

A quick example of this is just my personal opinion. The latest in Gasket technology sometimes referred to as a composite looks and feels like plastic. An example of a step backwards is in the reliability of the Gasket in the General Motors V6 intake manifold. This part looks like a strip of plastic with embedded rubber seals.
 
 
The check engine light is turned on when an engine misfire is detected because unburned fuel pouring into the exhaust manifold will cause extremely high tailpipe emissions. Also if the situation continues raw fuel entering the catalytic converter can cause internal damage to the catalyst.

This will also increase tailpipe emissions and will most likely lead to having to replace the catalytic converter which happens to be a very expensive part on most vehicles. For this reason computers can be very sensitive to engine misfires and illuminate the check engine light even if the problem is intermittent.

Misfire monitors

Picture of crankshaft sensor
Crankshaft Sensor
The onboard computer is capable of quite complicated misfire monitoring. The engine control module uses the crankshaft angle measurement to detect this misfire. It's actually quite amazing how it is performed. Click the read more button to see how it works.
 
 
Power sunroof problems reviewed. Many malfunctions in the sunroof system fall into 2 categories that can often be related to each-other. Water leak issues and electrical problems. Sometimes wiring or switch corrosion can be caused by the water leaks.
Picture of power sunroof
power sunroof

A power sunroof can slide the roof panel open or closed. You can also tilt the roof panel up in the back to allow fresh air into the passenger compartment. When driving down the road this can also pull a vacuum and remove stale air from the interior cabin.

In most cases power sunroofs are not that much different than electrically operated power window systems found in most automobiles. Many common parts are shared such as system relays, a master control switch and the motor assembly to perform the movement.

Note that most power sunroof systems are protected by a circuit breaker instead of a fuse. This is in case the sunroof begins to bind. It protects the motor by opening the circuit breaker. Often when people have power sunroof problems they will begin to look for the fuse when there is actually none. A circuit breaker will reset automatically when it cools down.