Genuine 1991 Mazda MX-6 Piston

1991 Mazda MX-6 Piston Parts and Q&A

• Q: What steps must be taken to prepare piston/connecting rod assemblies for inspection on 1991 Mazda MX-6?

  A: The piston/connecting rod assemblies have to be cleaned and the old piston rings of the pistons have to be removed before the inspection process can be done and new piston rings should always be installed in the process of reassembling. A piston ring installation tool can be used to remove rings off the pistons without nicking or gouging. Cleanse the top of the piston of all deposits with a hand-held wire brush or fine emery cloth, cleaning it with the wire brush, after most of the deposits have been scraped off, otherwise, the soft material of the piston will be eroded by the wire brush mounted in a drill motor. One must use a piston ring groove cleaning tool to remove any carbon deposits in the ring grooves or alternatively, any piece that was cut off the old ring can be used but it should not be made to strip away the metal or damage the grooves. The piston / rod assemblies are to be dried thoroughly after cleaning and they must be inspected to make sure that the holes of oil returning are clear. New pistons are not necessarily required, unless there is some damage to the pistons or the block is rebored, normal wear manifesting as even vertical wear on the thrust surfaces and a certain degree of looseness of the top ring. The pistons must be physically examined to find the cracks, scoring, scuffing, holes, and burns as these may show overheating or deviated combustion and therefore the cooling and lubrication systems must be inspected in detail. Pitting is an indication of corrosion that may indicate the coolant leakage which should not be repeated in the rebuilt engine. Measuring the piston ring side clearance with a feeler gauge and checking the clearance at several points, making sure that you use the proper ring in each groove; too clear can cause new pistons to be necessary. The piston-to-bore clearance is to be verified by measuring the bore and piston diameter, and the difference gives clearance, which must not be more than specification, rebore the block, and put in new pistons and rings. Also examine piston-to-rod clearance due to excessive wear by turning the piston and rod in opposite directions and if it is needed, remove the assemblies and have new piston pins and rebore at an automotive machine shop. Where pistons must be removed, these should also be submitted to a machine shop to be checked against bending and twisting, connecting rods to be directed to a machine shop to be examined against cracks and damage, old bearings changed, and caps tightened with fingers, after being wiped.