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Welcome to JUST ANSWER heavy equipment. With years of experience, I look forward to doing my best to help. Heat is generated by resistance of the oil flow. The squealing is the oil going thru a small orifice like a relief valve. If the drive loop filter is getting the hottest, look for a restriction there. The hot spot is the resistance.
Using a infrared thermometer the the end of the pump is getting the hottest. As you raise and lower the boom the pump temperatuer rises about 5F. Hard to with engine noise but does not sound like that is the area of the squeal. We changed the drive loop filter and no change. The only time you get the squeal is on the primary boom down.
What kind of problem is the overheating causing? You know that hydraulic oil is not considered hot until it gets above 220 degrees. anything over about 140 degress , you can't hold your hand on it.
It causes the primary boom to lower very slowly or at times not at all. As the temperature climbs to around 200 other functions are sluggish.
Boom has adjustable flow control valves on the base of the cylinders. Have you tried loosing them? Put there to keep boom from moving too fast.
the cylinder was the problem.