This machine has a hyd. motor driven fan and as one of several things I'd like to check is to see if fan is running at the correct speed. Anyone know where Cat hides the spec's on something like that? I have the paper version of service manual at work but was trying to locate something on the online Part Store. Can find instructions on remove and install but so far nothing about the fan system at all. Looked in spec's for cooling system and hyd. system but did not see anything right off. Thanks for any hints, Ken
Well guess I didn't look deep enough it's way down at the bottom of the page on the Electrohydraulic System instructions. Media # RENR6218 Guess I was kind of thinking the fan info would be in cooling system section, who knew!
A hydraulically-driven fan (or at least the drive part of it) will always be in the hydraulic system, as you've discovered. Not sure if the 988H is the same as a 992G but on the 92 there was a small filter built into a fitting in the hyd fan motor circuit that often got partially plugged and caused the fan motor to run slow and the cooling system to overheat.
Also on machines with hyd fans there is a check valve that open circuits the fan hyd circuit when you shut the engine down (and hence stop fan pump flow) this allows the fan motor to "spin down" to a stop. If it has a problem it can open circuit the fan hyd circuit and dump a bunch of flow which reduces fan speed and then things overheat. Had a 5230 one day down for 24 hrs which included a pump change during dayshift and we started nightshift and around an hour in i decided to check this valve, nothing seemed out of place and lots of oil was coming out so jammed it back together, started it up and off the 2 fans went!! In this case i believe it was an air lock, also just had a 24M with the check valve collapsed and this caused overheating.
Good thoughts from Gav. in the hydraulic fan lines group either the check valve for the oil cooler bypass or the anti-cavitation check valve for the fan motor could be dodgy.
Well hate to have to admit what I finally found to be the cause. I'll plead innocent due to the fact that I only had a few minute to look at this right at the end of the day. I did my original post at home after supper. Operator had said the coolant was right in the middle of the sight glass. Well I washed off the outside of radiator and ran through the calibration of the fan. Speeds were a little below spec's but not enough to cause a problem with temps only in the upper 70'sºF. Let him take it and it ran fine for a couple hours. Then it started getting hot. I noticed a large temp differential from top rad pipe to bottom, over 70º! First thought now was bad water pump. Just to check to see if there was exhaust gasses getting into the coolant decided to top off radiator right to the top of the filler neck. I figured one or two gallons would do the trick, well how about 7 gallons low on a 25 gallon system? Feel free to give me a dope slap! After six hours hard work operator said the gauge never moved off the top center mark. I have not replaced the sight gauge yet but will as soon as I can get to the dealer to pick up a new one. I will look into the possibility that this machine has the filter in the fitting to the motor and try to keep in mind the spin down valve if I have a fan speed problem with one of these hyd. fans.