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B A Star
08-07-2000 23:05:40
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Re: Hydraulics on 1855 in reply to Alex, 08-05-2000 14:26:28
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1855 Hydraulic problems, hum. How about a little service school on these systems trouble shooting?
First this is a closed center system, there isn't a charge system to the main pump(later tractors have a charge system) oil flows from the reservoir through a tube to the filter, then to the main pump by gravity and low pressure (suction) in the main pump when in demand. A simple test of the main pump is to heat the system oil to 100 degrees +. How do you know when it is warmed to 100 degrees, simply grip the line going into the pump, when it is 100+ degrees you can't hold your hand on the line. After heating the oil, shut off the tractor and remove the small return line (case drain) at the top of the main pump and install a standpipe line into a container. With the system pressure at standby pressure (2200 PSI) start the engine and measure the amount of oil flow. Any amount of flow in excess of 1 Qt. in 15 seconds means the pump has a problem, head it for the tree patch as it will be as cheap to replace it. Be careful when checkin as I have had a 5 gallon bucket blown out of my hands by the large amount of flow. Your problem could very easily be air in the system. Air can enter at any of the lines, fittings and/ or around the filter housing. The system has an air removal system built into the tractor, there is a small line from the top of the filter going to the cooler pump, it pulls a small amount of oil from the top of the filter and returns it to the resevoir (and takes air along with it), however if the air leak is too large it can't remove all of the air and the main pump sounds like it has a belly ake when you put a demand on it. Like we said any place on the inlet side can cause a problem, even overtightening the filter can and caveing in the bottom could cause the problem. How do you check for air in the system? Remove the hood and you will find hoses that connect the cooler to the return line going back to the resevoir (runs over the top of the engine). Get a good quality clear plastic hose and insert it inplace of the return hose. Now heat the oil to 100+ degrees and look for bubbles going through the hose. Any bubbles (even a small stream) will cause trouble like you have.
Remember that the pump is trying to get oil from any place it can when it is in demand. Even a leak in the cooling system can cause the problem, like overtightening the belt that drives the cooler pump and causing the drive shaft bushing and seal to fail allowing air to enter.
Interesting the pump is Mfg. by Vickers and is almost the same as the main pump on the 6000 & 7000 series John Deere tractors, and the secondary pump on the 8000 series, the difference being the Deere system is a pressure on demand system and uses a different compensator to regulate the pressure.
When purchasing filters be careful to get the proper one, the Oliver part is a 5 micron filter, filters with larger opening can cause steering system failures. Hope this helps to solve some problems.
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