Hydraulics overheating with backhoe removed

[Johntc23]

Hello, I've read my manual(s) and searched the site to see if anyone else has experienced this issue. 1968 JD 450 crawler loader with backhoe runs well, does everything expected, until the backhoe is removed. Hoses hooked together so hydraulic flows properly. When attachment is removed hydraulic tank running at 1/2 window is suddenly full. The longer one runs without attachment the hotter hydraulic oil becomes until it starts affecting bucket operation and lugging engine. Reattach the backhoe everything cools down and runs normally. I have blown out hydraulic cooler, no major accumulated debris. The filters and oil have about 30 hours on them. Use it in firewood light logging work. Sometimes it is a lot easier to get through the trees without the attachment. Yesterday it had to sit and cool for about 5 hours so I could get it out of a stand of trees and reattach backhoe. Any suggestions? Thanks

[JWB Contracting]

The quick couplers on your crawler are most likely the problem. When the hoe is removed and the crawler hoses are connected together they complete the hydraulic circuit. At times you may need to hammer the couplers together or alternatively you may need to replace them. You could also remove the couplers and connect the hoses directly together I'd you wanted to be certain before putting out your money on new couplers.

Do not run this machine until you solve the issue. You can and will blow up your pump in short order if you don't.

[Johntc23]

Followed the crawler path through the trees and noticed a stream of oil on ground. The coupler was leaking when hooked together. Leaking would reduce pressure increasing heat. Doesn't leak when backhoe is attached. Need to figure out why couplers don't hold pressure when additional lines are removed. Is there a valve which is designed to adjust pressure according to load?

[Stan Disbrow]

Hi,

Check to make sure the bypass lines you hook to the couplers when the hoe is removed are clear. I had one once which had a mud dauber nest inside the line which acted as a restrictor when oil flowed thru it. Caused heating of the oil and leaking at the coupler.

This sounds like the same sort of issue. Also look for a loose flap of rubber inside the hose. I have seen that before as well. There has to be something odd with the bypass lines, or the connector ends.....

Stan

[DrLoch]

Followed the crawler path through the trees and noticed a stream of oil on ground. The coupler was leaking when hooked together. Leaking would reduce pressure increasing heat. Doesn't leak when backhoe is attached. Need to figure out why couplers don't hold pressure when additional lines are removed. Is there a valve which is designed to adjust pressure according to load?

Your going aboout this the wrong way. You need to figure out why the quick disconnects aren't connecting together correctly unless you want to learn how to get the nose off so you can replace the pump. The heat you are generating by continuing to run the machine this way is going to have an effect on everything else in the system, pump, hoses, cylinders valving and the oil itself. Remove the quick disconnects and connect to two hoses together as suggested by JWB Contracting, then let us know if that resolved the heat issue, I'm quite sure it will.

The oil leaking out could be coming from a number of different area since you are effectivly deadheading the pump against the relief valve.

Once you do figure this out I would at the least dump the oil and replace it since you have no doubt broken it down.

[Johntc23]

One of the lines does appear weak and weeping slightly at a bend. I will change it and the couplings and see if the issue is corrected. Thanks for all the feedback.

[Johntc23]

Replaced the hose finally, backhoe detached. Oil flowed through system when connected to hoe. Quick disconnect fitting never leaked again. I'm thinking the hoe was dropped when system was warm and I couldn't get the quick disconnects to reseat. When hoses bent around to couple directly without hoe, line was restricting flow, it seems. New hose installed tank level went back to normal hydraulics working properly. Interesting side, hose never leaked under pressure, when turned off it would slowly put a puddle under back end. Thanks for all the input and suggestions.