My Tractor Forum banner

318 hydraulic leak troubleshooting

3763 Views 12 Replies 3 Participants Last post by  PED
Need some help troubleshooting 2 hydraulic leaks. These leaks showed up when I started using my new Buford Bucket and 3 point weight bucket.
Leak #1 leaves fluid on the ground when I park it. No much so I think the leak is mainly when I am actively using the front bucket. It lost about 1 qt of fluid after 1 hour of bucket use. It is not leaking at the filter or any of the hose hook up connectors. The underside of the control unit was wet so I wiped it down to see if I could see evidence of a leak. I exercised the hydraulics a few times and then shut it down. Nothing showed up while sitting still so I will need to check it more closely after using the bucket for a few minutes.
Leak #2 is related to my 3 point hitch with a weight bucket on it. Will not stay in up position. Over a few minutes, the weight bucket will drop to lowest position. No external evidence of a rock shaft cylinder external leak so I am guessing it is an internal leak somewhere.
Do not know if leak #1 and #2 are related or if they showed up when I started using hydraulics not previously use until I installed the bucket and 3 point.

Another "difference" is that I sometimes have a bit of forward creep now even when the control lever is in neutral. Did not have that previously. Can a low fluid condition cause that?

Any suggestion on trouble shooting this problem? I hate that thought of tearing everything apart to work on the hydraulic control unit since everything else is in the way.
1 - 8 of 13 Posts
The leak is very close to the valve set. That is the wet area and appears to be the source of fluid. I am hoping that both leaks are related. If the leak is one of the connections to the valve set, is it just a matter of tightening up the connections (assuming it is not a pin hole in a tube)?
I suspect this leak has been around since I bought this 318 because that area was very dirty and had collected a lot of oil/dirt. However, it did not show up as a major issue until I added the front bucket and weight via 3PH to jack up the pressure on those lines.
I can lift the front bucket and it will hold. However, if I lift weight with the 3PH, it will leak back down. As a result, I suspect the leak is in the lines to the rock shaft cylinder. I will load up some weight on the 3PH and see if that shows up a leak.
Hey there fellow Okie, where are you located?:Welcome1:
Longtown OK (aka Lake Eufaula)
I found a leak but not where I expected. The leak(s?) were in the hyd fittings to the steering control on the steering shaft.
My reading of the tech data and flow diagrams tell me that the steering gets fluid first then the flow goes to the accessories. If the pressure build up operates the way I think it does, loading up the accessories will force higher pressure in the lines which indicates that the steering control will experience the same higher pressures thus any loose fitting on the steering control could leak causing pressure drop in the whole system thus allowing the weight on the 3PH to drop. In effect, the fluid in the rockshaft cylinder would reverse flow back to the steering control and leak at the loose fitting. If true, I should be able to tighten the leaky fitting on the steering control that feeds fluid to the accessories and fix my problem. This could explain why a leak may have always been there but at a very low rate since there was no serious pressure in the system until I added the front bucket and the 3PH weights.
Tutor - does this sound right?
See less See more

When the loader is activated, the pump and the p/s valve see the pressure required, unless the steering is also engaged, in which case the two pressures are added together and the p/s and the pump see the combined total. At this point, flow may be affected as well.

When the 3PH is activated, the valves that are upstream, as well as the pump, see the pressure required to raise the hitch. Add in the extra info in the previous paragraph.

I understand what you are saying. The part quoted above is why I am thinking along the lines I am. I think the leaky connection on the p/s control is the "aux" output which is the source of flow to the loader and 3PH hydraulics per the flow diagram in the tech data. If the 3PH is generating higher pressure (aka...control is off center under load), that higher pressure must be seen on the input side of the 3PH control. That 3PH input is from the "aux" output of the p/s control and that is the connection I think is leaking at the p/s control (it is dripping).
I have not tried to dig into the rats nest of wire and tubes to tighten anything yet but that is my next step. It looks like I might be able to access the right fitting if I had a crow foot socket. Of course I do not have any so I guess I will need to head to town and buy a set. Any excuse to buy new tools is a good excuse. If that does not work, I guess I will need to break down and tear it apart.

The fly in the ointment here is (per your crash course) that you are implying that if all controls are centered (aka....parked with engine off but 3PH under load), there would be no way for the 3PH to drop except thru internal leakage. If true, my concern is that I may have multiple leaks...some internal and some external. I guess if I can stop the external leak that I can see, I will tackle the internal leak I cannot see next.
See less See more
One more small step. After looking closely at my parts tractor on which the engine and drive shaft are already removed, I can get much better access to the problem area. It looks like I need a "11/16 flair nut crow foot wrench" to get at the nut I need to tighten. There are 5 hyd lines which connect to the steering control and they are spaced very closely. It is impossible to use a regular 11/16 wrench....the 5 lines are spaced too closely.
A crows foot wrench won't fit either. Either a flare nut wrench, or remove one line that is easier to get to so that there is more room for dealing with the offending fitting.

I usually use a combination wrench.
Went out this evening and picked up some flare nut wrenches... both regular and crow foot. Will tackle it tomorrow.
Turning out to be more complicated than I expected. The flare nut wrenches I purchased (regular as well as the crow foot) had 2 problems. They were only 6 point (limits range of motion) so I need a 12 point wrench. Also, they were regular wrenches rather than thin wall. Combined, this prevented me from getting a wrench on the flare nut in the tight space. Now I am shopping for a "11/16 12 point thin wall flare nut wrench". Not available are typical hardware store. Back to on-line shopping.
In the meantime, I have lots of work to get done so I guess I will live with the leak and frequently top off my fluid.
1 - 8 of 13 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.