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catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 2334
Experience:  Field service technician for CAT 19 years.
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There, I'm trying to diagnose an issue on an old (1969) D9G dozer. Hydraulic oil i

Customer Question

Hi there, I'm trying to diagnose an issue on an old (1969) D9G dozer. Hydraulic oil is coming out of the side of the relief valve group whenever I move the blade. There is a flat bolt (no head on it) with a hole in it that the oil comes out of. I am not sure if this hole is threaded... The schematic that Finning sent of the relief valve group doesn't match what I am seeing when I look at the machine.
I can email a short video I shot of the issue in action, it is pretty tight in there to have a proper look... As well, I can provide the larger full tank schematic where I can point out this bolt, and perhaps someone could help in figuring out where it is on the relief valve schematic.
Submitted: 2 years ago.
Category: Construction and Road Equipment
Customer: replied 2 years ago. is what I'm dealing with. When the engine is revved up, there is oil flying everywhere.
Expert:  catmastertech replied 2 years ago.
Hello, I am sorry no one could help you earlier. I work out in the field during the day and answer questions at night. I hope this is not too late to help you. Can you post the serial number of this machine?Do you see the model or serial number of the hydraulic control? (Usually on the tank)I have only worked on two of these old iron machines and both were for fuel system leaks. I am not that familiar with the hydraulic control. I will research the books I have and see if I can find something better to help you with. You can upload most images and files to this site and help me pinpoint the problem. Can you tell me where that leak is located? (Left side of valve, Right side, bottom or under a cover)
Customer: replied 2 years ago.
Thank you for the reply.I have attached two schematics that the fellow from Finning forwarded to me. I have drawn a red arrow to the part in question on the full tank schematic. My issue is that the piece that the part is on is labeled as the relief valve, but I cannot find it on the relief valve schematic...When sitting in the seat and looking at the tank, it is on the right, but not further back than the back wall of the cab. It is underneath the coupler that brings three lines back to the tank, the one attached by 6, 12 sided, bolts.Bit of a breakthrough this afternoon as I stuck my phone in there to have a look and it appears that I can stick a hex key in where the oil was coming out and pull the whole plug/bolt out. Will return with tools/gumption in the morning, and will forward serial numbers.
Expert:  catmastertech replied 2 years ago.
Thanks for those images. I do see this is a 183 or 193 hydraulic control. I will start looking with these numbers to see what I can find. It does look like a plug to me but, you may find a spring behind it. Place some towels below if you remove it to catch anything that falls out. Be careful as it could have a strong spring or lots of oil behind it.
Customer: replied 2 years ago.
Sorry for the delayed reply, I thought I had a breakthrough last week. But 2 buckets of hy-tran on the ground proved me wrong... The serial number on the cat is 66A7480 and I couldn't find a number in the hydraulic tank.I pulled the cover off that is in the video behind the plug (plug was just a plug, no issue there) and found the gasket was shredded a bit from the center to the edge. Cover has part number 5J4485 and when I spoke with finning, the appropriate gasket is 9F8594. I cannot find these part numbers on the relief valve schematic, so I'm wondering if I'm in a different system?The new gasket seemed to fix the problem while I was parked and moving the blade up and down. Headed out to the stumps and 20 minutes later puked all of my oil out. Possibly from the same area.My questions:
What system is this gasket/cover a part of?
Could blowing it out be a symptom of a larger internal issue?Bringing in a more experienced head-scratcher this week, but any help would be much appreciated.Thank you.
Expert:  catmastertech replied 2 years ago.
Thanks for the update. I must get a different group of manuals to find this information. It is point to other hydraulic controls but, plugs can be used anywhere. I will dig into this to see what I can find and post back as soon as I have something that may help you.
Expert:  catmastertech replied 2 years ago.
I am not sure of the numbers he gave you but, here is what I think.
Your Hydraulic control is a model 193 with the serial number prefix of 27H.
I believe your video was of the external relief valve,
Serial No. 27H6166-Up and 28H9225-Up
Part of 5J3693 and 5J3691 Tank and Valve Groups
The plug that was leaking is a 9S-8009 and has a 4K-1388 O-ring seal on it.
Below is a link to the image of the relief valve. Copy and paste the link to your browser's address bar to see the Dropbox file image.
Please note in the cut-away view of the relief, the seat and relief needle are above this plug. Please be careful as they could fall out.

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