1987 D6H hydraulics getting hot and all the gauges don't work

[mountainview]

All, Can anyone help me try to figure out what is going on with a D6H that I just purchased. It shifts fine. The hydraulics all work fine but when the machine gets hot it start pouring oil out of the spool valve. Can't tell exactly where. I have taken the spool valve out and replaced all the orings between the slices. Temporarily fixed problem for a few hours. What can cause the hydraulic oil to get so hot? Is the hydraulic oil completely seperate of the transmission oil? And, all the gauges seem to be hooked up but none of them move. Are there fuses other than the ones next to the batteries?

 

[Cam85]

Yea mate the hyd oil is a system all on its own the first thing I would b doing is to get ur hands on a diagram that shows where the oil runs at a wild guess I'd say you've got a cooling issue.
First u need to establish is the oil actually getting hot or is it a pressure issue.
If it where me I would start with mech gauges and run some pressure checks try and narrow the problem down.

Now on the gauges u need them working pronto get our the test light and multimeter this could b as simple as a sender unit a broken wire or a clapped out gauge.

A manual should show u where all the breakers fuzes relays and electrical components are or should b

 

[mountainview]

I found a broken wire (power) to all the gauges. They all work now. I torqued the pass thru bolts to 85 ft lbs per Caterpillar's recommendation and ran for awhile. I cleaned the vent on the hydraulic tank thinking it might be plugged. Leak stopped but oil still getting very hot. I took the cap off the hydraulic oil tank and the oil is all full of air bubbles. Anyone know what might be causing this? Is the pump going out? Could this be my source of heat?

 

[trackdoc]

Sounds like the pump is drawing air.
Check all the hoses, clips and connections on the suction side of the pump.
When you are happy that the pump is not drawing air, check the system with a thermal heat gun.
It should be pretty easy to pin point the source of the heat.

 

[mountainview]

I pulled the floor cover in the cab and found loose and wet clamps on the suction side of the pump. Bought and installed heavy duty stainless clamps and the air bubbles in the oil seemed to clear up. I am still having an issue with the hydraulics getting hot. This is weird, I can pull the cap off the hydraulic oil resovoir and lift the blade till the oil comes up in the neck of the tank and stick my finger in the oil and it is hot but not hot enough that I can't stand it. When I go to touch the steel suction tube on the bottom of the tank I can't hold it. Extremely hot. Same is true on the supply tube that goes into and out of the top of the spool valve assembly. The top cap portion of the spool valve is also to hot to the touch. The actual control valves for the up/down and tilt you can touch and hold. Any ideas what could be causing this would be greatly appreciated. FYI, this weekend I took apart the control valves and replaced every single o-ring (Cat o-rings) in the thing to fix a hydraulic oil leak in it, oil leak fixed,but heat problem continues after 2 to 3 hours, and I am afraid the heat will take out the new o-rings if I can't find the source of the heat.

 

[Scrub Puller]

Yair . . . mountainview

As Cam85 mentioned I believe the first thing is to establish some temperatures . . . how hot is it really running, it just may feel hot to you.

After two or three hours running you can expect some heat . . . I think 180F would be about the max.

Other folks here would be more in the know than me.

Cheers.

 

[mountainview]

Last night I ran it for a few hours again and strapped a Fluke digital thermometer right on the pressure line to the top of the hydraulic control valves. Was running between 150 and 165 degrees. If you stop, raise and lower the blade a dozen or more times in a row, you can get the temperature to drop 10 degrees. This still seems like it is not using all the oil in the resovoir. Seems like raising the blade all the way up forces the majority of the oil back to the resovoir and cools it, hence the temperature drop. Anyone know what the inside of the tank looks like. Could the suction port on the tank and the return on the tank be so close together that it just keeps circulating the same oil? Also, can anyone advise and/or provide me with drawings/instructions on how to check high/low pressures of the hydraulic system?

 

[Nige]

Temperatures fluctuating like that makes me wonder if the hydraulic oil cooler circuit is working as it should. The cooler is mounted in between the fan and the radiator at the top of the radiator. Is the cooler blocked with trash and not getting air flow..?

 

[mountainview]

I am being told by the local Cat dealer that this unit does not have a hydraulic oil cooler. I will search around the radiator but was told that this serial numbered unit did not come with one and the oil is cooled thru the hydraulic oil resovoir. What is a typical hydraulic oil operating range once the machine is warm?

 

[Nige]

Don't keep us in suspense - what's the S/N..? Or at least the S/N prefix.

 

[mountainview]

6FC-00369
I would really like to check the high pressure at the hydraulic control valve to see if it is set to low. Can anyone tell me how to do that? Where and how do you check the low pressure?

 

[Mjrdude1]

We have a D7H that also had this issue, did not come with a cooler from the factory, we installed one. Our machine is a 2RG prefix and is a Japan built machine.
The cooler isn't cheap, but I would advise installing one unless this is a casual use machine.
Edit to fix SN prefix.

 

[Nige]

You're right, the machine wasn't built with a hydraulic oil cooler - how strange. The cooler arrangement is 5G-8902 that consists of 7C-9671 Cooler Group, 5G-9308 Lines Group, and 9T-6049 Bypass valve Group.

Let me get this right. You want to check the operating pressure in the hydraulic implement circuit, correct..? This particular machine has Load Sensing Hydraulics - that'll be fun ..........

 

[Scrub Puller]

Yair . . . Nige.

What would be the purpose and point of Load Sensing Hydraulics on a dozer?

I must be missing something, I just don't get it . . . or why Cat would build machines without hydraulic cooling unless there was a stipulation about the duty cycle and ambients they were to work in.

Cheers.

 

[Nige]

Mate, I generally work with the big stuff as opposed to what we in the mining industry derisively refer to as "Lawns & Gardens" equipment, and quite frankly when I get into something like this D6 I thank my lucky stars that I do TBH ..........

Regarding the hydraulic oil cooler I can only imagine that at the time Cat wanted to set a Base Price for the machine that was competitive with the competition, and leaving out stuff like this and making it "Optional Attachments" was probably the way to do it. I personally can't imagine buying any type of dozer without a hydraulic oil cooler unless I was taking it to somewhere that was really cold 12 months a year. Of course that's fine while it's in its original territory but the problem comes when a 2nd or subsequent owner buys it and moves it elsewhere and really needs the attachment that the original owner didn't need, if that makes sense.