Caterpillar 973 failure

[mecaniquin]

after that I communicate with you. where I learned a lot about the functioning of these hydrostatic. and what happened wrench 1/2. this is the fault .. number five.

when I was hpcu disarmament disarming the main control valve. In its whole. with the book in hand. I got the quick response valve is stuck or jammed. so much so that to loosen use a hammer and a small steel bar. fault number 6

 

[mecaniquin]

also remove the main valve. and got this. I think is important. fault number 7

 

[mecaniquin]

Tuesday hpcu place the machine in the starting Wednesday. and still has the same fault of hell. ah but no more. there is a screw which is called ..
underspeed cut-in adjustment screw. because this screw never wanted to move because I figured he had a factory setting. yesterday decided to move it. and it turns out it was turned all right. abutted against the valve that moves in there. that certainly is number 8. fails both so not turned with a screwdriver. I had to remove it completely, and turn by hand. 15 laps gave him backward. trying at every turn. and nothing. I need now is a tool according to the manual to adjust this valve with overspeed. underspeed cut-in tool (I think it's also the thing).

 

[mecaniquin]

okay. thinking a little about what happened to that machine, thinking a bit like csi lol I think the former owner at some point the fault is present in the o-ring broken or quick response valve or blocked suction. some people without knowledge tried to fix the hpcu and left two keys inside and all relief valves or other and linkage misplaced. I'm sure the friend bob I will say that the bombs. lol but not because I think this machine is now out of tune. or what you call the loops of the unit. there any way to adjust the underspeed or overspeed valve and screw cutting? I think it's my last hope. if not that then I will have to buy someday become a hpcu repowered. thanks guys. Goodnight.

 

[Cmark]

In your post #43, the first picture is of the overspeed adjustment. The second picture is the underspeed adjustment. The underspeed screw is the important one and yes, you need the tool and an accurate tachometer to set it.

Were the faces of the barrels and port plates in good condition?

 

[mecaniquin]

yes cmark. a barrel was not damaged. and bronze dishes were good. not scratch. the tool stay behind the piece that oscillates. (which carries the two large bearings) against the wall of the housing ... Too bad we did not take photos.
I had thought that there was a method to adjust these valves (without the use of these tools) then I will have to wait for one of these tools. I doubt that today's selling. another thing. in principle 30. use an oil after use a thicker 15W40. I now understand that this affects the differential pressure across the filter discharge valve. in a tropical country that oil recommend? TDTO here the cat does not exist.

 

[Cmark]

According to the OMM, 15W-40 is good for an ambient of -15 to +50°C.

Did you check the port plates and head for flatness? If there is any problem here you can get what's known as port plate separation which will make you lose charge pressure.

(By the way, the name of the oscillating part is "swash plate")

 

[mecaniquin]

bronze dishes that go in the pump head were perfect. and a barrel mark very, very thin. not even you could feel with your finger. I have taken piston pumps excavators and backhoes that are horrible and still work. I will confess that I am not an expert, but if you differentiate between good or bad. the case is that no pressure is set to manual. upstream of venturi 500 psi. 320psi throat. Charge pressure 210 psi. 280. servo supply and are all well. wrong.
venturi should be 450, 230 for a differential pressure of 180 as the book says. servo supply 350. No 280.
pressure filter 550. The differential pressure between filter and upstream of the venturi should be 25 psi. if I can lower the pressure in the upstream of the venturi 450 would be worse the differential with respect to the filter. would have 150 psi differential. all measured with full rpm hot oil. also do not know if this is something wrong under the top cover, because it fails to reach the neutral hydraulic servo valve adjustment. and I did go above several times. the manual says that with the lever in neutral to full rpm 200 + 40-15.because by making the hydraulic adjustment watches erratic shown. the pressures oscillate strangely when I turn on one side and the other not. this is crazy friend. in the weeks to change the oil less viscous one and try to bring pressure to their standard measures.
starting with the filter doing all the way to the end. shame it takes the cutting tool underspeed. I find it hard to get up. It is only for these machines.

 

[Cmark]

If I understand you correctly, you have 500psi venturi upstream and 320psi venturi throat giving you a delta of 180psi which is correct. Charge pressure of 210psi is also correct. Servo supply pressure of 280psi is wrong.

If you move the FNR to the brakes off position (which is the point where the underspeed valve raises but the pumps are not stroked) what are your charge pressure and brake pressures now?

Have you looked at media number RENR3686 in SIS? It takes you step by step through the various pressure tests. If you are working from a paper manual, you should find it in the Troubleshooting section.

 

[mecaniquin]

I have no cmark book. everything I see by the sis. It says 450,230 for the venturi. not 500psi. the differential pressure across the filter should not exceed 25 psi over upstream venturi. therefore he asked about the oil. in the sis it says that if the pressure differential is greater must be the oil outside temperature highly viscous or obstructed filter.
I change the filter and install a new one 1r0741. anyway I'll try to change the oil and put a sae 30 and then pressure testing again and tell him how I was. I will also look at the renr3686 thanks cmark

 

[Cmark]

Are you getting confused with "charge pump pressure" and "charge pressure", they are not the same thing.

Following the logical flow of oil from the charge pump, the first pressure reading should be (1)charge pump pressure, next (2)venturi upstream pressure, next (3)venturi throat pressure, next (4)charge pressure.

If your delta between (1) and (2) is >25psi then you have either wrong oil, blocked filter or faulty filter relief valve.

If your delta between (2) and (3) is <160psi then you have low oil flow meaning worn charge pump or low engine speed.

 

[mecaniquin]

I understand mark. I'm not mistaking. the charge pump is the small gear that goes in the front of the hpcu and measured at point 7. load pressure is another and goes on to point 8. So we're good. what I mean is that in the sis says the venturi upstream raises a pressure of 450 psi at full rpm and my reading gives me 500 psi. sometimes 520 psi. and throat rather than as sis says 230 psi. I 320 psi or 350 psi. although its pressure differential pressure is within the rules, they are still high ....
I have seen how the valve underspeed going up.
as raise the engine rpm with the brake lever off ...
but abuts the valve (above) when the 1800 rpm for approx. I can accelerate more. but the valve and this butt
. as if there is a lot of pressure and the engine is not yet a full rpms. let me change the oil. and bring a thermometer. for testing properly. I think oil is not correct and relief valves are out of range. I'm getting more and more convinced that this machine was sabotaged.

 

[d9gdon]

I'm getting more and more convinced that this machine was sabotaged.

I think you're right, I've been following the thread and don't see how some wrenches were accidentally left in the system when everything has to be adjusted so closely. I keep a mental inventory of tools when I'm finishing up with something like this.

 

[mecaniquin]

hello cmark. a question. you know your tool (underspeed cut-in tool group) have by chance a photograph of her? any specification? you know if she wears in a spring? try to make a similar. and I could adjust the valves. but not if they are set correctly. in the manual it says to tighten the screw 121 mm approx. take into account the height of the bracket with height of the upper deck. and fails to make contact with the valve underspeed. contact can do 136 mm approx. I got a tachometer and achieve adjust the overspeed valve. so:

2125 rpm to 2340 rpm (hi idle) light comes on. when decreasing rpm less than 2125 rpm the light goes out. adjusting the valve to the left.

also did the same for
Underspeed CUT-IN ADJUSTMENT SCREW. but adjusting to the right.

in order as the manual says. I do not understand is that if the bracket has the height of the cover, adjusting screw 121mm not making contact. however the spring is pushing all the way up. I just want to know if I was wrong in some detail of the tool. Here some photos

 

[mecaniquin]

 

[Cmark]

No problem. Here is what you need. As you can see from the second photo, the end of the contact is almost exactly flush with the bottom of the feet. I've never had to adjust it more than 1mm each way from the current setting.

The procedure is (briefly)

1. Wear some earplugs!

2. Set the engine RPM to the specified high idle.

3. Very carefully move the FNR control on the transmission until the underspeed valve raises to the top but the pumps don't come under load. That is what the homemade adjusting too on the left is for. It is too difficult to maintain the correct position of the FNR lever by hand.

4. At this point the contact tip on the tool should be just touching the shoulder on the valve and the test lamp just lights. Adjust it until it is.

5. Slowly lower the RPM until the test lamp just goes out. Adjust the underspeed screw until the lamp goes out at the specified RPM.

If I understand you correctly, you are doing this but the underspeed valve is raising high enough, correct? If so then you possibly don't have enough delta between your upstream and throat pressures to compress the spring.

 

[mecaniquin]

cmark thanks. that if the original part. last week I was bored and manufacture a homemade tool. I know that the screw from the big nut to the tip must be set to 121 mm. Now the height of the bracket obtained from the top cover. I just want to know whether the measures are the same as yours. my height is 136 mm bracket. that height is yours? I guess its original tool takes an internal insulator. place a 12v battery near the hpcu. the negative pole to the hpcu. positive to the bulb. an electrode through the tool. Insulating a straw. (cigarette) (plastic). and works. the valve completely underspeed spend up to 2125 rpm. the light turns from there to full rpm (2340 rpm approx) but if my bracket is high, I will get an erroneous measurement. I think. Here a picture. otherwise, the measurements made with the hot oil. but even still it is falling load pressure. 200 psi falls below 80 psi. applies the brakes vent .. you believe that the adjustment of these valves has something to do with the load pressure drop? or I'm just plowing the sea? cmark thanks again.

 

[mecaniquin]

 

[Cmark]

Here is the measurement (Photo1) but if you're making your own tool, the dimension doesn't really matter. What you need to know is that the tip is flush with the feet. (Photo 2)

 

[mecaniquin]

cmark ok. I will keep it in mind. I ask the question again. you think the load pressure drop is by improper adjustment of this valve? or they have nothing to do with the low pressure load?