Caterpillar 973 failure

I think we are losing something in the translation here. By the way, I think you are doing a good job in communicating a technical subject in a language that isn't your first language.

If I understand you correctly, you are asking "can an incorrectly set underspeed adjustment screw cause the system to vent?" My answer is No, (although others may have a different opinion); I have never experienced a situation where a maladjusted underspeed adjustment screw causes anything other than low torque to the travel motors or engine lugging.

cmark exact. that's what I ask. Speaking of motor overload. Right. when I power the pumps. the motor is overloaded before vent. it stalls. in order cmark. thanks again. I'm not a mechanic by profession. what little I know I owe to my father that if he was a good mechanic. I helped priate was a boy. you have helped me a lot and I thank you. I think at the end I will buy 18 barrels pistons and polish., yesterday talking to some mechanical caterpillar gave me a phone number of someone who apparently knows these hpcu. these machines are not common in my country. after a few days perhaps come and check the transmission. I just want to know exactly what to buy. although I'm not afraid of that transmission. if I have to remove it ten times, I do. just I do not want to make spending pistons or barrels. and then it appears that the adjustment was missing. Do you get me? again thank you and all the good will, and depending on what you tell me the mechanic informs me back with you. My regards, brother.

You also need to be sure that your problem isn't caused by low power from the engine.

Hello everyone. A pleasure to greet I wanted to tell you that a few days ago I resumed work on 973 ... I got in the main valve body that its springs had been changed. One is longer than the other. So look for the specs in sis. Spring 5 was replaced by 6. changed place And to change them there was no more ventilation ..
Also repair a chain .. and take a brush and some paint. Also install new board with mechanical watches. And I've adjusted the muffler. Now it looks more like a machine. but.......

Some of the work in the chain. Change of seal .. that supports the fat. And filling

And some paint internal results

okay. Now my question With the change of the springs in the main valve body, and the machine has not re-ventilated. But here is the doubt. Now the fault has mutated. It turns out that after doing an open field test, the machine rotates perfectly. And has strength that slides the chains against the earth .. but after five minutes .... (oscillates) or comes and goes. hard. And without force. The oscillating plates come in and out. Without my permission. Lower the load pressure. But it goes up again. And thus has mutated the fault. Within what little I know, my opinion is that an adjustment is missing. (I do not know) I think that if the piston pump had excessive leaks, it would not oscillate? or if? Cmark. ... or whoever may be interested, here is a link on YouTube for you to see the flaw. Note that the charge pressure gauge is below the large one. To your left down supply to the servo. Above the supply this upstream venturi. And to the right of the great meter is this brake pressure. Drops like the load pressure ... this is the link ()

OK. I'm guided by sis now. Tests and adjustments. Will make this section in the test .. Test 13.Make sure center pedal adjustment is correct. The bolt must go through the hole in the lever into the threaded hole in the valve. In the BRAKES OFF position, check the pressure to the top left plug in the main control valve.

A. If the pressure is greater than 860 kPa (125 psi), check for debris blocking the operate / brake spool.

B. If the pressure is less than 860 kPa (125 psi), from the following.
* Back flush hole. (See LOADER WILL NOT MOVE; PLUGGED ORIFICE IN MAIN CONTROL VALVE CAN BE BACK-FLUSHED in the Troubleshooting and Service Tips section of this publication.) * If this does not solve the problem, of Test 14 ..

I do this test. And in the left cap I have a pressure of 250 psi .. and charge pressure around 220.psi.

answer: A. If the pressure is greater than 860 kPa (125 psi), check for debris blocking the operate / brake spool.

I remove the spool in the main control valve without removing the body. And I get this.


speed-brake control stem Has been hit twice. I guess in an attempt to move her back. Maybe they thought she was stuck and beat her with an iron.

Now my question for you is. Does that hole drain oil? Because when blowing with my mouth does not enter or leave air. Is covered The blows have deformed it internally. Since it is as fine as a needle. I ask this question because in the hydraulic scheme does not seem to play a role there. I watched.


another thing. In the diagram there is talk of a hole 54. That hole is the one that is hit. ? Or speak of the hole start vent spool left? read this paragraph. As before, the oil from the servo relief valve is sent through external line (51) to replenish the drive circuits. The oil is also sent through charge pressure check valve (24), past the operate/brake spool and start/vent spool, to the pilot valve. When pilot valve spool (55) was in PARK, charge pressure oil was directed back to the start/brake spool to fill the chamber at the right end. The pressure in the chamber caused the start/brake spool to move to the left (position shown). With the start/vent spool in this position, the supply of charge pressure oil from the charge check valve is now sent back to the operate/brake spool where the flow divides. Part of the oil goes through tube (52) to reset the drive loops. The remainder goes through orifice (54) to the chamber at the left end of operate/brake spool (21) and to a chamber in pilot valve (5). When the pilot spool was in PARK, the chamber in the pilot valve was open to tank. This prevented the pressure from increasing in the chamber at the left end of the operate/brake spool. When the pilot spool is moved to BRAKES OFF (in either forward or reverse), the tank passage in the pilot valve is blocked. The pressure in the chamber at the left end of the operate/brake spool will now increase, causing the spool to move to the right. The spool will move until it makes contact with the end cover on the valve body (position shown). The spool is now in a position to send pressure oil through the brake line and to block the flow of upstream oil from the quick-response valve to the top of the underspeed valve, the chamber around the quick-response spool, the underspeed override valve and the spring chamber of the overspeed valve.

This is start vent spool. Has a concave hole. And if it is free. You can look the other way.



so. I want to simplify my question. The hole that is hit in the spool speed-brake drains oil or not? I do not know if I should drill there or not? I do not know if it's really a hole or a plug? Or acts as security, and opens to a certain amount of pressure. I do not want to hurt more than it already is. In the part book I could not even find their number (code) to know if they sell it or not. Thank you and happy night

Hello friend, greetings. I need the google translator again to communicate with you. I write to you after so long for two reasons. the first is that I wanted to thank you again for your support, all the knowledge acquired here is priceless. in thread 45 and 47 cmark explains about the separation of the pressure plates in the axial pumps. The mistake was mine because although I did not find scratches, there was certainly separation between the barrel and the bronze plate, therefore the loss of pressure of charge, I understood that after talking with some good people who repair hydraulic pumps. I bought new pistons and the faces of the barrels were flattened by them. so I wanted you to know that the big fault was by plate separation. I made some videos that I wanted to show later so that they could appreciate the behavior of it after the assembly. I was running to the side and made an adjustment on the synchronization valves and I was straight. I worked for about 5 hours and the machine did not enter the ventilation mode.

very good. However, when this machine does not bite, it kicks ... after these tests I could see that I had an oil canister for the final drive. The import duo cone seals were ordered, while waiting for them the machine did not turn on for about 20 to 30 days. Then when I turned it on, the machine did not move quickly. At first glance, I thought I needed an adjustment in the sub-speed shut-off valve. Install bulb tool, turn screw, and sub-speed valve back up and again wide movement in servo valves. Bravo ... I felt an expert in hydrostatic. Lower the radiator for internal washing. oil filter change, and some beautification in the cabin, lights, alternator, new teeth for the shovel etc ... and the machine would be inactive again a month. then it would not move again. It ran faster when the idle slowed down. completely remove the sub-speed shut-off valve and the internal reel was clogged. disassemble the main control use paste to grind valves. install, the machine remains the same. I'm going to the most technical part. pressure test. venturi differential. and throws me a differential of 20 psi ... at low and high engine rpm. I follow the instructions in the manual, I make a venturi pressure differential upstream minus the load pump, this test gives me a pressure differential of 20 psi.

I made some adjustments to the sub-speed and overspeed valve and now it doesn't even move. The sub-speed valve still does not appear up. take brake pressure out of curiosity and when moving lever f. p. r. towards the brakes without position, it goes from 0 to 200 as in thirty seconds, it takes a long time for the braking pressure to appear. Yesterday I decided to follow the manual and check the external line of the charge pump, good seals. dismantling main control, filter bypass valve was checked. the filter. quick response valve. Orings Venturi. internal springs reels The charge pump was checked in a test bed early today with positive and negative suction. They told me it was good. I put it back together I turned on at 3 pm. and follow the sub speed valve without appearing above. The only thing I didn't check was the internal suction tube of the transmission, the one with the screen. the manual tells me that if there is no differential pressure in the venturi, the problem must be upstream, bone, towards the suction. It is what I understand. If someone can give me a ray of light I would appreciate it.

P.d. When I write underspeed and translator place sub speed. I think they understand me the same.

How are you guys doing? I wanted to inform you that after reading the manual for a while, it occurred to me to change the filter to the hpcu. I had a 1r0741 filter on, replace it with a donaldson p556064. I had not changed it before because as I said before, the machine worked at the beginning with 15w40 mobil and a 1r0741 filter. I want to change the oil to a sae 30. Here it has the name of agrofluid. If I do not remember I think that caterpillar asks for an oil that meets the to-2 specifications. around here they sell a tek star brand oil. The model is JD-20MP tractor fluid. UTTO . says it exceeds the caterpillar to-2 specifications and others. In conclusion, I wanted to report that the problem was already resolved. I guess there was not enough flow to the venturi. That's why I want to add a less viscous oil. If you can comment on what oil to add, I would appreciate it. I already commented in another thread that the caterpillar tdto does not exist. there are also some oils here, super s 303. cam2 303. mobil fluid 424. castrol AGROF. Your opinions with these brands would be appreciated.

Cmark is the hydrostatic loader expert but I'm going to jump in here with a couple of comments that came up recently regarding another hydrostatic loader. https://www.heavyequipmentforums.com/threads/953b.79867/

1. The 1R-0741 filter Part Number is incorrect. You should be using an Ultra-High Efficiency element Part Number 132-8876, or Donaldson Part Number P165239. The use of the UHE filter is critical for correct operation of the hydrostat. https://shop.donaldson.com/store/en...iginalSearchTerm=132-8876*&_requestid=6952509

2. The oil that you should use in the hydrostat system is nothing more than a Hydraulic Oil of SAE10W viscosity. This will cover operation in an ambient temperature range from -20C to +50C. See below. The SAE30 oil that you propose is far too heavy a viscosity, even in your climate. If it is available something like Mobil DTE10 or DTE20 oil in ISO46 viscosity rating would work fine.



If you ever have problems with posting in English then please post in Spanish and I can translate it. I speak Spanish - I have to as my wife is from Colombia....!!

I can't speak Spanish,but I'm pretty good at double Dutch in the pub

nicky 68a said:

I can't speak Spanish,but I'm pretty good at double Dutch in the pub

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I speak fluent drunkenese in 16 languages......

Jajaja borracho muchos hablan en ese idioma. esta bien nige, entonces me haces dos sugerencias. La primera el filtro, creo que es fácil conseguirlo. Y la segunda es el aceite, el cual no veo tan fácil. Sin embargo trataré de conseguirlo y enviaré un video donde puedan observar la máquina en funcionamiento. En la tercera página de este hilo cmark comentó que si podía usar 15w40. Hago incapie aquí. No es que no quiera usar un aceite 10w es que simplemente no existe aquí. No hay mucha variedad y menos con los problemas que se viven aquí. De todas maneras trataré de conseguirlo. Esperemos también a ver que nos dice cmark. Les informaré como me fue. Gracias por responder nige. A todos gracias...

And translated that says - "Ha ha, drunkenese, lot's of people speak that language. OK Nige, so you are making 2 suggestions. The first is the filter which I believe is easy to get hold of. The second is the oil, which I don't see as being so easy. However I will try to get hold of it and I will post a video of the machine working. In the 3rd page of this thread Cmark commented that 15W/40 could be used. I failed to find it here [I'm assuming this refers to the 10W HYDO]. It's not that I don't want to us the 10W oil it's simply that it's not available here. There is not much choice, and now even less choice with the problems of living here. Notwithstanding I will make an effort to find it. We'll also see what Cmark has to say on the subject. I'll keep you posted how it goes. Thanks for responding Nige, and thanks to everyone."

OK, I will admit that I missed CMark's comment about using 15W40 on Page 3. From the extract of the Manual I posted above 15W40 does not appear in the recommended lubricants for the hydrotat, all it mentions is hydraulic oil of various viscosities.

Una consulta a mecaniquin. Puedes conseguir un aceite hidraulico de viscosidad ISO46..? Eso funcionaria.

Nige said:

OK, I will admit that I missed CMark's comment about using 15W40 on Page 3. From the extract of the Manual I posted above 15W40 does not appear in the recommended lubricants for the hydrotat, all it mentions is hydraulic oil of various viscosities.

Click to expand...

Very true. I admit I was surprised myself but it's the closest the OMM gets to mentioning the hystat so what can you say? If it were mine I would be putting hydraulic oil in the tranny but we can't escape that fact that it will run on 15/40. There's a video to prove it.