Have a D6N LGP that the parking brake will not release on. Cat technician recommended replacing the main wiring harness as it showed signs of corroding. Replaced it and three solenoids on valves. Still will not releasing. Technician thinks it is internal now. I'm at $12,000.00 dollars repair bill and no closer to getting issue resolved. I took the valves apart and cleaned them thoroughly, making sure the screens were not plugged with debris, made no difference. Has anyone dealt with this issue before? Serial number is ALY02368
Need to eliminate the electronic system before moving on. Do you know how to access Diagnostic Codes.? If yes, what Codes do you have that are Active.?
There are no active codes. Tech cleared all codes, restarted machine and showed no active one.
Last question before we move on. Does the SERV CODE icon light up during the panel self test after you turn the key on, then go out at the end of the test.?
Currently not by the machine, so can't answer yet. Will be by it in about an hour to find out for sure and can let you know then. Thank you Nige for your quick response.
Ok after checking there is one service code but it is not flashing. It is 036. 0091.02
I’m not sure I understand you. When the Codes are displayed on the screen of the Monitor Panel they are not supposed to flash. When the Code was displayed was the SERV CODE icon to the right of the display window lit or not.?
Yes it was lit.
It is lit by the sevice code. When the key is cycled it is not lit up by the hours though.
Apart from the fact this is Code is 096F03 and yours is 091F02, does your screen look like this when you are in the diagnostics menu.? (Your screen may be gray rather than orange) Are you saying that when you scroll back to the "main screen" that displays the hourmeter the SERV CODE icon goes off.? That doesn't make sense because the SERV CODE icon is supposed to be lit any time that there is an Active Diagnostic Code. That's how the operator is supposed to be initially informed that there is an Active Code.
Rechecked it and the service code does appear after about 10 seconds. Apparently I wasn't waiting long enough.
OK, now that makes sense. The panel has to complete the power-up self-test and then go back into normal operating mode before the SERV CODE icon will light up. 091F02 is incorrect throttle switch inputs. Probably nothing to do with your park brake issue but it really needs fixing before you proceed fiurther to avoid muddying the diagnositc waters. Attached the Troubleshooting procedures. I'll send you an electrical schematic as well. You're probably going to need it.
Here is what the screen looks like.
That's exactly how I would expect the two screens to look. Thanks for confirming that.
Had the all of the panels off to install new harness. Just put the panel with the throttle switch back on and reconnected the switch. Service codes are no longer showing.
OK, moving on........... Have any pressure tests been performed on the power train and brake system.? Do you have pressure gauges.? Do you know what all the pressure test points are and where they are located.? I would be extremely interested to see what happens to the pressure at the transmission main relief valve pressure test point when the park brake switch is cycled from ON -> OFF and back again.
Yes, Cat man tested the pressure. It was around 380 and fell to 40 when we cycled the parking brake.
I do have gauges and know where the ports are, however they aren't labeled.
Sounds like the time to make a blanking plate and close the oil supply off to the brakes on one side of the tractor then test again. It would appear that the piston seal for one of the parking brakes has failed.
What is a blanking plate? How do you go about closing off the oil supply?
The glib answer is that if you have to ask that question there is a possibility that you could be in over your head. Blanking plates are often used in diagnosis of leaks in systems containing oil under pressure to temporarily close off a part or parts of the system in order to help identify where it is leaking. Generally blanking plates have to be manufactured because usually they do not figure in most manufacturer's service manuals. This indicates that pressure is being lost in the high-pressure circuit to release the parking brake. Right now I can think of four possibilities: - 1. The service brake side of the brake control valve permanently dumping to tank. 2. LH brake piston seal failure. 3. RH brake piston seal failure. 4. A crack in one of the steel tubes that are inside the rear case that carry oil from the parking brake valve to the brake assemblies on the LH & RH sides of the machine. This is an uncommon failure but it does crop up from time to time.
Can you indicate on the illustration below which solenoids you replaced.? I assume two on top (1 & 2) and one down below (12).? On the service brake proportional solenoid valve #12 did you simply replace the solenoid.? Did you remove #12 completely for cleaning.? I don't know what anyone else thinks (and TBH I'm not 100% comfortable suggesting loading the parts cannon again when you are already in a $12k hole with no solution in sight) but before going any deeper into the brakes I would try a complete new valve assembly in #12 (174-4909 Solenoid Valve Gp). There is no guarantee that will fix the problem but it is the cheapest option that I can see at the present time.
I note from your photo of the hourmeter that the tractor has almost 13K hours on it. This would be around the time when the brakes would be due for overhaul. If a new service brake proportional valve didn't fix the problem maybe something to consider would be to bite the bullet and overhaul the brakes on both sides as a next step.? Again I'd like to hear other opinions.
Canvassing for other opinions on how to confirm whether or not the source of the pressure loss is a failed brake piston seal this idea was suggested by another HEF member, and I think it has a very good chance of success. It will require all three axle shafts to be removed from the machine so that it will be possible to see right through the rear end from one side to the other. With a light shining in from one side start the engine, release the parking brake, and look through the axle shaft tunnel from the opposite side of the tractor. If a brake piston seal has failed then there should be oil flooding down either close to where you're looking from or further away. If necessary move the light to the opposite side and repeat the test. This would identify which side piston seal had failed, or if indeed that is the problem. The procedure to R&I the axle shafts is attached. You will have to make a tool to do this but the instructions of how to do it are there.
Replaced all solenoids, and replaced the entire assembly on 12, as solenoid was stuck to and damaged it removing it. Honestly I was in over my head in October, $4500.00 worth of parts and after three days of Cat on site working on it and the wiring harness wasn't out yet, realized this was getting out of hand. Between other contractual obligations and health issues, am just now getting back to work on it. Thank you Nige for your help, I will remove the shafts soon and report back.
Any time there is an intention to remove the shafts the recommendation is always to coast the machine to a stop without using the brakes, then apply the parking brake. This gives you a fighting chance that the axle shafts will have no load on them and will slide out easily. You don't have that luxury so you may have to somehow nudge the machine back and forth to take the weight off the shafts if they will not slide out using the extractor tool. CAUTION: With the axle shafts removed the machine will have no brakes at all. Take all necessary precautions to prevent the machine from rolling once the shafts are removed. in response to a previous question regarding difficulty in interpreting the drawing of how to manufacture the axle removal tool I knocked up these instructions. There are 3 pieces to the tool; a piece of 1.5" diameter round bar x 3.6" long, a 130mm-long M16 bolt, and a 4-foot length of 1.5" bore Sched 40 pipe. 1. Drill a 16.5mm through hole down the length of the round bar. 2. Slide the M16 bolt through the hole in the bar and weld the head of the bolt to the bar using a 1/4" fillet weld all round. 3. On the pipe measure back 2-3/4" from one end and drill a 1/2" hole right through it. I'd also drill a hole right through somewhere around 2-3" from the other end (for a cheater bar if necessary). 4. Slide the adapter into the pipe leaving a hair under 1/4" of the round bar sticking out of the end. Weld the adapter into the pipe using a 1/8" fillet around the end and a 5/32" plug weld in each of the two 1/2" holes that you drilled through it in Step 3.
Got hit by spring rush. Was able to pull the axels out today. There is oil gushing on the left side in the interior. What is my next step?
LH final drive has to be removed and overhauled. The brake piston seal appears to have failed. This is where you are losing pressure. I would strongly suggest that you should remove both final drives for overhaul. This is based on the 13k hours shown on the hourmeter.
Thank you Nige for your help and expertise. Your input and insight has saved my bacon!
It was a collaborative effort believe me….! If you want the procedure to remove and strip the final drive just ask.
Can you confirm that oil only gushes when you try to release the parking brake.?
It gushes all the time, doesn't matter whether park brake is on or off. This is how far I got today. n.v
Nige, your a hell of a good man!
I'm not so sure. The question was does it **** oil every time the park brake switch is moved to the OFF position.? The response was that it's pouring oil all the time whether the brake control is on or off. That doesn't sound right to me but the OP has already started disassembling and any more testing is impossible at this point. So we'll have to cross our fingers and hope that he finds something obvious when it's all pulled apart.
I'm going to suggest something to look at while the final drive is out of the machine. Get inside the hole with a flashlight and inspect the condition of the steel tubes that carry brake/steering/whatever oil around in the back end of the frame. The illustration below is typical and the arrangement of tubes in your rear case will be different. There will still be a rat's nest of tubes in there though. I can't get away from a nagging feeling that there might be a split tube in there. See if you can spot a split in any of them, at the same time grab each tube and check if it is firmly in place where it enters the case. You shouldn't be able to move the tubes at all.
I was going to say when the tech tested the pressure what was he testing and when did it drop too low. Very vague description. If the brake pressure drops when the brake is cycled to on that is normal.
I wouldn't expect it to fall that much. I get your point regarding exactly WHERE he tested it though. Also it just says "pressure". I suppose the question at this point would be "exactly which pressure".?
If he was checking park brake pressure it drops right off when the brake comes on. It’s spring applied and oil released. That’s why I was afraid he might be misleading you. Sometimes I find we assume the poster has some working knowledge of the system when he tears into it but that can lead us all down the wrong path.
I agree. Assume often only succeeds in making an "ass" out of "U" and "me"........
Over the weekend we pulled the brake and planetary assembly and the brake and differential assembly out. Started machine and cycled parking brake off and on. No changes of oil flow. Found no splits in any tubes. No warning lights ever came on, possibly it is due to no shafts or other resistance. Could it be in the brake assembly?
Maybe starting the engine makes it difficult to see exactly where the oil is coming from. Try disabling the injection system. On the RH side of the engine below and behind the turbo you should find a 3-pin electrical connector on a branch of the machine harness with another identical connector hanging from a loop. It's marked CONN 37 in the illustration below. If you remove the one connector and install the other one that permits you to crank the engine on the starter without it actually firing up. That way you might be able to look into the hole while cranking and be able to see where the oil is coming from.
Finally had a chance to go back to machine. Here is a photo of where the oil is coming from by my fingers. Steady stream when idling and pumps more when at full throttle.
The second picture is another area oil is coming from. Other than that cannot see any splits or other damage to lines.
That is the lube feed and little to cause you any bother, the main pressure seemed low as i recall seeing 340 psi recorded, I would have thought the top pressure would have been over 400 + psi (not to tuned in on 6N's) the Brake pressure is always higher than the Transmission as the brakes have to work first, I have had lots of brake issues and often found it to be the priority valve the culprit, by pulling the shafts and looking inwards the amount of lube oil spraying about is crazy, so I never bother with this, even looking through the back plate there always looks to be a massive spray of oil coming from the right F/Drive area, the 2 top coils on the brake valve use PWM to control them, the lower coil/s use 24 volt for the foot brake and park brake.
We have ruled out electrical by replacing all electrical components brake related. Could it be a foot brake issue?
It is unfortunate that when you saw the oil flowing inside the rear end that you went ahead and pulled the final drive before confirming that it was necessary. The fact that oil was flowing with both the parking brake applied and with it released indicated that it was not the problem. I can understand your frustration in getting to the bottom of what's wrong but going off half-cocked isn't going to fix anything other than relieve you of large quantities of $$. If you want to get to the bottom of this then logical diagnosis is the only reliable way to move forward. It could be an issue with the service brake control but that would come out by going through the tests in a step by step fashion. As TCT pointed out above the brake hydraulic system oil supply is prioritized over the transmission by the priority valve. You posted this earlier. Can you post photos of the valves that you disasembled. I know you said the Cat guy did the pressure tests on the brake circuit but did he test any pressures in the torque converter/transmission side.? Do you have access to a pressure gauge (1 x 35psi max & 1 x 500psi max) and the necessary hoses, fittings, etc, to do the tests.?
In the illustration below there are three solenoid valves. Two on top and one down below. Did you replace all three of them.? Also you said earlier that you had opened up valves and cleaned them internally. Did you go into this one.?
Yes did replace all three. Also cleaned all three while it was apart. Yes, I do have gauges, not sure which ports to connect to. Wasn't able to make it out to the machine to get pictures.
When you removed the three solenoids to replace them did you also remove the complete valve from the machine and disassemble the guts inside each of the different sections of the valve body in the illustration above.? Parts are broken down as per attachment.
Yes, pulled everything apart, saw nothing. Sprayed with brake cleaner just in case there was something I didn't see and reassembled
Take a good look at the parts drawing. There is an orifice plug with a screen marked #14 on Page 1. Did you pull that out and inspect/clean it.?
yes, and it was clean. It looked like a small screen thimble.
Things in the electronic system to check. There are two resistors marked 14 & 15 on the illustration below. They are located just below the circuit breaker panel marked "B". Disconnect each one in turn, check the Part Numbers just to be on the safe side, and measure the resistance. Do NOT get them mixed up, they are different Part Numbers but the connectors for them on the machine harness are identical.
Do you have a multmeter capable of measuring duty cycle to check the signal from the service brake pedal position sensor.? If you don't then Cat ET is another way of monitoring the signal.
I checked the resistors, one read 1.508 and the other read .503. What range is acceptable for the duty cycle?
Was that measuring in K Ω .? If so that is correct because one is rated at 500 Ω and the other at 1500 Ω . When the service brake pedal is up the sensor should measure close to zero %, certainly less than 5% I would have thought. With the pedal pressed all the way down it should be 95+% duty cycle.
It was K♧(close as I could find). I will check the pedal hopefully tomorrow.
Obviously you will need the key on. I'm not 100% sure whether you will need the engine running or not. try it with the engine stopped first. While you are in that area you could also check the operation of the pedal position switch. The wires in the machine harness connected to it are 198 Red and G731 Grey. That switch contacts should remain open until you press the pedal right to the bottom of its travel. At that point the contacts should close. Closing the contacts of that switch applies the parking brake. See the illustration of the brake control valve in Post #47 above. After you've tested the pedal position sensor signal and the operation of the pedal position switch go to the brake valve and measure the current being supplied to the proportional solenoid valve (#12). You'll have to do this with all the wiring hooked up and the engine running. As the service brake pedal is pressed the current to the PSV should reduce.
Will do and report back.
When you first posted you went straight into the story about how the parking brake wouldn't release and what the Cat mechanic had done and/or recommended. Can you give a bit more back story (if there is any) on anything that you think might be relevant that happened in the time leading up to the point where the park brake quit releasing. Was it an overnight issue; good one day, not working the next; or did the problem slowly build up to the point where the brake wouldn't release.?
Prior to this, once or twice in the last 3 years brake light would be on upon start up and nothing would engage. When depressing the brake pedal it would reset. The day it happened, would be running and it would slowly come on then lock up. Shift the machine to neutral and it would reset. First time it did it, it reset and then ran for an hour without any problem. Then it happened again, reset and ran a half hour. Did this until would on releases for 5 minutes. Trying to finish a pond with severe storms on the way and 2 hours left to finish is why I kept going. Cat tech thought it was the parking brake, so that is the trail we followed.
Any warning lights, buzzer or SERV CODE icon when it did that.?
Yes, all of them. They all went off after pedal was depressed.
Which warning light(s) specifically.?
The brake warning light.
The "brake system electronic malfunction" light I assume, not the "Park Brake On" light.?
Correct
The brake pedal sensor has a pink G939, a blue 140 and a brown F790 going to the connector. Tag on this part of the harness reads BRAKE AJ_C28. When checking the duty cycle, it reads 99.9% and 100% when pedal is depressed.
What % does it read when the pedal is all the way up.?
That's the correct one.
99.9% up and 100% when depressed.
That ain't right. It should read close to zero with the pedal up. You're going to have to do some disassembly. First remove the sensor (2 screws with nuts IIRC) making sure that you keep everything in the same position without turning it. You may have to disconnect it from the machine wiring harness first. There is a slot (arrowed) in the sensor that is driven by a pin on the pedal shaft. When you get everything apart inspect for anything obviously broken, worn, or damaged. Mark the position of the centre shaft of the sensor with respect to the body. Hook the sensor up to the machine wiring harness and with the key on use a flat screwdriver in the slot and rotate the shaft slightly in each direction and watch what happens to the % output signal. Report what you find.
Do not forget to test the operation of the brake pedal position switch (circled) while you are in that area. The switch contacts should be open until the brake pedal gets almost to the bottom of its travel. At that point they should close.
Same readings as previously. At one point was getting no readings. Found a blown fuse and replaced it. Same reading as before. Moved on to check brake pedal position switch. Removed the connector housing. When reconnecting the wires back, the gray went on smoothly. The red wire arced on the brake pedal and melted the tip a bit. The key switch was off, but master was on. Blew the same fuse as before number 16 the power train control fuse. With pedal depressed duty cycle reads 99.9%, at up position it reads 98.3%.
The brake pedal switch power supply on 198 Red is permanent 24v from the battery. Makes no difference if the master switch is on or off. The only way to cut the power to that wire is disconnect the batteries. Apologies, I should have warned you. The brake pedal switch is a simple continuity test, open or closed. What were the results.? If the sensor % reading does not change when you rotate it with a screwdriver then it has failed and requires replacement. The Part Number is 214-4863.
The continuity test showed it is working. I will order the other sensor and let you know results when it is installed.
Hold on a mo'. Don't get too previous........... What I suggest is this. When you receive the new sensor as a first step hook it up to the machine wiring harness connector, put the key on, and make sure you are getting a varying signal from it when you rotate it with a screwdriver. Then set it to somewhere in the range between 0 and 5%, probably closer to 0% truth be told. At this point, and assuming the pedal is all the way up, you should be able to slide the driving tab on the end of the shaft straight into the sensor. The two fixing screws ought to be lined up bang on and pretty much drop straight in. Once you have installed the sensor and tightened the hardware test the output % again first with pedal up and then with it depressed all the way. It is very important that the % signal at each end of the pedal travel does not go below 0% with the pedal fully up nor above 100% with it fully pressed down. If the signal is outside this range the sensor might need to be calibrated (it may also generate a 113.0468.08 Active SERV CODE), and that procedure will require ET. I have my fingers crossed that it won't be necessary.
Ok, I will do as you say and then report back.
2 weeks and no update. Inquiring minds want to know. How was the new sensor dispatched.? By carrier pigeon.?
Ha, no pigeons involved. Been super busy, went to put on sensor today. The sensor isn't the right one, so will have to get this remedied. Is there any reason I shouldn't put the final drive back on the machine?
None whatsoever. How so.?
Was sent 266-1466, instead of 266-1478.
Put new sensor on yesterday. Checked the duty cycle and was 99.3 no load and 99.7 with brake applied.
That seems weird on the face of it. Did you try connecting the sensor to the machine harness before installing it on the brake pedal shaft and then rotate the shaft in the centre from one (internal) stop to the other while observing the % output.? You can feel the stops if you just turn it gently with a screwdriver. Another thought. With the sensor removed can you grab hold of the end of the shaft that turns the sensor guts while someone else presses the brake pedal to confirm that the shaft is actually turning.?
I tested it uninstalled and turning it with a screwdriver.
I am struggling to make sense of what is happening. When the sensor is rotated from minimum to maximum signal the duty cycle should change significantly, usually from less than 5% to greater than 95% Which wires on the machine harness side of the sensor are you connecting to when you measure the duty cycle.?
I connected to the red and black on the sensor side.
There are two sensors in close proximity in that area; the brake pedal position sensor and the decelerator pedal position sensor. On the machine side of the brake pedal position sensor connector what are the colours (and numbers if you can see them) of the three wires in the machine harness.?
They are black, green, and redish orange. Black has number 998 on it
That’s the wiring for the decelerator pedal sensor….. The wires for the service brake pedal position sensor connector on the machine side are 140 Blue, G939 Pink, and F790 Brown. On the illustration attached, the decelerator position sensor (lower) is #2, the service brake pedal position sensor (upper) is #7. One reason why the sensors won’t swap is the one operates on an 8v supply from the ECM, the other one operates on a 24v machine voltage supply.
The wires on the sensor side of the decel position sensor should be red, black, & white. The corresponding wires on the service brake pedal sensor should be orange, black, & white.
The brake sensor wires are brown, pink and blue. On the decel sensor they are brown, orange and green. This on the harness side. The original brake sensor wires are white, black and orange. The original on the decel sensor are white, black and orange. The new brake sensor wires are white, black and red. The original brake sensor part number was 214 4863. The new updated part number is 266 1478.
Can you see a Part Number anywhere on the decel sensor.? Please check the following with the key on and the sensors hooked up:- 1. On the decel sensor measure voltage between orange and brown on the machine harness. You should have 8v. Then measure the duty cycle between green & brown with the pedal up and with it down. 2. On the service brake pedal sensor measure voltage between blue and pink on the machine harness. You should have 24v. Then measure the duty cycle between brown & pink with the pedal up and with it down.
Decel number 160 2443. The volts on decel read 1.873 with duty cycle of 0 up or down. Service brake volts were 24.17 with duty cycle reading 99.4 up and 99.7 depressed.
Please try measuring duty cycle between the white (signal) wire on each sensor and machine frame ground with pedal up/down. Let’s see if that produces any sensible numbers.
That’s the correct P/N.
Readings come out the same.
Please try this. Start the engine and press the High Idle switch so that the engine goes to full RPM. Does the pressing the decelerator pedal work to control the engine RPM from high to low.? Also with the engine running measure the supply voltage to the decel pedal sensor.
The decel is not working now. This is a new development.
But it also wasn’t working before (some wiring not connected.?) IIRC. The thing is that without an 8v supply to the decel pedal sensor I’m pretty sure that it’s not going to work. Turn the key on and give it 10-15 seconds for the panel self-test to complete. Does the SERV CODE icon come on during the test and does it stay on or go out afterwards.?
Correct, had the panel off with the throttle control unhooked. Decel was working when I unloaded it. Serv code stays on. The active codes are: 036 264.08 036 263.04 113 298.02 113 468.08 113 468.13
036 264.08 - Decel pedal sensor position signal abnormal 036 263.04 - Digital sensor supply short to ground (this is why the decel pedal won't work) 113 298.02 - service brake pedal switch 113 468.08 - service brake pedal position sensor - abnormal frequency, pulse width or period. 113 468.13 - service brake pedal position sensor - requires calibration. Do you still have the brake pedal sensor disconnected.? If so then ignore the last two Codes for now. Here are the procedures for the 263-04 and the 298-02. I would suggest you tackle these two first. get them sorted then we'll move forward.
Wow,what a complex thread. The information here is priceless but well above my head. The days of hammers seem to have long gone. Good luck with the repair. I’ll keep watching
Update: Cat tech came and rebuilt the brake control valve. Removed final drives and rebuilt the brakes. Still the same. After more digging the problem was found to be the two brake solenoids put on the second day were in the right box but the wrong solenoids. Once right solenoids were installed everything worked properly. Thank you for everyones help.
That sort of thing can make anyone tear their hair out. If the label on the box indicates the correct Part Number why would anyone suspect that what's actually in it is not the same P/N.?
Must be the most unlucky person on the planet to get two solenoids identically incorrect in different boxes.
If they came from Cat labeled wrong I think you should be getting some serious compensation for their screw up. It seems extremely odd that the solenoids would be so similar that it wasn't obvious they were wrong or different. Was the Cat tech. the one who discovered the solenoids were wrong or was it more a process of elimination since everything else was replaced or rebuilt? I'm sure there are many who would have some choice words for Cat parts royal $$$! up.
One Cat tech pt them on, and a different tech found them. They did not charge me for the last week working on it. However they are still not willing to discuss the first round.
It was their mistake and a very costly one for you.
Your Cat dealer will simply bury their heads and won’t admit anything. You’ve been lucky to get a few week of labour out of them
Still worth going after them. It was a multi thousand dollar mistake.