I've got a 2009 Volvo L120F Loader that is throwing a Warning Brake System Failure message. Accumulators (new), Sensor SE5218, Solenoid MA5502 have all been swapped from a working loader we have in shop and it still hasn't solved the issue. We tested and measure the wiring from V-ECU to the sensors and solenoids (all within specified limits). Additionally my accumulator pressure is sitting around 1845 psi (I know its supposed to be above 1900, but it was at 1400 before I replaced the accumulators). I've bled the system, according to the service manual, and all my brake functions are working properly, and will pass a brake test. Any help is greatly appreciated.
What is your fan speed? When operating does it over heat? Do you have a quick attachment?
Paul, Fan speed I think is sitting around 440 RPMs, does not over heat, and no attachment just a plain bucket attachment(non-clamshell). Thanks for the quick response!!
Brake charging does not occur till pressure reaches 1780, cut out is around 2200. Do the accumulators hold pressure in the manifold with the machine off?
Are you measuring pressure off the accumulator manifold or monitoring what SE5502 sees on the display?
Correction, my accumulator pressure is now at 2050 psi with engine running. I am providing readings from SE5218 being sent to operators display in service mode. That's how I provided the numbers in this post originally. I do not have a pressure gauge compatible with the system. We are quite limited on what's available at the moment. Fan RPMs are at 420-440 and I have adjusted the speed sensor to the correct depth (1 +/- .2 mm) but did not change anything. I feel like this is really low. What is the correct Fan RPMs supposed to be at? Am I able to adjust PWM2601 for fan pressure to control speed? MA5502 is a solenoid though, not a pressure sensor.
Additionally, accumulator pressure gradually drops by 4 psi every 15-20 seconds with engine off.
With machine off pump the brakes until you have no pressure. Now start the engine and see what it will build up to. Like FWF said the brake charging pump will charge it to 2200 and kick off. With the engine still running pump the brakes and you should see the pressure go down and build up again around 1700 psi. If that is happening then your brake charging pump is working. Now shut the engine off when you hit full pressure on the brake accumulators. With the engine now off pump the brakes. I like to get 5 pumps before all the pressure is gone. I think the book calls for 3. Anything less than that you have a bad accumulator or accumulators.
By the way. The brake charging pump is mostly back up for charging the brake system. The machine passively charges the brakes through the hydraulic system as you work.
Paul, Accumulators are brand new and pressure sensor is brand new just installed yesterday before I joined this forum. That's what we originally thought as well after diagnosing that it had to be bad accumulators, but still a no go. That's why we are so boggled by this warning message. Everything works like it should. Starting to wonder if its just the V-ECU acting up?
Ok, the slow drop indicates you have some leakage at the one way check valve feeding the accumulators. 15psi/minute isn't terrible. Let's check basic health of brake system. 1) monitoring brake pressure, pump brakes till pressure is around 1400. 2) start machine and observe pressure climb. At what pressure does it stop? Should be roughly 2200 psi. This is cut out psi. 3) pump brake pedal watching pressure, do it slowly and deliberately, your watching for the threshold of when the pressure stops dropping and begins to build back up. This is cut in psi. This should be close to 1800. 4) repeat the process 2 or 3X to get an average. 5) now we gonna check max brake charging, once the brake pressure has reached its cut out pressure, we need you to curl the bucket back over relief. You should see an increase of at least 200psi. You should now be at or near 2400 psi. I suspect this is where your problem lies. Based on info you've already provided. If there isn't enough separation between max charging and cut out pressure, active brake charging runs over the pressure reducing valve for max charging. Since the sensor can't see the value it wants in 60 seconds, it continues to throw oil at accumulators instead of fan. What you'll need to do is adjust the reducing valve PB at the central valve. On that same block that you swapped MA5502, on the bottom edge, facing the trans is the pressure reducing valve for brake pressure. You want to loosen the jam nut and adjust it in until you reach 2400 to 2450 while holding bucket over relief. Good luck . BTW, make sure to place the frame lock before climbing into the turning joint. You could probably do this from underneath if she doesn't have belly guards.
Please let us know how things shake out.
Item 1 is pressure reducing valve for brakes.
Item 40 is inlet check valve. This will more than likely account for your bleed off as minor as it is.
OMG , I totally gotta learn to type faster
FWF, Thanks for the input. I will let you know what my results are. Also thanks for pointing out that check valve, it just looked like a regular hydraulic T-fitting whenever I was replacing the accumulators, didn't think anything of it.
The T is a T , the fitting that screws directly into the manifold is the check valve. The fact that you have a T fitting says you have hydraulic parking brake. That T feeds the park brake release valve. There is a slight, very slight chance that it is leaking a little. Not likely though. Easy enough to remove from the equation, just take the T and branch line off for testing purposes.
FWF, My results are as follows, 2) pressure stops at 1807 3-4) each time I pressed the brake pressure would drop down to around 1620-1660 psi before building back up my average was 1636 psi 5) with the bucket curled back there was no psi change in accumulator pressure. After completing this I went directly to the reducing valve to make adjustments. My guy sitting in the cab said that it jumped to 2150 psi and then would start dropping again as I kept adjusting. You could hear a change in the machine when it hit that sweet spot though at 2150.... Bad reducing valve maybe? Also this loader does have the clamshell attachment. I was mixing it up with another vehicle we had in shop. Would this make a difference in anything? I know Paul mentioned it before when he was originally asking questions.
Ok, let's back up to beginning. In the service screens there's a max fan speed test. This acts as bit of a hillbilly flowmeter. Full throttle, max test on you should see 1900 rpm or so. There are no adjustments that you can make to the fan circuit other than speed and direction (if it is equipped with reversing fan). This will tell us if your pump is healthy or tired. You've said, best pressure attainable with pressure reducing valve is 2150. That's not getting it done. And that was done using your bucket relief circuit. That says you have a parasite taking your oil. Remember that T fitting. You're going to remove it now. Cap the hose coming from the side so that you only have the hose from the central valve feeding the accumulators and the 2 hoses going to the brake valve. You have to cap that other hose, I suspect it will leak from tank quickly. If my suspicions are right, your park brake valve is leaking to tank.
I’m feeling aroused! LOL
What got ya, the leaking part?
BTW, Paul was onto something when he asked about the quick attach bracket for the bucket. Not whether it was a clam or grapple. So to simplify things, is your bucket pinned to your frame or is it on an attachment carrier. I don't have the schematics in front of me, but the diff-loc and quick attach solenoid valve are also components that could cause a leak to tank.
FWF, I've got good news I think. I mean we are making progress. But with that line disconnected and capped from the T-Fitting my pressure shot up to 2240PSI, but also with that line capped the accumulator pressure seems to leak down a lot faster. So I think I'm leaning back to it being that check valve into the accumulator block you mentioned. I'm assuming that the line going to the hydraulic park brake was more/less helping to keep the pressure from dropping faster than it actually being the root of the problem. Also, it is a attachment carrier after looking closer at it. From first glance it looked like it was only pinned, but it does have the hydraulic attachment lock tucked away under the bucket. I'm gonna double check these lines though and fittings going to the quick attachment. Lines look like they've been wet before and collected a lot of dirt or they are still leaking. Its hard to tell sometimes out here in the desert.
You're not there yet. We need you to check max brake charging. That may be higher than 2400 now, bring that pressure back down. Replace the check valve, and the park brake solenoid valve. I will try to get you part numbers . Are you losing hydraulic oil or is your transmission fluid gaining oil. Just something we have to look at.
Get yourself the non return valve and gasket. Then the park brake solenoid valve. Pay attention to the serial brake.
FWF, Appreciate the help big time! Just FYI I have the parts manual for this thing, so you don't have to waste time looking for them. On a side note, its takes about 2 weeks, maybe more, to get parts out to where I'm at. So after this you probably wont be hearing from me until then. I will keep you updated as soon as that happens!! V/r, Joshua
No loss in hydraulic oil/ no gain in transmission. I'm assuming your asking because of possible leak by into either system.
sorry i know this is a old post, but what ended up being the problem, i am having the same issue with my l90f
Hey buddy, welcome to the forums. For starters. Head on over to new member introductions. Say hi. Tell folks what you're up to and how you found our little slice of heaven. Then , when you're done with the mushy stuff, drop in wheel loaders forum, lay out your problem in detail the best you can. Include model and serial numbers so we can help you better. OP never got back to us on final solution, there are multiple possibilities. Never assume someone else's diag and correction are the same as yours, that's a good way to waste a lot of money. Good luck and welcome