I have a Lull 644D-34. Serial number 00AL25w24. The hydraulics seem to surge every 5-6 second at idle with no hydraulics in use. when I use the hydraulics the surging is harder and about every 3 seconds. does any one have any ideas?
Check the nitrogen charge on the accumulator. Also check the charging valve if the nitrogen pressure is ok.
Thanks for the reply Bill. I did check for pressure at the accumulator and it only had about a few pounds of pressure in it and a little bit of hydraulic fluid came out of the filler valve I did order an accumulator rebuild kit for it but I won't see it til mid April. Then I was reading my repair manual and it does state that the accumulator is to hold pressure for the brakes and steering. Do you think this is correct? Or do you have any other ideas? Thanks for your reply Steve K
check the suction strainer also maybe
Oil coming out of the charge port indicates the piston seals are leaking which also means the nitrogen escaped out the other end. If this were mine I would disassemble it first and check the bore and the piston for scoring before ordering parts. The most important aspect of the accumulator is the useful volume and pressure. You can use any style nitrogen accumulator as long as it meets the spec.
Thanks again Bill. Where can I find specs on the accumulator. I do no the one on the Lull is a discontinued part. I will probably have to order a replacement if the piston and tube checks out bad? Thanks Steve K
There may be a label on it by the manufacture. If not just measure the internal volume and subtract the volume of the piston and the end caps. The only volume you need to know is piston travel.
I will try this Thanks Bill
You had asked about the accumulator function. It does provide reserve pressure for braking in the event of engine failure. Very little volume so steering is not really helped. The orbital steering would exhaust the accumulator in a hurry. It also provides a sort of cushion to the hydraulic system due to pump pulsation. A bad accumulator will make it cycle like crazy just like yours is doing.
I would like to thank all of you that responded to this problem. I had a lot of problems findind a compatible accumulator. However I found a NOS one on ebay. But it did the trick no more surging hydraulics. Thanks
This is what my 644-TT is doing and I just replaced the 2300 dollar Accumulator with no change
Hi, Just looking for some help, I had a same surging problem with my cat m320f. I had the accumulator replaced by a dealer and within 30m of moving the machine I blew all seals from rear hub brakes all the way back to seal on the driveshaft/dropbox. Anyone know how this may have happened? Any and all suggestions/information would be greatly appreciated. Thanks.
Web equipment in virginia was very helpful when I talked to them about charging one earlier this year, very nice folks they have videos on rebuilding and charging accumulator for lulls.
I assume that axle has internal wet brakes. Are both axles blown and leaking?
Yes they are internal wet brakes. Only the back side of the machine started to leak. The dealer opened both hubs a recon that it is only the back right leaking. Everything got to do with charging and pressures was completed by the dealer as it came as an uncharged unit. There are 2 brake accumulators and only 1 of them were replaced as it was just under charged.
Sounds like a piston seal failed. It fills the axle housing completely and then when you hit the brakes it pressurizes the whole housing. The pressure finds the weakest point to escape which is seals. It may have a lot of scarring in the piston bore in the hubs- don't know. You'll have to tear it down. You'll have to measure the brake plates too and be sure they aren't worn too thin. Is there a vent somewhere in the axle housing? There should be. Does oil come out of it when you hold the brakes?
I have been told the brakes and related parts are just good order. I don't have access to the machine as it is in the dealers workshop. Could this type of failure be directly linked to the replacement of the accumulator? In there words "The brake accumulator has zero bearing on this fault as it is complete stand alone system that is built into these machines as a safety if you lose hydraulic pressure". They are declining the responsibility or the repair. I haven't had any problems running the lower pressure accumulator for 4-5months and within 30m of moving the machine all seals from hub to dropbox have failed. Is there a possibility of this being a coincidence of the replaced accumulator or is this a result of it?
No I wouldn't think they're related
What if the accumulator was overcharged/pressurized? After their works the brakes were slightly dragging. Could this have caused it? Again I didn't move the machine very far. Could air have gotten into the system during the changing process?
Was the vent open on this machine or could some one have plugged it. Reason I'm asking we have rebuilt a lot of wet brakes that have worn out or burnt up from dragging brakes or lots of use and they will be blowing oil out the vents before they blow the axle or pinion seals. I believe you called it in your last statement when you said the brakes were dragging. If that pedals on the floor look for dirt under the mat or under the back of the pedal not letting it come all the way back up, depending on how bad they were dragging the further you went the hotter they got until they melt the brake seals and maybe that might have gotten hot enough to melt the axle seals also.
The brakes started drag immediately after the works/replaced accumulator was completed. Before this the machine was in good working order. I'm not sure how the brakes could only start dragging after the works apart from an over pressurized accumulator. The brakes are released with springs, could the accumulator over come the springs and cause the brakes to drag?