Flu419 front hydraulic system normal pressure?

[Jamesm417]

I am wondering if the front hydraulic system of the FLU419 operates at 2,450 psi, like the rear system?

 

[rtrask]

I am wondering if the front hydraulic system of the FLU419 operates at 2,450 psi, like the rear system?

Take a look at the TM 5-2420-224-20-1 in chapter 1 it has a lot of specs. I know that the front circuit has a flow rate of only 8 gpm, compared to 26 gpm for the rear. I suspect that flow rate is more pertinent to what you want to know.

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[Jamesm417]

No, I was unable to lift a stump with my bucket, but couldn’t. (The backhoe lifted it with ease.)
i would like to measure the operating pressure to the loader. I’m hoping to use a couple of hydraulic quick connects with a gauge plumbed between them for testing.
I would like to know what the normal operating parameters are. I had no luck finding an operating pressure published in the TMs.

 

[Speedwoble]

In the main FLU owners thread, Jay Couch made a post that he had turned the pressure relief on the loader circuit up. I believe it was operating around 2400 and he turned it up to ~3000. Note, the military had the lower pressure to prevent damage to the machine. This Unimog is made for moving dirt loosened by the backhoe, not digging. The lowest working gears are not strong and putting it in working range and pushing with the loader will result in a grenaded transmission, or loader frame damage(likely not right away)

 

[simp5782]

All hydraulic systems operate in the 2300 to 2500 range on normal with the option to be turned up. Do not exceed your hose rating though. Most hoses are 3200 to 5000psi HOWEVER if you have not replaced those hoses on the truck recently blowouts are likely. GPM flow has nothing to do with it other than how fast it can go when operating.

I have a 6gpm electric 24v pump that runs 2500psi. It can lift the ramps on my trailer. Not fast but it will lift them.

 

[tennmogger]

The front hydraulic pump is belt driven so maximum pressure drops when the belt slips. That's the limiting pressure factor on this system. Check your belt, clean it, tighten if in good shape. The belt should ride high in the V pulley at the front of the engine, even a little higher than the outside circumference of the pulley. The belt is 12.5 mm wide.

A common problem is that a narrower SAE belt from a local source will fit but will ride down in the grooves, maybe even bottoming out. The belt will slip and drop the pressure. If the belt is loose or down in the grooves then you know the cure.

By contrast, the rear, PTO driven system in the rear (backhoe) is limited by a resettable pressure bypass valve.

Edit-update: The following applies to a standard U-406 and U-416, just fyi. (with a 419 your mileage may vary)
Operating pressure 150 Bar, about 2176 psi
Delivery 40 L/minute at 2550 engine speed, about 10.6 gal/min
Tank capacity of 18 L or 4.7 gal

(from 406 manual, section 55, page 1.1/3)

 

[Speedwoble]

The front hydraulic pump is belt driven so maximum pressure drops when the belt slips. That's the limiting pressure factor on this system. Check your belt, clean it, tighten if in good shape. The belt should ride high in the V pulley at the front of the engine, even a little higher than the outside circumference of the pulley. The belt is 12.5 mm

While I understand that is correct on the 406’s with steering wheel mounted valves, the FLU419 does indeed have a pressure relief in the valve stack behind the cab that runs the loader.

 

[SeeNebraska]

i just checked my belt, looks like its the narrower SAE belt. Does anyone have a PN for the correct hydraulic pump V belt? nobody local has one that looks right so i'll need to order online.

 

[SpoiledSpud]

FluFarm posted and rtrask verified the standard NAPA part numbers for the three belts in the FLU419 Owners Thread. Don't recall which is which off the top of my head.
Spud

 

[rtrask]

FluFarm posted and rtrask verified the standard NAPA part numbers for the three belts in the FLU419 Owners Thread. Don't recall which is which off the top of my head.
Spud

View attachment 749848

When I was looking into it, I took the NSN numbers, and did a look up on those, and got the dimensions from the spec. The dimensions were of course all metric. I then took the dimensions and plugged them into NAPA to find best fit. What I found was not an exact match, due to SAE - Metric conversion, but I decided it was close enough for government work. When I replaced my belts I had the cab tilted which made it relatively easy. FluFarm and others have replaced the belts with out tilting the cab, but found that adjusting the tension on the belt that drives the hydraulics for the front end loader particularly trying. I think his solution was to take a pair of vice grips to the threads of the adjusting bolt and tighten it that way. I would not say it was his proudest moment, but you do what you have to to get the job done. I will try to find the picture I took with the cab tilted so you can see what you are up against.





The picture is not stellar, but you can get the general Idea, the bolt head screws out pressing against the frame until the adjusting pulley gets the correct tension on the belt, then it is locked in place with the lock nut tightened against the bracket the adjusting pulley is mounted on. I think although I did not experience it, that you have almost no visibility to what you are doing when the cab is not tilted because where you can reach the adjusting bolt is from underneath, but from where you can see it you can't reach it.

 

[SeeNebraska]

thanks for the pictures. the hydraulic pump belt snapped yesterday so I have no choice except to try the replacement. I am not up for cab tilting this winter so your pictures should be helpful.

 

[rtrask]

Tilting the cab is not too hard, but if the only reason is to change the V-Belts out, probably it is overkill. I reread FluFarm's post on that, and the only time he needed the needle nose vicegrips was at the very end while tightening the lock nut.

I that belt is the inside belt, so you will need to take off all three. Use your judgment, but I would replace all three while you are at it. The clearance with the radiator is pretty tight, so count on a struggle to get them off / on. It may be worth it just to cut the old ones off. Again use you judgment, I did not have to deal with all that.

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[SeeNebraska]

there is a chunk missing from my pulley... wonder how long the new belt is going to last.

 

[rtrask]

Yeah, I foresee a tilted cab in your future. It is an old break, so maybe you can get by like you had for a while. The picture that I sent you was for the belt adjustment to the power steering. it is the outer most belt, so you will still need to remove it to get a replacement on. I wonder if you can weld a chunk of steel in an dress it up so it is not quite as sharp.

Good luck.

 

[SeeNebraska]

i looked again at this after posting the picture and it looks like the missing chunk is not the groove that the hyd pump belt rides in. I dont know what that groove is for but it doesn't look like it affects anything on my truck.

Yeah, I foresee a tilted cab in your future. It is an old break, so maybe you can get by like you had for a while. The picture that I sent you was for the belt adjustment to the power steering. it is the outer most belt, so you will still need to remove it to get a replacement on. I wonder if you can weld a chunk of steel in an dress it up so it is not quite as sharp.

Good luck.

 

[SeeNebraska]

finally got around to fixing this last night. It is really annoying but it is doable without tilting the cab. I had to loosen the radiator mounts so it could slide forward enough to slide belts between it and the fan blades. I dropped the small skidplate at the front of the frame to get a little better visibility but I dont think that was required. The only location that worked for me was to lay on my back under the truck. I would put one wrench on the head of the bolt and tighten it until the wrench was at an angle that it could hold itself in place while i fished the other wrench up. once i got the other wrench on, i could use one hand on each wrench to loosen the lock nut. Do that procedure about 20 times and i had enough slack in the PS pump belt to remove it.

I also removed the 10mm bolt that holds the cable harness clamp to the same bracket as the tensioner bolts. that way you can pull the harness out of the way for better access to the tensioner bolts.

 

[Tarek]

Thank you all for the pointers. Does anyone know which of the 3 listed NAPA belts is for the hydraulic pump? Thanks in advance

 

[rtrask]

I think it is the 9350, but do yourself a favor and replace all three. They are not that expensive and a real pain to replace. The one you need to replace is the inner one so you have to pull them all off anyway.

in the parts manual 1, pg 0177 0-4, It says the part number is 9365 I think that relates to the length. and like I said it was not an exact match, but it fit.

 

[The FLU farm]

Tarek, if my notes on the old belts are correct, the pump is 9440, the P/S is 9350, and the water/alternator is 9670.

 

[Tarek]

Tarek, if my notes on the old belts are correct, the pump is 9440, the P/S is 9350, and the water/alternator is 9670.

Thank you so very much for the response and follow up!!! I got in a major car accident the day I sent you the message and I am now just barely recovered, and resuming my life. Thank you again and happy holidays to you!!!!