Front Loader spool block 'squeals'

[baj33790]

Hi all,

Can anyone tell me what to look for to cure the 'squeal' from the spool block that I get when I lift or curl my front loader. I have checked the tightness of all the connectors and I am not losing fluid and it operates quickly, but just squeals when I lift it?

thanks

 

[Bob Rooks]

How long has it been doing this? Squealing is typically the sound of the relief valve unseating.

 

[RonMar]

What bob said! Is this a Jinma loader and valve? If so they typically use an O-ring or two in the valve and those sometimes fail. Does it make the same noise when the loader or bucket reaches the end of its travel and you continue to hold the handle(deliberately activate the safety relief valve)?

 

[baj33790]

Hi,

Thank you for your responses. Although I have had the tractor for over a year, the front loader has not had much use so I am not sure if the 'squeal' was always present or not. However I did some tests today, and found that on start-up, it didn't squeal at all no matter what I did. I tried your suggestion Ron, but nothing would induce it to make a noise. (I couldn't put a load in the bucket today, so it is just its own weight) After about a half hour of continuous movement of the arms and bucket, I noticed a slight squeal when I lowered the arm very slowly and by this time, the hydraulic pipes were getting warm, so I wondered if something changes as the fluid warms up and becomes less viscous? Even when it was warm, I couldn't make it squeal by forcing the relief valve to operate.

I don't know definitely who made the loader, I assume it was by the tractor manufacturer Jinma, the plate on the loader says LDJM244ETK-QS. Here are a few photos.

 

[Bob Rooks]

Hmm. What are you using for hydraulic oil? It is normal to sometimes hear a hissing sound when activating the controls. This is caused by a large volume of oil moving under pressure, usually through a restrictive 90 degree fitting or a valve spool.

 

[baj33790]

Hmm. What are you using for hydraulic oil? It is normal to sometimes hear a hissing sound when activating the controls. This is caused by a large volume of oil moving under pressure, usually through a restrictive 90 degree fitting or a valve spool.

Hi Bob,

I am using 10W30 universal transmission oil, for agricultural tractors gearboxes and hydraulic systems. recommended by the local agricultural dealers.

No, it is not just a hiss, its a high pitched 'squeal'

thanks

 

[Bob Rooks]

Actually, that's a little high on the viscosity scale, and personally I wouldn't recommend it. Besides wasting money, it doesn't have the AW additive package formulated for hydraulic applications. I would prefer a straight hydraulic oil AW32 for temperate climates and AW46 for hotter climates. Personally, I use a multi-grade hydraulic oil in all my machines (ISO AW 32/46/68. It performs very well in all climate conditions.

Something is causing the relief valve to lift during normal operation. This isn't good because the pump is trying to deadhead. Do you have quick connect couplers to disconnect/remove the loader?

 

[baj33790]

Yes, the loader is inserted into the main line from the pump, you can just see the connectors in one of the photos tucked under the tractor body.

 

[Bob Rooks]

Yes, the loader is inserted into the main line from the pump, you can just see the connectors in one of the photos tucked under the tractor body.

Aha! Those are known to be problematic, and also known to destroy hydraulic pumps and pump drives by failing and blocking the flow of oil. Some folks have taken them apart and removed the checks, others have replaced them with higher quality connectors, and others have removed them altogether. I believe that is the root cause of your issue.

 

[RonMar]

Again, what Bob said Aw32 hydraulic oil for most climates. 10-30 is awfully thick especially when cold and can be hard on the pump.

I kept the OEM quick connects and simply removed the ball checks from the inside. What can happen is if a spring inside gets weak it can allow the internal ball valve to seal and completely block flow and blow up the pump. If you unscrew the fittings from the hose ends and look into the threaded hole you will see a clip and a star plate. Behind the star plate is a spring and the check ball. Remove the clip and all the internals should come right out. Then put the fitting back onto the hose end. You MUST do this to all 4 hose end couplings(2 male 2 female) otherwise the fluid wont flow. The connections will drip fluid when disconnected, but since this only happens for a brief time until the connections are reconnected to their other counterparts, this is a minor issue IMO to retain the quick disconnect feature. I also put a large zip-tie in the groove behind the locking collar so the connections cannot be accidently released by brush/branches when operating the tractor.

You can fully load any hydraulic circuit at any time by simply operating it until the cylinder is fully extended or retracted and stops. If you do this and continue to hold the handle after the cylinder stops, the pressure will build and the safety will open and pass fluid as the fluid is ALWAYS in motion.

What you could have been experiencing was a piece of crud stuck in the relief and allowing it to bypass a small amount of fluid all the time causing the noise when you lightly loaded the system. By running it to its extents and opening the relief you may have cleared it.

Pumps can also make noise when passing small air bubbles or Cavitating which can happen with too thick of an oil...