3C hydraulics not responding

[CHRISEEBOY]

Hi guys,

I just need a bit of help to troubleshoot a problem im having with my hydraulics. Please bare with me whilst I describe the events that led to my problem.

I finally got my JCB 3C mk3 running after a problem with the engine. I had to take the hydraulic pump off and lost a lot of fluid in the process. I topped the fluid up with around 20 litres and it was my intention to close all the rams and check the fluid level in the cab. In order to close the rams I needed a running engine, which I now have. I started her up, lifted the front bucket and drove her to a new, more suitable location where I put the hydraulics though their paces. Everything worked fine but the fluid level tube in the cab was too dirty to see the fluid. I killed the engine and went about cleaning the tube. When I attempted to start her up again the key did nothing, as in not even a sound.

I figured the starter motor had got stuck as the previous owner had warned me this might be an issue. No attempt to hit the starter with a hammer had any effect so I bit the bullet and ordered a new one. Over a week passed before I fitted the new starter and the JCB just sat there for this time in the wind and rain. The new starter is now in and the engine starts and runs as it should. I got her up to full throttle and attempted to close all the rams, but now the hydraulics don't respond. I can obviously move everything in the down direction but just can't get anything up!

I dont understand what could have happened to immobilise the hydraulics. My first thought was to top up the fluid but when I opened the cap I could see the fluid close to the top and it was bubbling? If I had put too much fluid in then surely the hydraulics would not have worked when I initially fired her up? There is no way that over that week she stood there she could have gained extra hydraulic oil, only lost it.

Could anyone shed any light on how I should go about troubleshooting this issue?

Thank you in advance.
Chris.

[essexpete]

Chris I never had that problem with either of our 3Cs. The fluid you can see through the filler (I assume you are talking about the filler over the big filter housing) will not give you a level indication. I know this is obvious but is there any indication of a leak somewhere? Is the pump making a whining /groaning sound? Could the pump coupling be slipping?

[CHRISEEBOY]

I will listen to the pump when I'm next out there. What i dont get is why it was working and now its not, when the only thing I changed was the starter motor?

Is it possible that there was air present in the system when I first fired it up and that air has subsequently wriggled its way out and now my fluid level is too low? The only thing that put me off from that conclusion was the fact that I could actually see the fluid when I opened the filler cap!

Is it normal that the hydraulic oil climbs all the way up to the filler cap during operation and then perhaps settles down?

[Jeremy Rowland]

Chris, as Pete has suggested check that the oil level is correct first especially as you are not sure of how much oil you lost when you took the pump off? You say you put 20 litres back in; unfortunately I have no idea what the capacity of the hydraulic system is on that machine but it does sound like you may be low on oil, if not the only possible problem could be with the pump drive as you have taken it off the machine.
If you end up taking the pump back off the machine to check the drive, make sure you have a couple of blanking plugs so that you don't lose the new oil that you have just put into the machine.

Jeremy

[essexpete]

IIRR the hydraulic oil capacity is close to a 205l drum. If the reservoir was practically empty 20l would hardly be noticed.

[CHRISEEBOY]

Guys, I know I took the pump off but the hydraulics worked absolutely fine when I put it all back together. The JCB has now been stood for over a week and the only difference is it has a new starter. I'm keen to rule out the pump as it worked fine and there is no reason to believe it broke.

When I took the pump off I put freezer bags and cable ties over the two hoses, one by one, and caught as much oil as I could in an empty 20l container. I managed to collect about 5L but I'm estimating I lost about 15L down the driveway as the return hose took me by surprise! This is the reason I only put 20L back in the system. I have another 20L on standby but didn't want to overfill it.

I know I need to check the oil level but I'm not sure how to do this other than to close all the rams and use the sight tube in the cab. I can't do this until I can operate the hydraulics. I've been back out and opened to filercap, the oil level has now gone down so I will be able to get more in.

What are the symptoms of too much oil?

[agrimax]

Can't think of why it was working and then not after doing nothing relevant to it!!
If there's too much oil,it will simply be forced out of the tank breathers til it's at a low enough level to stop coming out...
IIRC,the oil fill point is through a large plug screwed into a rubber hose above the return filter. You're not seeing the actual oil level in the tank as it has to go through the filter first to get into the tank. There's another large plug on the side of the filter housing with a large spring behind it and a plunger.This is the filter bypass valve. Take the plug out,and the spring and the plunger.Refit the plug and refill through the top plug.You will be able to fill much quicker. Don't worry about the rams being open or closed at this stage.If the sight tube isn't clear to see through,now is the time to replace it.Bring the oil to around half way up the tube and refit the spring and plunger on the side of the filter housing. If you still have no working hydraulics,check the pump is turning(you can always hear the hum on a 3C). Then make sure the pump suction hose is clamped tight and not drawing air at either end and also that it hasn't collapsed internally blocking the oil flow

[CHRISEEBOY]

Thanks Agrimax, thats really useful.

I dont suppose you also do an idiots guide to "how to replace a sight tube"?

[CHRISEEBOY]

I finally got that plug off the side of the filter. I couldn't budge it with my massive adjustable spanner so I had to buy a 57mm impact socket and the impact wrench made light work of it. Managed to pour 20L into the tank in less than a minute! The previous 20L took about a week of constant mini top-ups everytime I walked past the digger. The hydraulics are now up and running and very responsive. Thanks again for the advice agrimax.

[agrimax]

Great that it was a simple fix...Don't know why JCB felt the need to have freshly poured oil going through the filter in the 3C3,unless taking out the bypass valve. Don't recall it like that in the MK2 and the 3CX is certainly straight into the tank.