3CX engine and hydraulic problems.

[Slugs]

Hi, Just joined the forum- I have a 3cx white cab 1983, Perkins 4.236- which i bought about a year ago it is a bit tired but only used occasionally. I have replaced a few hoses and a load of hydraulic oil.
Engine breathed quite badly and used quite a bit of fuel.
Only issue was when trying to lift loader when digging into a pile whilst making forward motion it would massively Labour the engine and would go into a stall if I carried on. I tend to mainly use the rear actor so not a huge issue up to now.
Also when stabilisers reach the top it would do the same.
Recently when using for a good days work, when operating the rear slew that also has the same huge labouring effect on the engine. On the same day the engine started making a metallic noise.
Put a test gauge on the first test port on the loader valve assembly and did a pressure test although didn’t want to run the engine for too long, when operating services read about 1k psi and when ram closed around 2500- 2,800 psi briefly but then laboured the engine on all services with rams closed.
Renewed (blocked) hydraulic filter,changed tank fluid, cleaned tanks. Re tested- just the same.
With further investigation, sump off, it has revealed a big end has destroyed itself. Bearing cap was round the wrong way so looks like someone has been in there before, crank journal is bad. Taken the engine out and intend to remove the crank and as a minimum get it machined with new bearings. Access the pistons/liners when out.
Compression test on the bad rod was 300 and the rest 310,315,360psi.
I was looking for some advice on the hydraulics as i think I have two issues here rather than the engine slightly down on power was causing it.
I undid the drain bung on the bottom of the rear slew- nothing came out but a few drips of oil.
Sorry for the massive download of info......

[essexpete]

Re the hydraulic side have you got an extending dipper? (no euphemism). It has not been unknown for the control pedals to stick one way or the other. (I am assuming the function is controlled by foot). The Jacks on older machine always seem to take some dragging up. Failing the obvious then I wonder if the main RV is functioning correctly.

[Slugs]

Non extending (I didn’t feel the need to extend my dipper thanks)....
I am new to plant/hydraulics so am trying to learn quickly....i am very grateful for your reply.
I have a copy of the full workshop manual but am struggling to convert the test procedure to real life problems! Do you think If it were the MRV not functioning correctly that could mean it’s not opening and exposing the engine and pump to its maximum (or increased) pressure which if the pump and engine are worn could give these symptoms?
Whilst the hydraulic fluid is drained if I stripped the MRV assembly out would you expect to visually diagnose a fault or is it all about the testing process in situ? (Wait until the engine is back in).
Thanks again...

[essexpete]

Fred might have some ideas or someone that has worked on hydraulics. If the engine was knackered some of those services would pull the revs down quite rapidly I guess.

[FOWLER MAN]

Hi Sam,
I don't think the main relief valve is the problem, even if it was wound right in, as the service line valves are set only marginally higher and they would relieve the pressure before loading the system as you describe.
I have known the feed pipe to the Hydraulic pump, (pumps), to collapse internally starving the pumps of oil. This will load the engine and is usually accompanied by noisy pump and hydraulics. It's worth a check.
My gut feeling , from what you say, is that your problem may be a result of partial engine seizure.
Please let us know how you get on.
Fred

[Slugs]

Thank you both for your advice.
I will overhaul the engine then see how the hydraulics perform.
The short fat pipe feeding the pump is in externally poor condition so was going to change it anyway, will be interesting to see if it has broken up internally. When cleaning out the tank I was able to feel around the pipe and appeared ok.
One thing I did find that might be useful to others is on the n/s tank the return pipe (from the filter) has a protruding steel pipe (inside the tank) with a crimped end with some small holes in it - this was absolutely full of pieces of an old gasket only about one hole left clear (looked like pieces of an old inspection cover seal) -however on the small test I did before removing the engine this made no difference.