Thwaites Dumper Difficulties

[Dumperdick999]

Hi Everyone, and Happy New Year!

I’m new here, but am hoping one of you clever people can give me some pointers so I can mend a problem with my old dumper.

Having looked on here and a bit of Googling, I think my dumper is a Thwaites PH2, although I’m happy to be corrected if not. I’ve attached a few photos which will hopefully assist.

Anyway, it was working perfectly well until a couple of weeks ago when it was stood, ticking over, then the rev’s started to drop and it stalled. As the rev’s dropped, it sounded very much like when the hydraulics are under load, as usually it would need a good push of the accelerator pedal to keep it running whilst steering or activating the bucket.

When I went to restart it, the starter motor would not turn the engine over, as if there were additional load being placed upon it.

I made sure the bucket lever was in the ‘neutral’ position, and also made sure that the steering was not under load, but to no avail.

Usually, it turns over nice and quickly, and with a little puff of Easystart, fires up pretty easily. But, even thought the battery is fully charged, there’s too much load on it for the starter motor to turn.

I did wonder if there was any way I could isolate the hydraulics to remove that from the equation, but can’t see any way to do it.

If anyone knows how to isolate the hydraulics load or as to what the root cause may be, I would be really grateful for any pointers!!!

Thank you


John

[essexpete]

Have you checked the oil? I doubt it is the hydraulics, it sounds more like a partial engine seizure
I guess you could unbolt the hydraulic pump to see if it will turn, you might need to catch the oil if you take off the feed and output pipes to allow the pump to move? Is the gear lever and gear selection moving OK?

[Dumperdick999]

Hi EssexPete,

Thanks for your thoughts. I’ll have a look at the oil at the weekend and see the levels are like.

I take it a partial seizure is likely to be pretty terminal for the barrels/pistons? Or might I be lucky and find some oil might free things up a bit?

I’ll let you know when I’ve checked the oil.

Thank again, much appreciated


John

[essexpete]

Hi EssexPete,

Thanks for your thoughts. I’ll have a look at the oil at the weekend and see the levels are like.

I take it a partial seizure is likely to be pretty terminal for the barrels/pistons? Or might I be lucky and find some oil might free things up a bit?

I’ll let you know when I’ve checked the oil.

Thank again, much appreciated


John

John, I think your use of Easystart for starting implies that the engine is very worn and was lacking compression. There could be any number of failures, but most likely piston ring damage. Edit on re-reading original post I realise the starter will not turn the engine, all points to engine seizure. That could be a ring failure picking up on the bore or even a lack of oil on another component. Did the engine knock loudly on first firing up?

[Dumperdick999]

Hi Pete,

Yes, the engine did always knock on start-up and it never fired up without some Easystart.

I checked the oil level today and you’re right, it was very low indeed. I took the rocker covers off the top of the engine, and it seemed rather dry in there. Assuming the barrels/pistons were shot anyway, I pushed the valves down to open them up and sprayed a bit of WD40 in there to see if it would free it up at all. It did, slightly. The engine would turn very slowly but it didn’t sound very healthy! So, I think you’re right.

Also, when I went to take the rocker covers off, I noticed that the rocker oil feed pipe had broken at the T-joint, which might explain how all the oil has disappeared.

I’ve order 2 new piston/barrel kits, new gaskets and a new oil feed pipe, so hopefully the old girl will be back to her former glory with a few hours of TLC.

Thank you very much indeed for your help on this Pete, I very much appreciate it.

My best,

John

[Dumperdick999]

Hi Pete,

I’m had a couple of hours spare this afternoon so spent it taking the top of the engine off.

The barrels looked ok to the naked eye, no scouring and the pistons slipped out easily.

However, one of the big end bearings was well and truly stuck, so your predictions were right!

I’ve ordered some new big end bearings, so that’s a project for another day. I’ll still replace the barrels and pistons/rings as I have new ones now.

Thank you again.

John

[essexpete]

I am not expert but a careful inspection/ measurement of the crank will be needed.
Thank you for keeping us posted.