Which model Thwaites is this?

[SiH]

Hi folks,
I’ve just got hold of this dumper, that has been sat in a field ,bucket high in brambles and ferns for a fair few years. It has a lister 2 cylnder engine, but dont know the model or hp as the injector cover plate has been lost (along with the model info) and replaced with one made out of alloy. It looks to have a 4 speed box, with a forward/reverse lever next to it?
The engine is a hand start, but seized solid, probably due to the 2 or more gallons of water that came out of it?!! Looks like wet got into the silencer then manifold and backed up into the engine over time, but I’ll know more when I strip it down this weekend.
I’m after as much info on the dumper model, and engine as I can get, as it looks like I’ll need it to get it going again, so any info appreciated please. It may well be more sensible to get another engine,(any ideas on hp on this one?), rather than rebuild this, but I’ll see how it looks. Cheers folks!

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Apologies for the pics being upside down! Dont know how I managed that.

[essexpete]

Probably the aldrive 3 tonner? At a guess from mid 70s to early 80s

[cobbadog]

They are still upside down when I look at them here in Australia too!

I would try to strip and repair what you have, with in reason. Just because it is ceased doesn't mean that it wont run again. I have unstuck a few different types of engine from tractors to stationary ones and they are perfectly ok again now. Not much money spent on them just time.

[Jeremy Rowland]

Simon it is possible to free off a seized engine I think part of the trick was to put WD40 and vinegar down the bore, let it soak and gently try and rock the engine backwards and forwards; Fred is more of an expert on this than me as I have never had to free off a seized motor, must be worth a try before taking the thing to bits, so remove the fuel injectors and take a look into the cylinder with a torch then pour said mixture into the cylinder and let it stand for a day or so then give it a try. Good luck with it.

Jeremy

[SiH]

Hi all,
Many thanks for your comments lads. There is no movement at all at the starting handle,-absolutely solid, either direction. I whipped the heads off today, and both pistons were 1/3 of the way down the bores roughly, which were also both full of water on top of the pistons. Once the water was removed, the bores didn’t seem too bad rust wise, although there is the odd scabby bit. I poured some coke cola onto the piston tops, as I’ve a friend who swears by this!? So we’ll see. But I cant help thinking that everything below the pistons is going to be rusted solid, due to the 2+ gallons of water that came out when it was drained.
I think I’ll do as you say now Jeremy, and see if it will budge in a few days after soaking, before I do anything else. Thanks again chaps for your input!

[SiH]

What engine do you think it is? I think it looks like a lIster ST2, but havnt a clue on hp?

[essexpete]

Should think in the 15 to 20hp band? Another thing supposed to be good at freeing and lubricating is ATF.

[cobbadog]

The amount of water drained from the sump may not have done much damage the same as the bore. A couple of days is not long enough to unseize an engine that is stuck. It takes time to have any effect on the stuck engine. Using coke or vinegar mixes does work just takes a lot longer. A mixture with good results is the ATF as mentioned but mixed with acetone. This really penetrates and helps dissolve rust and carbon.
Another thing to try now that you have the heads off is hydrochloric acid , BUT this is a very strong attack on rust and must not be left for more than 1 hour then it MUST be flushed out and diluted with lots of water. I use this method for removing rust inside fuel tanks, very effective.
Again we cannot emphasize enough hat the procedure to unseize an engine takes time not hours but sometimes a few weeks of soaking.
A passive way of doing can be molasses and water left to soak for a week. Mix it to about 6:1 (water:molasses). It stinks like a brewery after a while but it is less aggressive.
Try to gain access to the flywheel and try rotating the engine backwards first. This is just in case a ring has let go and has dug into the bore. I had this happen once doing a lawn mower engine. Tried for ages to turn the engine over in its normal direction with no luck, then tried winding it backwards and that worked for that issue.
So many ways to do this job and everyone has their own preferred way but all of them take TIME to work.

[SiH]

Thanks again chaps,- advice gratefully recieved. I knew it may well take a while, and must admit I like the idea of hydrochloric acid, even though it is pretty evil stuff eh. I’ve got a few bottles of it, so may well give it a go in the next week when time allows. But the atf and the molasses ideas sound good too, and im I’m in no rush, so might well give that a go first and use the acid as a last resort. Thanks guys, I’ll let you know how I get on.

[FOWLER MAN]

Hi Simon,
I have only now seen this post . I have in the past had reasonable success using vinegar in seized bores, but I would think Hydrochloric acid may be a bit too corrosive.
With the Lister ST you can remove the crank case door from the side of the engine. You may then be able to get at the big end bolts, (Depending on where the pistons are in the bores), and lift out the pots complete with piston and conrod.
You would then be able to give the pistons a good bump with a hammer and block of wood or even get them pressed out. Hopefully you will then get away with honing the bores and a new set of rings.
You will find a workshop manual for the Lister ST which you can download free on the Winget Dumper website. I will be happy to answer any further questions yu may hve as I know these engines well.
Good luck.
Fred