Hello everyone, I am writing from Italy.I am a collector and restorer of vintage tractors.Recently a local museum commissioned me to restart and restore this giant Caterpillar screper model DW 21.I have some experience with Caterpillar, I have a working 1944 D7 3T and a currently non-working D8 14A.Regarding this screper for me it is a completely new vehicle, and I believe I am the only one in Italy that is about to embark on a similar restoration!Currently I have been able to verify that the main motor runs free.I pulled the cooling fan manually checking that it did not slip the belt and the motor moved.My first problem is in the pony engine.It is blocked and when the main circuit is filled with water, it comes out of the pony engine's exhaust manifold.
I'm afraid of ice damage.
at the moment I have disassembled all the connections of the pony engine to completely disassemble it and look for the problem.my first question is this, to remove the pony engine is it necessary to remove the water pump as well?The space between the pony engine and the water pump is very small and the cabin doesn't helpI am waiting for the workshop manual and the spare parts catalog that I bought on e bay but which will arrive only next month
thanks everyone for the help

 I will try to post some pictures, but I have a bit of difficulty

Got yourself a real project there!!
I don't understand your question about interference with pony removal and water pump. Cooling plumbing for the pony just consists of inlet and outlet water lines to the main engine. Nothing to do with water pump. I'm wondering if your referring to clearance with the compressor????

my fear is that the pony engine will not be able to slip out of its housing in the flywheel housing before it comes to rest against the water pump. the compressor could also be a problem, do you think it needs to be disassembled?
Im sorry for my basic english.. 
thank for help! 

Did you removed the rear poney bracket support connect to the big motor and after the bracket is removed you need to tilt the poney on side frame and he should came out

pictures say a thousand words. a photo or 3 will help show the issue.

if i understand you correctly when you fill the main engine radiator water flows out the pony engine exhaust. yes that isnt normal and possibly means something is cracked from freezing as you say or something has rusted away. either way it needs to come apart to find the issue.
take plenty of pictures. there are a couple of retired dealer mechanics on the forum.

Dw 21 updates

I know it's been a long time since my last message.
Jobs in agriculture didn't give me time.
I went on with the work! right now I'm waiting for the carrier to bring the scraper to my workshop (obviously when it arrives I'll post some photos!)
Unfortunately I was not able to start it in the place where it is. Too much work is needed and the place is too far away from me. it was not easy to find a carrier that loads it without the scraper being able to leave.
Furthermore, with its 3.5 meters of width, special permits are needed for transport.
However I managed to disassemble the pony engine, unfortunately the block is irreparably cracked by ice, the chamber that leads to the rear of the engine in the exhaust manifold is broken. unfortunately the break is internal, it is not possible to get there with any tool to weld it.
For this I am looking for a cylinder block, the part number is 8f 4681.
Could anyone help me? I found on the internet blanchardused part. would appear to have a used block for $861. Do you think it's a fair price?
thanks everyone for the help

That seems like a high price but a lot will depend on your location.
8F4681 options here....www.machinerytrader.com/parts/search?Par...681&SearchType=Start

Many thanks!
I am in Italy, I know that it will cost me a lot of transport, but here it is very difficult to find breakers that have spare parts of this type for the old Caterpillars, up until about twenty years ago something was still found but now it has been too many years that no one has use pony engines

Hi, Manuel ITA.
This company might be worth a try too:

antiquecrawlerparts.com/

His name is Chad Enyeart and he is based in Wyoming, U.S.A.. He has an e-mail form on his site under "Contact".

Just my 0.02

finally we were able to take it home to be able to start the restoration