Radiator leaking after changing oil cooler pipes

Hi guys,

Just changed the oil cooler pipes due to a burst hose extension. Went for the ones with the welded section and all went in fine. However as soon as I ran the engine to settle the new oil in I had coolant leaking from the radiator like mad. I have a feeling I could've buggered the connection from the expansion tank to the radiator. All hoses are dry, it's just pouring out from the rear of the radiator.

Any good ideas on where to start to find a possible leak? Was hoping to go to my first green lanes with my nephew today but it's off the cards now. We still had fun doing the pipes though

What motor are we talking about, a little info with model year and engine can help a lot in getting the right info you need.

1989 90 with a 300 tdi. Thanks for the reminder

Here's a pic. It's leaking from the middle right of the radiator find and runs along the bottom and drips on the floor. It's missing lots of fins and looks like it's had a good life so I'm just going to put a new one in. I'm guessing it's just a leaking tube in the radiator as all the hoses are sound.

my guess is a spanner slip and a bash on the rad. Although my rad leaked from the small pipe just above the top oil cooler pipe. I caught it with a spanner and the tiny plastic spigot broke off.....

Yeah I must've done something to mess it up. Thanks for your help

A leak from a pipe joint in the top or bottom tanks can often be repaired by either soldering or brazing, whichever is appropriate. Even an ali rad can be repaired.
A leak from somewhere in the radiator core is a different kettle of fish and usually requires either a re-core or a complete replacement rad.
You could try one of the many chemical leak stoppers on the market but there's no guarantee that it would seal the leak or if it did, how long it would last.