Mystery substance in radiator

[TMarsh]

Doing some routine service checks on my 1930 Coupe. Driven very often, has 5000 miles on motor and all running gear. I do all my maintenance and built this coupe up from a true basket case. Flushed block, new radiator, thermostat, moto meter cap with no signs of leakage. Car runs very well, and I currently have no particular issues with it accept the following:
Checked Oil, OK no issues. Checked radiator and found it at the level just above fins like always. Noticed something in radiator neck that appeared to be dark cotton like material. Not to much, but enough to concern me. Got possibly an amount equal to a small cap full. Planning on flushing the radiator tomorrow and seeing what I find. Use only Prestone green 50/50. Any suggestions, could be gasket material but looks more like fibrous cotton.

 

[Synchro909]

What is the history of the engine? Was it left sitting for years and maybe a mouse nest was built in the water jacket? How well was it flushed before the rebuild?

 

[Bob Bidonde]

This a possibility. The cooling jacket in the block and the cylinder head behind Cylinder #4 is a trap for debris. Perhaps the stuff you found was trapped there, but is now breaking loose. Another possibility is that there is cloth in the cooling system because sometime in the life of your car a sock or nylon stocking was put on the water outlet neck to serve as a filter. Yet another possibility is that somebody stuffed a shop rag into the cooling system to keep out debris and forgot to remove the rag. In any event, it is time for a cooling system flush with a strong cleaning solution. Snyder's has a strong flush called Thoro-Flush. It is an industrial strength cleaner that from my experience works really well. It is on Page A-133 of Snyder's catalog.