thanks chaps im even more confused i have taken it back to the garage who fitted the head and they checked it and said that because i flushed it through without draining the block and then added new antifreeze blue one it has reacted against the other antifreeze in the engine and caused the black scum has anyone ever heard of such a reaction? help!

- (#12805) adrian, 16 Aug 04 05:34

I don't know what happens, but the antifreeze I have been using tells you in no uncertain terms not to mix with others.
After reading your message I will make sure I never do.
Hopefully a flush or 2 may sort it. The block can hold a few litres so the flush needs to be very thorough if you don't undo the block drain.
- (#12805) chris turner, 16 Aug 04 06:12

Yup. the newer red antifreezes don't mix well with the older blue ones. That's in simple terms, someone can go into greater detail about organic acid technology vs silicates etc...

- (#12805) David Miller, 16 Aug 04 08:43