Sooty Water Pump Bolt 300tdi

Hi all,

Bit of an odd one perhaps... I'm in the process of changing my water pump on my 300tdi and one of the 3 long bolts has come out covered in soot.

Seems a bit odd to me so thought I'd see if anyone's got any thoughts?

Cheers,

Sam

It's not soot, it's probably oxidised zinc plating (that was on the bolt).
Are you using pink (HOAT) anit-freeze ?

Thanks miktdish, that makes more sense! Using blue antifreeze but I can't guarantee it's never had pink in it. I've fully drained (as best I can) and back flushed the system so hopefully that'll help

Quick look around the internet ....

Blue is a Mono Ethylene Glycol ((CH₂OH)₂) based antifreeze.
Glycol reacts with oxygen to produce carbon dioxide and water gases and is very very poisonous.

Red (OAT) antifreeze is a lot more friendly to iron and alluminium based alloys but not to organic compounds (like leather), however it didn't offer a high level of corrosion resistance to lead so wasn't suited to older (per 1950's) engines.

Newer, Pink (HOAT) antifreeze extends the life of rubber and plastic components and reduces electrolysis within the engine.
HOAT is the common antifreeze used in modern engines and is a combination if IAT and OAT technologies.

OAT was not good with copper and brass however it's not easy to find base OAT antifreeze these days as the technology has advanced.
We now have P-HOAT, Si-HOAT, Nap free HOAT and NOAT.
None of those have a detrimental effect on lead, zinc, brass and copper.

I think that the reason some folk won't use a modern antifreeze is because of the transition from Blue to Pink/Red (MEP to OAT) and our dad's wouldn't use it because it reacted with copper and brass and the German auto manufacturers (as well as Honda) used it and they were ruining the British motor industry ....
However, these days, the moderm antifeeze types are far more efficient and less damaging than the older Ethylene Glycol based formulae.

Get rid of the Blue, flush with water at least twice and refill with a modern HOAT variant, it won't damage your 300tdi engine or your cooling/heating system.