Something like copper grease in the filler neck?

[Shiuko]

As the tittle says, there is something that looks like copper grease in the filler neck on my car, any ideas what could it be and what does it does in the cooling system?
Thanks

[SiH]

Are there lots of small particles?
Sounds like a \'stop leak\' sort of affair - the sort of thing that someone would bung in to fix a hole in a rad, or as a temporary fix for failing water seals...

[buckman67]

Are there lots of small particles?
Sounds like a \'stop leak\' sort of affair - the sort of thing that someone would bung in to fix a hole in a rad, or as a temporary fix for failing water seals...

Yeh I agree ! Us old timers would call it " Radseal ". Famous for fixing small leaks in your water system, and just as infamous for sealing holes you didn\'t want sealing i.e. radiator cores, heating matrix cores, small water cooling ducts etc etc etc....

[Shiuko]

So it isn\'t something that you\'d use in a car that has just being rebuilt, right?

[buckman67]

If it was rebuilt by a chimpanzee you would almost always need it ! .....but generally no not at all .
It could be old emulsion ( new is much lighter )caused by condensation which generally builds up in the filler neck and nothing to worry about.
Clear out the mess and see if it re-occurs.  If it does get a pressure test done or flush and re-fill with antfreeze etc that will locate it very quickly.

[Lil-Steve]

If you had it rebuilt because of the seals last time could just be a mix of oil and water it usually presents as a cream to brown scum with the consistancy of mayonaise.
 
As suggested get the coolant system pressure checked ASAP
 
To clean it out drain the coolant then pullout the block drainplug remove the highest filler neck then apply hosepipe on decent power to filler neck and keep an eye on the colour of the water coming out.
 
Radweld/Radseal is the son of satan :eek, you\'d be better pouring treacle in your rad LOL

[BlitzBoy]

if its just rebuilt, you do get a lot of crap in the cooling system eg excess sealent etc etc.
as they guys say, do a few running in miles, flush the cooling system, then refill with fresh coolant, and you should be cool

[Mazdarotaryparts]

This is a product called K-Rad seal that we sell as an insurance for Rotarys that if put in the water system can be left and not flushed out will stay active just incase there is a problem in the future indeed I am told that quite a few manufacturer\'s actually put an additive of this type in the system on the production line.

This is a special ceramic sealer not to be confused with any rad seal type product which WILL block the water ways inside the housing

We have sold this K-Seal  for the last year or so and I believe in this product enough that when we brought our RX-8 with just 6,000 miles on it I put a bottle in to give me future insurance.

Lastly as many over look this, only top the water up via the engine filer cap, leave thje other two alone so the system can find it\'s own level

For more details on this product please follow this link

http://www.mazdarotaryparts.com/b-fd-c002-k-seal-water-sealerb-1229-p.asp

[buckman67]

This is a special ceramic sealer not to be confused with any rad seal type product which WILL block the water ways inside the housing

I think sealers in new or newer cars is not a major issues as the water passagways are clear and fast flowing. But when you get to older cars where the water channels are performing fine but " furring  " up and narrowing I dont know how any type of water leak sealant can differentiate between a genuine leak and a furred up slow flowing heater matrix or water channel.
I won\'t be putting any type of sealant in my car, i\'d rather fix the leak.

[Mazdarotaryparts]

I think sealers in new or newer cars is not a major issues as the water passagways are clear and fast flowing. But when you get to older cars where the water channels are performing fine but " furring  " up and narrowing I dont know how any type of water leak sealant can differentiate between a genuine leak and a furred up slow flowing heater matrix or water channel.
I won\'t be putting any type of sealant in my car, i\'d rather fix the leak.

Before this product came on the market I too would have said like you have that  "I don\'t know how any type of water leak sealant can differentiate between a genuine leak" but as I said this is not to be confused with conventional old fashioned seals and will add that technology moves on.

I have had to accept recently that technology moves on with the new Prolong Oil we have just announced because after telling people for the last god knows how many years that you can only put "standard mineral oil" in a Rotary a new product has come along that can help the Rotary in many different ways just like this K-Seal product can