So what do you think guys? I used to have an MG ZR and this spelled the end of all times - Head Gasket Failure, potentially new Engine Head, hundreds and hundreds in repair and labour... I've had this car three weeks... Tell me it's not had it already?  Coolant was just under the ---LOW--- level so topped it up to max with Pink OAT, noticed when I unscrewed the cap it had this gunk under and around the expansion tank rim.

https://imgur.com/CYEMNsA

 

https://imgur.com/ZZcYReD

Thanks

That might be grease that someone has put on it so the cap dose not stick. Happens a lot on the focus

Hmm that may be it - it didn't have an oily aroma but then again I don't know what emulsified oil smells like as I scrapped the MG before it had a chance to knacker itself.

34 minutes ago, dezwez said:

That might be grease that someone has put on it so the cap dose not stick. Happens a lot on the focus

Quite agree. I have put silicone grease around my coolant cap as it got stuck. Does the coolant look "oily" or clear? 

Is this an engine that would require a new de-gas hose?

25 minutes ago, Micro said:

Quite agree. I have put silicone grease around my coolant cap as it got stuck. Does the coolant look "oily" or clear? 

Is this an engine that would require a new de-gas hose?

Hi,

 

I believe it doesn't require a new DG hose as the one I have is a thick rubber - Ford Dealership also confirmed this.

 

There's no crud in the coolant tank that I can see. Possibly just grease, but it didn't have a similar consistency to grease - it disappeared when rubbing in between two fingers where I'd expect grease to last longer.

Sprayable greases are usually quite thin. This would also explain why it's all over the cap and not just where it might be required on mating faces.

also the white is above the rubber seal in the cap and if it was emulsified oil/water it would not really be above the seal I don't think. It does look to me like it is probably silicone grease and it is very common for these caps to be greased as they are famous for getting stuck and snapping off in the filler hole

I'm no chemist, but its probably just a cheap or spray grease or similar that has went that way with the heat of the expansion tank over time. It will have been an attempt to grease up the cap to stop it sticking (common fault and there are many a thread on here advising to put a little grease on the cap threads etc).

From looking at the pics of the coolant and tank there doesn't appear to be any issue. Give said cap and top of tank a good clean and apply a little grease, I can't remember the recommended one for the coolant cap (have  search on the forum).

Obviously don't try to open the cap unless the car has been sitting good while/cooled down/de pressurised a bit.

 

Silicone grease is the best option as it is inert so won't react with the rubber o-rings, safe on plastics and will withstand the heat of the coolant.