Technical Greasy deposit and pressure in expansion tank coolant overflow

[Bazzar]

Hi all,

I've searched and searched, by can't find a definitive answer to my symptoms:

I have a low mileage Ducato 2.8JTD '02. All seems mostly normal when running, except that it blows the contents of the expansion tank out through the cap on longer runs. It doesn't overheat, nor is the system running empty, it just seems to be the liquid in the tank itself that gets expelled.

On top of that, there's a vaseline-like, greasy, jelly substance that has collected on the inside of the tank.

I know the instant reaction may be head gasket, but there's nothing else to suggest that to be the case, no emulsion in the oil, no discoloration of the coolant, no overheating - nada. Sadly, I don't have the tools for a pressure test.

I've read elsewhere that there is a possible connection between the pressure and water pump failure, but I looking for an answer from someone that maybe knows this engine a little better.

Advice gratefully received, questions answered promptly!

Many thanks!

 

[DucatoMiltonKeynes]

High pressure in the cooling system comes either from the coolant boiling (which it's not in your case) or anything from a tiny leak to a massive one from a cylinder letting combustion gasses into the cooling system. Water pump failure will cause the coolant to boil very quickly as it's not being circulated through the rad.
The leak from a cylinder could be head gasket or a micro crack in the head or block.
As it sounds like a tiny leak, I would get some Steelseal into the engine and see what happens. Use Steelseal, not Radweld or K-seal. It's probably best to get it on Ebay if you can't find it locally.

 

[Bazzar]

Thanks for the quick answer - I've tried steelseal, as some hairy BTCC bloke swears by it (although being sponsored by them perhaps lent weight to that!), but I think that I perhaps should have used more of it - I only bought 1 bottle as its not the cheapest thing to test... I'll try it again.

Interestingly, something else happened this week - one of the intercooler pipes popped off. I put it down to not being tightened properly last time it was off, but could there be something more sinister in that?

 

[DucatoMiltonKeynes]

Maybe another bottle will do it. As long as you follow the instructions and idle the engine for an hour and then let it cool completely, it should work.
It's likely the intercooler pipe was not done up tightly in the past. There are some fairly high pressures in the boost system. A partial blockage in the intercooler can make the pipes pop off and also reduce power. That's almost always caused by the engine breather pumping oil mist into the induction system or occasionally a slightly leaking turbo oil seal.

 

[Bazzar]

You're awesome - I'll do that and see how we go on!

 

[moodrater]

If the coolant has been replaced with water the boiling point will be very low vaseline deposit could be some kind of sealant. You can get a test kit or get a garage to test for contaminants in the coolant to rule out gasket