Aluminum head note.
 

From BW Found this on Wikipedia - Benzworld.org - Mercedes-Benz Discussion Forum

Automotive repair

Sodium silicate can be used to seal leaks at the head gasket. A common use is when an aluminum alloy cylinder head engine is left sitting for extended periods or the coolant is not changed at proper intervals, electrolysis can "eat out" sections of the head causing the gasket to fail.

Rather than remove the cylinder head, "liquid glass" is poured into the radiator and allowed to circulate. The waterglass is injected via the radiator water into the hotspot at the engine. This technique works because at 100-105 °C the sodium silicate loses water molecules to form a very powerful sealant that will not re-melt below 810 °C.

A sodium silicate repair of a leaking head gasket can hold for up to two years and even longer in some cases. The effect will be almost instant, and steam from the radiator water will stop coming out the exhaust within minutes of application. This repair only works with water-to-cylinder or water-to-air applications and where the sodium silicate reaches the "conversion" temperature of 100-105 °C.

Otherwise known as waterglass I believe. Unethical used car sellers and dealers used to buy tons of the stuff. It puts a glass like coating on the water passages as well. One source of supply was at drug stores.

Get it in the crankcase instead of the radiator and you've just become a Cash For Clunkers participant. That's the same stuff they were required to use to grind the engines to a halt. I'd rather have a leaky head.

Waterglass
 

My Gilbert chemistry set taught me about waterglass but that was back in the 1950s and I don't seem to remember anything about it now. :eek: I wonder why that is? :D

Let us know if this trick works!

Jeremy

note to self, do a coolant flush and change

Does it seek the leak and plug it like some AC system sealers claim or does it line the cooling system?

Sixto
87 300D

Both. It will even seal up a cracked block sometimes. The glass overall coating does add some insolation effect between the casting and the coolant.

If you ever pul a head that appears to be glass lined in the fluid passages it is the waterglass someone used you are seeing. Two many people overdose with the stuff I suspect. The stuff was initially marketed many years ago to seal leaking boilers up.

would it work at all for a cracked head?

If the choice is between the waterglass and the wrecking yard for the car then there is nothing to lose. The stuff was used a lot when the ideal of an aluminium head was well in the future.

On the otherhand if the car is worth keeping a more conventional repair is better. I also find the mercedes cooling systems not to have excess capacity by much of a factor. So any loss of heat transfer by the glass coating in the water passages has to also be a consideration as well.

The waterglass is and was capable of sealing up rediculious situations. I tend to visualise it as a last ditch effort with all the inherant risks.