Steam Coming Out the "Expansion Tank" Hose

Over time, as steam escapes the coolant will become more concentrated and its level will fall, and circulation flow is falling with it. Once the level has fallen below the maximum head that the coolant circulation pump can develop to push it over the weir that has been created between the coolant return pipe and the decreasing coolant level, coolant circulation will stop. If the engine continues to be used, then not long after that it will sieze-up and will want removal and replacement, which will be particularly inconvenient if a load is left on the crane hook at the time as often the weight of the engine is part of the counterbalance arrangements for the jib and the load.

Telephone Liebherr and arrange for a Service Technician to attend and remedy the fault without delay/today/this morning/immediately.

It would be best if the crane were designated "out of order" and not used until the fault has been cleared.

As long as the level of the coolant is tolerable, i mean not that low to the extent that the coolant flow rate is affected, do i still have to worry about the actual temperature of the coolant?What might be the range or the estimated actual temperature of the coolant if steam is cominng out on the expansion tank cap hose?

Wrong approach. Worry about the crane conking out with a big load some distance off the ground.

Fix the problem before it develops into a crisis. Stop posting here and phone Liebherr instead.

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so far all the answers of my posts is call the technician.

"so far all the answers of my posts is call the technician."

If you believe this to be incorrect, by all means ignore this advice. Perhaps refer to the manual supplied with the machine, instead of calling.

I believe PWSlack is quite correct in his comment.

It is dangerous as far as this is a crane and you might face what has already been said about the safety...

The reading of 75°C looks too low for a diesel engine (or any internal combustion engine). You would expect the reading to be ~85 or 95°C. Therefore, this gauge needs to be checked and replaced if faulty.

Steam coming out is a sign of too high a temperature (> 95 or >100) and /Or a faulty seal on the cap. High Temperature will increase the pressure in the expansion tank and open the cap seal to release excess pressure >> Steam and condensation will show at the hose end.

Therefore, you need a pro to check the system and remedy. The sooner the better and the sooner the less costly it will be later on ...

With a low temperature (if it is really low) the cause for that could be a hanging thermostat. Get a point and shoot thermal device and measure the temperature of the outside of the case as near to the temperature probe as you can get. If the temperature is indeed 75 and you are losing water past the pressure cap, the thermostat is bad, but you probably also have a bad head gasket. A small compression leak from the high pressure in the cylinder while running will overpower the pressure cap and the results will be what you describe. If the temperature is wrong, you might be overheating without knowing it. Either way says repairs must be done, but it probably also means that the engine will not shut down in the middle of operation, just that you will be increasing the cost of repair by continuing to operate it.

Thanks for reminding about the possible gasket failure (cylinder head) and also seals might have failed, allowing combustion gas into the cooling water, increasing the pressure and releasing via CAP! yes, this is also a possibility. This can happen whether the temperature is normal or below.

This condition can sometimes, provoke a difficulty to kick start the engine if enough water sips into the cylinder while at rest and cold (Hydraulic pressure in cylinder).

the OP should have checked that possibility and give us more info (whether he is having any difficulties at start (Not allways but some times?).

If your what appears to be steam is steam and the coolant is well below boiling then I suggest is is gas mixed with coolant appearing to be steam. Inside the engine this is not good as you will have lost coolant contact with cooling jacket surfaces resulting in hot spots and serious damage. Steam is not a good coolant probably never will be in an engine. You probably have a blown head gasket or possibly a crack in a coolant jacket allowing combustion gasses into coolant. You can test for this by capturing the gas being released from the expansion tank and maybe even a sniff test will detect the smell of diesel or what ever fuel is used. If you put a balloon over vent and capture the emission and the balloon fills you can bet the farm that you have compression gas leak. Do not be afraid to call the manufacturer for input they probably have seen most of everything with this equipment.

If it were a gasoline engine an adapter on spark plug hole and injecting compressed air may show which cylinder is leaking. With a diesel this test is more complicated and time consuming.

This "steam" is the mechanical version of the electronic "magic smoke" that sometimes appears just prior to catastrophic failure of the device from which it is emitted.

No one here is going to fix your problems for free. Call a service tech.

You could replace the water with motor oil. That would cure the "steam" problem.

Early on the GE handbook, which was a huge catalog of all GE offerings, had a page with a spoof, with a bogus offering, the "Smoke Inculcator" the write up was very tungue-in-cheek about how it could put the smoke back into a failed electrical item. Since the handbook was designed to last many years, no prices were given. I always wondered if anyone had ever tried to order one. I would have loved to have received that call. What you need is a "Steam Inculcator"