Overheating issue-advice.

[Kappy]

The one at the top of tank is to purge the air out of the radiator top tank, the one at the bottom should go into the bottom radiator hose because this is where the water is drawn into the motor.
Where the radiator cap goes on that neck, is there a small pipe that comes off there? If there is, run a hose from there into the 2 ltr plastic bottle, a soft drink bottle or milk bottle will do the job fine, the drink bottle is a bit stronger so possibly a better choice. If you can find one of those 3 ltr Coke bottles and some where to fit it sitting on a plate or something, that would be even better because they are extra strong bottles .....

T1 Terry

The one on the side has no tube on the neck.

[Kappy]

Kappy may I suggest you see if this chaps ph number works?

YES I DO HAVE ALL MANUALS ON DVD CONTACT ME tram1one@bigpond .com or 0892798872
Sorry Kappy! I was thinking you had a Merc.
This link is for you John if you need it!!?? (Kalibenz)

Yes I have a merc, pretty sure its a
Mercedes-Benz OM366 engine, nearly 6 litre straight 6.

[jon_d]

Kappy,

This site might help.
https://barringtondieselclub.co.za/mercedes/366.html

You might have to contact this person for access. steve@barringtondieselclub.co.za


Also, re:

When the Buzzer/light went off on the flat, sitting on 2000 rpm 5th gear @ approx 88kmh as top speed is 91km/h .

It may have just been driven to hard??? Into a headwind? When we were heading into Coober Pedy, I was down to about 78ks. It was sort of saying, I can go faster if you want too but I don't want too. (The bus is capable of +115.)

[T1 Terry]

The one at the top of tank is to purge the air out of the radiator top tank, the one at the bottom should go into the bottom radiator hose because this is where the water is drawn into the motor.
Where the radiator cap goes on that neck, is there a small pipe that comes off there? If there is, run a hose from there into the 2 ltr plastic bottle, a soft drink bottle or milk bottle will do the job fine, the drink bottle is a bit stronger so possibly a better choice. If you can find one of those 3 ltr Coke bottles and some where to fit it sitting on a plate or something, that would be even better because they are extra strong bottles .....

T1 Terry

The one on the side has no tube on the neck.

I think you might need to take the expansion tank with you when you get the radiator cleaned and get them to fit the overflow tube into the neck of the tank and ask them for the correct pressure cap with the seal under the cap that is designed for and overflow recovery system.
That expansion tank is really an air purging tank designed to bleed off air from the radiator top tank by drawing in water through the bottom hose/pump inlet and the excess water flows through that hose from the radiator top tank to the expansion/purge tank. This system was often used where air could get trapped somewhere in the system because the normal filler is not actually the highest spot in the system or the top radiator hose might not be a smooth incline from the top of the engine to the top radiator tank. I have seen purge hoses from the top of the thermostat housing on some engines and even purge hoses from various spot along an alloy head. V8 Rover engines that are performance modified often have this design added because they can suffer from steam pockets trapped in top of water jacket chambers within the head turning them into percolators and eat a hole out through the water jacket.

T1 Terry

[T1 Terry]

I just enlarged the picture of the purge tank for a closer look and that would have to be close to the worst designed system I've seen. The top radiator hose goes down from the top of the engine cooling system outlet begging for air to get trapped, so I'm guessing there must be another purge hose connected to the top outlet from the engine as well, but is that the one that goes to the bottom of the surge tank? The maximum water level you could get into that surge tank would be about 2/3rds full, but that tag sealed valve? in the top of the tank serves what purpose? Does it have an overflow hose as well? Maybe that is the "hail Mary" valve that spews out water and steam and what ever else if the system suffers a serious overheat, or that was where the original rad cap went but the body doesn't allow for a neck to extend from there to some where outside the body line?

T1 Terry

[Kappy]

There is a hose at the top of the expansion tank that appears to purge back to the top of the radiator.

I will tank the cap to Perth on Thursday and see what I can glean.

The thing is its been good for approx 11000 k's except for 2 occasions that were back to normal in under an hour.

I suspect, Cap, poss thermostat and maybe sender unit, process of elimination.

I have a leaning towards thermostat , as my experience with thermostats when temp is reached the coolant level drops.

Doesn't seem to be happening.