Bongo Fury

Hi to all. I'm new to all this and so this may have already been discussed so I apologise if I'm going over old ground and for being stupid if I'm missing something obvious. The air bleeding process is, we all agree complex and requires at least two people of whom both need to know what they are doing. Mazda have placed the air bleed tube at the highest point on the engine and the process works we all agree. I was wondering if the same could be achieved by making up a hose that went directly into the expansion tank instead. If an expansion cap was purchased and the spring assembly removed and a hole drilled through the cap with a hose connector fixed through it with a length of hose. Could the same bleeding process not be carried out needing only one person to do the bleeding and monitoring of the expansion tank with the second person only needing to know how to hold the engine at steady revs?
Once the bleeding process is complete and no more air is being expelled the hose that is fitted to the expansion cap could then be lowered to the maximum fill level mark and excessive fluid would siphon down to the correct mark. the adapted cap could then be removed and the original cap fitted.
The reason I'm saying all this is that I have to work on my own and don't have the luxury of a second person to assist. I have made up a rod to be able to stand on the passenger side and operate the accelerator pedal and I have also made up a holder to keep the funnel up high whilst I trot round to the expansion tank to check on its level but single handed it is an onerous task and whilst checking the tank I obviously need to let the throttle go down to idle. Any thoughts on why this wouldn't work before I start spending money and time experimenting would be really appreciated.

Further to my ramblings I wonder if a non-pressure cap could be used and the overflow pipe lengthened and converted to act as the bleed tube, replacing the flat cap with a pressure cap when the work is done?

Several points to note here, as you guessed previously discussed;
1. There is already a third spigot on the de-gassing tank for this purpose, its used on the 2l petrol engine, but is sealed (undrilled) on the diesel and v6. Mazda knew something we didn't when they designed it.
2. There is already a kit on the market for adding such a pipe with a valve when not bleeding, however whilst it appears to not cause problems I am not aware of it being added to an engine that's been known to have problems.
3. As I see it the air-lock forms in the engine on the diesel and v6, the flow of coolant is not sufficient to move the blockage, hence the overheating. The activity used in the bleeding process is designed to help force a rapid change in pressure and hence increase the flow rate briefly within the engine this seems to be sufficient to move the air-lock on engines that have the problem. Not all engines seem to have the problem, possibly poor maintenance has affected the flow ?
4. I don't see how adding the extra pipe will bring about rapid changes in pressure/flow rate on its own, it will allow air to escape from the highest point, but so does the current bleed tube, which is what happens with the bleeding process.

Thanks for the reply. I guess i'll have to educate the wife into the mysteries and privileges of the Bongo!
The problem I have is not knowing if I have a problem or not. Having owned the bongo for just a month now the only time it pushes water out of the overflow is if I start it up and don't drive off. if I leave it for 5 minutes to idle it will start to overflow. it's not overheating at that point and its still too early for the thermostat to open. it does sound like a head gasket but no white smoke no overheating at all when driving and after bleeding I can exclude all the air, no bubbles. Digital temp gauge bolted to rocker cover doesn't go over 85. the other issue is it's a Ranger head and does not have the three way connector so I've cut into the hose between the two way and turbo so the bleed tube is not at the top of the system. I can't believe that couple of inches difference would trap enough air to cause a problem. when the engine is cold, left over night and the pressure cap removed in the morning there is a loud hiss and I can see the pipe from the rad relax. I've ordered a sniff test from Amazon so will give that a try. really reluctant to pull the head off if it ain't broke.

I'm not the expert here, but reading the responses its very rarely the gasket its merely the cheapest option for a garage to quote for when explaining the fault. Once the head is off then the crack should be found, usually between the exhaust port and the coolant system hence no oil involved, and just pressurising of the coolant system from exhaust gases.