Self bleeding system

weebrian · Post by **weebrian** » Wed Jan 16, 2013 11:58 pm

I am the first person to admit that I am not really mechanically minded. A friend of mine, an experienced mechanic, has come up with an idea for a self bleeding setup. I have no idea whether it makes sense or not but would welcome any comments you have.

He suggests drilling a small hole 1 or 2 mm in the thermostat body which apparently would allow air to release from the system without the thermostat opening. His theory being that any air trapped would find it's way through the hole and up to the expansion tank.

The way he said it seemed to make sense but I'm not really sure whether he is talking through his backside or not. I can't imagine that if it was a viable idea, surely everyone would be doing it.

Post by **Bongoplod** » Thu Jan 17, 2013 12:09 am

Yes the air probably would be released,quickly followed by all your coolant,and then your fun really begins

Brian

Post by **Simon Jones** » Thu Jan 17, 2013 12:15 am

That won't work

. At least 3 reasons spring to mind:

1) it's a pressurised system to increase the boiling point from 100 degrees. If you've ever made a hole in can of coke: that's what happens when you let pressure out the system: you loose the liquid

2) a small leak in the system will actually introduce air into the system as it will get drawn in. Once air is in the system, it then expands, forms air pockets which pushes coolant out the system. See current thread: http://igmaynard.co.uk/bongo/forum/view ... =0#p580150

3) just like bubbles in lemonade, air will rise to the top of the system so having a 'bleed' hole close to the bottom will not work. This is why Mazda put the bleed pipe at the highest part of the system as this is where the air will naturally end up.

All basic physics

Driver+Passengers · Post by **Driver+Passengers** » Thu Jan 17, 2013 1:15 am

I'm not 100% sure I've understood correctly. Obviously drilling a hole through the housing is wrong, but I thought that the jiggle pin in the thermostat already let air through, which I think is what you mean, Brian?

I think the problem is that air (from wherever) will tend to settle in the head/heaters, which is already a problem not solved by having the jiggle pin/hole in the thermostat body.

Post by **Simon Jones** » Thu Jan 17, 2013 9:43 am

Ah, perhaps I misunderstood this

. Maybe he means drilling a hole in the rim of the thermostat body as opposed to the thermostat housing? Phew! As D+P says, there is a little jiggle pin / bead which is designed to allow air and a small amount of coolant to bypass the valve. The only thing that needs to be done to ensure this works correctly is it fit the thermostat the correct way round (pretty certain it will only fit one way) & also fit it with the jiggle pin / bead uppermost so any air at the top can pass thru more more easily.

weebrian · Post by **weebrian** » Thu Jan 17, 2013 9:52 am

Yes, obviously if the hole were in the housing you would dump all of your coolant but the hole is only in the thermostat itself so the system would stay pressurised.

Driver and passengers thanks for clearing that up. Even I wouldn't consider a hole in the housing ! I think my pal thought that all the air would find its way to the thermostat but if as you say, some would build up in the heads then his approach wouldn't work in the case of the Bongo.

Incidentally, how would the coolant system be filled originally in the factory?

Driver+Passengers · Post by **Driver+Passengers** » Thu Jan 17, 2013 10:07 am

Simon - I think the thermostat gasket only fits one way but can be rotated around the thermostat if you want it to. The whole thing sits back at an angle so as you say, jiggle pin 'to the top', which I think is towards you - I forget.

Brian - factory fill is probably one of three ways, but I'm just guessing...

- fill from radiator/tank, bleed as per service manual (see-saw method is new but reliable, other bleeding methods prove to be reliable too)
- vacuum fill, much faster (probably ok on new, pliable hoses, not once they're old and crusty)
- via some nipple on a low metal pipe, not sure anyone has really worked out what it's for

Northern Bongolow · Post by **Northern Bongolow** » Thu Jan 17, 2013 1:20 pm

the jiggle pin is fitted so that its at the highest point, this pin is also a FLOAT.when there is no coolant behind it it drops open to bleed behind of air,when behind fills with coolant it floats and seals the hole--------------cheap auto self bleed system.

briwy · Post by **briwy** » Thu Jan 17, 2013 3:10 pm

weebrian wrote:.

Incidentally, how would the coolant system be filled originally in the factory?

Most vehicles are filled in the factory using a pressure system so I assume Bongos were the same.

Dave Aber mentioned a DIY system for doing this. Perhaps he will along to say how it worked out.

Driver+Passengers · Post by **Driver+Passengers** » Thu Jan 17, 2013 3:43 pm

Dave and I used his thing on my van one evening last year. It's a venturi thingumyjig with a non-return valve, powered by an air compressor. It sucks the air out to not quite a vacuum, indicated on a pressure gauge. When it's down to what you want, you put a hose into a bucket of coolant and open a valve - it sucks the coolant in.

Old hoses can be crunchy and will not collapse under the pressure of the atmosphere as well as new hoses would (I'm guessing) and you probably don't want to stress old hoses in this way for fear of weakening them.

After 5 minutes idling, my rad fans came on. I was watching my add-on engine bay temp sensor instead of the add-on head temp sensor and didn't notice. We bled the normal way and went for fish and chips. I boiled over two weeks later and after that determined that either head or gasket had failed - turns out it was just the gasket.

These systems have been used successfully, but I for one will never use one on my van again.

dave_aber · Post by **dave_aber** » Thu Jan 17, 2013 4:56 pm

The kit I have is a Sealey vac coolant filling kit. Used on many vehicles with much success to fill cooling systems - inc my Bongo.

I have now used this kit twice. Once on my van, and once on Matt's. By my maths, it's had a 50% success rate.

I very much doubt I'll use it again.

Pity, as it did seem to work well first time, but the risk is just too great with a Bongo.

Driver+Passengers · Post by **Driver+Passengers** » Thu Jan 17, 2013 4:58 pm

*sorry, Dave*

dave_aber · Post by **dave_aber** » Thu Jan 17, 2013 5:02 pm

Not at all.

Who knows if it was the root cause of your gasket going? Just dented my faith in the vac method - like you say, probably ideal on a new system, but it is perhaps a wee bit too much strain on an older one.

Driver+Passengers · Post by **Driver+Passengers** » Thu Jan 17, 2013 5:16 pm

I reckon it's likely because the thermostat gasket was incorrectly refitted that day - causing air ingress, etc...

When we removed the thermostat which sits in a recess on the bottom and against a flat machined face above, it was stuck to the flat face above. Instead of peeling it off and refitting to the thermostat, I plonked the thermostat back in the recess and tightened it up against the gasket above. I'm sure me and Ady saw a dribble from the housing at some point.

Anyway, off topic.

peterrc · Post by **peterrc** » Thu Jan 17, 2013 5:36 pm

Given that the air traps are known in the Bongo system would it not be possible to connect in bleed tubes that could be bled remotely?

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