Alternative bleed method?

[spout]

Drain the whole system, flush it out if required, refill using a 50:50 mix, then extend the bleeding hose out the car door and sit it pointing into the expansion tank opening. Have additional mix ready to pour from a jug with a narrow spout to pour past the extended bleed hose into the exp tank.

Run engine to fully warm, rev engine at intervals and observe what's coming out of bleed hose into the exp tank.

From my experience the coolant would travel the other way.......being sucked through the bleed hose as the engine is rev'ed ?????????

(I'm guessing the circulating coolant running past the hose connection pulls the coolant through?)

[waycar8]

The pumps will be controlled by a light activated switch which will be pointed at the low coolant alarm warning LED, so no electrical connection to the alarm. Good point about the coolant flowing into the tank shorting out the low coolant alarm, but if the pipe is put fully into the expansion tank, then it shouldn't be an issue. If I could find a pump that is happy to run 'dry' then it could run all the time & the level should be maintained at the correct level a it will be pumped back in as soon as it comes out the bleed pipe.

The other thing that may work would be to extend the bleed pipe up to the expansion tank, so it would rely purely on the force of the water coming out. If this works, then it solves all the complicated stuff. Anyone tried this approach?

Well when I bled mine a few months back, I used a piece of hose pipe to extend the bleed hose up to the expansion bottle, it worked up untill the engine got to temperature and the hose pipe became soft under the heat so I pulled it apart and stuck the bung back in the bleed hose.

[Trouble at t'Mill]

I have to confess I haven't tried any bleeding of the system at all (as the existing coolant was clean and already had some additive, I just topped up the antifreeze level by slowly draining from the rad bottom plug whilst keeping the antifreeze pouring in the expansion tank), so I don't know what sort of force the coolant comes out of the bleed pipe - but reading on this forum, it would seem it can be with reasonable force! I also read that the bleed pipe should be pointed downwards but should at some point be the highest point in the system?

Waycar seems to suggest it can be done? Rubber hose, or possibly plastic central heating pipe should do the trick.

[teenmal]

Drain the whole system, flush it out if required, refill using a 50:50 mix, then extend the bleeding hose out the car door and sit it pointing into the expansion tank opening. Have additional mix ready to pour from a jug with a narrow spout to pour past the extended bleed hose into the exp tank.

Run engine to fully warm, rev engine at intervals and observe what's coming out of bleed hose into the exp tank.

From my experience the coolant would travel the other way.......being sucked through the bleed hose as the engine is rev'ed ?????????

(I'm guessing the circulating coolant running past the hose connection pulls the coolant through?)

Hi Spout.if you use the bleed hose, that is on the flow not the return,it should expel the fluid.

Cheers Mal..

[lizard]

What an excellent idea, you must have a brain the size of the universe . If this works it will be wonderful

The idea was to devise a one-man operation solution. It's not that I dont trust my other half with the business end of the coolant system, but I'd like to see if it can be done. The other goal to is to find a solution to the question of when the system is fully bled. If we can find a method which doesn't require continual intervention, then it could be left for an hour or so to just sort itself it.

If all goes to plan, I'll have a go at the 'long pipe' method this weekend

It took me all day to bleed the bongo, once to flush out all the old coolant, again to put in the antifreeze, with the Misses burning her hand and dropping the funnel . The third time appears to be success

If this idea works, Simon, you'd be elevated to, to, er, ..what's higher than a Supreme Being?

What's after supreme being

Great Architect of the Universe,

Most High, Potent, and Noble Prince,

Great High Lord of the Universe,

The Omnipresent Elder of the World

[haydn callow]

Trouble at Mill....did yoiu do that with the engine running ???(drain via rad drain) As this is suction side of pump it can be dodgy.(suck air in)

[spout]

...if you use the bleed hose, that is on the flow not the return,it should expel the fluid.

I’ve been thinking about this. Bear with me!

The bleed hose is just a connection onto/off a flowing circuit. Whether it is before or after the pump is purely relative (it’s both!).
With the bleed hose open to atmosphere the coolant system can’t get pressurised, and as the connection is at the high point there is no reason for fluid to escape.

Unless of course any trapped air in the system circulates round to this point, raises up the hose forcing any fluid in the hose out. There shouldn’t be a constant flow (unless the hose is lowered enough for the “siphon effect” to come into play). Any loss of fluid will be replaced from the expansion tank.

So this is how the “normal procedure” bleeding works, ie bleed hose held high and open to atmosphere – lets air out (with occasional burbs of forced fluid) as it circulates round to the connection but doesn’t let the coolant flow out. Similarly any air in the radiator circuit can rise up to the expansion tank. The space left by any bled air is replaced by the fluid in the expansion tank (level musn’t drop enough to let air be sucked in).

I’m going to start a bit of an argument now by suggesting that the see saw method might actually restrict the bleeding process.

With the see saw method the bleed hose is always full of fluid (with an additional head within the funnel). Will this now not make it harder for any air bubbles passing the connection point of the bleed pipe to exit the system? Perhaps not?

I did notice during my see saw bleed that revving the engine caused the level in the bleed hose to drop, I’m assuming this is caused by the venturi(?) effect of the circuit flow past the bleed connection. Air could then be pulled into the circuit if allowed to drop too far. On idle the levels stabilised.
Revving the engine with the bleed pipe open to atmosphere (in the “normal“ bleed procedure) wouldn’t pull any air in. I don’t think. As the flowing coolant hasn’t the same pull on air as fluid.

During the normal bleed procedure the rev/idle cycles aren’t there to warm the engine as such, but are designed to get any trapped air to the bleed points (bleed hose and top hose off radiator to expansion tank). Revving (and consequent speed up of the coolant) forces any air into motion, and then the idle cycle allows this freed air to collect and exit the bleed points. I think I’ve got this right.

So after repeated cycles all the air should be out. Except of course for the air in the bleed hose. This can be taken out by simply lowering the hose to the same level as the expansion tank before plugging it.

So what advantages do the see saw or other alternative methods have over the normal procedure? And have I been correct in my assumptions?

Perhaps I was just lucky with my first coolant change? It’s all very worrying.

[haydn callow]

All I can repeat is...I have bled our Bongo at least 6 times...(not because there was a problem but I was trying to develop somthing) and at least another 6 Bongos for other prople....I always use the see saw method, adapted from a method I saw at Allans Garage at Plymouth....I have never had any problems whatsoever and also NEVER had to top up the following day...I.E. ALL air has been removed during the bleed process.
It works for me.
Bleeding a Bongo is not rocket science..You just need to know/understand a couple of basic points and be methodical in the procedure.

[haydn callow]

During the normal bleed procedure the rev/idle cycles aren’t there to warm the engine as such, but are designed to get any trapped air to the bleed points (bleed hose and top hose off radiator to expansion tank). Revving (and consequent speed up of the coolant) forces any air into motion, and then the idle cycle allows this freed air to collect and exit the bleed points. I think I’ve got this right.


This Rev/idle cycle is done to get the coolant hot enough to get the Stat open....Once this happens...providing the basic instructions have been followed you are home and dry. The water pump gets the coolant moving (and any air.) once the air is moving it will find the higest point and escape.

[Trouble at t'Mill]

Haydn, no I drained the rad with the engine off, and made sure the fresh antifreeze was poured in steadily enough not to allow the expansion tank pipes to be uncovered. It took around 3 litres before neat anti-f started coming out the rad tap - fine for me as there was already a fair a bit in the system.


Spout, of course you could be absolutely right - it's an untried method as yet. Certainly, your experience of the bleed pipe water level falling with increased revs would suggest a venturi effect as you say.

However, there will be a difference in pressure in the pipes depending on how close to the pump flow or return ends you measure; the whole cooling system has some resistance to water flow, hence the water at the point of having just been 'pushed' by the pump will be at a slightly greater pressure due to the resistance of the water in front of it. Similarly, at the 'return' end of the pump, there will be an overall reduction in pressure. This is similar to domestic central heating systems - it's very important where you connect the expansion pipes going to the 'header' tank in the loft, as connecting this at the 'return' end of the system could cause air to be drawn into the system. This all applies - as it does to our car coolant systems - to unpressurised systems, of course.

Hopefully Simon will be trying this out for us

I guess, to give it the best possible chance of working, the connecting pipe should be kept as low as possible in its run - no higher than what's needed to get it going in to the expansion tank filler?

(There must be some award trophy - perhaps made out of an old coolant pump - than could be given...)

[teenmal]

...if you use the bleed hose, that is on the flow not the return,it should expel the fluid.

I’ve been thinking about this. Bear with me!

The bleed hose is just a connection onto/off a flowing circuit. Whether it is before or after the pump is purely relative (it’s both!).
With the bleed hose open to atmosphere the coolant system can’t get pressurised, and as the connection is at the high point there is no reason for fluid to escape.

Unless of course any trapped air in the system circulates round to this point, raises up the hose forcing any fluid in the hose out. There shouldn’t be a constant flow (unless the hose is lowered enough for the “siphon effect” to come into play). Any loss of fluid will be replaced from the expansion tank.

So this is how the “normal procedure” bleeding works, ie bleed hose held high and open to atmosphere – lets air out (with occasional burbs of forced fluid) as it circulates round to the connection but doesn’t let the coolant flow out. Similarly any air in the radiator circuit can rise up to the expansion tank. The space left by any bled air is replaced by the fluid in the expansion tank (level musn’t drop enough to let air be sucked in).

I’m going to start a bit of an argument now by suggesting that the see saw method might actually restrict the bleeding process.

With the see saw method the bleed hose is always full of fluid (with an additional head within the funnel). Will this now not make it harder for any air bubbles passing the connection point of the bleed pipe to exit the system? Perhaps not?

I did notice during my see saw bleed that revving the engine caused the level in the bleed hose to drop, I’m assuming this is caused by the venturi(?) effect of the circuit flow past the bleed connection. Air could then be pulled into the circuit if allowed to drop too far. On idle the levels stabilised.
Revving the engine with the bleed pipe open to atmosphere (in the “normal“ bleed procedure) wouldn’t pull any air in. I don’t think. As the flowing coolant hasn’t the same pull on air as fluid.

During the normal bleed procedure the rev/idle cycles aren’t there to warm the engine as such, but are designed to get any trapped air to the bleed points (bleed hose and top hose off radiator to expansion tank). Revving (and consequent speed up of the coolant) forces any air into motion, and then the idle cycle allows this freed air to collect and exit the bleed points. I think I’ve got this right.

So after repeated cycles all the air should be out. Except of course for the air in the bleed hose. This can be taken out by simply lowering the hose to the same level as the expansion tank before plugging it.

So what advantages do the see saw or other alternative methods have over the normal procedure? And have I been correct in my assumptions?

Perhaps I was just lucky with my first coolant change? It’s all very worrying.

Its always best to keep the end of the bleed hose submerged in fluid,the same as bleeding brakes ets.

[spout]

Its always best to keep the end of the bleed hose submerged in fluid,the same as bleeding brakes ets.

Yes. But slightly different here.
Bleeding brakes is pushing fluid through the system, not bleeding off it.
I think.

[spout]

However, there will be a difference in pressure in the pipes depending on how close to the pump flow or return ends you measure; the whole cooling system has some resistance to water flow, hence the water at the point of having just been 'pushed' by the pump will be at a slightly greater pressure due to the resistance of the water in front of it. Similarly, at the 'return' end of the pump, there will be an overall reduction in pressure. This is similar to domestic central heating systems - it's very important where you connect the expansion pipes going to the 'header' tank in the loft, as connecting this at the 'return' end of the system could cause air to be drawn into the system. This all applies - as it does to our car coolant systems - to unpressurised systems, of course.

Ah......

[spout]

Bleeding a Bongo is not rocket science..You just need to know/understand a couple of basic points and be methodical in the procedure.

I'm beginning to understand...................I think

I suppose keeping the bleed hose full of fluid should reduce the risk of air entering then, and that's why this method was developed. Guess I just had trouble keeping the levels right during the rev/idle cycles.

[haydn callow]

I find I can control the level in the funnel/tank with the engine revs.