coolant flow - (follow up to cooling diagram)

[Ron Miel]

Looks like the flows through the head has got others as baffled as me. (or possiblly not interested?)
So, I think the subject line, 'COOLANT FLOW' is exhausted. I'm pretty confident with what we have found out. Thanks for all your help.

Just leaves one area not discussed fully (based on known facts), and more to the point, I suspect one not totally understood by the majority of folk - me included. Seen it done but not fully understood what I was looking at.

I make no apologies for bringing up this old chestnut, (it is a major part of the cooling system) but I believe that knowledge to date has been based on guesswork and the 'I know better' attitude.
Personally, I need to understand how things work, not just take someone elses word for it.

What is the subject? BLEEDING.

Reason for bringing it up is that I think I may have a very simple solution to the black art (based on factual knowledge gained in this thread). Can't think how no one has thought of it before. (or perhaps they have)

I'LL BE BACK!!!

Yes, PLEASE, Steve!

I for one have got a big hose job pending but will wait until we see all what you think, so hopefully it will be fairly soon - although you sure deserve a break from all this for a while.

Me, I would go down the pub.

Meanwhile, again, congratulations on a great job

[widdowson2008]

Thank you Ron.
If I am right, then the solution is so bloody simple and cheap (around £15 for a lifetime fix) - and it has huge bonus attached.
OK - need to ask a few questions first.
1 - Why are we concerned about air locks? Damage to the head?
2 - On a system refill, where, phsically, are these air locks?

Having studied the system, would I be right in assuming the answer to 2 above is:
a) in the top of the head (plus the top engine end of the hose to the top radiator connection)
b) in the front and rear heaters
c) below the thermostat housing (plus the top end of the hose from the radiator bottom connection)
If so, which can cause the most damage , and why?

Any more?

[Ron Miel]

Thank you Ron.
If I am right, then the solution is so bloody simple and cheap (around £15 for a lifetime fix) - and it has huge bonus attached.
OK - need to ask a few questions first.
1 - Why are we concerned about air locks? Damage to the head?
2 - On a system refill, where, phsically, are these air locks?

Having studied the system, would I be right in assuming the answer to 2 above is:
a) in the top of the head (plus the top engine end of the hose to the top radiator connection)
b) in the front and rear heaters
c) below the thermostat housing (plus the top end of the hose from the radiator bottom connection)
If so, which can cause the most damage , and why?

Any more?

Off the top of my head, without pouring over animations again ('cos I'm busy on other stuff online):

- air trapped in the head, because of high combustion temperatures and hot spots caused by lack of coolant flow, plus in the case of the WL-T engine at least, possible inter-valve thin area weakness.

- air trapped anywhere upstream of the head, which can still migrate to, and add to, air already trapped there

[dave_aber]

Right, now we are really getting somewhere.

Steve, for what it's worth I have to say that your methodical scrutiny of these subjects so far is to be applauded. I'm sure that by applying the same process and level of attention to detail we/you will enlighten the masses (those that care) about the finer points of the bleeding process.

I've not had the dubious pleasure of having to bleed my van yet, but I'll be much happier doing so once I fully understand what I'm doing - as opposed to knowing how to do it, as I feel I do already from all the good advice on here in the past.

I look forward with interest to your next thread.....

[widdowson2008]

Any more?

Off the top of my head, without pouring over animations again ('cos I'm busy on other stuff online):

- air trapped in the head, because of high combustion temperatures and hot spots caused by lack of coolant flow, plus in the case of the WL-T engine at least, possible inter-valve thin area weakness.

- air trapped anywhere upstream of the head, which can still migrate to, and add to, air already trapped there

Cheers Ron
I think the only way air can get into the system is via the thermostat housing, from either the heater circuit or the bottom hose connection. Is this what you mean by 'upstream'?
Gets better

Anyone else any ideas?

[dandywarhol]

Thank you Ron.
If I am right, then the solution is so bloody simple and cheap (around £15 for a lifetime fix) - and it has huge bonus attached.
OK - need to ask a few questions first.
1 - Why are we concerned about air locks? Damage to the head?
2 - On a system refill, where, phsically, are these air locks?

Having studied the system, would I be right in assuming the answer to 2 above is:
a) in the top of the head (plus the top engine end of the hose to the top radiator connection)
b) in the front and rear heaters
c) below the thermostat housing (plus the top end of the hose from the radiator bottom connection)
If so, which can cause the most damage , and why?

Any more?

I think you've answered your own question well - air will trap anywhere there's nooks and crannies (is that a term understood south of the border ? ). Heater matrices are a good example plus any small pockets in the head passages. ANY air will cause the coolant to be reluctant to circulate, therefore the air pocket will superheat and cause damage. The Mazda bleeding method which was designed and tested by a design team DOES work - and as long as the bleed pipe is higher than ANY part of the cooling system then, with the assistance of the water pump spinning at over 2500 rpm then all the air will be purged - but NOT GUARANTEED if there's silt trapped in matrices etc.

[Ron Miel]

Any more?

Off the top of my head, without pouring over animations again ('cos I'm busy on other stuff online):

- air trapped in the head, because of high combustion temperatures and hot spots caused by lack of coolant flow, plus in the case of the WL-T engine at least, possible inter-valve thin area weakness.

- air trapped anywhere upstream of the head, which can still migrate to, and add to, air already trapped there

Cheers Ron
I think the only way air can get into the system is via the thermostat housing, from either the heater circuit or the bottom hose connection. Is this what you mean by 'upstream'?
Gets better

Anyone else any ideas?

Probably Steve - as I say, no time right now to look at all the flows again. What I mean is trapped air which is either in the head, or still being pumped in the direction of the head, under whatever state of thermostat opening. As a corollary, any air which has pumped out of the head by entraining into the passing flow of coolant, is "downstream" - relative to the head.

[widdowson2008]

enlighten the masses (those that care) about the finer points of the bleeding process.
fully understand what I'm doing - as opposed to knowing how to do it, as I feel I do already from all the good advice on here in the past.
I look forward with interest to your next thread.....

Thanks Dave
methodical scrutiny? Is there another way?
enlighten the masses (those that care) about the finer points of the bleeding process. That includes ME
fully understand what I'm doing - as opposed to knowing how to do it Me too
good advice on here in the past Couldn't agree more.

We'll get there with a joint effort I'm sure.

Gotta say, it's looking promising at the moment. Sometimes the obvious things are the most difficult to spot, and I think this may be one of those occasions.

[widdowson2008]

I think you've answered your own question well - air will trap anywhere there's nooks and crannies (is that a term understood south of the border ? ). Heater matrices are a good example plus any small pockets in the head passages. ANY air will cause the coolant to be reluctant to circulate, therefore the air pocket will superheat and cause damage. The Mazda bleeding method which was designed and tested by a design team DOES work - and as long as the bleed pipe is higher than ANY part of the cooling system then, with the assistance of the water pump spinning at over 2500 rpm then all the air will be purged - but NOT GUARANTEED if there's silt trapped in matrices etc.

Hi Dandy - thanks for your input.
nooks and crannies term understood south of the border ? Yep. We're not totally thick down here ya know. well...........not totally.
Mazda bleeding method....DOES work 100% with you there.
silt trapped in matrices Slight spanner in the works. What actual damage would a blocked matrix(ces) cause?
Worse case scenario - If both the matrices were completely blocked, then the thermostat would be reacting purely from the flow via the bypass (head), in which case, it would open accordingly (but quicker). Would this result in any damage do you think?

[dave_aber]

or would the damage only be done when the air is somehow released from wherever it's been hiding to somewhere critical, and high-up, like the head?

[widdowson2008]

Another thought.
If there is air in the heater matrix(ces), then how would you know? other than the heaters not warming up. Is there a way of determining this other than switching the heaters on?

[Northern Bongolow]

the damage can occur in 2 ways, either the air(lock) prohibits the flow of the coolant in say any pipe or heater,it doesnt really matter where it is,the result is the same,no flow.
or the air is held in the head,and damage is then caused.

the system is just several loops and no matter what/where,it must be purged,
the problems arise,when flows are already restricted,bad rads,cruddy systems etc,where the purging is made more difficult.

and in my experience no two bongo's are alike,and will bleed differently.

[widdowson2008]

Cheers Ady
Don't think it answers my question though.
Let me put it another way. Suppose you completely blanked off the heater system. What would happen? We know that folk have removed the rear heater from their vans without any noticeable difference. What happens if both heaters are removed?

I can see this swiftly moving into the realms of 'anyone got a heater for me to chop up'. Would really like to avoid that if possible. Boss is already requesting disposal of dissected thermostats, cylinder head, expansion tank, ECU, et al.
Alternatively, has anyone actually got an old heater which could be ..............errrrrrrr .................looked at?

[dandywarhol]

I was thinking more of partial blockages in the matrix pipes, especially at the ends and coolant flow is restricted thereby trapped air will be difficult to purge out.
The way to test a (partially) blocked matrix is to physically feel it with the palm of your hand and check for cold spots

[Ron Miel]

>
...ANY air will cause the coolant to be reluctant to circulate, therefore the air pocket will superheat and cause damage....
>

Questions arising from that dw:

- Do you really mean that the air pocket will "superheat"? Isn't superheating a term restricted to the failure of contained/undisturbed liquids to boil (off), even at temperatures above their normal boiling points, due to their internal formation of very many small vapour phase bubbles, with high surface tension preventing normal expansion into larger escaping (boiling) vapour bubbles? When eventually released by disturbance (e.g., a pipe burst) superheated vapour (steam in the case of water) finally "explodes" out of the liquid in a very dangerous fashion.

- If you just mean very very hot air, isn't that condition primarily restricted to air trapped in direct contact with the cylinder head's extreme direct heat of combustion - and unable to carry away that combustion heat in the same way that pumped liquid coolant does, hence build up of hot spots where there is trapped air rather than flowing coolant?

- If I've got that right(?), then in extremis, of course, if/when there is enough trapped air to create an air blockage somewhere (anywhere) else in the system, which also prevents sufficient coolant flow in or out of the engine block, particularly the head, then the reduced-flow coolant itself will also very quickly become greatly overheated in the head region (probably then actually also creating a superheat vapour situation as a by-product), and that's when we see catastrophic flash/total overheating of engine and coolant.

- Is that about right? If so, damage isn't normally done at the heater or wherever (and that's what we see isn't it?) but at the combustion site (the head), as a result of air trapped at the heater or wherever.