coolant flow - (follow up to cooling diagram)

[widdowson2008]

....partial blockages in the matrix pipes, especially at the ends and coolant flow is restricted thereby trapped air will be difficult to purge out.

OK - if the air is 'difficult to purge out', would that also suggest that it may stay put even under normal running conditions? Not trying to trip you up Dandy - just establish the various possibilities.
Do you know what the heater matrix is like internally? I know the inlet/outlets are on the bottom, but have no idea what happens inside.
I wouldn't have thought it would be just a cavity because it would be impossible to get all the air out. (wouldn't it?)
AND, if that's not the case, then what IS inside?
Could it be just a finned pipe?

[Northern Bongolow]

spot on ron, didnt i just say that

[Ron Miel]

spot on ron, didnt i just say that

Yes, you did but not fully explained, or explicit as to the full mechanics of the process(es), which is why I tried to spell it out a bit more - i.e., it was your post which prompted my latest bout of verbal diarrhoea, as many might just regard it

[Northern Bongolow]

you can get powder for that you know.but dont take it yet,your doing just fine.

[Northern Bongolow]

steve if the heater matrix internals are made the same as the main rad,then its made up of a series of very fine (3mm) wide vertical shafts, which are about 10mm apart, and 20mm front to back joined by top and bottom tanks.the all ally ones are better as the vertical shafts are twice the width(6mm)ish.

[widdowson2008]

Gotta admit, Ron & Dandy are more than several rungs above me at this point. When you two have sorted this bit out, could you put it in plain English/Scottish for the simpletons amongst us cos it sounds interesting?
Was going to ask something else here but I'll refrain until last bit is clarified - need to understand what you are saying before I move on.

Ady
Gonna take a look at the rad pics you posted a while ago and compare.
Main difference I can think of immediately is that inlet/outlet pipes on the heaters are both at the bottom, whereas the main radiator is IN at the TOP/OUT at the BOTTOM.

EDIT: had a lookat your main radiator pics and I can see how that works with inlet and outlet at top and bottom. How does/can this principle apply to inlet/outlet both at the bottom?

[Northern Bongolow]

thats exactly why i said that elevating the front of the motor can give you greif when bleeding.but also it can help shift it

[widdowson2008]

Getting a bit out of sync here

[mikexgough]

Factory Method.....on a diesel......as pictorially demonstrated........

same method.....Translated here but not 100% in english context an example of that is
"Air hose without removing the plug" should read in context........... remove the air hose plug.... so as you can also see once the 1st 6 mins of 2500 revving is done you replace the plug if bubble free and the bottom hose is hot, then do the rest of the rev/rest sequence....so the system can purge the rest of the trapped air into the de-gas tank.........

That's all from me on the bleeding subject..... as you know...........Hairs can be split for hours and days on this subject as can merits of doing it this way or that way................. over to you guys

[widdowson2008]

Cheers Mike. Think you gave me this before but I lost it - Saved now

[Ron Miel]

Gotta admit, Ron & Dandy are more than several rungs above me at this point. When you two have sorted this bit out, could you put it in plain English/Scottish for the simpletons amongst us cos it sounds interesting?
Was going to ask something else here but I'll refrain until last bit is clarified - need to understand what you are saying before I move on.
>
>

Sorry, been offline watching telly. Anyway, assuming you're serious there Steve, I'll try:

Air trapped in t'cylinder head during coolant refill starts off cold but then gets dead hot when the engine runs, due to dead hot bangs in the cylinders, aka combustion. However, if there's only trapped air in the cylinder head, and nowt anywhere else in the system, it might only cause hot spots until it gradually disperses and it will not necessarily cause a full engine overheat and instant death - 'cos there's still nowt to stop coolant also whizzing through and carting away lots of heat.

In radiators, heaters, pipes, hoses, the little white(?) plastic tank, and other nooks and crannies well away from the head, there is nowt happening to add much heat to locally trapped air - except hot coolant flow when the engine runs, and that probably don't add much 'cos the coolant is nowhere near as hot as combustion and whizzes past too fast to lose much heat in the process, plus the air constantly loses heat to the outside by conduction, anyway. So air in those other places is nothing like as hot as the dead hot cylinder head air, and is not likely to directly knacker anything.

BUT if there's enough air trapped in any of those other places to actually block coolant flow to the cylinder head, unless the engine is immediately switched off the inevitable result is a very rapid uncontrolled heating up of the cylinder head (thermal runaway), and speedy death of the engine - even though it's caused by air blockage elsewhere.

[dandywarhol]

>
...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.

I wondered if "superheat" was the wrong term to use...........................I mean more of your second explanation - very hot air.

Trapped air, like trapped wind, although how long does human gas stay trapped for can eventually try to rise to the highest point I imagine, and if air is present in the system (with the exception of the expansion/degassing tank because it's higher than the engine) then the coolant cannot circulate properly IMO. I recall trying to get a Rover 25 engine bled and eventually found a bleed valve in the system - until that was opened and the air purged out the engine just continually overheated to a dangerous level. I guess it's much like having an airlock in your house central heating system - until its bled of air the radiator remains cool, once bled the coolant can circulate and in a vehicle's case, dissipate the heat via the pipes and matrices.

A heater martix is exactly like a mini radiator with core tubes.

[widdowson2008]

Thanks Ron/Dandy - clear to move on now.
Said it before and I'll repeat it - treat me as thick on this subject, because I AM. Learning all the time. Thanks for your patience.

Dandy - you've done it again - sorry Can you explain core tubes please? (Told you I was thick)

In our case (the heaters), are these vertical or horizontal tubes? and how do they relate to the 2 bottom connections? Can you point me to something that might explain?

Meanwhile, I'm attacking this in the only way I feel safe with, so expect some more diagrams soon.

ps.Ady has a spare rear heater but the miserable sod aint gonna cut it open for me. I think that's bloody mean don't you?:lol:
oops - sorry Ady - just noticed you're around. Thought you were off to bed.

[Northern Bongolow]

bloody right he's not going to

[widdowson2008]

bloody right he's not going to

C'mon - you know you want to really in the name of science?