coolant flow - (follow up to cooling diagram)

[Northern Bongolow]

fast fingers kisty again.lol.

[missfixit70]

fast fingers kisty again.lol.

You'll get people talking

[widdowson2008]

.......(the resistance link between primary and secondary systems) only then does the system work as one with equal resistance throughout.

I agree with everything blanked out but don't understand the remaining green bit.

Did you know there is a direct and constant mathmatical relationship between the bypass (cylinder head) and radiator connections. As the stat moves between the rad closed and bypass closed states, the flow area from each varies BUT what doesn't vary is the sum of these flows. It is a fixed and finite number. ie. (flow from head+flow from rad) is constant. This applies until the bypass is closed.
If the stat continues to open further (which it can if the heater return exceeds approx 95 deg.C) the rad connection increases allowing a greater flow from the radiator.
Does this have any bearing on the system?

[missfixit70]

If the area around the stat bulb exceeds 95 degrees, doesn't that mean the returns from the rad have exceeded 95 degrees, in which case you are way out of "control" & into overheat territory anyway as this is the engine inlet temp? If the rad & fans haven't brought the temp down by that point it's probably too late to worry too much anyway?
I'm 2 Crabbies to the wind so I may be wrong

[widdowson2008]

If the area around the stat bulb exceeds 95 degrees, doesn't that mean the returns from the rad have exceeded 95 degrees, in which case you are way out of "control" & into overheat territory anyway as this is the engine inlet temp? If the rad & fans haven't brought the temp down by that point it's probably too late to worry too much anyway?
I'm 2 Crabbies to the wind so I may be wrong

Now I am truely confused.
It has been stated that unless the stat has closed the bypass, the Bongo is not fully bled.
Tests show this to happen at 95 degrees, but above you say that above this (say 96 degrees?) is way out of control.
Does this mean that the recommended bleed system relies on the cooling system to be out of control?
Please tell me I missed something.

94/95 is the temperature I recorded at which the stat reaches bypass closed position. Don't forget, the stat I am testing is in a pan of water - not a Bongo. Just seeing what happens at what temperature.
And I'm not sure whether the rad return will ever get 95. Not yet anyway.

I'll have some accurate monitored temperatures from around the cooling system in a couple of weeks when the test vehicle is equipped and had its stat and coolant changed. Currently being fitted with lots of bells and whistles, gauges and led's - sounds great.

But yes, I reckon you have hit the nail - if 95 is recorded at the stat, you have lost control (or are about to)

Can you ship some Crabbies up this end? Could do with one or two. Head hurts - going to bed

[Northern Bongolow]

hi steve

imo the entire system circuits including the bottom hose to stat could PROBABLY exceed 95 degrees easily,the only two things that will save the engine from then on are the rad fans ,which will kick in shortly,or rapid air flow through the rad ie easing off down hill coasting .

ady

[The Great Pretender]

Now I am truely confused.
It has been stated that unless the stat has closed the bypass, the Bongo is not fully bled.
Tests show this to happen at 95 degrees, but above you say that above this (say 96 degrees?) is way out of control.
Does this mean that the recommended bleed system relies on the cooling system to be out of control?
Please tell me I missed something.

94/95 is the temperature I recorded at which the stat reaches bypass closed position. Don't forget, the stat I am testing is in a pan of water - not a Bongo. Just seeing what happens at what temperature.
And I'm not sure whether the rad return will ever get 95. Not yet anyway.

The 94/95 that you are getting is flow from the primary circuit with a little help from the secondary that has a higher resistance so less flow until the bypass is fully closed and all the legs are balanced (have the same resistance). Is it possible that the continued opening of the stat at above that temp is panic mode passing as much coolant as possible through the rad in an attempt to contain an overheat?

[widdowson2008]

hi steve

imo the entire system circuits including the bottom hose to stat could PROBABLY exceed 95 degrees easily,the only two things that will save the engine from then on are the rad fans ,which will kick in shortly,or rapid air flow through the rad ie easing off down hill coasting .

ady

Wish I knew ady but will have to wait until these tests on the Bongo are done. May have a better idea then. I'm hoping they will be pretty conclusive, but having said that, I was always an optimist.

[Northern Bongolow]

as the great pretender,sorry i dont know you name, rightly suggests successfull bleeding only takes place when all the elements/cicuits are open and are pressure balanced. allowing full flow around these circuits.
ady

[missfixit70]

Ok trying to think this one through properly, just reading back through the epic so far You've probably answered the (incorrect?) questions I threw up with this post

Yet more ............. FLOW diagrams this time!!!!!
Stat CLOSED
Stat @ 2.6mm lift
Stat @ 5mm lift - FULLY OPEN
Stat @ 8.5mm lift

These diagrams suggest that the ONLY flow which has an immediate effect on the wax cylinder (and hence stat lift) is that from the heater circuit.Flows from cylinder head and radiator both seem to pass through the engine BEFORE seeing the wax.

Any thoughts out there??????

I think it's too simple to say there is one temperature at the stat (ie 95 degrees) as it depends on the flow priority, if the returns from the rad are not really mixing in the stat with the "primary heater flow", & this flow at a higher temperature having the most effect on the stat bulb, it doesn't mean the engine inlet is at that temperature, as you'll have a much greater flow of cooled coolant (not very much cooled when bleeding as you are trying to raise the temp, basically by simulating the rad not working as it's stationary with no air flow) coming from the rad & mixing as it enters the engine.
As it gets to the point of the stat being fully open & the top disc sealing off (at 95 degrees hitting the stat bulb, but not as hot actually entering the engine) the engine is going to keep getting hotter until the rad fan/s are triggered (hopefully we'll know at what temp/how long for soon - I tried to measure it, but it all happened too fast & I kept being in the wrong place ).
Once there is airflow across the rad, the bottom hose temperature drops within a very short space of time, thus bringing down the engine inlet temp, & subsequently the engine temp, this will have the knock on effect of reducing the heater circuit temp as this is dependant on the engine temp, so the stat will close in again (& the fans shut off once time/temp? criteria met - ecu info needed )

You have to bear in mind that bleeding the engine while stationary is raising the temperature as if the rad isn't working correctly, but even with the high temperatures that are attained the engine, in good working order should still be within control parameters, as you still have the element of control from the fans once the stat has fully opened.

As for the continued opening beyond 95 degrees, not sure how far beyond the 95 degrees it'll go before the fans'll kick in? I reckon that extra amount of lift is more of a "safety valve" for the stat.
At that amount of lift does the cross sectional area of flow allowed in exceed the cross sectional area of the inlet pipe from the bottom hose & what effect might that have?

I see i've taken too long trying to write this lot & been beaten to it

[widdowson2008]

as the great pretender,sorry i dont know you name, rightly suggests successfull bleeding only takes place when all the elements/cicuits are open and are pressure balanced. allowing full flow around these circuits.
ady

Need answers that my tame (or maybe not ) scientist will provide - need to get some data.

[missfixit70]

hi steve

imo the entire system circuits including the bottom hose to stat could PROBABLY exceed 95 degrees easily,the only two things that will save the engine from then on are the rad fans ,which will kick in shortly,or rapid air flow through the rad ie easing off down hill coasting .

ady

Wish I knew ady but will have to wait until these tests on the Bongo are done. May have a better idea then. I'm hoping they will be pretty conclusive, but having said that, I was always an optimist.

I think you may get temps that high from the rad returns if the system really isn't running right, but the fans kicked in on mine before the engine outlet/top hose/inlet to the rad got to upper 90's, with approx 15-20 degrees cooling on a static rad (while bleeding, depending on ambient temp & wind), I think the max rad outlet/bottom hose temp you'd get on a healthy system is @85 degrees before the fans kick in. The highest I managed to measure was 75 degrees.

[Northern Bongolow]

i agree 100 per cent with what you say kirsty,sorry i had to provoke you into a little fight to get the best out of you, .hope your not mad, you always come up with the goods,

regards ady

[missfixit70]

Just had to try & bump start the brain a bit I'd relaxed after being stood down from being on telephone standby for Baz

[widdowson2008]

Just had to try & bump start the brain a bit I'd relaxed after being stood down from being on telephone standby for Baz

Rang Baz earlier this evening to see how he was progressing - waiting for Jaylee at that point.
Any news?

From your earlier post: At that amount of lift does the cross sectional area of flow allowed in exceed the cross sectional area of the inlet pipe from the bottom hose & what effect might that have?

In short - NO
The areas are as follows:
inlet pipe diameter at stat =31mm, area = 755mm²
Mazda stat lift @ 95 deg.C = 9.5mm, which equates to a flow area of 497mm²
(Blueprint stat lift @ 95 deg.C = 8mm, which equates to a flow area of 439mm²)

Brains dead - can you think of effect?