Bongo Fury

Great inputs here and clever, clever animation!

It's my belief that the cracks occur when the coolant has trapped air or steam - much like Ady's theory/practice when refuelling, and the same principal when syphoning fuel from a tank - unless there's an absence of air, the fluid won't circulate.

By carrying out the bleed procedure as the Mazda designers instructed, having the bleed tube higher than any part of the cooling system (including the expansion/gassing tank) a combination of convection and water pump assistance will soon purge any trapped air.

Back to the cold shock theory - I mentioned before, that's one reason why the head has 2 supplies of different temperatures of coolant and the 'stat is on the return side - to stop a cold shock and to cut down emissions

dandywarhol wrote: ... the head has 2 supplies of different temperatures of coolant and the 'stat is on the return side - to stop a cold shock and to cut down emissions

Hi dandy - This is the bit I suspect, but can't prove without actually chopping an engine block up (and I can't see that happening) so any guidance would be much appreciated.
The 2 different supplies? Where do they come from?

Using the colour coded diagram, the way it appears to flow is:

Feed 1
BLUE PORTS - From the cylinder water jackets lead directly to the main exit chamber.
MAGENTA PORTS - From the cylinder water jackets lead directly to the main exit chamber.
RED PORTS - From the cylinder water jackets feed jackets around the inlet valve seats, then to the main exit chamber.
GREEN PORTS - From the cylinder water jackets go to feed jacket around the exhaust valves, then to the inlet valve seats, then to the main exit chamber.

Feed 2
YELLOW PORT - is directly from the oil cooler (I think but can't prove) and straight into the main exit chamber

(Animation of flows in the pipeline but proving a bit awkward to include ALL info in one animation - gets messy)



BTW, thanks for kind comments - much appreciated.

Northern Bongolow wrote:agreed steve unless your using bongonads method!! it can take some shifting,when im delivering fuel into an underground storage tank,like a petrol station,an airlock in my 4 inch delivery pipe can hold back 3 or 4 thousand litres of fuel,maybe weighing 3 tons.and thats dropping 4-6 feet all the way.

Hi Northern Bongolow,

There probably is or was a dip in the vent line from the tank to the vent stack with fuel lying in it from a previouse tank overfill.Or if it was a Spirit tank,the vapour recovery PRV could have been acting up.

Did you get fuel running out of the vent pipe on the pump.

Cheers..

Northern Bongolow wrote: the amount of trapped air usually found to escape when the bypass is shut(stat open fully)is approx 2 standard cups full in my method of bleeding.does this equate to the volume of the head roof??? full length.

Ady
In answer to your query on the volume air TRAPPED in the head of the roof (shown in the diagram)? It is approximately 20 cubic inches (430mm x 60mm x 13mm).


This thread is getting very bitty Have we lost the plot

Hi Northern Bongolow,

There probably is or was a dip in the vent line from the tank to the vent stack with fuel lying in it from a previouse tank overfill.Or if it was a Spirit tank,the vapour recovery PRV could have been acting up.

Did you get fuel running out of the vent pipe on the pump.

Cheers..[/quote]

hi teenmal.no pump used,just gravity.like you indicate ,the reason must be fuel lying in an horizontal link to tank. or a vapour line dip, really,this was only stated to illustrate the power of air/airlocks,but thankyou anyway.

widdowson2008 wrote: In answer to your query on the volume air TRAPPED in the head of the roof (shown in the diagram)? It is approximately 20 cubic inches (430mm x 60mm x 13mm).

This volume can be virtually negated by raising the front of the Bongo whilst bleeding.

The Great Pretender wrote:

widdowson2008 wrote: In answer to your query on the volume air TRAPPED in the head of the roof (shown in the diagram)? It is approximately 20 cubic inches (430mm x 60mm x 13mm).

This volume can be virtually negated by raising the front of the Bongo whilst bleeding.

Very true Mel. But the trapped air would still be there in the hose wouldn't it? It would still need forcing out.

Northern Bongolow wrote:Hi Northern Bongolow,

There probably is or was a dip in the vent line from the tank to the vent stack with fuel lying in it from a previouse tank overfill.Or if it was a Spirit tank,the vapour recovery PRV could have been acting up.

Did you get fuel running out of the vent pipe on the pump.Cheers..

hi teenmal.no pump used,just gravity.like you indicate ,the reason must be fuel lying in an horizontal link to tank. or a vapour line dip, really,this was only stated to illustrate the power of air/airlocks,but thankyou anyway.[/quote]

Hi I meant the forecourt pump EMC

Cheers..

oh i dont know im outa there!!!!!

widdowson2008 wrote:

dandywarhol wrote: ... the head has 2 supplies of different temperatures of coolant and the 'stat is on the return side - to stop a cold shock and to cut down emissions

Hi dandy - This is the bit I suspect, but can't prove without actually chopping an engine block up (and I can't see that happening) so any guidance would be much appreciated.
The 2 different supplies? Where do they come from?

.

I'm of the understanding the different heat inputs are at the thermostat housing side - before the coolant circulates back into the engine - unless of course one puts a 'stat AFTER the head

dandywarhol wrote:

widdowson2008 wrote:

dandywarhol wrote: ... the head has 2 supplies of different temperatures of coolant and the 'stat is on the return side - to stop a cold shock and to cut down emissions

Hi dandy - This is the bit I suspect, but can't prove without actually chopping an engine block up (and I can't see that happening) so any guidance would be much appreciated.
The 2 different supplies? Where do they come from?

.

I'm of the understanding the different heat inputs are at the thermostat housing side - before the coolant circulates back into the engine - unless of course one puts a 'stat AFTER the head

Think (HOPE) you might have got this wrong Dandy or I misunderstand what you are saying.
I'm only talking about the head at this point.
Coolant INTO the head comes from the block - vertically upwards through the head/block interface.
Coolant goes OUT of the head to the radiator top connection on the farside AND to the thermostat housing via the bypass on nearside.
PLEASE TELL ME I GOT THIS RIGHT

Yeah I with you ok - the majority of the heat of course, is around the top of the block/head area but its the blending of different temps that the return circuit to the block happens by having the stat on the return IMO and this very quickly gets around all the water jackets in the block and head. I think we're all on the same track here - (Just waiting for TGP to blow a fuse )

At the end of the day,its airlocks or steam which cause the cracks and ultimately the damage. Remember - even a faulty expansion cap/minor leak will cause the system not to pressurise, therefore lower the boiling point of the coolant - result? - instant steam/airlocks

dandywarhol wrote:Yeah I with you ok - the majority of the heat of course, is around the top of the block/head area but its the blending of different temps that the return circuit to the block happens by having the stat on the return IMO and this very quickly gets around all the water jackets in the block and head. I think we're all on the same track here - (Just waiting for TGP to blow a fuse )

At the end of the day,its airlocks or steam which cause the cracks and ultimately the damage. Remember - even a faulty expansion cap/minor leak will cause the system not to pressurise, therefore lower the boiling point of the coolant - result? - instant steam/airlocks

Nice to see the way this thread is going, your getting close to my way of thinking.
Nice that pressure and temperature are involved and agree about the position of the stat with regard to emissions as IMHO it is God today and takes preference over engineering design.
The concept of 'blending' needs looking into, assuming coolant flowing though all the ports into the head at a constant speed picking up heat is wrong. Flow will always take the easiest path. If the ports to number 1 cylinder are the same size as the rest what is stopping most of the flow using those ports reducing flow from the rest, then building temperature from 4 to 3 and 2 ?

Here's another one from me...... I know sometimes many of you think my posts,comments and suggestions are “Off the wall” and sometimes controversial and for that I apologise.
I have been doing some digging with chaps "in the know".....or rather garage owners/mechanic friends....

Why do the WL-T heads crack......? good question........ this seems to be a common fault with the WL-T engine(in all of vehicles it is used in) and most seem to crack between the valves, various schools of thought on why at that point (other than the heads are very thin at that point and prone to failure- I am told post 2001 Ford changed the head design and the Diesel Bongo finished at around that time) This head issue is not just a WL-T issue, other Ford engines are known to suffer in a similar way.
Some great ideas as to why the cracks happen have been put forward and now for some ideas, although no absolute answers, I have collected today from folks who spend their lives working on vehicles. I am not going to say who said what and from what type of garage, just an overview of what the Trade think....
One school of thought argues the overheating scenario, and suggests that poor coolant ratios and type among the reasoning, others even say that lubrication is part of the issue, by using the “wrong” grade even though factory recommended is used and saying that 10/40 the way to go as it is suggested that the lower grade oil gives reduced protection, by “running” away from protecting the head components and then the head therefore heats up more with less lubrication and less heat dissipation through the lubricant and in certain circumstances it has been known to find a snap camshaft..... they all suggest the thermostat is a weak area and should be changed with the coolant......as many of us on BF suggest.
So I guess you need to make your own mind up on this...as to why the cracks occur and I don't suppose there is an absolute answer as all overheating scenarios can and do have different factors...
No one I have spoken to has suggested that air locks cause overheating unless one of the above factors are played out which then results in an air lock being formed then "superheating" of the head with costly end results...
I guess regular Maintenance is the key as Muz has proved with his Bongo, using recommend fluids and components, this doesn't just apply to Bongo's....... all vehicles should be maintained that way.

g8dhe wrote:
Do you have a view of where the Temperature Sender fits into the head ? I think its always been on the other side of the photo's as it were;

Not as such, but a different slant on the dissected head........ I have had these pictures sine July this year(courtesy of an owner in NZ) but have refrained from posting before, so I apologise for that but it was a decision I made to hold onto the information until I had done further research. As the donated head has now also been dissected and with the permission of the owner of the pictures I am publishing them on the forum.




Here is another cross section that is cut through both the port for the 3 way tee and the Water Temperature Sensor, which clearly shows the height of the outlet to the Top hose and how much lower the outlet to the tee is.



although not to scale this illustrates the above in a diagram..... just to add to the mix and to show........... as has been suggested, that any trapped air leaves by the top hose route....... then it will subsequently follow the coolant flow as we already know, into the radiator top tank, then coolant branches off to the Expansion/de-gas tank.... before going around the system again.... I will get my coat.....

mikexgough wrote: .........g8dhe wrote:
Do you have a view of where the Temperature Sender fits into the head ? I think its always been on the other side of the photo's as it were;

Not as such, but a different slant on the dissected head........ I have had these pictures sine July this year(courtesy of an owner in NZ) but have refrained from posting before, so I apologise for that but it was a decision I made to hold onto the information until I had done further research. As the donated head has now also been dissected and with the permission of the owner of the pictures I am publishing them on the forum.


Here is another cross section that is cut through both the port for the 3 way tee and the Water Temperature Sensor, which clearly shows the height of the outlet to the Top hose and how much lower the outlet to the tee is.

although not to scale this illustrates the above in a diagram..... just to add to the mix and to show........... as has been suggested, that any trapped air leaves by the top hose route....... then it will subsequently follow the coolant flow as we already know, into the radiator top tank, then coolant branches off to the Expansion/de-gas tank.... before going around the system again.... I will get my coat.....

Dandy - thanks for reply - glad we are on the same page otherwise I would have wasted a lot of time barking up the wrong tree.
Mike - The above agrees with what I was saying earlier.
The reason I asked what causes the cracking was to stimulate others who do know into replying. I know NOTHING other than what I have seen myself.
I have one more animation to add (working on it at the moment). This one shows the actual path the coolant takes through the head from each of the inlets. I dont know why Mazda chose the paths, but others probably will. Post soon.