coolant flow - (follow up to cooling diagram)

[dandywarhol]

With the combustion temperature at over 1000 degC (yep 1000!) any airlocks will have a hugely detrimental effect on the surrounding area - airlocks means the coolant can't circulate.....................something's got to go...............either crack or MELT

[widdowson2008]

That's bloody hot Dandy. Can't imagine this happening within 2 feet of my bum.

First of two animations. This one shows MAIN longitudinal flow chamber through the head.
Next one (with a bit of luck) will show the lateral flow paths (to, and between valves).
I do hope thes are making some sense to someone

[mikexgough]

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.

As for agreeing what was said earlier, this was raised in July about the relative heights of the "bleed" hose and the top hose outputs.....but I am not going to get into a spat about who said what and when as life is too short......

On to head cracks.......now putting the Bongo cooling system aside for now....... lets just take the engine.....nothing else......not even coolant flow....just the basic engine design.....

Having been chatting to mechanic pals and looking around the conclusions I have come to is that the faults are in the Ford design....

The same engine is fitted to Mazda BT-50 etc and the Ford Ranger (leave the Tee jobby out of this) and yet they suffer the same issues as the Bongo/Freda in respect of the heads and camshaft breakages...... There have been a couple of camshafts break in Bongo's as we know.....
The same head cracks have been reported in the BT-50/Ranger camps too....so the Bongo/Freda is not alone.....it appears to be not some singled out Bongo design fault due to the cooling system but a Ford engine design issue.

I am told.....not witnessed.....so If I am wrong please say....that the head is "thin" walled around the valve area.....and as such common sense says any overheating issues will always damage the weakest points....
The WL-T head is known to have been modified in 2001 and the WL-T engine is still being made and fitted to Rangers in certain markets like Thailand.....it is probably circumstantial that the Diesel engine option for the Bongo was withdrawn at a similar time, whether it was due to head issues or perhaps Japanese emission regulations who knows and I am sure conspiracy theories will be out there......
I guess what we need to do to conclude as to why the cracks occur and as such a problem with the WL-T engine and discover what factors lead to the failure of camshafts and what factors cause the overheating....... especially as the same problems occur with the 2 other vehicles that have a "standard" cooling system set up.....nothing like the more complex Bongo/Freda pipework

As for Heads in general...........from a reconditioner....... we don't have much to worry about......

"I think its more of a design fault than anything, the way they cast in sand does not help lol, they can have thinner walls due to the casting is one reason we were told , the aftermarket amc made heads seem to be better "

"off the top of my head and the problems
navara- older ones threw a conrod out the side of the block , cracked heads newer ones not so bad but still cracked heads

L200- cracked heads older ones were really bad newer ones we are seeing more and more but mainly blown gaskets ,you may get a new gasket to solve it
outlander- uses the vw tdi pd engines , they crack under the injector port inside and flood the oil with coolant

pajero-4m40t- they warp badly and cant be skimmed due to ceramic inserts , new head required , broken belt can wreck the camshaft caps and rockers and the camshaft , seen a few of them


freelander petrol - really bad at warping, the gasket rings bite into the head and they require skimming, we buy gasket sets in bulk for the k16 engines, they leak around the inlet manifold but most garages or owners dont notice i and whip the head off for a skim and most dont need skimmed , other get the grooves due to over heating, they require roughly 20 thou off to get flat again 40kmiles on a k16 engine is around the time they let go , more than 40kmiles and your lucky, we have heard them lasting 30kmiles after a skim and going again , there is a new multilayer gasket that is supposed to solve it but needs the bottom ladder on the engine changed i think

we dont get many freelander diesels in although i did one the other day that snapped a timing belt and bent 3 valves
the old 200tdi and 300tdi can warp badly, when they warp we have to skim it flat then drop the valves back down below the face of the head, you have 2 options then, you can get a saver shim, its a thin metal plate shaped like the gasket and it takes up the space we skim off or you drop the valves by cutting the seats , that get expensive , we opt for the shim or new head

the older cast iron ones blow a gasket get skimmed a few thou and are good to go , don't get many in due to age or many on the road

td5- most we get in are cracked as above
the bmw engined landies crack in a bolt hole at one of the corners

toyota wl/t engined and the ford ranger-they crack between the valve seats"

Nuff said.........

[widdowson2008]

Hi Mike
In answer to your question 'is the head "thin" walled around the valve area', the thinnest I can find is 4mm in the immediate valve area. (5mm at the crack)
Not knowing what is the 'norm', I can't comment on whether this is adequate - leaving that to them that knows.

Reading through the rest of your post, I think if I ever had to consider any of that when purchasing a vehicle, I would be put off buying and become a perpetual pedestrian.

[mikexgough]

Hi Mike
In answer to your question 'is the head "thin" walled around the valve area', the thinnest I can find is 4mm in the immediate valve area. (5mm at the crack)
Not knowing what is the 'norm', I can't comment on whether this is adequate - leaving that to them that knows.

Reading through the rest of your post, I think if I ever had to consider any of that when purchasing a vehicle, I would be put off buying and become a perpetual pedestrian.

I guess what I am saying is............ and disagree folks if you want, but the evidence is out there.......... That ALL the vehicles produced that use(d) the WL-T engine are known to suffer overheating, cracks in the heads, warped heads and also known to break camshafts...... which means that Cracked heads etc, is NOT just a Bongo/Freda specific issue......

The other vehicles that use the WL-T engine all have "simple" conventional type cooling systems and not the amount of extra plumbing of a Bongo/Freda, which really kind of eliminates the more complex Bongo/Freda cooling system as being the absolute culprit and root cause for head failures and associated issues.......

I would also just add that a failure of a component in the cooling system could well be a factor in a head failure but the self same thing applies to all the other vehicles that use the same WL-T engine.....but then they have simpler cooling systems.......

Over to others......

[Northern Bongolow]

think its time we got an old block to chop up .
leaving aside the percentage of heads that appear to be damaged by garages,or individuals that dont know how to bleed the bongo,by whatever method.it still begs the question whats going on here.are the water ways in the block compromised,so that the flow through is restricted to the head,this may happen with the silt build up that we have seen in the front rad,and heater rads. i agree with mikes statment about the importance of oils used.and the importance of the correct antifreeze/mix.but still feel the important factor is the stat. any thoughts.anyone got an old block??

[haydn callow]

Lets not forget we are talking about 15 year old engines here ??

[widdowson2008]

Lets not forget we are talking about 15 year old engines here ??

VERY good point Haydn and one which needs to be stressed.
In everything I have done so far, this has ALWAYS been in the back of my mind.
Many other pertinent factors should also be remembered such as:
1 - The Bongo was not originally designed for this country.
2 - It was not designed for boy racers.
3 - It was designed for a country that takes maintenance VERY seriously.
4 - We hear of the bad things that can happen. There are Bongos out there (probably the majority) that don't have these problems.
etc, etc, etc......

Personally, I reckon it is a sturdy machine, and given the right care and attention should go on for years.

[mikexgough]

Lets not forget we are talking about 15 year old engines here ??

VERY good point Haydn and one which needs to be stressed.
In everything I have done so far, this has ALWAYS been in the back of my mind.
Many other pertinent factors should also be remembered such as:
1 - The Bongo was not originally designed for this country.
2 - It was not designed for boy racers.
3 - It was designed for a country that takes maintenance VERY seriously.
4 - We hear of the bad things that can happen. There are Bongos out there (probably the majority) that don't have these problems.
etc, etc, etc......

Personally, I reckon it is a sturdy machine, and given the right care and attention should go on for years.

I agree......... the 15 year age on some engines could have some of the silt type build up that Ady says....lets be honest some vehicles in Japan sit around for much of the time, unlike here in the UK where many use their vehicles daily.....hence the oppourtunity for silt build up over time...

I agree with all the above 1-4 .........I guess my only caveat would be as I have already said, that the engine has been used in other vehicles that have been sold in the UK and also other harsh environments like South Africa/OZ/NZ so will be abused and not as fastidiously maintained like the Japanese like to do .....and the WL-T is as I say is still being sold today in Ford vehicles.....but with the post 2001 modified cylinder head.....

Now..... why or what really causes the overheating and added issues.....with this Diesel engine.... ......

[widdowson2008]

Sorry to butt in Mike - I now have the final (I think/hope) animations for the coolant flow.
Tried to do it in 3D but it got EXTREMELY messy, so presented it in 2D.
There are basically 5 routes through the head (from the block), and I have kept the same colour coding I started with.
Sorry for repeating anis but this is the head story in full.

Note: TAKE A FEW MOMENTS TO STUDY THE RED & GREEN PATHS - QUITE INTERESTING.

Pic 1 - Coolant ports from the block to the head


Route 1 (Yellow)


Route 2 (Blue)


Route 3 (Magenta)


Route 4 (Green)


Route 5 (Red)

[Northern Bongolow]

well done steve for all your hard work.i must just say,that in my humble opinion,i hasnt really pointed to a head design fault. or has it.
to me it just points to looking after your cooling system properly.i know you cannot help what you inherit.maybe bongo's that come up for sale should come with a certified cooling system,with x rays to prove.

[mikexgough]

well done steve for all your hard work.i must just say,that in my humble opinion,i hasnt really pointed to a head design fault. or has it.
to me it just points to looking after your cooling system properly.i know you cannot help what you inherit.maybe bongo's that come up for sale should come with a certified cooling system,with x rays to prove.

Fully agree, good work Steve with the flow diagrams......... and I would also advocate looking after the cooling system.....

Now back for yet more input/thoughts from me...... We will all probably say that the WL-T engines weakest link is the Double Valve type Thermostat, which I think we can all say could be troublesome and also advise that it should be replaced at coolant change times as added protection and peace of mind, especially at the minimal cost of the item added onto the cost of the coolant.

I may also have another idea what could be a contributary factor with cylinder head issues. Having looked at the ECU/ engine fans known switching temperature(as per workshop manual) of 108c, I now have no doubt the "trigger" temperature is the same on the other vehicles that use the WL-T engine as the part numbers I have checked from the other vehicles,cross refer to the Denso part that Mazda uses in the Bongo/Freda so then I decided to take a look into coolant types and the boiling points of them.

After doing some research, I found some information which could contribute to head issues, and as such it is only fair to share and enlighten owners.
A Green "universal" coolant(from a well known manufacturer) at the 50% recommend mix has a boiling point is 109c and a Red OAT based coolant from the same manufacturer at the 50% recommended mix has a boiling point of 130c.
From those figures you can see the differences between the Fans switching on temperature of 108c and the different type coolants boiling points.
You can draw your own conclusions from it as I am not going to get into a spat about which coolant is best etc, but it clearly shows from the figures that the green coolant will only just be in the parameters of the engine limits (before the fans kick in) by 1c before it's boiling point is reached and the Red gives a 22c more protection before it's boiling point is reached.

On another note, a chemist also tells me that silicates. when present in coolants,will coat the engine internal waterways and therefore create an insulation effect over time. Which could be a reason that the Japanese choose not to have silicates in their coolants?

You can make your minds up from the above information about the effects it can have on the cylinder head, but I am not trying to scaremonger folks, just to provide facts from where owners can make their own informed choices and form their own opinions.

I am now looking through engine oils too and the viscosity differences against operating temperatures at around 100c to see if we need to add that to the thinking....or not... especially as some camshafts have broken on these engines.
I am just looking to see if the theory that has been suggested,that the 30w oil give a lesser protection at higher engine temperatures thus raising the temperature of the head sufficiently to cause any damage, as compared to a 40w oil in the same scenario or to see if the theory is utter rubbish and indeed it doen't matter whether the 30 or 40w oils are used.

[dave_aber]

Interesting observation about the different boiling points of the coolants there. Are the temperatures stated the boiling points at atmospheric pressure?

If they are, then the standard 'green' boiling point of 109° will be raised once the system is pressurised - giving a greater margin between fan operation point and boiling.

[Ron Miel]

According to this article http://www.basf.com/group/pressrelease/P-10-155, albeit promoting BASF Glysantin, we're only really safe using Mazda's own FL22 coolant pre-mix (which does not contain Glysantin) - unless we've introduced non-Mazda components (e.g., silicone hoses) into the system, in which case, back to the drawing board: http://www.igmaynard.co.uk/bongo/forum/ ... 21&start=0

EDIT: It's certainly consistent with many observations which have been recorded on this forum, anyway.

So, depending to some extent on an email answer currently awaited from Comma Oil (or the continuing lack of one), regarding one of their Glysantin-based silicated coolants, as currently in my engine, I may now ditch my silicone hoses and switch to FL22

[mikexgough]

Interesting observation about the different boiling points of the coolants there. Are the temperatures stated the boiling points at atmospheric pressure?

If they are, then the standard 'green' boiling point of 109° will be raised once the system is pressurised - giving a greater margin between fan operation point and boiling.

Nothing stated........... but I would hazard a guess they are at atmoshperic and not pressurised, I agree the margin will be better when pressuried but I would not like to put a figure on the difference of the margin....