Diesel vs Petrol - Either more or less prone to this overhea

[dave_aber]

What's the construction of the petrol Bongo engines, 2.0 and 2.5 ? All alloy?

[mikeonb4c]

All alloy engines are often OK - everything expands and contracts at the same rate.

All iron engines are often OK - everything expands and contracts at the same rate.

Alloy head on Iron block? - hmmmm two things expanding and contracting at different rates......... maybe not so OK

Indeed (your last point) ! But I have gained the feeling that aluminium alloy is a trickier material as well (although much less important than cast iron. Random thoughts are:

* Trickier to cast and weld without introducing fault lines
* Not as strong
* Less conductive than iron (so harder for it to smooth out hot spots)
* Lower thermal capacity, so it is affected more by thermal energy
* More prone to fatigue

...but please challenge the relevance of all these as I'm only putting them forward as points for debate - I'm no engineer.

Interestingly, the only car I damaged the head on due to overheating was the all alloy (I believe) Coventry Climax engine in my first car, a Hillman Imp. It was a common problem with them I was told at the time.

Do both the diesel and the V6 have mixed alloy/cast iron construction? If so, we are I guess still searching for why the diesel might suffer more problems than the V6 (we are not even sure that is so of course but...)

[francophile1947]

It was a common problem with them I was told at the time.

It sure was Rumour had it that the head gasket became a service item

[ex25er]

I'm certainly no expert but...

I wonder whether the diesel engine being indirect injection (i.e. with much of the combustion taking place in precombustion chambers within the head, rather then directly above the piston) places more stresses on the head itself making fatigue of thos particular part more likely? Maybe even more so, being turbocharged?

Every cloud has a silver lining though.... this system of injection / combustion places much less stress on the rest of the engine, so even if your head's fubar, your bottom end should go on for ever and ever....

Phil

[g8dhe]

...but please challenge the relevance of all these as I'm only putting them forward as points for debate - I'm no engineer.

OK I'll bite

* Less conductive than iron (so harder for it to smooth out hot spots)

Wikipedia says that's not the case, the conductivity of Alu. is about 5 times better than Cast iron.

* Lower thermal capacity, so it is affected more by thermal energy

Interestingly Alu. has a higher specific capacity BUT(and its a big but) it melts at a much lower temperature so overall its capacity is lower volume for volume
See here for details

[mikeonb4c]

...but please challenge the relevance of all these as I'm only putting them forward as points for debate - I'm no engineer.

OK I'll bite

* Less conductive than iron (so harder for it to smooth out hot spots)

Wikipedia says that's not the case, the conductivity of Alu. is about 5 times better than Cast iron.

* Lower thermal capacity, so it is affected more by thermal energy

Interestingly Alu. has a higher specific capacity BUT(and its a big but) it melts at a much lower temperature so overall its capacity is lower volume for volume
See here for details

Interesting stuff Geoff and thanks. OK so it conducts heat better, which blows the hotspot theory out the window. The thermal capacity (what the 2nd article calls heat capacity) is higher (Le Creuset cast pans use cast iron I think for that reason) but anyway, I can't think how to translate that into any usefu theory here. What really caught my eye in the 2nd article you posted though was the section headed 'Temperature and Strength' as this sounds to me like it could be very relevant (what happens to aluminium over 100c plus the effect of heat cycling over time). What's your view?

[New Forest Terrier]

Totally unscientific and probably rubbish, but overheating seems mainly a problem with neglected Bongos. Either those imported for sometime and neglected since or poor quality recent imports.

The main demand is for diesel and when supplies in Japan were plentiful what was imported was almost all diesel. Many of these have been in UK for some years and have had little or no specialist attention. Looking for mine I saw some neglected horrors, disasters waiting to happen.

Petrol V6's and 2l have only started to be imported in any quantity, as supplies became limited. As the export demand is overwhelmingly diesel, there are probably far more good petrols in Japan for importers to choose from, so the quality of petrol Bongos coming in is higher.

Looking for mine I bought a V6 because it was easier to find a good petrol. Also I could not resist the V6 purr. Once heard that was the Bongo for me.

When I first joined Bongo Fury only a year ago I was one of only about three with a V6. Now the numbers have increased considerably but they are still seen as a bit of an exotic toy.

Once they have been around long enough to be neglected will the situation be the same.

[mikeonb4c]

It'll be interesting to see, NFT.

[g8dhe]

What's your view?

To be honest I'm not sure that I have one! My thinking would be that who ever designed the engines would have built in sufficient strength at the required temperatures for the "life" of the engine. Simply because if you don't then when the engine is are run at the extremes of its design range then there will be early failures and that costs money from the company in the short term and reputation in the long term.
I can see NFT's point of view although perhaps to say "neglected" is a bit strong, I would suggest that you don't always know that a problem is developing, given the heavily damped temperature gauge, and by the time that an overheating event is visible then the damage is already done. However checking the pipes and watching for loss of water is an obvious thing for any vehicle.
I would very much like to see some genuine figures on numbers and types of Bongos and failure rates, how to obtain those figures is another matter, even a survey on here is not going to get any sensible results as it would really only show the numbers interested in the subject and almost by definition those interested would be those who have had failures and hence the figures are skewed from the start!

[cheffy34]

Totally unscientific and probably rubbish, but overheating seems mainly a problem with neglected Bongos. Either those imported for sometime and neglected since or poor quality recent imports.

The main demand is for diesel and when supplies in Japan were plentiful what was imported was almost all diesel. Many of these have been in UK for some years and have had little or no specialist attention. Looking for mine I saw some neglected horrors, disasters waiting to happen.

Petrol V6's and 2l have only started to be imported in any quantity, as supplies became limited. As the export demand is overwhelmingly diesel, there are probably far more good petrols in Japan for importers to choose from, so the quality of petrol Bongos coming in is higher.

Looking for mine I bought a V6 because it was easier to find a good petrol. Also I could not resist the V6 purr. Once heard that was the Bongo for me.

When I first joined Bongo Fury only a year ago I was one of only about three with a V6. Now the numbers have increased considerably but they are still seen as a bit of an exotic toy.

Once they have been around long enough to be neglected will the situation be the same.

Agree with that statement NFT it was the purr for me Had me hooked instantly sorry guys but why buy a diesal not for me i'm affraid as i like big purring engines and how many mid engined vans can you buy as a petrol v6 if i was to buy a diesal i would buy a transporter even if the spec isn't as good when i first joined 2 year ago as a v6er i can only remember a couple of others i got used to no one answering my techi questions we are still thin on the ground as v6ers but there are alot more about now shame cos i enjoyed being in the elite crew IMHO the tintop v6 should not be converted either mine is gonna be a class 6 individually reclinable seater only, i have big plans for my mpv when time and spares come my way Upshot is in my eyes buy a v6 any second hand car you buy you run a risk of overheating, plod your way through the servicing and treat it well, just take reasonable precautions with the cooling system, it is your choice which way you go but at the end of the day it will be down to how quick you react to it overheating


Dar


Dar