For all Bongoliers, especially the Polish Invaders!

[dandywarhol]

A long post but hopefully succinct

This is my last post on this topic, because it’s probably been done to death by now.

The Bongo cooling system is perceived to be its Achilles heel but as thousands of Bongos/Fredas are running in the UK alone and according to a recent BF poll, it is only affecting a minority. It’s unfortunate that we usually hear of the faulty ones but fortunate that there’s heaps of information on these hallowed pages.

The system design is not unique to the Bongo, others have used a similar setup since the early 80s but the engine/chassis layout means there’s a lot more associated pipework to the Bongo cooling system.

I’ve trawled through a lot of the archives on here and technical publications – there’s so much in BF it must be a minefield to the reader. I’ve come to the conclusion that all the failures on member’s vehicles have been due to a fault in the hardware (hoses, radiators etc.) and that the design is not to blame.
Here’s a list (not exhaustive!) of potential Bongo weaknesses. Most of these could apply to any 10 year old plus vehicle:

Faulty workmanship by a previous repairer – use of a non Mazda headgasket and old cylinder head bolts WILL result in gasket failure (again)

Coolant loss: perished hoses, metal pipe corrosion, radiator leaks, pressure cap seal/spring failure, heater matrices leaking – anywhere coolant can escape the air can get in when the system cools down and “sucks” in the air – even minute pin pricks!

Air in the system: this is probably THE main cause for engine failure. There should be NO air in the system, otherwise it can “pocket” and cause massive local hotspots. Coolant cannot be compressed therefore it has to move (circulate), air can be compressed therefore the fluid circulates less and air pockets occur. If the air pockets are in the cylinder head then its death to the head through distortion or cracks at the localised hotspots.

Chocked radiators/heater matrices: It’s been reported that Mazda use small bore water tubes in the radiators, presumably to increase the surface area of the radiator to reduce the coolant temperature. These can get choked by a variety of reasons – poor maintenance i.e. coolant not changed/flushed at regular intervals, mixing of incompatible antifreeze solutions, insufficient antifreeze/undistilled water causing corrosion. As the matrix gets choked the radiator becomes less efficient – it could also be caused by a damaged air conditioning matrix which sits directly in front of the radiator and could starve the radiator of air supply at the most critical of conditions. Overheating occurs but ONLY when the system is under duress, i.e. prolonged driving at low speeds in low gear, altitude, towing in hot conditions etc………..
The bongo is a “Japan home market” vehicle. Due to its geographical location Japan can have extremes of temperature – the Bongo is designed to deal with this. The radiator only comes into force under extreme conditions of high temperature. Under “normal” conditions the engine cooling is carried out by a combination of water pipes, hoses, matrices, reservoir tank and PART of the radiator. A weak point in any cooling system is the thermostat valve – it’s designed to REGULATE the operating temperature at its optimum. Its weakness lies in constant opening/closing at high temperatures. It’s controlled by a wax element which melts at a predetermined temperature which opens the valve to allow coolant flow. The design of the bongo (and others) system is that the thermostat is on the RETURN side from the radiator and is in little use therefore it will therefore be more reliable. Some manufacturers are now fitting electronically controlled servo actuated thermostat valves to regulate the cooling better and to make it more reliable.

TGP’s aftermarket design of reverting to a “conventional design” by putting the thermostat before the radiator will work perfectly ,I’ve forgotten now what temperature of ‘stat he is using, but it will need to be of a higher value than standard otherwise the engine temperature will be too low overall and could lead to excessive fuel consumption and premature engine wear due to the engine components not reaching the optimum temperature and running tolerances. I believe that it would be necessary for the TGP design to be virtually tested with higher and higher value thermostats to find the optimum running temperature – like the manufacturers do – in other words, test the system to destruction and back a bit!

This is not an exhaustive list of what can go wrong but any “older” vehicle will have similar problems, in fact many 13 year old cars are scrapped by now – it’s the Bongo’s general lack of corrosion which makes them last so long.

I think it’s imperative that the Bongoliers who are travelling to Eastern Europe this summer have a COMPREHENSIVE cooling system checkover, including a pressure test for leaks, before setting off. If not for your own peace of mind, you probably owe it to Keefysher who’ll be tearing his hair out if the convoy is delayed through overheating problems! It would be well worth an hour of labour time by a technician EXPERIENCED in Bongos – not just someone who can read a Haynes manual and who’s mother once slept with a mechanic!

I said at the start this will be my last post on the topic as I’ve decided to bow out and spend more time with LIFE!

I’ve become a bit disillusioned lately with some nasty PMs, the politics and attitudes.

We’re off to Cz Rep, Slovakia and south Poland in July – remember the secret wave as we might cross paths on return to Zeebrugge on August 6th.

Alan

[haydn callow]

That is a lot of sense and I agree with all of it !!! I am now involved with Delica's, Hilux Surfs, older Landy's....they all have similar set ups and problems. There is nothing wrong with the design of the Bongo cooling system.

[Grahame at work]

Alan

Excellent text sir. And good advice.

I do have one point that is purely based on my own Bongo and may or may not be the same on others. You say “……thermostat is on the RETURN side from the radiator and is in little use therefore ……..”. I have been monitoring several temperatures in the cooling system for the past couple of months now and have found the thermostat to operate between 85 and 92C and it reaches this fairly quickly. So I suggest that to say it is in little use is not correct – it does its job in controlling my engine temperature in a dynamic and consistent manner at all times.

I trust you are not bowing out of the forum altogether as you experience and knowledge is invaluable to this forum.

Enjoy your holiday – probably will not spot you as we are not heading back until the Friday and will be generally in North Germany after Gdansk.

Many regards Grahame

[Peg leg Pete]

I think Alan has made some very relevant points Hope you do not become too disillustioned Enjoy your trip

[mikeonb4c]

Enjoy the trip Dandy. If you are like me, you'll slip back on here, but I too have had a strong urge to rest at times. Go with it and hope to hear from you on here in the fullness.

Mike

[lizard]

Excellent, this should be added to the overheating fact sheet. Compulsury reading for all newbies.



All the best