Bongo Fury

I was looking at an article on the Rover 'K' Series engine on Austin Rover Online, and I wondered if the following issue with thermostats might be relevant in any way to the Bongo?

"Thermostats over time, can weaken, causing a rush of cool water into the engine when the stat opens causing Thermal Shock - a major problem on 1.8-litre Rovers and Land Rover Freelanders."

That could be a similar issue I guess, you want the stat to stay shut while it's warming up to get the engine up to temperature. I don't know about thermal shock on the bongo as the stat mixes the returns from the heaters, turbo & the small flow from the expansion tank coming from the top of the rad which is fed from the warm/hot engine outlet as well as the recirc flow from the head (warm/hot coolant) coming in the top of the stat, so even if the spring was weakened enough to allow some flow through, I'd be surprised if it slammed fully open, more likely just to creep open to a certain degree, allowing an amount of cooled water to enter the stat & mix with the other warm flows & maybe overcool the engine?
It depends which way the rover stats are, if they're talking about the wax stat getting weak & "lazy", then it will have the opposite effect with a bongo (due to the way the stat is fitted) & the stat will fail to open when it should, or open late (at a higher temp) & cause the bongo to run hot or possibly overheat.

munroman wrote:I was looking at an article on the Rover 'K' Series engine on Austin Rover Online, and I wondered if the following issue with thermostats might be relevant in any way to the Bongo?

"Thermostats over time, can weaken, causing a rush of cool water into the engine when the stat opens causing Thermal Shock - a major problem on 1.8-litre Rovers and Land Rover Freelanders."

The K series engine is a nice design, the head problem is due to its coolant system. Basically................... Sorry, memories, it like the Bongo has coolant boiling in the head, this leads to hot spots around the exhaust valves. Over time and remember the K is a modern light engine this will cause valve problems then head warping or cracked heads. I spent a lot of time resolving this issue on a K engined Caterham race car. I believe Land Rover eventually accepted there was a problem and moved the stat.

munroman wrote:I was looking at an article on the Rover 'K' Series engine on Austin Rover Online, and I wondered if the following issue with thermostats might be relevant in any way to the Bongo?

"Thermostats over time, can weaken, causing a rush of cool water into the engine when the stat opens causing Thermal Shock - a major problem on 1.8-litre Rovers and Land Rover Freelanders."

This article might enlighten you more..... Here ...... gives an insight as to the way the Bypass part of the Bongo system works too

mikexgough wrote:

munroman wrote:I was looking at an article on the Rover 'K' Series engine on Austin Rover Online, and I wondered if the following issue with thermostats might be relevant in any way to the Bongo?

"Thermostats over time, can weaken, causing a rush of cool water into the engine when the stat opens causing Thermal Shock - a major problem on 1.8-litre Rovers and Land Rover Freelanders."

This article might enlighten you more..... Here ...... gives an insight as to the way the Bypass part of the Bongo system works too

A very interesting read. Big thanks to munroman for leading us towards this discussion

I noticed tired thermostats excerbated the problem. It all suggests that the Bongo cooling system (all components) needs to be kept well fettled

Wouldn't a weak Bongo stat tend to stay more closed than it should. ??

The article is not an exact science for the Bongo, just gives a rough idea of how the Bypass element works on a return flow system....nothing more and shows how they Rover engineers overcome the cooling system issue when the K series motor was of larger cubic capacity.....
In essence the article is nothing to with Bongo's, just an illustration of a bypass thermostat housing and how a poor design by a UK manufacturer led to needed modifications.

I nearly changed my Bongo to the K series mod but never got round to it and anyway I don't believe there is anything wrong with the Bongo system...However, I do have a Thermostat and "inhose" adapter if anyone wants to try it...

haydn callow wrote:I don't believe there is anything wrong with the Bongo system...

There isn't..... it just needs nothing more than the usual regular maintenance intervals like the rest of your engine...

Just keep an eye on your pipes and hoses etc. when you check your levels....as you would with any vehicle....

haydn callow wrote:Wouldn't a weak Bongo stat tend to stay more closed than it should. ??

Depends what has weakened I suppose, if it's the spring/s, then it would open more/sooner than it should, therefore overcooling.
If it's the stat that's weakened & the springs are ok, then it will open less/slower, leading to undercooling - overheating.
(IMO )

mikexgough wrote:

haydn callow wrote:I don't believe there is anything wrong with the Bongo system...

There isn't..... it just needs nothing more than the usual regular maintenance intervals like the rest of your engine...

Just keep an eye on your pipes and hoses etc. when you check your levels....as you would with any vehicle....

Fully agree, from chatting to people recently with cooling issues, I wonder if the Mazda stat may be a better option than pattern parts, just to make sure both the stat part & the bypass control /shut off disc work exactly as they should & hopefully last a bit longer?
As I mentioned recently in another thread, I know of an 18 month old stat, that when tested against a new one was significantly lazier, worth bearing in mind. I for one will be changing my stat every couple of years to be sure, small price to pay for peace of mind.

haydn callow wrote:I nearly changed my Bongo to the K series mod but never got round to it and anyway I don't believe there is anything wrong with the Bongo system...However, I do have a Thermostat and "inhose" adapter if anyone wants to try it...

I agree. The only issue might be that it needs to be working reasonably close to 'as designed' in order to be safe (and may not be on old ones that have not been kept well fettled). If it isn't, the theory then is that the cast iron block / alloy head issues come into play.

I'd have to re-read the piece to remember why they thought a tired stat made things worse, but I think it was it became less responsive so that it let down the dynamics of the system by not meeting demand to both open and close as required. Which taught me something (assuming the Bongo system is like the K series, which it may not be) , as I had thought the stat just opened once and stayed open.

can I just chuck my twopenneth in, how about a thermostat that opened at 72ºC & not 82ºC. Would this make any difference, over to you boffins

maxheadroom wrote:can I just chuck my twopenneth in, how about a thermostat that opened at 72ºC & not 82ºC. Would this make any difference, over to you boffins

sounds a bit iffy to me

Normal thermostat opens at 82ºC, lets cold coolant in from rad, rad fans are controlled by the ecu at a certain temp to cool the coolant in the rad whilst the coolant in the engine is getting up to temp thus giving the fans time to cool the coolant in the rad ready to go back into the engine?

With a thermostat that opens at 72ºC, would open at 72ºC let the cold coolant in from the rad then that coolant would heat up to 72ºC to the same as the one in the rad before the fans on the rad kick in to cool the coolant thats in the rad thats going back into the engine, so I would imagine that you would be running your engine hotter as the coolant isnt get chance to be cooled down ready for when the stat open back up.

It would probably ok whilst drivng with the force of air getting to the rad but I would imagine if its a hot day and in stop start traffic it would be a problem

might be total cow poo I am talking about as I have a limited knowledge on the way the coolant issues go but it makes sense to me

Now let the arguments commence