Coolant and Radiator and Stat

[mikeonb4c]

Lower temp reading I'd put down to a new stat, most of us that have fitted new stats & have tested them against the old stat have found the old ones to be much lazier than the new ones, ie opening later (higher temp) & slower. New stat means it opens at a lower temp, thus keeping engine temp lower.
Could also be an element due to the flushing, but it doesn't seem like Dave noticed much coming out & didn't do a chemical flush to shift any stubborn crud, so it does point more at the stat being the main factor IMO.

Interesting isn't it, as it seems to suggest its v. good idea to change stats if in any doubt. I know everyone slags off the std temp gauge but, if nothing else, it is still useful for telling you how healthy your stat. is. With my old one, it was 10 mins driving before it moved slowly off the stop. Once the new one was fitted, you could 'see' the needle kick off the cold stop after about 5 mins driving.

What's also intersting is that I'd imagined that once the stat was open, it stayed open as coolant never dropped to the point where it wanted to close again. But I know nothing about how these things actually work (come in widdowson ) and the Bongo system does seem a little unusual too. So the stat is likely to be moving as part of flow regulation then do you think? More important than ever that it is in good nick andresponsive if so.

[missfixit70]

I'm not sure if the standard unmodified gauge would show that difference TBH, I may be wrong of course
As for stat operation - http://www.igmaynard.co.uk/bongo/forum/ ... =3&t=36433 - still under consideration

[mikexgough]

I know everyone slags off the std temp gauge but, if nothing else, it is still useful for telling you how healthy your stat. is.

What's also intersting is that I'd imagined that once the stat was open, it stayed open as coolant never dropped to the point where it wanted to close again. But I know nothing about how these things actually work (come in widdowson ) and the Bongo system does seem a little unusual too. So the stat is likely to be moving as part of flow regulation then do you think? More important than ever that it is in good nick andresponsive if so.

The Std Temp gauge is a reasonable guide when un damped, Mike..... I must agree there....

And your thoughts about the stat being part of flow regulation means you have a good understanding of the system.... well done that man...... And for me...... Change the coolant = change the Thermostat too..... = little chance of cooling system issues between changes of coolant....not withstanding any pipe/hose issues that can occur.......
Now what about the cooling fans...?..and how they link in with the cooling set up.......
And why don't you see an imported Bongo(not one that has been registered) with nothing else than the standard temp gauge?....

[mikeonb4c]

I'm not sure if the standard unmodified gauge would show that difference TBH, I may be wrong of course
As for stat operation - http://www.igmaynard.co.uk/bongo/forum/ ... =3&t=36433 - still under consideration

It can't show the dynamics like a Mason or TM2 might, but it's a bit like the Doc checking your knee reflex. If it gives an obvious jump, it's a strong indicator that it is working OK. Definite difference before and after changing the thermostat, enough for me to know what the difference is and, by deduction, to be reasonably confident the stat. will be behaving responsively during normal engine operation.

[missfixit70]

I'm not sure if the standard unmodified gauge would show that difference TBH, I may be wrong of course
As for stat operation - http://www.igmaynard.co.uk/bongo/forum/ ... =3&t=36433 - still under consideration

It can't show the dynamics like a Mason or TM2 might, but it's a bit like the Doc checking your knee reflex. If it gives an obvious jump, it's a strong indicator that it is working OK. Definite difference before and after changing the thermostat, enough for me to know what the difference is and, by deduction, to be reasonably confident the stat. will be behaving responsively during normal engine operation.

Dave's is a Mason modified gauge - so not a standard gauge reading:? As I said, I don't think the unmodified gauge would show the difference, it'll just sit at 11 oclock IMO with a new & old stat.

[daveblueozzie]

As Kirsty said mine is a modified temp gauge (Mason alarm) it was always sitting at around the 1 o'clock position, and went higher,even nearing the red line when i was driving hard or towing my little caravan.
Since fitting the stat the gauge now reads under the 11 o'clock position.
I know some might say why change a stat if its working, I don't know how long the stat was in the bongo before i bought it, and its been in there three years since. it might have lasted another few years or gone bust next week. for the price of the stat ,worth changing.
I think flushing as much crud out of the pipes and radiator,fitting a new stat and fresh strong coolant has also got to help with the temp gauge reading lower.

[missfixit70]

Just spoken to someone who's changed the stat on 2 bongo's, one which had been in for an in indefinite period at least 3 yrs - the length of ownership) & one that had the stat changed about 18 months ago. Tested in a pan, the 18 month old one was considerably slower in opening than a new one, & the older one was even slower & wasn't fully open by the time the water boiled.
From this, it would suggest that it may well be a good idea to change the stat every 2yrs when the coolant is changed.

[mikeonb4c]

I'm not sure if the standard unmodified gauge would show that difference TBH, I may be wrong of course
As for stat operation - http://www.igmaynard.co.uk/bongo/forum/ ... =3&t=36433 - still under consideration

It can't show the dynamics like a Mason or TM2 might, but it's a bit like the Doc checking your knee reflex. If it gives an obvious jump, it's a strong indicator that it is working OK. Definite difference before and after changing the thermostat, enough for me to know what the difference is and, by deduction, to be reasonably confident the stat. will be behaving responsively during normal engine operation.

Dave's is a Mason modified gauge - so not a standard gauge reading:? As I said, I don't think the unmodified gauge would show the difference, it'll just sit at 11 oclock IMO with a new & old stat.

Yup, know that (its in his first post and what got my curiosiry going). The unmodified gauge does show the difference, but only because of the way it kicks off the C end stop before and after. No good at measuring the dynamics, as stated earlier (because - as you say - std, gauge is heavily damped in mid range). My thoughts then for those with unmodified gauges:

* If it moves off the C stop in 5 mins after start-up and you can virtually see the moment it kicks off, you have a healthy stat.

* If it takes 10 mins from start up and the move from C seems sluggish, you probably have a tired stat.

Interestingly , mine is still showing the same healthy signs 3yrs after fitting, so I reckon owners need not get too hung up about changing it every 2 years.

I'm still surpirsed at the idea that the stat might be opening and shutting on a Bongo - I thought stats were only intended as a shut-off valve while engine was below a threshold which was passed once engine was up to working temp - anyone know more about this (TGP for example?)

[missfixit70]

* If it moves off the C stop in 5 mins after start-up and you can virtually see the moment it kicks off, you have a healthy stat.

* If it takes 10 mins from start up and the move from C seems sluggish, you probably have a tired stat. Interestingly , mine is still showing the same healthy signs 3yrs after fitting, so I reckon owners need not get too hung up about changing it every 2 years.

Sorry Mike but that's wrong, the stat does not open while the engine is warming up, it remains closed until @82 degrees, so how could it be opening, or have an effect on temp at the lower end of the gauge?
The only way it can slow down the warm up is if it was jammed open after an overheat, this would probably prevent it from warming up to normal range at all.

[bigdaddycain]

* If it moves off the C stop in 5 mins after start-up and you can virtually see the moment it kicks off, you have a healthy stat.

* If it takes 10 mins from start up and the move from C seems sluggish, you probably have a tired stat.

If only it were that simple Mike. Unfortunately just TOO many variables come into play to make it accurately gaugeable. Coolant strength,rad age/condition,ambient temps,That's just if the bongo is sat there ticking over from cold. If the vehicle is being driven, then many more variables kick in, driving style,gradients,whether the traffic lights are green or red. Plus all the previous variables... Very hard to gauge indeed.

[mikexgough]

* If it moves off the C stop in 5 mins after start-up and you can virtually see the moment it kicks off, you have a healthy stat.

* If it takes 10 mins from start up and the move from C seems sluggish, you probably have a tired stat.

If only it were that simple Mike. Unfortunately just TOO many variables come into play to make it accurately gaugeable. Coolant strength,rad age/condition,ambient temps,That's just if the bongo is sat there ticking over from cold. If the vehicle is being driven, then many more variables kick in, driving style,gradients,whether the traffic lights are green or red. Plus all the previous variables... Very hard to gauge indeed.

Wise words their young Ste............
I think there are some "common" Mason readings on here( mine & Kirsty have a similar output on the gauge) but that is all, as you say and we have discussed the variables come into play.....My Bongo might warm up faster than someone else's due to the fact we live in the flat lands and can get main road running within 5 mins from home than someone who is on start stop town running
I would go with Kirsty and advise a Thermostat change when coolant change takes place as the system will be "broken" which is a prime time to change the 'stat........ lets be honest, if your changing the cambelt and you saw the other drive belts were suspect, you would change them as a precaution..... similar mind set

[mikeonb4c]

Ste- I take your point. I'm not suggesting any of this can tell you about the health of your cooling system (too many variables) but I think the 5 min to move off the stop is a reasonable (if approximate) rule of thumb to propose as a benchmark. And if the 'lift-off' off from the C stop is clean and visible, this more than anything else is an indication of a healthy stat.

Kirsty - sorry m'ducks I don't understand. The stat is much like the rad presure cap. Once you exceed a trigger point, it opens. Once it does that, the temp sensor notices hot coolant starting to flow past it. If stat opens cleanly and properly (i.e. is healthy) the sensor gets a large volume of hot water past it at once and gauge moves decisively off the stop. If stat is 'lazy' then the sensor doesn't get the same surge of hot water and moves off a little more slowly. That's what I put the different behaviour of my gauge needle down to anyway.

Mike - you are quite right and perhaps I should have stressed that. You can only make comparable readings under comparable driving conditions

Other folks - do whatever you think best. That's what I generally do.

[missfixit70]

Kirsty - sorry m'ducks I don't understand. The stat is much like the rad presure cap. Once you exceed a trigger point, it opens. Once it does that, the temp sensor notices hot coolant starting to flow past it. If stat opens cleanly and properly (i.e. is healthy) the sensor gets a large volume of hot water past it at once and gauge moves decisively off the stop. If stat is 'lazy' then the sensor doesn't get the same surge of hot water and moves off a little more slowly. That's what I put the different behaviour of my gauge needle down to anyway.

I'd suggest you read through the coolant threads here Mike, as I posted earlier - http://www.igmaynard.co.uk/bongo/forum/ ... =3&t=36433

The stat is nothing like a rad pressure cap, it reacts to temperature, not pressure & it controls (at 2 points) rather than just lifts at a pressure like a safety valve.
The stat reacts to temperature at the inlet side of the head, it opens at @82degrees, so the engine MUST already be warm (& reading so on the temp gauge) before the stat opens. The gauge takes it's measurement from the outlet side of the head, nowhere near the stat.
As the engine is warming up, the stat has to be closed, the coolant is circulating around the heater circuit, the turbo, a small amount through the top of the rad through the expansion tank & back through the return from the heaters, It is also recirculating around the engine through the bypass circuit from the head back into the top of the stat housing. The temp gauge will rise while it is in this flow state, with the stat firmly shut.
This flow continues until the stat begins to open once/if the temp has reached around 82 degrees at the inlet side of the engine, at this point the gauge (edit) should start to level out or possibly drop slightly as the flow of cooled coolant from the rad is allowed through.
This is a simplified breakdown of the operation of the coolant system that many people have been working on behind the scenes, with Steve (Widdowson) doing an admirable job of putting it all together (so much so he's had to take a holiday to recharge )

If the stat is "Lazy" it will not open at the point it should to allow cool coolant through from the bottom of the rad, also it will not be shutting in the bypass flow around the engine meaning less cool coolant coming into the engine than there should be & more hot recirc coolant flowing back around the engine, leading to the engine running hotter than it should & eventually overheating, as it is my belief that even if the fans reach cut in point, if the stat does not fully open allowing full flow through the rad AND shutting off the hot coolant recirculating around the engine, it just won't be enough to cool the engine when it's working hard.

The different behaviour of your gauge needle is as BDC describes, purely different warm up conditions - absolutely nothing to do with the stat this is FACT.
This is not me putting myself forward as a self appointed expert, this is me putting forward FACTS (other than the last little bit about the fans, which I'm pretty sure of )

[mikeonb4c]

Kirsty - sorry m'ducks I don't understand. The stat is much like the rad presure cap. Once you exceed a trigger point, it opens. Once it does that, the temp sensor notices hot coolant starting to flow past it. If stat opens cleanly and properly (i.e. is healthy) the sensor gets a large volume of hot water past it at once and gauge moves decisively off the stop. If stat is 'lazy' then the sensor doesn't get the same surge of hot water and moves off a little more slowly. That's what I put the different behaviour of my gauge needle down to anyway.

I'd suggest you read through the coolant threads here Mike, as I posted earlier - http://www.igmaynard.co.uk/bongo/forum/ ... =3&t=36433

The stat is nothing like a rad pressure cap, it reacts to temperature, not pressure & it controls (at 2 points) rather than just lifts at a pressure like a safety valve.
The stat reacts to temperature at the inlet side of the head, it opens at @82degrees, so the engine MUST already be warm (& reading so on the temp gauge) before the stat opens. The gauge takes it's measurement from the outlet side of the head, nowhere near the stat.
As the engine is warming up, the stat has to be closed, the coolant is circulating around the heater circuit, the turbo, a small amount through the top of the rad through the expansion tank & back through the return from the heaters, It is also recirculating around the engine through the bypass circuit from the head back into the top of the stat housing. The temp gauge will rise while it is in this flow state, with the stat firmly shut.
This flow continues until the stat begins to open once/if the temp has reached around 82 degrees at the inlet side of the engine, at this point the stat should start to level out or possibly drop slightly as the flow of cooled coolant from the rad is allowed through.
This is a simplified breakdown of the operation of the coolant system that many people have been working on behind the scenes, with Steve (Widdowson) doing an admirable job of putting it all together (so much so he's had to take a holiday to recharge )

If the stat is "Lazy" it will not open at the point it should to allow cool coolant through from the bottom of the rad, also it will not be shutting in the bypass flow around the engine meaning less cool coolant coming into the engine than there should be & more hot recirc coolant flowing back around the engine, leading to the engine running hotter than it should & eventually overheating, as it is my belief that even if the fans reach cut in point, if the stat does not fully open allowing full flow through the rad AND shutting off the hot coolant recirculating around the engine, it just won't be enough to cool the engine when it's working hard.

The different behaviour of your gauge needle is as BDC describes, purely different warm up conditions - absolutely nothing to do with the stat this is FACT.
This is not me putting myself forward as a self appointed expert, this is me putting forward FACTS (other than the last little bit about the fans, which I'm pretty sure of )

Sorry - I was trying to consider that the stat is in some respects to temp what the rad cap is to pressure (i.e. it opens at a threshold point). I do understand the distinction between the two.

The different behaviour of your gauge needle is as BDC describes, purely different warm up conditions - absolutely nothing to do with the stat this is FACT.

But this would not explain why I had such obviously different behaviour (my 'before and after') under identical driving conditions (my daily journey to work, same time of year, same load, same route, same temps) after fitting a new thermostat.

Please don't think I'm imagining you see yourself as a self appointed expert. that would not be the case. I think though that the facts may yet need a little establishing.

I don't want to see this thead wander off into another dreaded cooling system debate. I'm offering some observations in case they are helpful, and which I will be using to guide my own action in the future, but I'm not about to call myself an expert!

[missfixit70]

You are making assumptions about the cooling system that are just not applicable to the bongo, but if that's how you believe it works, then I'll leave you to it