Bongo Fury

missfixit70 wrote:Got to agree Rita, plus if you put the fans in front of the rad as suggested by Mike, wouldn't it get in the way of cooling flow while in motion.

Ah, sorry, should have made it clearer that that was just idle musing. But being serious, I doubt it would matter much, mainly because everything is determined by the sensor telling the fan to switch on. So if it did impede airflow on the move and thus reduce cooling system efficiency, the sensor would just activate it a bit sooner. The real reason I was minded to muse about it being in front was because if it was in front, then any airflow spreading sideways as the fan creates a pressure between it and the (air resistant) rad. matrix is at least likely to flow or be dragged back through the matrix in the area not directly covered by the fan, thus making better use of that area. On the other hand, if negative pressure is used to pull air through the rad matrix by positioning the fan behind it, then there is the possibility of pulling ambient air in from anywhere and leaving the outer area of the rad. matrix without active air cooling. But its a very minor consideration and probably taken care of by positioning the fan close to the rad and/or fitting a shroud that effectively ensures air must be drawn through the rad. matrix. Or else, simply rely on a bit of over-design/excess capacity. Its this last bit though that designers want to be paring down in this carbon emission conscious age.

easy enough to check by sticking a piece of paper over the front of the rad once the engine's warm with the ac on. it'll either suck on or blow off.

missfixit70 wrote:easy enough to check by sticking a piece of paper over the front of the rad once the engine's warm with the ac on. it'll either suck on or blow off.

good idea - might check that tomoz

mikeonb4c wrote:

missfixit70 wrote:easy enough to check by sticking a piece of paper over the front of the rad once the engine's warm with the ac on. it'll either suck on or blow off.

good idea - might check that tomoz

..............don't be sticking any part of your anatomy anywhere near it Mike

Some facts about the stat and housing
The following drawings were produced from accurate measurents taken from the stat and housing.

New Stat provided by Ian
Housing generously provided by Allans and Doone (complete with old stat)
2nd Housing, also a kind offer, being provided be Chris - ebygum8 (For dissemination and hydraulic tests)

1 - Stat travel from spec. is 8.5mm FACT
2 - Stat travel Fully open to Fully closed is 5mm FACT
3 - from 2 and 3 above, 3.5mm has been built in to the stat as over run. This is when the valve completely closes the bypass but the wax continues to expand.
The main valve continues to lift a further 3.5mm pushing the spindle through the centre of the bypass valve disc.
There is a small clearance between the spindle and the disc allowing this movement.
As the stat enters this last phase, and the spindle passes through the disc, it takes with it the circlip which is retaining the disc to the spindle.
In doing so, it allows a small passage of coolant through the gap between spindle and disc. THIS IS A FACT.

And so, as people have said before, WHEN THE VALVE IS CLOSED TO THE BYPASS, EFFECTIVELY IT IS NOT A 100% LOCKOUT.
We are NOT talking huge flows here.

Stat component parts


stat - Fully closed at 0mm stroke


Stat in a mid position at 2.5mm stroke


Stat in a Fully open position at 5mm stroke


Stat in an over run position at 8.5mm stroke

Nice work Steve
What about possible failure points?
We know it can & does fail in the closed position (from bongo garage/mechanics accounts), presumably from the wax capsule failing/degrading.
Do you reckon it's possible for it to fail open? Maybe spring failure or frame failure?
I suppose the sealing face could get jammed open with crud? could it possibly get jammed open on the spindle with unequal spring pressure on one side of the disc?
Any other possibilities?

missfixit70 wrote:Nice work Steve
What about possible failure points?
We know it can & does fail in the closed position (from bongo garage/mechanics accounts), presumably from the wax capsule failing/degrading.
Do you reckon it's possible for it to fail open? Maybe spring failure or frame failure?
I suppose the sealing face could get jammed open with crud? could it possibly get jammed open on the spindle with unequal spring pressure on one side of the disc?
Any other possibilities?

Testing/dissecting is certainly bringing up some interesting stuff. I am currently writing up my findings as part of this excercise and am not quite there yet, so bear with me on this one.
Your questions are easily answered - Let me get my s**t together cos I want this to be correct!

At this point though, I would say that in many of your past posts, you have banged on about thoroughly flushing out the coolant system AND fitting a new thermostat. ESPECIALLY ON A NEWLY IMPORTED VEHICLE - INSIST THAT THIS IS DONE. You have no idea just how right you are!!!!!

Keep banging the drum - this one item alone is WELL worth any costs.

Will get back soon with more data. (for those interested)

missfixit70 wrote:Nice work Steve
What about possible failure points?
We know it can & does fail in the closed position (from bongo garage/mechanics accounts), presumably from the wax capsule failing/degrading.
Do you reckon it's possible for it to fail open? Maybe spring failure or frame failure?
I suppose the sealing face could get jammed open with crud? could it possibly get jammed open on the spindle with unequal spring pressure on one side of the disc?
Any other possibilities?

Hi,Some of the reasons a thermostat can Fail OPEN,

this can happen if the sensing element binds up,

the return spring breaks or a piece of rust or debris jams it open.

Or its a Fail Safe type thermostat.

rita wrote:

missfixit70 wrote:Nice work Steve
What about possible failure points?
We know it can & does fail in the closed position (from bongo garage/mechanics accounts), presumably from the wax capsule failing/degrading.
Do you reckon it's possible for it to fail open? Maybe spring failure or frame failure?
I suppose the sealing face could get jammed open with crud? could it possibly get jammed open on the spindle with unequal spring pressure on one side of the disc?
Any other possibilities?

Hi,Some of the reasons a thermostat can Fail OPEN,

this can happen if the sensing element binds up,

the return spring breaks or a piece of rust or debris jams it open.

Or its a Fail Safe type thermostat.

if the sensing element binds up - agree with that one
return spring breaks - I think it would just 'flop about' if the upper spring broke wouldn't it? probably tending toward closing due to coolant flow direction. Need to think about the lower spring
piece of rust or debris jams it open not quite sure where said rust/debris would get lodged to cause a jam - any specific ideas? In the sensing element perhaps?

Fail safe? - working on that one

widdowson2008 wrote:
Stat in an over run position at 8.5mm stroke

Test 13-12-09 - (Abusive testing)

It would appear that the above diagram is exactly what happens in reality with the exception that I pushed it 1.5mm more than the diagram .

 stat in housing clamped to bench
 heated via port with Bosch blower heater (probably classified as excessive to the point of abuse)
 hissing sound – possibly wax escaping – ie: reached end of possible stroke
 5mm over-run recorded (3.5mm on drawing) ie: disc came into contact with bypass port with 5mm more stroke to go
 Stat remained ‘stuck’ in this position ie: Open, but sprung back when gently persuaded. - This suggested that the stat CAN in fact get stuck in the OPEN state when subjected to excessive temperatures

Will try again to see if it still works after this harsh treatment

A question to yer red.. Could this indicate previous excessive overheating of an engine?

widdowson2008 wrote:  Stat remained ‘stuck’ in this position ie: Open, but sprung back when gently persuaded. - This suggested that the stat CAN in fact get stuck in the OPEN state when subjected to excessive temperatures

Will try again to see if it still works after this harsh treatment

Any idea what the temperature was that caused it to stick open? Could it be that these stats do actually fail in the open position after being subjected to very excessive overheat? (when working correctly) Or is that just a "fault" with some?
I'll try & remember to see if I kept my old stat that was a bit lazy, I'll send it up to you Steve so that you can do some comparative testing to see whether it'll do the same under similar conditions.

jaylee wrote:A question to yer red.. Could this indicate previous excessive overheating of an engine?

If you mean, overheating of an engine that this particular stat was fixed in, possibly, aint got a clue not knowing its history.
The point I was making is that stats CAN get stuck open.

missfixit70 wrote:

widdowson2008 wrote:  Stat remained ‘stuck’ in this position ie: Open, but sprung back when gently persuaded. - This suggested that the stat CAN in fact get stuck in the OPEN state when subjected to excessive temperatures

Will try again to see if it still works after this harsh treatment

Any idea what the temperature was that caused it to stick open? Could it be that these stats do actually fail in the open position after being subjected to very excessive overheat? (when working correctly) Or is that just a "fault" with some?
I'll try & remember to see if I kept my old stat that was a bit lazy, I'll send it up to you Steve so that you can do some comparative testing to see whether it'll do the same under similar conditions.

Look forward to your stat arriving. .......welcome my child..........

As explained to Jaylee, my point was that a stat CAN get stuck open - I've seen it.
Now the embarrasing bit....... I was so busy cremating the stat that.................well..........er...........I didn't get a temperature.
OK - big mistake, but it aint gonna happen again.
All I can say in my defence is that I had an epic battle yesterday (an annual affair) with some Christmas tree lights that refused to give up the duff bulb. When I found the bad one and replaced it, ....ping....another. 6 bloody bulbs later, and the whole thing working, I got the boss out to put her blessing on it and, you guessed, ......ping. so I gave up, and this morning, woke up sort of
So not really a fair test - Whole thing to be repeated tomorrow in a more gentle manner (and armed with measuring gear this time)

Fair comment.. My train of thought was an overheating event might not have cooked the engine, but may have been enough to stick a stat..?