Cooling system diagram

[widdowson2008]

I am tring to find a diagram showing the coolant flow path.
This is the best diagram I can find and whilst it is a clear diagram, it doesn't explain the flow very well. http://www.igmaynard.co.uk/bongo/member ... eating.pdf
For example, it shows in red the flow when the thermostat is closed(note 1 on diagram). This appears to go from engine to radiator top to expansion tank............and then where?
If the thermostat doesn't open, then how does the flow get from the expansion tank back to the engine? Is it via the smaller blue line through the thermostat?

[stilldesperate]

Hi Steve,

I think you right about the blue out the exp tank, up to the stat.

Looking at it, I believe the red into the rad (before the stat opens), comes back out the top, into the expansion tank. The blue out the expansion tank then goes to the top of the stat, and round the engine.

SD

[widdowson2008]

The reason for asking this question is that my bottom hose doesn't seem to be getting hot (or even warm).
I can only think of 2 reasons for this:
1 - the thermostat is not opening (assuming that the coolant by-passes the thermostat on the thin blue circuit line)
2 - the radiator is bunged up
I have a TM-2 fitted with the connection at the front/passenger side of the engine block and the maximum temperature it records is 115 deg.C.
Under steady driving conditions at around 60mph on a motorway, it will get fluctuate between 96 and 102, suggesting that the thermostat is indeed working, so it suggests that the rad may be blocked. However, (I think it was maxheadroom) said his bottom hose didn't get hot so I thought I was OK.
I have asked previously on the forum what temperature is acceptable for the engine when the TM-2 is fitted in this position in an attempt to determine what temperature is NOT acceptable for the engine.
I was a little dissapointed with the replies because none of them gave me this information, but I did learn is that all engines produce slightly different results. Also, some members who tow sheds around are experiencing temperatures up to 120 deg C with no problems, which suggests that their engines are quite happy.
The only suggestion made was that I move the sensing point to a cooler part of the engine block at the back, and indeed, this is the new recomended position for fitting the TM-2.
Surely this is defeating the object of having the TM-2. I would have thought that the value of the TM-2 was that it indicated the hottest temperature. Thats how I am using it and will continue to do so.

I hesitate before pressing the 'submit' button because this is sounding like a 'no confidence' vote for the TM-2 but I can assure you it is just the opposite. I trust the readings displayed and drive accordingly. If the TM-2 packed in for any reason, I would buy another one - it is a spledid piece of kit and essential for monitoring the engine.

[helen&tony]

Hi
Steve
Yes...the TM2 is excellent...and it seems to be reading what you would expect , with the exception of the 115....but that's only a tad high. I bought mine a couple of years or so ago, and have put the sensor in various places. The trick is to monitor what your own engine reads on various journeys, and not so much wonder about the top and bottom readings if your engine is running well, but to notice if any reading is out of the usual range FOR WHERE YOU HAVE YOUR SENSOR. If you have your sensor alarm set at literally a few degrees higher than normal, then , should it set the alarm off, it is up to you whether to stop and check.
Mine is set such that in summer, if I park for 10- 15 minutes, the alarm sounds in summer, as it gets to 40 plus Celcius over here, and the heat from the engine sets everything off, including the scavenger fan, but 4-5 minutes driving lowers the heat and turns the fan off. The actual temperature on the TM2 is quite reasonable when it all happens.
The cooling diagram is a little confusing due to the colours, as the return from the expansion tank should not show blue (in my opinion), as no cooling takes place in the tank. If the colour was red, it accurately shows the cooling system in 2 parts, as this is what is popularly considered, and the only time the "Bottom Half" of the cooling system operates, is under duress. The diagram also shows an arrow on the timing cover indicating a flow out of the block. Personally, I feel that it would better serve showing the other way, as it would currently indicate all cylinder block flow as outward, and nothing flowing back.
As regards the bottom hose...mine only gets hot after a good workout over 40 miles in the kind of heat we get here, but in the height of summer when the aircon is permanently on , the fans cool the rad anyway, and the bottom hose cools down, as the top half is under the influence of the fan switching on and off frequently.
I hope this allays your fears, but if you want a full breakdown of temperatures experienced in the journey I mention, PM me, and I will give you an average set of readings taken every few miles.....my bet is that it is similar to your engine.
Cheers
Helen

[widdowson2008]

Thanks Helen - this is exactly the response I have been looking for.
Will send PM

[helen&tony]

Hi
No probs...will PM you back later today or tomorrow morning...we are out and back again like a fidget today, sorting out computer hassles for other folk...
Cheers
Helen

[mikexgough]

I was confused at the diagram too..... My engine is much the same as yours and Helen's, I replaced the radiator in July due to a minor leak at the seam, after bleeding, the bottom hose just gets what I would consider to be luke warm which means coolant is circulating and the radiator is cooling down the coolant mixture before it gets recirculated.
My fans work identical to what Helen described and I don't have a TM2 so can't give you any readings, my mason alarm has raised the needle to 55% of its working range in normal use and under load goes to a maximum of 70%

[helen&tony]

Hi Mike
Yes...I've done the replacement rad...I had the option of having it cut apart and re-cemented, but decided to go for an all-metal one from Iezura...personal choice...I also think that I may cut the bottom transmission cooler off, and go for an external cooler and thermostat if we keep the Bongo running as the main vehicle, as I'm not impressed with the setup as is...winter over here, the transmission takes too long to heat up, and towing over mountains CAN, and I repeat CAN...(as not everyone has the same problem) overheat the transmission to the point when the driving capability suffers in summer.
Cheers
Helen

[haydn callow]

It would be pointless putting the TM-2 sensor on the hottest part of the engine as that would reach enormous tempretures.....Unless somone else has the sensor in exactly the same place as yours, comparison would be meaningless.....this is why we have a recommended position...this then does give us meaningful readings to compare.(and it has proved to do so)
At the end of the day ...wherever you have the sensor is (within reasen) is o.k. co's if you overheat the sensor (wherever it is ) will reflect this.
You say you have recorded 115 on the inlet side front.....is this under a rocker bolt..( that is a high reading for a inlet rocker bolt)...can you post a photo.
I would suggest you move it to the Back as we recommend and then you should read between 85/95....in normal driving and a few degrees more towing.

[widdowson2008]

Hi Haydn
Image as requested.
The sensor is fixed to the recommended position you originally specified when I got it and becuase I have become acostomed to the readings, I am reluctant to move it (unless you can convince me otherwise - but you will need to be very convincing as I think you got it right the first time)

[haydn callow]

Ah! sorry..that's exaust side...115 is fine there....I would still move it as that is close to the HOT exaust.....up to yo but you can go off the 127 max alarm temp there.
Up to you......your readings will only be relevant to you...Strongly suggest you move it.

[widdowson2008]

Ah! sorry..that's exaust side...115 is fine there....I would still move it as that is close to the HOT exaust.....up to yo but you can go off the 127 max alarm temp there.
Up to you......your readings will only be relevant to you...Strongly suggest you move it.

I think it would be a worthwhile excersise to find out where all TM-2 users have theirs fitted (with before/after data) so that a true picture can be drawn. Is their an easy way we can do this? From reading through posts on the subject, I can't find anyone who has shifted it.

What was the reasoning behind moving the recommended fixing point?

I must emphasise that I am NOT suggesting this unit is anything but excellent. I would never even think of removing it. Superb piece of kit and well worth the outlay.

[haydn callow]

The feedback I have suggests that most peeps who fitted where yours is have now moved it to the new position and all who have bought them over the past 6 months have gone for the back of the head,
We decided that where yours is , is to close to the exaust valves etc and was giving unrealistic readings and when towing we were reaching the top tof the TM-2 scale...
Thats the advice/feedback....now it's up to you.

[widdowson2008]

So the fundamental reason for the re-location is to protect the TM-2
If this is so, I can live with it in its current location because:
- I will NEVER tow
- If the temperature goes above the 115 mark, I would stop and investigate/rectify

My reason for leaving it where it is, is that it is showing me what the temperature is at (probably) one of the hottest points on the engine.
I have also simultaneously taken the temperature at this location with a very accurate thermal imaging camera and a temperature probe. The readings from all 3 agree within 1 degree C, so I am happy that the TM-2 is accurate.
The engine is running sweet - it has that typical diesel 'chuckle'. It pulls like a Trojan and responds beautifully. The readings on the TM-2 fluctuate between 96 and 102, with the occasional lofty 115 reached when pulling up longer inclines, so I am quite happy that the thermostat is doing its thing and the engine doesn't object to the occasional 115.
If there is ever an overheating situation, then surely, the best place to detect the problem is precisely this point on the engine - this is the point which will suffer first. If you place the sensor in a position reading, say 10 deg lower, then by the time that position has reached 115, the original position will be 125 - and that may be too late.
Please tell me if you think this reasoning is a load of b***ocks - I am just trying to apply a bit of logic to this because I don't understand the intricacies of the thing.

What I will NEVER do is ditch the TM-2 'cos it has become a 'friend'
If I bust it, I will buy another .....and another, and another.......

As you said, it is my choice

Incidentally, do you have any feedback on temperatures (in both fixing locations ideally) - would make interesting reading

[haydn callow]

If you think the hottest point of the engine is the best place to take readings then there is always a exaust manifold bolt...
We are not protecting the TM-2, it's just that it only goes up to 127C and then it will be quite happy to sit there.
Where you have it at the moment I have recorded readings of 90/110 normal driving and 124 towing.....As 124 is obviously much higher than the coolant temp it seemed pointless.
Where we now locate the sensor..we get readings of around 85/95 normal running and up to 110 towing.....using a infer red thermometer I know that this is within 2 degrees of actual coolant temp. And as this is what we are worried about it makes sense to me to do this.
Short of putting a sensor into the coolant with the problems that "could" involve...I am happy we are doing the best thing.