Cooling system diagram

[haydn callow]

Where you have the sensor....readings of 127 plus have been recorded by other peeps....this is not overheating and the nearest coolant to this point will be much lower.....move the sensor a couple of inchs to the manifold and you will get readings of ...whatever "nearly" red hot iron is.

[haydn callow]

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)

That bleed pipe is in a funny position.......close to hot metal......best to route it over the alternator and put a "split" hosepipe sleeve over to protect it....is it clipped up around the chassie??

[widdowson2008]

TM-2, it's just that it only goes up to 127C and then it will be quite happy to sit there.
Excellent - my TM-2 is safe from destruction

Where you have it at the moment I have recorded readings of 90/110 normal driving and 124 towing......
Again - exactly what I wanted to hear - my system seems OK

As 124 is obviously much higher than the coolant temp it seemed pointless
Not convinced about this - see reasoning below.

Where we now locate the sensor...........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.

Not so sure about this last bit
Are we really interested in the coolant temperature? Is it not the head temperature the important bit? Surely the purpose of the coolant is to keep the cylinder head/block within an acceptable operating temperature range for the materials from which they are manufactured. ie:primary concern is cylinder head/block, secondary concern:coolant
Haydn, I'm not trying to be smart here or score points. I am trying to think it through.

[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)

That bleed pipe is in a funny position.......close to hot metal......best to route it over the alternator and put a "split" hosepipe sleeve over to protect it....is it clipped up around the chassie??

Sorry? Bleed pipe? HELP!! which one is that? Please remember, you are talking to a complete novice here - a dunce when it comes to this sort of stuff.

[Doone]

The bleed pipe is the long dark grey/black pipe in your photo. It can rub against things and wear through - some bleed pipes are extra short, probably because this has happened. And if it gets too hot it's likely to perish more quickly.
I have pm'd you a link to my husbands website, where you'll see a photo of it and advice about it. Some people encase the pipe in a length of split garden hose, to help to stop it rubbing on the bodywork and you can cable tie it to hold it in position.

[widdowson2008]

The bleed pipe is the long dark grey/black pipe in your photo. It can rub against things and wear through - some bleed pipes are extra short, probably because this has happened. And if it gets too hot it's likely to perish more quickly.
I have pm'd you a link to my husbands website, where you'll see a photo of it and advice about it. Some people encase the pipe in a length of split garden hose, to help to stop it rubbing and you can cable tie it to hold it in position.

Bleed hose repositioned and secured
Many thanks Lorna

[widdowson2008]

Sorry Haydn, it was you who pointed out my bleed pipe - many thanks for that - I have been out and re-routed/secured it. and yes, it is secured to the chassis (now)

[dandywarhol]

My tuppenceworth - I really can't see any point in having the sender so close to the exhaust system - the manifold could easily reach 200 deg.C under load! surely the whole idea of the TM2 is to detect abnormal temperatures before damage is suffered so putting it somewhere near the coolant passages will give an accurate state of affairs.

It's possible the thermostat won't come into operation until the cooling system does reach abnormally high temperatures - then it opens to allow the radiator circuit to operate and cool the whole engine down - remember the thermostat is in the RETURN side of the system.

I just found out recently that the reason that more manufacturers are putting the thermostat in the return side and operating with a bypass system is to regulate the coolant temperature more closely and to avoid extremes that the "conventional" setups use. This then allows the designers to use tighter piston/cylinder clearances to aid thermal conduction between the pistons and cylinder/water jackets, increase compression pressures and prevent compression blowby and emissions.

[helen&tony]

Hi
Yes to that, Dandy...I have mine on the other side, but Haydn's idea of the standard placement makes good sense...I just haven't got around to it yet.
Cheers
Helen

[widdowson2008]

Having read back through this post, I realise that a lot of the queries I had have been answered. Many thanks for the contributions.
I’m afraid this post was deflected very early on from the real reason I asked the original question. MY FAULT ENTIRELY- I should never have brought the TM-2 into the mix.
What I was trying to do, and still am, is to get a simple circuit diagram of the cooling circuit to understand how it works. I have absolutely no knowledge of how the system works and am trying to rectify that.
The only diagram I could find was linked in my first post and created by Bellhill.
Whilst I understand most of the circuit, I was confused by the blue line from the expansion tank to the thermostat.
It appeared from some of the replies I got that others thought the same. Ie: the thinner line from the expansion tank to the thermostat should be red, and not blue as shown in the diagram. The reasoning was that no cooling takes place in the expansion tank and therefore this line should be red. And if the point of entry at the thermostat is on the engine side as opposed to the radiator side, then it starts to make sense to me. (I think)

The cooling process is quite involved (for me) – anything is simple when you know the answer.

Would I be correct in thinking the following:
When the engine starts, the flow of coolant is:

THERMOSTAT CLOSED
engine/radiator/expansion tank/thermostat/engine (via thermostat bypass) – not sure where the turbocharger fits into this.

During this time, the radiator fans occasionally start, suggesting that the elevated temperature at the top of the radiator (from the returning coolant) is being detected and dealt with.

This recirculation process will continue until the thermostat detects a certain temperature at which point it will open causing cold water from the radiator to flow through the system.
This will continue until the thermostat detects its 'set temperature' at which point it will close and the system will revert to a recirculation mode.

[alphabetter]

Would I be correct in thinking the following:
When the engine starts, the flow of coolant is:

THERMOSTAT CLOSED
engine/radiator/expansion tank/thermostat/engine (via thermostat bypass) – not sure where the turbocharger fits into this.

During this time, the radiator fans occasionally start, suggesting that the elevated temperature at the top of the radiator (from the returning coolant) is being detected and dealt with.

This recirculation process will continue until the thermostat detects a certain temperature at which point it will open causing cold water from the radiator to flow through the system.
This will continue until the thermostat detects its 'set temperature' at which point it will close and the system will revert to a recirculation mode.

Actually I drew that cooling diagram originally, but it was modified and reposted several times over several threads!

Your theory above is interesting and makes sense to me. I would raise two questions though:
1) I agree that we need to understand how the turbo fits in.
2) The thermostat can't totally cut-off the thin blue line from the tank because it's also the return path for the interior heaters.

[dandywarhol]

It's my understanding (and some will disagree) that only the radiator's top tank is in use for the majority of the time. The coolant circulating around the various pipes and heater matrices is sufficient. When the engine temp becomes higher than the thermostat predetermined opening time the stat will open allowing the radiator to come into the circuit until the coolant cools enough to close/partially close the 'stat again.

I believe the stat is opened by a combination of heat transfer from the engine side AND the rising coolant temperature convecting through from the radiator top tank.

This is why you really need to rev the engine with the vehicle stationary in order to open the thermostat. I've climbed some steep accents (Pas of the Cattle to Applecross for example - sea level to over 2000 ft in around 5 miles, stopped at the top with the bottom hose still just warm.

[haydn callow]

Dandy...thats what I belived ...untill....I did the 2p mod to my temp gauge (this makes the needle move over the whole scale) Once the engine is up to normal running temp which on mine is around 86/92 on my TM-2.
Two things happen..
1.. the TM-2 starts fluctuating between 90 and 86C in about 60 sec cycles.
2.. the gauge needle reaches a "normal" temp and then moves left/right in time with the TM-2.
As ther is absolutly no connection between the gauges and as this coinsided exactly with the Stat open/close temps I must assume that the gauges are reacting to the Stat opening/closing at very frequent intervals.

Anyone interested in this mod....go to the webshop below for a free download on the homepage......You only need a 100ohm resistor (less than 5p from Maplins) or I can send you one...

[haydn callow]

I know this has been debated to death in the past. But I am changing my thoughts on the whole subject..
I assume your cooling system is in "tip top" condition...
You are getting very hot coolant coming out of the engine via the top hose and then moving down through the rad and also being cooled as it does so, the stat is open co's the engine is hot so the cooled coolant passes along the bottom hose and through the stat to be reheated in the Head.
I used to think the bottom hose was cool co's the stat was closed...Now after more thought and watching my gauges fluctuate around the 85/90C temp range I belive the stat is opening/closing all the time and the radiator in good condition is doing it's job very well.

[widdowson2008]

Excellent Dandy - The soup becomes a little clearer.

But this has thrown up another query

It's my understanding (and some will disagree) that only the radiator's top tank is ........

Are you saying that (in your opinion) the radiator has a top tank and by suggestion, a bottom tank?
or is it that the radiator is zoned?
or perhaps,
the circuit from rad to expansion tank can cope with the engine cooling requirements under normal running conditions, and the lower half only needs to be brought into play when the engine is working extra hard?