Cooling system

[Aethelric]

Thats what the diagram at the top of the page says TGP.

Dave

[The Great Pretender]

Thats what the diagram at the top of the page says TGP.

Dave

OK, so when does the stat open?

[Aethelric]

I think it should start to open when the water flowing from the header tank reaches around 82C. It won't open fully at first, just a little to mix the cooler water from the rad with the hot water from the tank.

After a run as you describe, my bottom hose feels warm. The thermometer would show it as somewhere between 25C and 35C.
I went out with the dog today, about a 20 minute drive to the coast and mostly downhill. The thermometer showed about 22C.
It was mostly uphill on the way back and it showed 35C when I got home.

If I sit with the engine idling for about 30 minutes, the bottom hose gets quite hot which means the stat is passing more water, but I can still hold it. It shows as about 50C. 60C is a fairly precise temperature to measure by hand - its the threshold of pain, where you really can't hold something. Its when the cells start to die. I've never had the bottom hose that hot yet, but the weather is still damned cold.

TGP, if your bottom hose is always clay cold, are you sure you have not got a blocked radiator?

Dave

[The Great Pretender]

I think it should start to open when the water flowing from the header tank reaches around 82C. It won't open fully at first, just a little to mix the cooler water from the rad with the hot water from the tank.

After a run as you describe, my bottom hose feels warm. The thermometer would show it as somewhere between 25C and 35C.
I went out with the dog today, about a 20 minute drive to the coast and mostly downhill. The thermometer showed about 22C.
It was mostly uphill on the way back and it showed 35C when I got home.

If I sit with the engine idling for about 30 minutes, the bottom hose gets quite hot which means the stat is passing more water, but I can still hold it. It shows as about 50C. 60C is a fairly precise temperature to measure by hand - its the threshold of pain, where you really can't hold something. Its when the cells start to die. I've never had the bottom hose that hot yet, but the weather is still damned cold.




TGP, if your bottom hose is always clay cold, are you sure you have not got a blocked radiator?

Dave

[Aethelric]

And your point is?

[The Great Pretender]

And your point is?

Your not paying attention, go stand in the corner.

[Aethelric]

Yesterday I moved my thermometer to the head and went for a run. It seemed to do the same as most folks have reported on other threads - sitting around 97C under low load and going up to a little over 110C (Don't know how much above as thats as far as my thermometer goes - but I don't think its much as it comes down below 110C very quickly when the load goes off) under heavy load.
I'm sort of happy with that, BUT there is another thread on here from brorabongo which gives interesting data about fitting a new rad:-
http://www.igmaynard.co.uk/bongo/forum/ ... &hilit=100

Basically with the new rad head temperature dropped by around 8-10C.
I think the thermostat acts like a mixer tap, much like a on on a shower. It has hot water from the header and cooler water from the rad coming in. It starts to operate around 82C. If the rad is working well - cooling the water AND allowing a free flow of water then the stat does not have to open very far. If the rad is working under par, i.e it is still cooling the water but its reducing the flow, then the stat will have to open further. It may have to open fully - which means it has to get up to 95C. Around 8-10C hotter than with a free flowing rad.

I've already fitted Haydn's alarm, I will be fitting Flippa's hoses and I guess a new rad at the same time. I'll probably install a permanent thermometer in the head too as I can't think of another way to check if the radiator fan is still operating properly.

Don't know about "not listening" TGP but this thread has been an education for me. Thanks to all

Dave

[Grahame at work]

Hi Folks,

My experiment 2 is under way.

I have moved the temperature sesnors to the hoses that feed the heaters either side of the engine.

When running with no / little heating set there is very little difference in the readings I was getting but with both heaters going full blast I was getting about 6C difference. And the lower of the temperaturs is on the hose going to the stat housing.
So I conclude that the 'conventional theory' is correct and the pump 'pulls' from the stat housing and 'pushes' the coolant throught the block up through the head and out of either the bypass back down to the stat or around the radiator circuit (or a balance of both depending on operating conditions).

Now I also connected into the temperature sensor for the ECU and I am monitoring that. I get a voltage of around 600mV when I drove into and out of town this morning. It varies approximately in line with the Mason gauge.
However I have not been able to assess what the calibration is. The workshop manual gives resistance readings at 20 and 80C and it gives ECU terminal voltage on the sensor at 20 and 60C. I don't think it is linear and so can't assess what voltage I should be seeing at 108C which is when the fans should come on (and that is what I'm interested in)
Anyone got one of these sensors that can be checked?

regards Grahame

[Aethelric]

Hi Grahame, the 600mV may be the base-emitter voltage of a transistor in the ECU, so although the resistance may change, the voltage may not. Or it could be a simple potential divider.

[alphabetter]

When running with no / little heating set there is very little difference in the readings I was getting but with both heaters going full blast I was getting about 6C difference. And the lower of the temperaturs is on the hose going to the stat housing.
So I conclude that the 'conventional theory' is correct and the pump 'pulls' from the stat housing and 'pushes' the coolant throught the block up through the head and out of either the bypass back down to the stat or around the radiator circuit (or a balance of both depending on operating conditions).

So if I understand you - the flows are in the direction shown on this version of the diagram (ignore the notes for now). Is that right?

[Aethelric]

Hi alphabeta and Grahame
Looking at alphabetas original flow diagram and my slightly modified one, the main difference is the flow between the engine and the heaters - on the other side from the thermostat. Can your dual thermometer check the direction of flow here?
Dave

[Grahame at work]

Hi folks,
An update on my temperature measurements.

Aethlric – I think you are asking me to do what I have already done. My sensors are here: -


TGP – Yes I am confident that your flow diagram is correct except that I think it may be misleading to show the small hose from the header/degassing tank to the heater circuit as blue.

I have knocked up a quick schematic on Visio to get an idea of how I want to present an alternative cooling diagram. I have to annotate it yet and add some more arrows and improve the stat image.
What does anyone think?



I have deduced that the ECU coolant temperature sensor is an NTC thermistor as it appears to follow the standard curves but I don’t know what circuits it interfaces to in the ECU. However I think I have got a calibration.
I took a longer route to work this morning and managed to get the fans to come on. I noted the voltage on the ECU coolant temperature sensor and have used that as a third point for establishing an approximate calibration. This is based on the workshop manual which gives a voltage for 20C and for 60C and it states that at 108C the fans should be on – so three points.
Unfortunately it doesn’t follow any standard curve so I’ve done my own ‘best fit’.

If anyone is interested I'll post tomorrow (left it at work )


I see no value in continuing to monitor the heater hose circuits so I’m going to move the sensors to the radiator return hose (where I have a thermocouple just now) and the radiator top hose – i..e the output from the head and the input to the thermostat. – or the input to the radiator and the output from the radiator but to avoid the wind chill factor I think they will have to be placed inside the engine compartment fairly near the engine.

regards Grahame

[The Great Pretender]

Grahame love the schematic, red for the hot side of engine, blue for cool side to me was the way of understanding what way the coolant is flowing and not the temp.



As your pic correctly shows all the pipes falling to exit the engine bay how can the bubbles of air/gas that I have added get back to the rad?

I think most of us have a radiator type of central heating system at home. Normally the flow and return pipes enter the rad from below as do the Bongo pipes. If air/gas gets into the rad it stops there as it wont travel down so it needs venting.

I dissagree that there is no value in continuing to monitor the heater hose circuits. The temperature at the rad end and the stat end of the main bottom hose holds the key to how the system works. I intend to put sensors on each end when im fit enough to fiddle about.

When the system is up to temp, at speed the bottom hose dosn't supply the engine. Run around at low revs for a few minutes and there is flow there.

[dandywarhol]

I reckon the last part of your question TGP is that the radiator is pretty efficient at cooling (even though it's behind the a/c exchanger) so the airflow is doing a good job at keeping that large surface area cool when thevehicle is moving - until the revs increase and the vehicle slows down. Then the airflow can't keep the radiator surface/coolant cool and the stat opens

[The Great Pretender]

I reckon the last part of your question TGP is that the radiator is pretty efficient at cooling (even though it's behind the a/c exchanger) so the airflow is doing a good job at keeping that large surface area cool when thevehicle is moving - until the revs increase and the vehicle slows down. Then the airflow can't keep the radiator surface/coolant cool and the stat opens

Remember this?


Listen very carefully I will say this only once.

The bottom hose from the rad is the key to how the system works and anyone can check it out. You dont need fancy equipment just your hand and a little common sense.

Drove from Wigan to Burnley today 35ml on the motorway at 60 to 70 mph, as soon as I left the motorway I stopped and felt the bottom hose, it was COLD.

Now it dosn't take Einstien to understand that as the Bongo isn't overheating the cooling system must be working.
Ok so as the rad is hot at the bottom as your little pinkies should find out, logic says the coolant is flowing elsewhere.
So if the coolant isn't returning to the engine through the bottom hose where is it flowing. Any light bulbs going on yet?

Yep you have got it, it is flowing through the degassing tank.