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Bruce Sutherland
United Kingdom
1568 Posts |
 Posted - 23/06/2009 : 00:29:00
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(1) Further to Steve's comments about the K Type having a standard-fitment top hose thermostat and by-pass, please can anyone scan the picture in the K Type shop manual and post it on this website?
(2) The performance of radiators/heat exchangers is a function of the mean temperature difference of the 2 fluids (for a radiator = water and air) so increasing the water temperature with a top hose thermostat provides an aid to warm/hot weather cooling performance.
(3) I would echo Graham's comment about inadequate water flow with thermo-syphon (i.e. no water pump) cooling systems. In modern-day traffic conditions at low road speeds/engine speeds, both airflow and waterflow rates are marginally low - increasing airflow alone with an electric fan may be insufficient and a water pump becomes highly desirable to achive adequate water velocity through the 'tubes' else a laminar waterflow results - laminar flow significantly reduces the water-side heat transfer coefficient which can result in overheating.
A water pump should give a higher water flow and turbulent flow in the 'tubes' with much better heat transfer and a noticeable improvement to hot weather cooling at low speeds/traffic jams/hill climbing.
(4) A clean and corrosion/rust-free (water-side) cooling system - NO BROWN RUSTY DEPOSITES in the radiator - also aids cooling performance. Use a 50/50 good quality anti-freeze ethylene glycol/water mix..........it's the anti-corrosion additives you're after!
Bruce. (PB0564) |
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Gerhard Maier
Germany
874 Posts |
Posted - 23/06/2009 : 12:44:25
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Bruce, here are some pictures about the K-type thermostat, Gerhard
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Edited by - Gerhard Maier on 23/06/2009 12:48:43 |
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Peter Scott
United Kingdom
1240 Posts |
Posted - 23/06/2009 : 17:42:57
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Hmmmm. One minute we are debating the minute detail of 'original' cars and abhorring any deviations from the 'correct' spec. The next we are discussing electronic sensors. 
What year where electronic sensors introduce for MMM cars? I cannot trace them in any parts listings. 
Peter
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Bruce Sutherland
United Kingdom
1568 Posts |
Posted - 23/06/2009 : 19:17:27
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Gerhard, many thanks for the K Type top hose thermostat pictures.
I wonder what diameter was the by-pass pipe off the bottom of the thermostat? Also I presume the pipe to the bottom tank of the radiator went into the cast stub pipe for the bottom hose?
Interesting to see the manual adjuster to the by-pass 'butterfly' valve.................presumably there was no automatic actuation.......before the days of bellows type or wax-element type thermostats?
Bruce. (PB0564) |
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Peter Green
United Kingdom
1682 Posts |
Posted - 24/06/2009 : 00:00:16
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Bruce,
The by-pass pipe to the bottom of the radiator went into the bottom tank adjacent to the bottom hose.
Peter.
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Bruce Sutherland
United Kingdom
1568 Posts |
Posted - 24/06/2009 : 00:19:30
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Thanks Peter, but what diameter was the pipe?
Bruce. (PB0564) |
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Brian Kelly
USA
526 Posts |
Posted - 24/06/2009 : 03:40:53
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Hi Bruce,
From what I recall the spigot on the radiator has an O.D. of 0.5".
Thanks to David Naylor for allowing me a photo session with his blown K1.
Brian. |
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Gerhard Maier
Germany
874 Posts |
Posted - 24/06/2009 : 13:10:43
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Hi Bruce,
the O.D. of the by-pass pipe at the bottom of the thermostat is half a inch (12,5mm).
How the thermostat works, I donÆt know, but from the picture below, it seems that with the manual adjuster to the by-pass butterfly-valve, you could perhaps pre-adjust the tension of the bi-metal spring in the butterfly, to alter the open/close characteristic of that thermostat?
So maybe it was even more advanced, than the nowadays wax-element type thermostats?
The part shown in the photo I found in a autojumble, but was a to big a size for a K-type thermostat.
Gerhard
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Bruce Sutherland
United Kingdom
1568 Posts |
Posted - 24/06/2009 : 13:16:28
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Brian and Gerhard, many thanks for the additional info.
Bruce. (PB0564) |
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Bruce Sutherland
United Kingdom
1568 Posts |
Posted - 05/07/2009 : 00:43:18
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Paul, thank you for your update and good to hear that thereÆs been no evidence of cavitation on your water pump but I suggest that the better technical solution when fitting a top hose thermostat, as demonstrated by the MG factory-fit thermostat in the K Type and in nearly all subsequent modern engine cooling system designs, is to have a by-pass. I guess weÆll just have to agree to differ on this one.
Bruce. (PB0564) |
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Cymber
United Kingdom
966 Posts |
Posted - 05/07/2009 : 13:42:28
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I agree with Bruce. My own view is that with a thermostat there should always be a bypass, even if only a small one, to keep the coolant in the engine moving in the period before the thermostat opens even more so in a blown engine. In the MMM case where pumps are now used instead of thermosyphon the flow rate even with a permanently open bypass should still be greater than with the original system on thermosyphon only.
We Rolls-Royce engineers must stick together!!!
Maurice Blakey. |
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Gordon
United Kingdom
692 Posts |
Posted - 05/07/2009 : 21:12:23
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In this interesting thread the dangers of boiling have been made clear but I would like to add the following obsevations:
The onset of boiling will occur very locally starting as microboiling which gives an insulating layer just where you don't want it. I suggest that neat glycol, with no water, with the right additives will prevent this and improve cooling efficiency within the head reducing thermal gradients. There are expensive commercial products (Evans NPG+ http://www.dieselsite.com/index.asp?PageAction=VIEWPROD&ProdID=350). I suspect that an approach to Bluecol or Comma would establish the water content of their "neat" antifreeze solution. The Evans site tells how to eliminate any remaining water in the system when you change over. I like the idea because it treats the fundamental problem and should reduce peak thermal gradients within the head which can be only good. There is anecdotal infromation from people who have used the Evans NPG+ with great effect. Perhaps you dont even need a water pump!!!
Gordon |
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Bruce Sutherland
United Kingdom
1568 Posts |
Posted - 05/07/2009 : 23:50:08
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Yes. 
Bruce. (PB0564) |
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Cymber
United Kingdom
966 Posts |
Posted - 06/07/2009 : 20:46:13
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Paul, Bleed holes in the thermostat do give an effective bypass but this is via the radiator which defeats the object of having a thermostat which is to keep warm up time to a minimum. Bleed holes are neccessary to prevent airlocks when filling but only need to be small indeed many automotive thermostats have a jiggle pin valve which shuts off the bleed hole when the engine starts.
Maurice |
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Peter Scott
United Kingdom
1240 Posts |
Posted - 06/07/2009 : 21:39:58
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I believe in belt, braces, piece of string and keep your hands in your pockets.  So boiling is more of a concern to me (especially when I was in a 20 minute traffic queue on my way home from Shelsley yesterday  ) than a slow warm up. Therefore the answer for me is leave as standard with a water pump.
But a very interesting thread. As was said earlier....each to his own solution.
Peter |
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