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MG TD TF 1500 - Water Works

Elementary question, notwithstanding the engine efficiency of thermostat cooling, if it is removed does the result adversely affect cooling per say. I have removed a defunct 'stat from my TD and, strangely, it now seems to be running hot! Any ideas please? Always kindly yours, Peter.
P J Wilgoss

Peter, Sometimes by removing the thermostat and leaving the system open will result in a situation as you describe, usually because it lets the coolant move faster through the radiator and not giving it enough time to cool. PJ
Paul161

Paul, that makes perfect sense as you describe it. I bulked at the cost of a replacement (mean old codger that I am) so perhaps a phone call to BandG tomorrow will be money well spent. Thanks for a very quick response. Peter.
P J Wilgoss

PJ. I suggest you contact tom lange at MGTRepair.com. He produces a stainless steel housing with a replaceable thermostat. Very high quality item and worth every penny. It'll be the last housing you'll ever buy. From a satisfied customer.


Cheers

Bill Chasser
TD-4834
W. A. Chasser

Tom can be reached at tlange@acadia.net
Cheers,
DW DuBois

Email enquiry sent to Tom, thanks, Chaps.
P J Wilgoss

For information, Tom is out of stock and is waiting for an expected delivery soon, he hopes. Regards, Peter.
P J Wilgoss

Peter I have modified an existing thermostat housing using a modern Waxstat thermostat, for just a few dollars. If interested email me pjbm at bigpond dot com & I'll send you the details. Cheers
Peter TD 5801
P Hehir

Peter,
I disagree with the suggestion that the problem comes from fast moving water in the radiator - things are not as simple as that !

The faster it goes then the more water there is to transfer heat.

I direct you to an article - see link below:

http://www.mgccyregister.co.uk/technical-information/the-xpag-files/cooling/xpag-overheating/

This provides some interesting insight

Regards,
Mel.
Mel Pascoe

The speed with which water moves through the radiator has little to do with the cooling ability. It is the pressure of the system in both the radiator and block that plays the biggest part. Without the pressure applied by the water pump, tiny bubbles tend to form at the surface closest to the radiator fins and water passages. These bubbles prevent an effective transfer of heat. With sufficient pressure from the pump and the blockage provided by the thermostat, bubbles are minimized and thus a better heat transfer is achieved. The (clean) surface area of the radiator is also a major factor.
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090015029.pdf
Lew3

My stainless thermostat has a reduced bypass hole, so that overly-fast water circulation is not a problem. Also, my Stant stainless thermostat has a small bleed hole, to allow easy filling and avoid air lock.

See http://mgtrepair.net/Thermostat.html for photos of both.

Tom Lange
MGT Repair
t lange

Peter,
The old thermostat had a sleeve that moved up to block the bypass when the stat opens. Without that sleeve, the bypass is open to return hot coolant right back into the water pump intake.
Unless you are running a heater, cut a small gasket with no hole to block the small bypass elbow on the thermostat housing.

Coolant flowing faster will remove more heat and NOT run hotter.
JRN JIM

Peter W, I agree with Jim's assessment on the sleeve & the bypass. My take on the gasket that Jim mentions however is to ensure that whatever you use, say brass or stainless sheet, that a small hole IS provided in that bypass gasket. This is necessary to prevent the possibility of an airlock. The beauty of the original thermostat design is that as the temperature of the block varied not only would the thermostat open & close but the bypass port would also close & open in concert. This ensured that there were an almost infinite number of positions where one or other of the "valves" were either open, partially open or fully closed. This is how the desired temperature was maintained. The purpose of blocking off the bypass port is to mimic the action of the original thermostat which ensured that this port remained closed on start up. Once operating temperature is reached the thermostat will have opened fully thus allowing the unrestricted flow of coolant back to the radiator.

During operation the Waxstat thermostat I fitted to the original housing pictured below either opens or closes in response to the temperature of the coolant in the block, just as the original did. The bypass gasket (with the 1/16" hole) is also visible sandwiched between the two paper gaskets. Running a car without a thermostat is no solution at all & guarantees that wear on #1 will follow. Bores in cars that have been run without thermostats invariably show much more wear in #1. So my advice Peter is to use a thermostat & if, like me, $$ are an issue then modify your existing housing. The whole exercise will cost you less than 10 GBP. Cheers
Peter TD 5801

P Hehir

Typo.. "this port remained closed on start up". Obviously that should read "remained open on startup". If both the thermostat & the bypass were shut there would be no flow at all. This is why the 2 small holes are necessary in the top of the thermostat. See pic above. More detailed info in the Neil Cairns article "XPAG Water Flow - Cooling". Cheers
Peter TD 5801
P Hehir

You're probably running a bit hotter due to the bypass hole being left wide open. The original thermostat was an excellent design that opened and closed that port as needed. If you install a modern thermostat then you will need to address that opening either with a blanking sleeve with a small hole in it or a modified housing. I wouldn't just drop a modern thermostat in and call it a day.

Speed of coolant flow does affect cooling efficiency, but it is not the only factor. Adding pressure doesn't really increase cooling ability so much as it raises the boiling point of water. This would allow you to run less antifreeze which would increase cooling efficiency, but raising the pressure by itself won't cool better.

My TC ran without a thermostat at all through the previous owner and probably 12,000 miles into my ownership before I rebuilt it. I never noticed one cylinder being more worn than another. First I've heard of that theory.
Steve Simmons

As it was explained to me Steve #1 gets the benefit of the cool water from the radiator first as it is directly adjacent to the stream from the water pump. Running without a thermostat prolongs the time required for the engine to reach operating temperature which means #1 is cooler for longer. Wear with moving parts in an engine is greatest when the engine is cold. The greater wear in #1 can been seen by comparing the diameter of the bores. It may only be a few thou but it does demonstrate the value of keeping a functioning thermostat. Cheers
Peter TD 5801
P Hehir

Dear all, once again I must thank you all for your expert and informative views and comments. Tom L I am sorry that your housings were not available at this time( hope you received my email and Pics) so I purchased an Item from Brown and Gammons for immediacy. And yes the by-pass outlet was restricted to a small hole, unlike the original housing. The stat was loose in the housing but retained with a circlip, unlike the original again. Now this replacement is cast in aluminium not stainless like Tom's offering so not as durable I guess. I have fitted it and all is now well, no more rad noise or fuel evaporation so all seems well and has borne out all the expert advise contained within this posting. Once again I would like to thank you all and commend the BBS Site to all. Happy MGing wherever you may be. Regards, Peter W Norfolk UK. Now the next problem is.................
P J Wilgoss

The restriction of a thermostat is needed to produce head pressure at the pump to prevent cavitation
Len Fanelli

This thread was discussed between 17/07/2016 and 27/07/2016

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