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MG TD TF 1500 - Modern Thermostat

I have acquired a Moss style conversion thermostat housing with a removeable thermostat. Looks like a standard 52mm type. Testing shows it begins opening at 160F. In researching the archives, I determined the following, so if I'm off base, please someone jump in and let me know.

1. As the bypass opening is below the modern thermostat, and there's nothing to block it when it's open as the original thermostat did, I should blank off the bypass elbow, and if desired, drill a small 3/16th hole in the blanking gasket (coke can or such).

2. Some say to drill a few small holes in the modern thermostat, I'm assuming around the flat outer circumference area, to allow a small flow of coolant during warmup so the water pump is not pushing against a complete dead end.

If I have got somethin wrong here, please let me know, and if I am correct a confirmation would be appreciated.

Larry
L Karpman

Larry - The 3/16" hole in the blanking plate is all you need for sufficient coolant flow during warm up, it is not necessary to also drill hols in the thermostat. The only other thing that I see is that a 160°F is rather cool for the XPAG engines. Our TD is just getting the choke released at 160°F (71°C). The thermostat in our TD is 85°C (185°F) and the engine noramlly runs at that temperature until we start up a long, steep hill. I would bet that your engine will run at 80°C to 85°C regardless of the lower temperature thermostat. Cheers - Dave
David DuBois

I concur with my very experienced friend Dave (Hi Dave!) and would add that since Larry is in the Texas Panhandle, any thermostat would probably be fine, as it is important to reduce the flow of water slightly through the radiator. i.e. it doesn't work to run without a thermostat!

warmly (or cooly)
dave
Dave Braun

There is a small hole often already in the thermostat flange to allow air bubbles to go through before the thermostat opens and not create an air pocket. Some aftermarket ones nay not have this "bleeder" hole. It can be added. It is generally about one eight inch diameter just inside the area where the flange of the thermostat sits on the elbow. If you are really into this, you can orient the hole so it is at the top of the thermostat as the theory is the air bubbles are at the top of the hose. I'm not sure about the later due to some turbulence from the water pump.
I added a small hole to mine as it wouldn't hurt anything.

FWIW
Dallas
Dallas Congleton

Sorry, left that part out. Boiled it with thermometer in the pot to see what I had in there. I am replacing the thermostat with a 82C Waxstat with "jiggle" pin. Thanks for the input all.

Larry
L Karpman

Hi All,

A question that has popped up in my mind recently is just how long does it take to warm the TD up?

I have a '68 midget, and it only takes 2-3 minutes for the temperature gauge to start moving, and it's warmed up soon after.

The TD takes significantly longer, possibly 5-8 minutes before there is any movement in the gauge, and then it takes 2-3 miles of driving before it is warmed up enough to remove the choke.

Could this be the result of a stuck-open thermostat?

Thanks,
Scott
Scott

My temp gauge takes about the same amount of time (5 to 8)...however, with the heater hooked up the way it is, it is about 2 minutes before i feel a tiny bit of heat...by the time the thermostat opens, there is lots (?) of heat coming through.
gblawson - TD#27667

Hmm, I guess that is consistent with mine. I also have a heater (a round Smiths heater which sits behind the dash and blows down). It also starts generating heat pretty early (a few minutes).

Scott


Scott

Scott, how do you have your heater hose run? have any pics?
thanks
mkg grogan

Hey Scott,

I would also like to see how you mounted the Smiths heater under the dash. I have a Smiths I am thinking of mounting in my car.

Thanks,
Evan
Evan Ford - TD 27621

The location of the temp sensor bulb could also have an impact on how long it takes the gauge to move. The later MGs have the sending unit screwed right into the cylinder head up front near the number 1 spark plug.

Most TDs have a small threaded hole on the radiator header tank that will accept a temp sending unit. The one is measuring the temp of the block - the other is measuring the temp at the rad top tank. If the water level is down, sometimes that temp bulb will not even be making contact with the coolant.

This and the build up of debris inside the t series block can really impact running temp. I have scooped out spoonfuls of debris from the t series blocks - 50 years of muck!

Be sure to clean out those water passages also,

JD
J Delk

Went out today looking for a 52mm 180F thermostat to put into this Moss type housing I acquired that allows a removeable thermostat. The one in there is marked and was tested at 160F, a bit too cool. Trouble is, none of the parts houses I visited listed thermostats by size, only by car model. None of the ones I tried for MGB, MG Midget, Austin Healey, Triumph, etc. would fit (too wide). Also, other than temp marking, there is no brand name on the one I have.

Does anyone know a specific car model thermostat that fits into the Moss removeable thermostat type housing? Appears that's the only way I will find one. Thanks in advance.

Larry
L Karpman

Opps, must have mistyped the first time on Google. Looks like a 90 Mazda Miata thermo is 52mm. Going up to NAPA store now to see if it fits.

Larry
L Karpman

OK, I returned from NAPA, and for the housing "I have," it requires a 48mm thermostat. generally for a lot of Toyota 1.5L,thru 2.4L engines. Fits fine, but is not quite as thick on the edges, so the circlip that holds it in place is about 1/16" above it. Rattles a bit. Perhaps I can cut a gasket for the ridge it rests on.

Larry
L Karpman

Larry,
FWIW here's my two penny worth
Stick with the 160 deg F unit, it's not too cool in the TD.
The 82 deg C stats are for use in pressurised systems like TF etc. I run my TD with a 77 deg C stat listed for a stationary pump version of the Hillman Imp engine.
Regards
Graham (honorary Dave)
TD/C 7822
G.D. Smith

Ok, as we say in Texas, "Ya'll got me a goin'" I dropped the car off today, after a beautiful 60-65 mph 20 mile Interstate highway run to East Dallas. Dodgin' the big rigs was lots 'o fun :-)

In any case I put a 180F thermo in the housing last night, so now I'm a bit perplexed as to whether I should have left the 160F in there. I don't know what the original TD thermo was rated at though. Not too late to call the shop and have them swap back to a 160 though. Any difinitive info out there? The archives leave me guessing.
L Karpman

Larry,
In my MGB I change out the T-Stats with the weather as it gets hot here in Idaho (as in Texas) in the summer. I run a 160 in the summer and the B never goes above N. I change out to a 195 in the fall when the temps drop and I get a good amount of heat all winter. The problem in the TD is it is not easy (damn near impossible if you ask me!) to change out the T-Stat without major work, so I comprimise and put in a 180. If you run a 160, it will be optimum for the hot weather in TX, but you will run cold in the winter. So it depends on if you choose to run in the colder weather...if so I'd go with the 180. If you will only be running in the hotter months, a 160 will work nicely.
Hope this helps!
Bob D
Robert Dougherty

Bob. Actually I will run the car much more in the winter than the beastly hot Texas summer. At 95-105F, I have little desire to be without a/c and be roasted by the sun. That was fine when I was young, but at my age now it's uncomfortable and hazrdous to one's health. That's why I chose the 180 over the 160. Can always dress to be warm (ish) in a convertible, but no way to keep from roasting in the summer :-)We'll see hot things go with the 180. If I run too hot, I'll pop the 160 in. Thanks for the input.

Larry

L Karpman

A UK Vauxhall Corsa thermostat drops straight into the original housing (after removing the remains of the original contraption. It has a bleed hole so the elbow needs to be blocked off

Jan T
J Targosz

This thread was discussed between 04/11/2006 and 08/11/2006

MG TD TF 1500 index

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