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MG MGA - Thermostats Again

I sprang a water leak from the thermostat housing today. I have taken it all apart and did a thermostat test while I was at it, only to find it did not open until very close to boiling point.

Is the attached photo of my thermostat sleeved? It's been in the car for 12 years. It's a Smiths version 74 degrees (165 F). What replacement should I go for in the UK climate. Same again as I do not suffer from overheating? I did not spot the sleeved thermostat on Moss Europe. Can someone give me a pointer.

Thanks

Steve


Steve Gyles

Steve,

You can try Angloparts. This picture is from an advertisement. Wim.


Wim Betzel

Steve,

Your photo shows the original fitment sleeved thermostat. The sleeve rises up as the thermostat opens to partially close off the bypass channel in the cylinder head.

Wim's illustration does not have the sleeve. Sleeved thermostats are still available from time to time as new old stock on Ebay, and from autojumbles.

In my Magnette I use a 74°C in summer and 82°C in winter, but to be honest it doesn't seem to make much difference to the running temperature.

Andy


Andrew Dear

Steve,

Moss USA is selling a 160⁰ F sleeved thermostat, http://mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=47024 . I installed this model last year and it solved my overheating problem. When she is running (that is another story), it has been a very constant 190⁰- 200⁰ F. Since I am in the Seattle area I suspect that our climates are similar.
In addition to the thermostat, she has a re-cored radiator and overflow tank.

John
jjb Backman

I can offer a barely used sleeve for use with a standard thermostat. It's decorating the workbench at the moment.
dominic clancy

I ordered a blanking sleeve from MOSS, thinking I would add it to the new thermostat which replaced an original sleeved thermostat. When I got it, I found it replaces the thermostat and is not designed to be fitted with the thermostat (although there are no instructions with it). My original thermostat looked like the one in Steve's photo but was unfortunately damaged.
Now I'll try to get the MOSS sleeved thermostat, if they have it in California. Dominic - I'll take your sleeve if it can be installed with a new thermostat.(email me directly, please)
Regarding Andy's comments re running temp for different thermostats, I asked this question some weeks ago, but no-one offered an answer. A 74 degree thermostat opens at 74 degrees, and an 82 degree thermostat opens at 82 degrees. With the engine running normally at around 90 degrees (195 F) water temp, both these thermostats are wide open. So why would fitting a different thermostat affect running temp? (One opens earlier, that's all, in my opinion)
Please tell me if this theory is incorrect.
Peter.
P. Tilbury

Peter

I had not really thought of it like that before, it has got me thinking. I am guessing that the idea is to get the engine up to running temperature as quickly as possible and hence get off the choke. This will be governed partly by the temperature of the air going into the carbs and also the starting temperature of the engine as a whole. Therefore 74 degree thermostat for a warm summer day and 82 or higher (88) for a winter day.

Steve
Steve Gyles

Ho Hum, I appear to have a dose of Dominicitus.

I bought a totally standard 74 degree thermostat today. I calibrated it against the 74 degree sleeved one in my first post. Both operated identically, so there was nothing wrong with the original. Nevertheless, I fitted the new one.

I then did a long road test. Previously I ran 175 to 185 degrees. On the run I could not get the temperature above 160, no matter how hard I pushed.

So, if it is not the thermostat, what has caused the change? Could it be the new raked screen has caused a totally different airflow pattern over the bonnet (hood), resulting in more cooling air going through the radiator?

I guess the only way to be more certain will be to put the original thermostat back.

Food for thought.

Steve
Steve Gyles

Isn't it just the cooled flow from the bottom of the rad coming through the bypass and hitting the temp sender because there is no sleeve on the thermostat to block it? Or have I misunderstood the way it works??

Andy
Andrew Dear

Andy

I don't know. May be someone can explain it to us. My engine compartment certainly feels a lot cooler than normal. It does not have the impression of being a localised cool spot around the sensor.

Steve
Steve Gyles

Nice to know that I am not the only one after all. And it's running about the same temp as mine with an 80C thermsotat- I'd better go downstairs and check that my engine hasn't suddenly emigrated to Lancashire.....
dominic clancy

Dominic

I think the swept screen is a red herring. I do not recall seeing a lower temperature when I did the sports windscreen test drive immediately before the water leak.

All I then did was replace the thermostat, housing, gasket and top hose. Instant 15 to 25 degree drop in temperature. Could that sleeved thermostat account for that temperature change? I struggle to believe it. I will get round to experimenting shortly. All that fag of draining the system again!

Steve
Steve Gyles

I have been having a lot of over heating so I put in a sleeved thermo. with a thermostat and now the temp. spikes from 160 to over 215 in a few seconds and then drops almost as fast to 19-195. I beleive as most of you do that adding the sleeve leaves very little room for the thermo. and thats why it spikes? Help me understand? Tom
Tom Peotter

This thread was discussed between 21/09/2008 and 25/09/2008

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