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MG TD TF 1500 - Removing a removable thermostat...

Hi All,

After reading the "bloddy thermostat" thread, I decided that it was time to try and figure out why my car takes so long to warm up. I suspected that the thermostat might be stuck open, or there was no thermostat in the system. The cooling system in my car hasn't been touched since at least 1978, so the hoses all needed to be replaced anyway.

The thermostat appears to be a replaceable type, and is held in with a copper sleeve. It's very similar to the one shown in the picture at:

http://www.ttalk.info/modern_thermostat.htm

I can't get the copper sleeve out in order to get the thermostat out... I was thinking that galvanic corrosion might have somehow bonded the copper sleeve and housing together. I soaked the housing in vinegar and that helped clean up some of the cooling system corrosion but the copper seems stuck...

Any thoughts on how to separate these two?

Thanks,
Scott
Scott

Scott - I had that type of thermostat/housing in our TD for some time. Once the brass sleeve become corroded inside the aluminum housing, there is no way that I d=could find to get it out without destroying it. Check that the thermostat is oriented the correct way and then toss it into a pan of water, along with a candy thermometer and heat the whole thing up. Watch the thermostat and the thermometer to see what temperature it opens at. Someone may have stuck a 160F/70C thermostat in it. Cheers - Dave
David DuBois

Hi Dave,

How do you know when the thermostat opens up? I can use my fingers to push it to what I believe is the "open" state, but the gap is so small it's hard to see.

I thought about putting water on the non-bypass side to figure out when it opens, however there is a small hole through the thermometer which appears to be an original part of its manufacture and that lets any water placed there drain through.

The thermometer that is in there says it is a 180 degree thermometer. It would be good to see exactly where it opens up.

Scott
Scott


I think I just answered my own question...

I put the thermostat housing under the faucet and used my finger to plug the bypass hole. The water flows pretty easily through it so it's open at least some of the way. I can use my fingers to push it open even further, however it never really closes up.

I've never played around with a thermostat before, but I would think that there shouldn't be much flow through it before it is supposed to open up.

Scott
Scott

Scott - It should open fairly wide as the water heats up. If the thermostat is 180, it should start opening at that temperature. Cheers - Dave
David DuBois


Since the thermostat leaked so badly even when fully closed (who needs the little bleeder hole anyway?), I hammered it out and got the copper sleeve out.

Then it was time to find another 50mm thermostat to replace it... Yeah, right. I went through EVERY thermostat in one auto parts store and only one was close (49mm). I then went to NAPA and we found a 49mm one that could take a rubber gasket around the edge. It was tight, but with some Vaseline it went right in. Because of the rubber gasket, the copper sleeve needed to be shortened by a few mm but it's all back together, and it seals much better. I drilled a very small air bleeder hole and it looks good. I checked it and it opened up at 180 degrees so I'm now ready to tackle the next part of the system: pull the round Smiths heater hanging behind the dash so I can lubricate the fan motor and replace the coolant hoses. Not looking forward to that one!

Also took the time to pull the grill for repainting. I found 2 broken anchor studs in the shell so those got repaired too. I just hope I don't find anything else while I'm in there!

(This all started with side curtain recovering!)

Thanks,
Scott
Scott

This thread was discussed between 08/12/2008 and 10/12/2008

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