Sticky thermostat

[alainmoran]

I'm reviving a 69 2-door which hasnt run for over 8 years, and whiile the engine is now running, the thermostat doesnt seem to be opening since I'm not seeing any flow in the radiator.

I've left it running for as long as I dare (a few minutes), but no sign of any circulation. Luckily I have a spare thermostat, so that isnt a problem, but how on earth to get the thermostat cover off!!

The cover itself has corroded where it comes into contact with the studs, so while I can easily get the nuts off the top, getting the cover off is proving to be a little more difficult!

Any ideas?

Alain

[bigginger]

I've just been recommended Coca Cola for a seized engine - I wonder if theres any mileage in building a little well around the studs with Plasticene, and filling it with that...

[Multiphonikks]

Hi Alain!

If you're worried about damaging the actual studs on the thermostat mount, then get along to Waitrose and get some of their toilet cleaner which dissolves limescale.

I can't remember what the active ingredient is, but make sure you get the limescale remover type. Pour a little of that on each stud, and it'll start to fizz. Eventually you should be able to get the thermostat cover off like that.

However, be careful. It took us nearly 3 hours to loosen Hebe's thermostat cover, and it's also pretty easy to damadge the housing and the head if you try and use sharp implements to prise the cap off...

[Willie]

If the car has stood for such a long period I would suggest that
you should not worry about preserving the housing anyway. These
housings rot quite badly,(the stub part on to which the rubber hose
fits crumbles away) so have a new housing ready. A wood chisel
is useful for sliding between the joint but the FLAT side of the
chisel must be facing the cylinder head so that it doesn't damage the
steel.

[bmcecosse]

Try not to break the studs in the head ! But seriously - it takes ages for the car to warm up properly to the point where the stat opens - so let it run for longer and I am sure the stat will eventually open - you will feel the heat in the top hose. Watch your fingers on the fan !

[rayofleamington]

I've left it running for as long as I dare (a few minutes), but no sign of any circulation

Well as it is the middle of winter a few minutes isn't long enough (unless the car is in a heated workshop).
Either way as the engine is old and the thermostat housing/studs sounds fairly decrepid you may as well carry on the hard work of stripping it down.
I once drove a Minor up the M1 for 30 minutes with a failed thermostat (it didn't open) and it all seemed fine (overambitious first run after the MOT). As it hadn't complained I tried 80mph up hills with 2 people in but then the car did get 'upset' (bolied dry and stopped working...) After refilling the rad a lot of times to cool down the white hot engine we managed the rest of the 120 mile round trip at 50mph. The engine was fairly tired anyway but it didn't suffer too much and I believe it is still giving good service for the new owner.
If it had been the middle of summer instead of the middle of winter I doubt we'd have got off so lightly.

[Onne]

My thermostat was stuck open all the time, that's not nice either, although better for the engine. The housing on mine came off a treat, like new!

[bmcecosse]

Yes - in 40+ years of cars I don't think I have ever heard of a stat sticking shut - they fail to the open position. The story above is the first instance of stuck-shut I have heard !!

[rayofleamington]

Yes - in 40+ years of cars I don't think I have ever heard of a stat sticking shut - they fail to the open position. The story above is the first instance of stuck-shut I have heard !!

I've only seen one 'stick' shut - that was on my dad's princess whilst driving across Spain in Mid summer. Fortunately he had enough tools to change it in a lyby. We'd done 1500 miles of the journey without problems until that day and rather than see if it was just a one-off my dad slung the thermostat and carried on without it - It didn't need a new stat until we were back in the UK. That princess had over heated a few times the year before when we first got it but I don't know if that is related to the thermostat failing or maybe the other way round.


The one in my Minor hadn't 'stuck' - it had just lost all its wax so would not open regardless of how hot it got (I tried a pan of water but gave up after 5 mins boiling it).

Needless to say - I carry a lot of water and tools on the first long run with a new Minor as my foolhardyness of wanting to use a new car before it has been properly serviced has led to many an anecdote Or maybe that just comes from rescuing unloved Minors - they all have their different quirks...

[Kevin]

Its always useful to put a liberal amount of Copper grease on the studs to help stop the corrosion.

[Arfron]

I agree with all that has been said about the various fluids etc . One method we used to use , to help free the cover on the A40's / 1100's / Marinas etc , was to insert a bit of broom handle , or box spaner into the housing and gently wag the bar up and down to help free the unit . It worked about 7/10 times !! Arfron

[bmcecosse]

Lost all the wax - new one on me - first time for everything !