Technical Thermostat flap replacement

[Dorisinblue]

The thermostat flap mechanism on my 500F collapsed so I have bought a new replacement/repair kit.
I am now struggling to understand how the spring on the rod is tensioned, I think it should keep the flap closed when cold and the
Thermostat opens against the tension when hot but can’t seem to get the spring positioned to achieve this.
Any advice or a photo would be appreciated

 

[Toshi 975]

Have you got the remains of the original flap to compare as there are two different styles for the 500 and the 126.

 

[GrahamH2]

The thermostat flap mechanism on my 500F collapsed so I have bought a new replacement/repair kit.
I am now struggling to understand how the spring on the rod is tensioned, I think it should keep the flap closed when cold and the
Thermostat opens against the tension when hot but can’t seem to get the spring positioned to achieve this.
Any advice or a photo would be appreciated

The thermostat internals were missing from my car so I also bought a kit. It is a puzzle as there seems to be two configurations of the mechanism and the (AutoBella) kit has parts for both but I eventually worked it out. I hope the pictures help.

 

[grubscrew]

Here’s a pic if it helps.
The spring has a slight force on keeping it closed. The stat overrides that when hot…..or at least it should

 

[Dorisinblue]

Thanks all. Yes I have the correct replacement flap, it’s just the spring which appears to be wound the wrong way. It’s interesting to see how Graham has assembled the mechanism with the spring inside the air box. My thoughts were it was originally outside on the rod - the straight part of spring sits in a small recess on the air box and the angled part fits into the triangle of metal which fits as a cam on the rod . All held in place by a nut. This should keep the flap shut when cold.
Anyway, I’ve now found another spring lurking in my-bits and bobs box and it seems to do the job so I’ll refit the air box and see how it goes!
Thanks for your photos- a great help!

 

[GrahamH2]

Thanks all. Yes I have the correct replacement flap, it’s just the spring which appears to be wound the wrong way. It’s interesting to see how Graham has assembled the mechanism with the spring inside the air box. My thoughts were it was originally outside on the rod - the straight part of spring sits in a small recess on the air box and the angled part fits into the triangle of metal which fits as a cam on the rod . All held in place by a nut. This should keep the flap shut when cold.
Anyway, I’ve now found another spring lurking in my-bits and bobs box and it seems to do the job so I’ll refit the air box and see how it goes!
Thanks for your photos- a great help!

My car is the 500R which has the spring inside the air box; I believe the earlier cars had an external spring. In my kit of parts there were also some items that would suit an external spring and it was a confusing until I realised there were two different configurations. A top tip is to search on Ebay as often sellers have good pictures which can help to identify what and where things go. It was an Ebay listing that showed me how to assemble the thermostat device.

 

[ciccio500]

Hi all, sorry to hijack another thread, but I figured it's kind of the same subject. My 500L doesn't have a thermostat, or the flap at the bottom of the thermostat housing. It's my understanding that people removed them in southern Italy due to the heat. Would driving the car without this set up be massively detrimental? Apart from not running great when cold?

 

[Noah500]

Someone else will no doubt be along soon but when I got my car the thermostat itself was missing, though the flap was still in place I would think that starting up and the first few minutes running in cold weather wouldn't be great but I can't imagine any actual damage being done. Since you're in the UK I think it would be a good idea to get a thermostat, flap and fixings... Good luck!

 

[ciccio500]

Someone else will no doubt be along soon but when I got my car the thermostat itself was missing, though the flap was still in place I would think that starting up and the first few minutes running in cold weather wouldn't be great but I can't imagine any actual damage being done. Since you're in the UK I think it would be a good idea to get a thermostat, flap and fixings... Good luck!

Thanks Noah,

I only drive it when the weather is good, it doesn't leave the garage in the winter. I was more worried about overheating, as I'm sure I've read somewhere that bizarrely this can happen? A couple of years ago it had to have a top up engine rebuild as one of the pistons fried. I was told it was something to do with the carb, making it run lean, but I'm wondering if the lack of thermostat could've contributed.

Fran.

 

[giardini]

Hi all, sorry to hijack another thread, but I figured it's kind of the same subject. My 500L doesn't have a thermostat, or the flap at the bottom of the thermostat housing. It's my understanding that people removed them in southern Italy due to the heat. Would driving the car without this set up be massively detrimental? Apart from not running great when cold?

I'm fairly sure that running a cold engine with an open / missing flap, and running it with a closed flap AND the cabin heat duct open (which no one would
think twice about) both have the same effect on temperature. I think the function of the thermostat flap is to provide cabin heat / defrost as soon as it's
available (or in cold weather), and has nothing to do with managing cold engine temperature. On the other hand, combining a closed cabin heat duct and a (stuck) closed thermostat flap in warm weather would be asking for trouble. That would explain your observation about the southern Italians' reputation
for removing / disabling the flap.

 

[Noah500]

Yes... in cold weather, even with functioning thermostat and flap installed, I find that if the cabin heat duct is open then the engine takes longer to get up to working temperature and struggles a bit, particularly under acceleration, so I usually have no heating for a couple of miles until the engine's warmer.

 

[ciccio500]

Thanks both. As I said she doesn't see the light of day from October to April normally other than to turn her over regular and move back and forth to stop the tyres from squaring off or the brakes seizing. But with this freak mini heatwave we've just had this weekend she was out and about as normal. So I don't really have any use for the cabin heating, that is always shut. I've got all the replaceable parts for the thermostat and the housing flap, but if it's wasted time and energy, I might just focus on other bits.

 

[The Panda Nut]

The thermostat flap mechanism on my 500F collapsed so I have bought a new replacement/repair kit.
I am now struggling to understand how the spring on the rod is tensioned, I think it should keep the flap closed when cold and the
Thermostat opens against the tension when hot but can’t seem to get the spring positioned to achieve this.
Any advice or a photo would be appreciated

LOOK AT WHEELER DEALERS. The epuode on the Fiat 600 covered this nice and clearly. Quest on demand I think.