Cold weather driving with or without thermostat?
 

Just finished buttoning up my Fordor after putting in a new engine and would like to put some miles on it before putting it away for the winter.

I have a 160 degree thermostat that goes in the upper radiator hose but took it out last year seeing no benefit during summer driving.

Now that it's cold (and going to get much colder) I imagine that the t-stat would become more beneficial. My only concern is that since it's located in the top of the upper hose (instead of the head like a modern car) and the air temps are very cold, it could take too long to open or not open at all thus causing more damage than running too cold.

I'm probably overthinking this. My gut says it'll probably be fine either way but I'd like to hear from people with firsthand experience. Thanks.

Re: Cold weather driving with or without thermostat?
 

Run a thermostat ALL the time. Live in the mountains of Arizona. We probably do not get as cold as you in the winter, but the A warms up faster with the thermostat and runs better when warm.

Re: Cold weather driving with or without thermostat?
 

If you have an upper coolant neck temp gauge, could partially block the radiator with a piece of cardboard.

Re: Cold weather driving with or without thermostat?
 

I did think about using a piece of cardboard but I only have a motometer which is to say I really have nothing :D. I think I'll put in the thermostat and try it out.

Re: Cold weather driving with or without thermostat?
 

Partially blocking the radiator with something (cardboard, thin pressboard, etc.) is the way to go. Block about 1/2 of it. If it seems to run too hot, trim it down to only block the bottom 1/3rd. Don't over think it. It will be fine.

When you block the radiator, it allows coolant to circulate well through the block while the engine warms up, to help keep the temperatures in the block more uniform. It will take longer for everything to get fully warmed up, but eventually it will get there.

A closed thermostat in the upper hose really stops coolant from moving in the engine block. Those small vent holes that they have added to the thermostat do not let much coolant flow through the block while it is warming up, so the water is stagnant while heating up. This puts a lot of thermal stress on the block, head, and head gasket.

Then the thermostat opens and a rush of cold water comes into the hot block from the radiator. More thermal stress. The warm water hits the thermostat and it partially closes again. You get these cycles of hot and cold water in the block until the coolant temperature is stable in the block and the radiator (similar to the partially covered radiator).

If you really want to use a thermostat, you need to add a bypass hose between the upper outlet hose, on the engine side of the thermostat, and the water inlet on the side of the engine. I used a 5/8" heater hose. This lets coolant circulate through the block while it warms up with the thermostat closed.

Once the thermostat starts to open, some of the hot water goes into the radiator, but most of it goes back in the inlet side of the engine. The engine warm up is fairly fast and very smooth -- no big temperature swings up and down. Much less thermal stress.

I have a temperature gauge installed in the water outlet and I can watch the coolant temperature go up nice and smoothly.

Re: Cold weather driving with or without thermostat?
 

Hi Jim,
Any chance you can post a picture of your motor showing the above? Am considering converting my A to thermostat next year once my cooling issues are resolved.


Thanks

Re: Cold weather driving with or without thermostat?
 

Sure, but it will be a while.

Out of town.

.

Re: Cold weather driving with or without thermostat?
 

Well Jim, you just confirmed everything I've been thinking and brought up some other important info. I had thought about the thermal shock when the thermostat opened but not the stress on the engine due to no coolant flow before it opens.

I do like the cardboard idea, follows the kiss principle nicely. Planning to take it out tomorrow for thanksgiving. Supposed to be a high of 17 in our area :eek:

Re: Cold weather driving with or without thermostat?
 

I initially put a thermostat at the top of the radiator hose and as you fear, it was slow to or did not open. Moved it to the bottom of the hose, hold it in place with a hose clamp and it works fine. The stat opens gradually as the water heats up.

Re: Cold weather driving with or without thermostat?
 

Yes, getting the thermostat as close to the engine as possible really helps it open before the engine gets too hot. But the coolant is still stagnant in the block until the thermostat does open, which I don't think is good for the engine. (Modern engines have bypassed the thermostat like this since they were introduced in the mid- to late-30s.) . :cool:

I'm sure there are many dozens of guys that have driven thousands of miles with the thermostat near the block and with no bypass hose, and had no problem. They are lucky. I'll bet there are others that have experienced head gasket failure and never thought that it might be caused by that thermostat... :eek:

YMMV.

:D

Re: Cold weather driving with or without thermostat?
 

I would agree that if you use a thermostat you should also use a bypass hose. Like Jim said, thats the way auto makers have done it since they started using thermostats and theres a reason they do it that way.

Re: Cold weather driving with or without thermostat?
 

I run a 180 thermostat all year. I drilled a hole in it to allow a small bypass during warm-up. It really wasn't necessary, if you put your thermostat in a pan of water and watch it as it heats it does open slowly. I used to use the cardboard trick but it was hard to regulate.

Re: Cold weather driving with or without thermostat?
 

I run a 160 deg T'stat in one of my cars and a 180 deg in another. With both, especially the 180, I have noticed the temperature swings Jim mentioned even though I have drilled another 2 X 1/8" holes in it. I see the sense in the bypass hose but I like to keep my engine bay looking resonably original. The T'stat is invisible and the hose not so I wonder about drilling more holes in it.
Your thoughts?

Re: Cold weather driving with or without thermostat?
 

Synchro, Jim says he uses a 5/8" heater hose as a bypass so if you drill 3 more 1/8" holes you would have the equivalent of one 5/8" hole.

How well this works in practice is another matter but it would be interesting to see.

Re: Cold weather driving with or without thermostat?
 

Would the swings in temperature of water be relative to the ambient air temp. which affects the start up water temp? Maybe not so much swing in Florida winter weather and more swing in say a Main winter. Just asking!

Re: Cold weather driving with or without thermostat?
 

https://vintageprecision.com/product...ing/index.html

Jim, purchased one of these. Could you run a hose out of one of the lower plugs?
Have been using cardboard but not the best in cold rain,snow.

Re: Cold weather driving with or without thermostat?
 

Ryan, I now have 3X 1/8 holes. I am wondering about significantly more, maybe 6, 8 or maybe 10. I doubt I would ever end up with as much bypass this way as Jim's 5/8 hose. For that, I'd need 25 X 1/8" holes. There would not be much T'stat left if I did that!:rolleyes:

Re: Cold weather driving with or without thermostat?
 

Re: Cold weather driving with or without thermostat?
 

Re: Cold weather driving with or without thermostat?
 

Riiiight 5x diameter does not equal 5x surface area :o