Winter / Summer thermostats

[Shelly Harris]

My MK II brings back memories I had long forgotten. It gets very cold in Chicago winters and I now remember changing out the thermostats in my cars of years ago with the change of seasons. It all came back suddenly when driving my MKII back from the mechanic last week when it was 15 F outside and the car's temp gauge just barely got off the C mark. Frankly I don't even know for sure if there's a thermostat in the engine. During the summer the temp has no trouble getting into the mid-range of the gauge.

Long ago I had an old Volvo which instead of a thermostate change had a chain you'd pull off the dash which would draw up a shade in front of the radiator. If I drive it again this winter I'll cut up a sheet of cardboard and put it in front of the radiator.

[Barry Wolk]

Thermostat change is two bolts, a gasket and some sealant. Cheap peace of mind.

You can test your thermostat on your stove in a pot of hot water. If you do replace it, the original had a bypass built in. I checked mine for operation and reused it.

[depmike38]

Something else to consider if it's not warming completely up is whether or not it ever gets completely off the choke. Might affect the mileage and/or load the plugs.

[Roger Zimmermann]

Long ago I had an old Volvo which instead of a thermostate change had a chain you'd pull off the dash which would draw up a shade in front of the radiator. If I drive it again this winter I'll cut up a sheet of cardboard and put it in front of the radiator.
It's usually a sign that the thermostat is blocked open.
Some cars many decades ago had a similar system than the Volvo; I saw also many cars with a cardboard in front of the radiator...However, the day you have to drive on a long distance at "normal" speed, you may overheat the engine!

[Barry Wolk]

I have a 1977 Lincoln Town car. At 13,000 miles it would overheat. The previous owner replaced the water pump, thinking the rusted impeller was affecting performance. In fact, due to the limited use the car saw, all of the sediments that are normally kept in suspension settled to the bottom of the radiator and solidified, blocking water flow from the lower third of the core.

It baffled me as to why it would run hotter the faster I would go. D'oh!

Now, that's a horizontal core and the Mark II core is vertical, but the passageways can still plug, diminishing flow.

[Nick DeSpirito]

I had a '40 Caddy Limo that had shutters for a thermostat behind the radiator.

I heard that the Mark II thermostat is a 2 step. Is that true, and what do they mean by 2 step?

[Roger Zimmermann]

I heard that the Mark II thermostat is a 2 step. Is that true, and what do they mean by 2 step?
Close and open?:rolleyes:

[Shelly Harris]

To remove the thermostadt should I first drain out the coolant level a couple of inches from the rad. cap level?

[Barry Wolk]

Since water seeks its own level you will need to lower it below the bottom of the thermostat housing.

[Shelly Harris]

Since water seeks its own level you will need to lower it below the bottom of the thermostat housing.


Yes, that's what I meant. I want to check it out as I'm not sure there's one in there.

[CarMan]

My MK II brings back memories I had long forgotten. It gets very cold in Chicago winters and I now remember changing out the thermostats in my cars of years ago with the change of seasons. It all came back suddenly when driving my MKII back from the mechanic last week when it was 15 F outside and the car's temp gauge just barely got off the C mark. Frankly I don't even know for sure if there's a thermostat in the engine. During the summer the temp has no trouble getting into the mid-range of the gauge.

Long ago I had an old Volvo which instead of a thermostate change had a chain you'd pull off the dash which would draw up a shade in front of the radiator. If I drive it again this winter I'll cut up a sheet of cardboard and put it in front of the radiator.

Never restrict the airflow through the radiator. I would imagine you can just use a 195* thermastat and it should be fine. We're talking like we live in the Arctic.

[Shelly Harris]

I know we don't live in the arctic, but when I turn up the inside heat I like it to blow hot.

I pulled the thermostat this afternoon. I placed it in hot water and it opens. Put everything back with fresh coolant. Still can't get the temp into the mid range of the gauge. This was at idle. Streets are too bad to drive around.

[Shelly Harris]

I took to the streets this morning. Highest the temp would go on the gauge was between the C and the beginning of the mid-range. I then cut up a piece of cardboard to place in front of approx. 80% of the radiator. Temp then ran up to a spot about 1/4 into the mid-range and held there.

[Nick DeSpirito]

Well, at least you know you won't overheat in the heat of summer. :D

The needle on my gauge always runs just up the the top of the center bar in the summer. I've been told that's where it's supposed to be. I don't know what it goes to in cold weather because I haven't driven it in the winter.

[Mark_II_Mark]

Over the years I've collected quite a few NORS thermostats for the Mark II, as the attached pics demonstrate. The Flexons are 150 degree & all the rest are 180 degree.

The Continental/Lincoln '56/'57/'58 Chassis Parts Catalog lists the 168-173 degree t'stat for the Mark II & Lincoln and the 157-162 degree, 137-142 degree, & 177-182 degree for Lincoln only vehicles. Since the engines were basically the same, it's anybodys guess why there was such a wide variety of temp ranges.

I suspect that the deeper thermostats are designed to function with the bypass feature of the engine while the shallower t'stats completely bypass the bypass, so to speak.

More piss-poor FoMoCo engineering & design? Quite possibly...

[Don Henschel]

I took to the streets this morning. Highest the temp would go on the gauge was between the C and the beginning of the mid-range. I then cut up a piece of cardboard to place in front of approx. 80% of the radiator. Temp then ran up to a spot about 1/4 into the mid-range and held there.

Make sure the hole in the cardboard is centered with your fan so it doesnt cause the blades to pull on one side. This causes needless stress on your water pump bearing. You should have used a thermometer to see what temperature your thermostat opens. I push the valve slightly open with my fingers and poke in a thin piece of wire, release so it's pinched in the valve, and hang the thermostat in a pot of water.Do not let it or the thermometer touch the bottom of the pot and watch as the water heats up. When the thermostat opens it will release the wire and drop. A 180 degree thermostat is good for all year. Make sure you observe the toward rad marking on the thermostat so it's not installed backwards.

[Shelly Harris]

Good advice. Wish I had it before I buttoned everything up. I had no idea that a thermostat had a "towards Rad." indication... it looked completely circular to me. Seems to be operating ok.

[Don Henschel]

Towards rad or towards engine is usually marked on them. These thermostats operate with wax. When the wax gets hot it melts and expands pushing the thermostat open. If this contained wax is on the cooler radiator side, it will take way too long to open, resulting in an engine with eratic cooling behavior.
When I install a thermostat I take a peice of wire or string, tie the wire to the thermostat, pass it through the thermostat housing, and tie to a pencil to keep the thermostat centered and snug in the housing so it cant drop out of place and get pinched when you bolt the housing on. This will save you a cracked (and very hard to find) housing.

[Mark_II_Mark]

Famous last words of a Mark II owner: "Seems to be operating ok". Shelly, FYI, read the manuals & examine all parts closely prior to installation for those pesky little "clues". Somewhat like the thermostat, the oil pressure sending unit is marked with an "up" & directional arrow symbol for installation. Why, PPP (piss-poor planning) or better yet, ask Wm. Clay.

I've always found that the best way to learn from one's mistakes is a simple redo. Since you weather is crappy & your Mark II is going nowhere fast until the spring thaw, remove the thermostat & check to see if you were lucky enough to get it right inadvertently the 1st time. At least if you reinstall the thermostat correctly a 2nd time, you'll know for sure. If not, Murphy's Law will most assuredly pay you a visit at the most inopportune time, IMHO...

[Don Henschel]

As for removing the thermostat again, if your thermostat is not stuck open, it's probably installed right. If backwards, the engine will run very, very hot untill the heat reaches the wax compartment on the other side, then will cool down very fast, and then this cycle will repeat over and over. I have run into this in the past with complaints from the customers of eratic cooling temperature. I dont worry about mine running cold because I don't run mine at all in winter. Cardboard sounds funny but works. Up here we call it a Saskatchewan thermostat;)