VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Over Heating engine 38

I have always run a 160 Deg. In the hot weater they will run above that, usually about 180 Deg. or so. There is no reason to run over 180 Deg. in the old engines in cars that are not driven in cold weather.

old 216

I found the Thermostat specifications from my 1941 Chevy shop manual.
For a 180 degree thermostat, it should begin to open at 180 degrees and be fully open at 195 degrees F. I tested two brand new plus my original bellows thermostat. All worked to specification but the old bellows type allowed for more coolant flow and was much more responsive to temperature change. It also had a small hole as a bypass to aid in warming up the engine. I installed the bellows thermostat.

Charlie;

I mis-spoke It is a 180 degree thermostat. But specified to be fully open at 195 degrees which it does. The water pump is the last easy and relative inexpensive thing that I can change. I would have liked to known that it works properly.

Bert

A '38 thermostat should start to open @ 140 - 145 deg. 38 Chevy Spec. I run a 160 in mine. Plenty of heat in the winter and now that the engine is broken in no over heating in the summer. I don't get it out on truly hot days but on warm days ~80-85 deg. it'll run @ the 180 mark & up to about 190 when slowing to town speeds after being on the highway. 70 deg. & below it never gets over 160 when moving.

I hope that none of you are under the false notion that I've promoted the idea of running a 190-195 degree thermostat. While that has not been laid at my door specifically, I do sense "tings."

Let me explain myself. Some time ago I read that in order for motor oil to be at its most efficient is should reach a temperature of 190 or so. I don't know how that meshes with multi-grades. Maybe Chipper could weigh in on this question.

I run a 180 degree thermostat. It serves quite well with no overheating or any symptoms of overheating. The top tank stays at about 1/3 to 1/2 full. The needle stays around 180 most of the time. A little hotter at prolonged idle and a little cooler going down the road on the "sweet spot", i.e., 40 MPH.

I think the 140 and 160 degree thermostat are a bit too cool but believe that is just my own way of thinking. I have no evidence that those temperatures are harmful. To each its own.

Just wanted to clear the air that I am not an advocate for no stinkin 190 degree thermostat.

Charlie

My actual choice would be a 170 but they have not made them for about 50 years.
This summer when I do a cooling system flush on the '50 and '57 I am going to try 180's.
My '50 had the original 180 Deg. thermostat in it (was dated bellows type) ( a 180 came with a heater). I put the 160 in years ago.

Charlie;

The specification that you posted is great. It shows that the thermostat is a 160 degree bellows type. I will change mine to a 160 degree and see what happens.

Thanks; Bert

my 38 runs at 180 according to temp gauge, but quickly rises if i idle for long. The temp around here has been around 100 degrees. Is that normal or should i be concerned.
Mike

There is not enough air or coolant flow through the radiator at idle to cool at 100 deg. ambient. I would not be concerned unless you begin to loose a lot of coolant.

thank you, she seems ok.

took my wife for a spin in our 38 town sedan today with the outside temp floating around 87 degrees. I must have a 180 thermostat because thats what she warms up to. After driving a bit in very slow traffic the temp sat at 212, when I started rolling about 40 mph the temp went to around 200. Any thoughts?
Michael
PS. I have been considering an electric fan, but prior conversations lead me to believe there is a problem with my cooling system.

I would be disconnecting both radiator hoses and reverse flushing (water and air pressure bursts into the bottom hose). Also remove the thermostat and water and air bursts in through to water pump inlet. You can also test thermostat by dunking it fully into suitable container of water with a thermometer and heating, note at what temp it starts to open and when fully open. Most thermostats have a stamp stating fully open temp.
Tony

Given that the narrowest place coolant must pass trhough in the cooling system. I would consider the flues in the radiator are partially stopped up. Accordingly, I would look at the following in this order:

A. Radiator. A proper reverse flush may do the trick. You can take the hoses off and use a blower chuck on your air hose and blow back up throught the flues from the bootom hose outlet. A good chuck made for this purpose is a "kalamazoo." Fill the radiator and then let the water rush out the bottom outlet. It should rush out rapidly and have no sucking noise at the top.

b. Test for a headgasket, craled jead pr block by removing the thermostat, replacing the housing and then filling up with water to the top of the housing. Trip the fan belt. Crank the engine and look for bubbles. There should be none. If so and the bubbles are small then it may be a cracked head or block. If they are large and the wateer is more rapidly stirred or forced out then it is likely just a blown head gasket. Peice of cake.

c. Plugged block. Reverse flush it from the petcock at the left rear of the block. Fishing for rust may help some also.

d. Calapsing bottom hose. Not too likely but it should not colaspe. Might need a new hose. If the elbow has been eleminated, get a hose with a wire in it.

e. Bad thermostat. Not likely but does happen.

f. Bad temperture gage or sending unit. Stick a thermometer in the radiator filler and see what the actural temp is.

You'll notice that I didn't mention the water pump. Unless it is leaking, forgedabouit. (NY/NJ speak)

Go in the above order with the exception that you may want to reverse the order on the reverse flush and the Æ’ill up and release test, and you will likely discover the culprit.

Mext time leave the missus at home. Bad things only happen when they are along for the ride to the DQ.

Good luck,
Charlie

Safe to assume that something is amiss?
-In a healthy system what temp would I expect to see
=ambient temp-around 90 degrees
=idling-around 5 minutes

I have no idea as to why, when an engine is running hot, the thermostat rating is blamed. All the thermostat is there for, is to help raise the coolant to the most efficient operating temperature to support good combustion or to slow coolant flow in frigid weather to raise the temperature. Once it's open, the coolant is circulating at it's designated speed to allow the engine temperature to be maintained, IF the rest of the system is in order. The rating of the thermostat allows it to open sooner or later, not too control too high of a temperature.

First make sure the thermostat is opening correctly, the engine coolant passages aren't blocked, the radiator hoses aren't collapsing, and the radiator flow is unimpeded. If a radiator shroud was part of the original design, make sure it's in place, too.

The problem also is the younger guys are accustom to modern cars where the temp. seldom rises above normal.
On "old" cars there will be increase in the temp. reading on the gauge depending on operating conditions and ambient temp.
Years ago it would have been common for a radiator to overheat and the radiator require additional water in hot weather.
It also takes a little knowledg on the part of the driver to keep things cooled down such as increasing the idle speed when car is standing still and even driving in 2nd gear if traffic is going along under 20 MPH. and it is 90 Deg. in the shade.

Retarded timing will also contribute to overheating. My 32 would overheat on a long uphill pull or if idling more than 3-4 minutes. Down the road at 35 MPH I could drive all day with no problems. Use a heat gun and check the radiator at the top and bottom and note the temp drop. Not sure what it should be on a 38 but mine was about 40-50 degrees. If you have a significant drop then the cooling system is working OK. Retarded timing allows the fuel mixture to burn low into the cylinders and causes increased temperature transferred to the cooling system and lower power. With lower power the tendency is to increase throttle opening and that simply increases the problem. If you know the radiator is clean, the water pump is working, and the thermostat is opening and you still have a problem then try increasing timing advance until the engine pings and then just back it off to where it stops.

You didn't say that the water was boiling out and blowing all over the car. If your engine is newly rebuilt it will run hot until the rings smooth out the cylinder walls, this is normal. Make sure when you fill the radiator that you allow enough thime for the water to completely fill the block, if there's an air pocket in the block or head then you will boil the water and it will erupt out the radiator. You don't need a thermostat but if you want one be sure to use the 180 style, gasoline engines run best at 180-190 degrees. As long as the water is not blowing our the top of the radiator then you don't have an "overheating" problem. Normally the water level will be a couple inches below the overflow tube. You have to put at least 2000 miles on the engine before it really starts to develop it's power and run cooler. I know this from many years experience, I didn't read it somewhere.

In my case the engine is not fresh, I bought my 38 Town Sedan from Texas a couple of year ago and do not know the history except she was supposedly had a mediocre restoration 20 years earlier. My 38 is not boiling over or giving any indication of overheating except the temp gauge floating in the 212 range while idling, but moves toward 180 once rolling

If the engine has been bored out you may have thin cylinder walls. What size are the pistons? I'd use another temp gauge or use a laser temp gauge to very it's accuracy.

Does your temperature continue to drop after extended driving with good air flow?

If not I would suspect the radiator as mentioned before. I took mine (39) out when I was having similar problems and it tested fine for flow. Back in it went and overheating continued. I did all that was mention above and still only slight improvement.

In the end it was the radiator core, I replaced it and have had no problems since.

Dave

If you are in SoCal there was a good shop that did mine in Azusa, I can't think of the name but Carmine in the SFV region will know.

My temp does go toward 180 when cruising along. I live in East Bay San fran Bay Area. Starting to cool down already so won't be as much of an issue until next summer. I only got her on the road this summer so I don't really know what normal operation is but comparing to modern cars I get nervous when the temp gauge moves to the right.

mike
my all stock 39 with the og 216 runs no higher than 180 and that`s all the way to 101 degree heat in traffic going in a show.
39 is all stock, 16`s, not lowered , none of the "other" stuff guys do down here with cars, my 39 runs nice and cool
""" (k o wood) no problems last 10 years i have owned it
hope you figure your issue out

Good to know, mine is all over the place. I don't want to take her out even in 90 degree weather. This will be a winter project getting the cooling system straightened out.
Thanks
Mike

Just a note.

Remember that the engine is not like a hot blooded animal. Heat is entirely a different thing when considering what's too hot. It's metal. The engine is comfortable at higher temps than you would think.

Up to a limit, merely consider that the first issue is whether the engine will boil or not owing to the atmospheric pressure on the coolant and then eject the coolent to a point where it is not circulating any more.

As long as there is coolant in and around the engine head and block there is not going to be much damage. Just don't pour cold water in. At least if you're not sure if it's cooled down enough, run the engine whilst adding coolant slowly.

I know you all know this. I'm just not happy unless I can type something once in a while.

Best,
Charlie