Overheating

[GregDeK]

Question…

I have a 15 roadster that cools via thermosiphon. Worked beautifully, stayed right at the midpoint on the motometer. It recently started misbehaving. Pegged out on a 3-4 mile run. When I got back, I noticed the fan was not turning. It was a recent restoration and while the fan had grease put into it when it was reassembled, it did not have the accumulation of many years. I never thought of twisting the grease cup. Fixed that. Went on a ride today. Overheated again, although it stayed right below the top of the meter.

The car is new to me. I got it in late March, drove it in the spring and early summer. Temps were lower then. This afternoon the temp was 91 and it was probably 94°-95° when it pegged out the first time.

Question is, is my overheating due to the hot temperatures or is it something else? Has anyone else had a similar experience?

[Jerry VanOoteghem]

Is your fan now turning completely free? How tight is your fan belt? Maybe consider buying a ball bearing fan hub.

[Kerry]

Overheating is when steam is blowing out, the monometer nearly up to the top on a hot day is normal on older condition radiator.

[Norman Kling]

Many things can can cause overheating. One of course, is whether the air can go through the radiator. If it is idling or fast idling, especially if the fan is not turning can heat it up quickly. Another thing can be caused by clogged water passages in the radiator which would need to be boiled out or rodded out. Note to rod the radiator the tanks must be unsoldered and would be more expensive than boiling but would work better if they are severely clogged. An old radiator sometimes the cross fins which are cooled by the air rushing through will have corroded where they are connected to the tubes. In that case you would be better off with a new core or a new radiator, which is quite expensive. The next possible cause would be rust and sediment deposits in the block and head which must be cleaned. many times they can be cleared by removing the head and running a snake into all the water passages in the block and head and then thoroughly flushed out and blown out with compressed air. Also look for cracks in the head or block, especially those around the valve heads which can cause exhaust to go up into the water jacket.
Also climbing a steep hill at low speed can cause it to get hotter than usual. If the steam is not coming out the radiator overflow or around the radiator cap you are very likely normal in hot weather. Just be careful not to let the motometer go all the way up. Many of them will stick up and not be able to shake down so it will need to be relplaced. A small leak somewhere, especially in areas near the front and back corners of the engine near the manifold can cause a slight seepage of coolant which might not be detectged, so before you drive be sure to check the coolant level and if you stop for a while such as when you stop to see a viewpoint or go to eat, after it cools off check the level again. It should be no lower than the middle of the upper tank. Some will go out the overflow as the fluid expands with heat, so it is normal to drop a bit after driving. One more thing. If you have been driving hard on a hot day and then turn off the engine, it is normal to gurgle a bit for a minute or two. So check the Motometer while the engine is running but not after you park.
Norm

[John kuehn]

Do you know the history of the radiator? Did the former owner have it cleaned? If it’s the original radiator after many years they can still look good but not cool as it should. Nearly all Model T’s eventually will have their radiators replaced. It may just have a fan issue it it very well could be. Good luck.

[speedytinc]

Drain enough coolant to see the tops of the tubes.
They can be partially clogged with calcium build up or rust flakes from the motor.

[Erik Johnson]

Retarded spark can cause overheating. Make sure the timer is set-up correctly.

A lean fuel mixture can cause overheating. If the car starts to run hot, richen the mixture.

Make sure the oil-level in the crankcase is above the lower petcock. Always check the oil level before venturing out.

[TWrenn]

Do you know the history of the radiator? Did the former owner have it cleaned? If it’s the original radiator after many years they can still look good but not cool as it should. Nearly all Model T’s eventually will have their radiators replaced. It may just have a fan issue it it very well could be. Good luck.

I'd have the radiator checked out...obviously here we don't know it's age, condition, round tube, flat tube....blah blah

Dean Yoder, who is no doubt THE most traveled Model T'er on earth next to Constantine, doesn't even USE the fan on his! Yep, I seen it with my own eyes! And it's amazing how richening the carb will pull down the temp too. Not tons of course, but enough to get ya by!

[Drkbp]

Easy check on your radiator, timing and fuel settings......
See what the temperature of your coolant really is. You can do that running at idle in your driveway.
Never had a Motormeter but you're probably fine. The car is designed to run near 200 degrees.

I run 50/50 antifreeze in my July 1913 engine and used a kitchen thermometer that I have checked on the
stove. A "boiling water" on the stove point showed well beyond my "in radiator" temps.
Ran it, starting from cool, sitting in my driveway for an hour. Just don't set it up with a "tailwind" because
the radiator/engine needs the fan at "idle" and very slow speed. As others have said, fan not needed at speed.
Ran a little cooler with the hood closed.

This was done years ago at 70 degrees ambient but the car just doesn't boil, even today at 90+ in Houston.
It will "glurk" once or twice when I come back from a drive but that's it. No loss of coolant.

[GregDeK]

Thanks also to the ones who posted recently. I generally keep the spark advanced about 2/3rds. I will try adjusting the carb. Seems I did that yesterday but she started to miss a bit. Will try again to be sure. I generally don’t adjust the mixture, I leave it the same from start to stop. That could be part of the issue. Thx !

[TWrenn]

Thanks also to the ones who posted recently. I generally keep the spark advanced about 2/3rds. I will try adjusting the carb. Seems I did that yesterday but she started to miss a bit. Will try again to be sure. I generally don’t adjust the mixture, I leave it the same from start to stop. That could be part of the issue. Thx !

I forgot to mention above to maybe give your radiator the "4 second test"....You can do it with radiator in the car, but it's also a bit easier believe it or not out of the car. I've done it both ways.

1. Drain the system...retain your antifreeze assuming it's pretty good.
2. Disconnect top and bottom hoses from the RADIATOR. Not the engine...if you leave radiator in the car.
3. CAP said openings on the radiator...I use No-Hub fittings on mine.
4. Fill the radiator with plain ol' water, all the way to the top.
5. Here's where having it out of the car is a bit easier...but, grab the bottom cap you attached and start counting, or of course to get technical you could have a 2nd. person use a stop watch. Point is, a perfectly GOOD radiator will evacuate basically completely (there'll be a little "residue water left") in 4 SECONDS. 6 Seconds, your radiator is fairly good. 7 seconds, you better be planning on maybe having it boiled out. Anything over, it's junk. Trust me, after replacing 4 of 6 radiators, including brass, this works.

Now, go test it!!

[Steve Jelf]

There are many approaches to an overheating Model T. Some of them will help for awhile, but are ultimately futile due to the passage of time. Over the course of a century the fins of a radiator can work loose from the tubes, so they no longer radiate as they should. The only true cure is replacement, which can be done three ways. You can gamble on a used radiator, but that brings up an important question: Why isn't it still on a car? The second choice is to buy a new radiator. A third choice is to have an original radiator recored. If you can find a qualified radiator shop, this will do the job and save you several hundred dollars. Looking at brass era Fords at the Old Car Fesitval, you will see that buying new is the most popular choice. At one recent OCF I found that my 1915 and one other brass era Ford had obvious recores. All the other brass era radiators were new. If I had the choice again I would go with the recore. The only problem I ever had with mine was a leak at the overflow tube. An old radiator guy knew what to do, and I was back to driving the same day.

https://dauntlessgeezer.com/DG96.html

Leak at the overflow tube.

He had me back on the road PDQ.

[Erik Johnson]

Even though you keep the spark lever advanced 2/3 of the way when driving, you should still check to see if the timer is set up correctly.

There are a lot of threads on the forum regarding setting the ignition timing when installing a timer.

[Jerry VanOoteghem]

Even though you keep the spark lever advanced 2/3 of the way when driving, you should still check to see if the timer is set up correctly.

There are a lot of threads on the forum regarding setting the ignition timing when installing a timer.

Erik makes a good point. There is no "correct position" for the spark lever judging simply by how far down it is. These cars have been adjusted, tinkered with, and had aftermarket parts installed for 100 years, making timing by "position only" very inaccurate. Setting the proper timing, (15 degrees past TDC, with spark fully retarded), is a good starting point. Then, advancing until the engine seems to give the best acceleration/power is where to run it while going down the road, with further adjustments made for hill climbing, etc.

[Norman Kling]

Be careful if you order a radiator on line to be delivered by one of the delivery companies. Many years ago I ordered a brand new radiator for a Model A and when it arrived it had a hole punched in it. If you live anywhere near or even within 100 miles it is better to travel in person to pick up a new radiator. A re-core can be done by a good local radiator shop if they can obtain the right core for it.
Norm

[TWrenn]

Brassworks really packs a radiator well. Literally surrounded by that expanding foam stuff within plastic bag material to keep it from infiltrating the fins. Likely no better way to pack a rad. But if within a day's drive I totally agree with Norm.