26 Coupe Overheating

[dunoon]

I took my coupe out this afternoon for a spin. haven't driven it much since it was finished late last fall just a couple miles from home. It overheated once a few weeks ago found the fan belt had came off. Today took her for a longer spin about 6 miles everything was fine temp was good till about a mile from home then saw the thermometer was all the way up. Figured the belt came of, checked it ws still on, figured I might have ran out of water, when cooled checked level was about an inch above the tank bottom. When I was driving her daily about 59 years ago never had an overheating problem except when I drove it in a parade. When restoring I had the radiator cleaned and checked out. So Im at a loss what going on. any suggestions would be greatly appreciated.

[Norman Kling]

Even though the radiator has been boiled out, a couple things can cause over heating. One would be the attachment of the cross fins to the tubes has corroded and there is not a good transfer of heat from the tubes to the fins. The air actually blows through the fins to cool the fins and as the water heats the fins the heat is dissipated. The other problem is rust and hard water deposits inside the block and head. This happens especially when water without rust inhibitor sets in the engine for many years. Unfortunately, the best way to correct this problem is to pull off the head and run a snake through all the passages and thoroughly blow out the particles and wash down with water. Important to clean out all the passages including the "steam vents" which are small holes about 1/4 inches in the corners of the block and between the cylinders. Then put on a new gasket and hope it works. You might need to buy a new radiator.\
Norm

[TWrenn]

I'm voting for either a re-core or a replacement. If you replace, be sure to get a flat tube radiator.

It also wouldn't hurt to pull the head and make sure all the tiny holes in it and the block aren't plugged up. It happens.

[TXGOAT2]

If you aren't getting actual boilover, it could be that the gauge is not working correctly. It's normal for
a Model T to run close to the boiling point of water. It should not boil over, though, at least not under any ordinary operating situation. I'd also check for dragging emergency brakes and/or dragging transmission bands. If you definitely have a cooling system issue, removing the radiator hoses and flushing the block and radiator with a garden hose may improve the situation. If nothing else, it will give you an indication of whether or not you have a lot of debris in your cooling system. Applying a strong garden hose stream to the lower radiator outlet and using a rag or sponge as a gasket to cause reverse flow through the radiator can often dislodge debris that has collected on the upper header plate and in the upper ends of the radiator tubes.

[bron-hertford-nc]

From yesterday - at friends house to adjust his bands . Complains about overheating previous weekend. We finish - says let's ride down the street. Starts right up, switches to mag, brings spark lever down and seems satisfied - I just reach over and take it halfway down - what a difference. He was driving as if he was on battery . A little explanation about finding the mag sweet spot I think will take care of hos overheating issue.
Good Luck

[George Mills]

More than a few Model T want to run at 195 degrees or so with all being good. That doesn't leave enough for any small things to happen.

1- Let it steam out the overflow and cool, if the top of the tube plate is still covered by 1/2" or so, you be good on the 'how much' part. (sounds like you did this)

2- Make sure your tires are inflated proper. Underflated tires can add a few degrees to what is going on.

3- While idling, open the needle valve on carb by 1/8 turns at a time 15 seconds apart until the first hint of a bog down/skip. Go the other way 1/8 turn...thats your sweet spot and every car has one. Too lean makes things get hotter than expected.

4- Watch your spark under load. Some will tell you doesn't matter, just pull if down to 7 o'clock and leave it for all conditions, others will tell you that each speed/condition needs a different setting. Yours may want adjustment.

It's all a balancing act on those variables. If you have a machine that wants to run at 195 or so (I use a meat thermometer in the neck) then you have to pay attention to the variables...

If you have one that wants to run at 185, then you have more room on being sloppy with settings...

Might want to get a grill radar thermometer...they are pretty cheap now. Shoot the top tank at bottom, shoot the lower tank, there should be a 5-10 degree change between the two. If they are equal, you probably should look into a recore...or call Bergs for a new one. Try the settings thing first...it's cheaper

[speedytinc]

Drain the radiator down enough to look & the top of the tubes. You can see a few. Look for rust chunks blocking the flow & if its still clean inside. If some tubes are obstructed, pull & back flush up side down with your garden hose.

[dunoon]

I'm beginning to wonder if it might bee the fan, maybe when it gets hot the fan starts to seize, when the belt came off the fan belt was pretty tight and this time it was a lot looser. I'm going to run it with the hood off so I can see the fan while I'm driving and see if the fan stops when it overheats. If the fan is OK then I'll flush out the engine.

[John kuehn]

When a T starts getting overheating issues two things are usually the reason and in no paticular order.
The radiator and the water circulation in the block.

If the head hasent been off the engine for many years it’s time to remove it and clean out the small passageways in the head and especially in the block. Those small holes in the block need to be cleaned out and if they aren’t your engine won’t cool well.
Then there is the radiator. Original radiators do eventually get to the point that they won’t dissipate the heat. They may look good but that can fool you. A new or recored radiator can make a big difference.

[dunoon]

It ain't the fan, I got the car boiling and the fan was free. So I guess I'll try flushing the engine and the radiator. I was at an auto show yesterday and a guy with a 16 T suggested trying Water-Wetter has any one used it? Also what flush do youse use, was thinking of using something, instead of just water. All suggestions are very welcome.

[TXGOAT2]

If you're sure it's actually overheating, I would try flushing it. I'd use plain water in an old radiator. A chemical cleaner may cause it to leak.

[DickC]

I had the same problem with a 1924 touring. I could not figure out the cause after cleaning the radiator and the block. I ended up buying a new square tube radiator. When taking the old radiator off, I turned it over and heard a rattle sound. Turns out the baffle in the top tank let go and rested on the top of the core. The result was no circulation. Was it once in a lifetime occurrence or a common problem? Worth a check! Dick C.

[Alan Long]

What do you guys think is the correct temperature range for a standard Model T ie (no water pump)
Do you expect (as stated above) 10 Degrees is the normal drop in temperature across the radiator?
Using a infra red heat sensor gun, is the top and bottom radiator tanks the correct location to measure temperature?
Alan in Western Australia

[perry kete]

I too had the top baffle come loose in a radiator and blocked the circulation and removed it only to reinstall it later because the purpose of the baffle is to distribute the water evenly across the cores.