Hot coil

Henk_Brough

After a long time busy with the restoring of my 1937 212 engine I started up the engine.
On its own the engine runs well, but if the engine runs about 20 minutes the coil is so hot I can bake an egg on it.
The weekend from 17/18 August I planned to go to the Annual Rally of the Brough Superior Club in Oxford England.
I know it always is a risk to go with an old car for a long distance ( also we must take a ferry from Holland to England ).
I must also do a lot of more miles ( 200 so far ) the commimg days. The problems are the hollydays this time of the year. My wife ask for some attention.
But now the problem :
I changed the condensor for a new one..........no change
I changed the distributor cap for a new one ......... no change
Carefully check the points ( 0.5 mm 35 degrees and the timing...... no change
I tried several coils The blue Bosch is the best one. Of course the one I have driven thousends of miles.... no change.
New cables, new plugs etc. are already on, but changed them too............no change.

I' am desperate now. Before I did the engine it runs always very well and I did several trips to England.
I did the restoring of the engine because of mechanical problems.
Now the engine is very silent and runs perfect, but why the coil is so hot ??????
Has someone an idee about the problem??

RL Chilton

Are you running a coil with an internal resistor? Is your system a 6V system? Typically a hot coil is because your resistance is wrong. I believe if you don't have an internal resistor, then you need to have a resistor wire attached to your coil.

Best to PM Park W here on the forum. He's an electrical engineer and a whiz with Hudson wiring questions.

Park_W

Henk, if everything is still pretty much in the original arrangement, my guess is that the coil has failed internally ... the insulation on the wires has failed, and many of the windings are short circuited together, making the coil draw much more current than normal. And that makes it hot.

RL Chilton

Although he did say he tried "several" coils and always had the same result . . .??

tigermoth

i thought the purpose of a dropping resistor was to drop 12v to 6v for the coil in a 12v system. i have to do some research... regards, tom

Geoff

Originally the coils were 4 volts, with a resistor, which gave full 6 volts to the coil for a real hot spark for starting, and then as the resistor heated up the voltage dropped back to 4 volts. Check if your distributor has a resistor on it, and if so, is this wired in series with the ignition circuit from the switch. If no resistor, check that you are indeed using a 6 volt coil. More modern 12 volts systems also use a resistor, for the same purpose ( good cold starting spark), and you can use on of these coils for your 6 volt system. It will be marked "12 volt, to be used with external resistor". If you are still having problems then you need to check the actual voltage going into the coil. It could be that your charging system is faulty, and putting too much voltage in, so you will need to adjust the voltage regulator. That's the one main failing of the "idiot lights" pioneered by Hudson, you have no indication of what is actually happening, apart from the fact that the generator is charging something. Good luck,
Geoff

Henk_Brough

Sorry, indeed I have not given you all the details. I hope to do it better now.
The Hudson-Brough has a 12V system. In fact I have also put on an LPG system. with 80 l tank.
Under the car is so much room, so you cannot see the extra tank from the outside.
In Europa LPG in about 1/3 of the prize of petrol. On modern cars the street tax is much higher for LPG cars. For cars older than 40 years there is no roadtax at all.
The car in the past always runs better on LPG.
After the restoring of the engine I also did the distributor. New points new rotor, new cap, etc.
On older cars here it is rather common to use the blue 12V coil from Bosch. There is no need for resistors at all. As sead the cars runs perfect in the past with this coil.
Indeed I changed the coil for during the tests. ( 4 different coils, including a brand new
Bosch, a Ford coil, a Lucas coil, etc.) The blue coil where I did thousends of miles was of course the first one.
In fact is the car runs better on Patrol now the on LPG. Thats a sign that the high tension is a little low after about 6miles ( heat op of the coil ). LPG needs a higher ignition tension !
But also running on patrol the coil gets hot. So hot that the engine will stop.
The first 6 miles the engine runs perfect on LPG. Than it starts to misfire . I not done it
but I' am pretty sure the engine will stop.
I talked with several knowlogable people, got some help at home. We did all the tests
I talked about yesterday. Even so far that we take just for the ignition a separate battery.
The small spring on the rotor hits the carbon point in the distributor cap.
The distance between the rotortip and the 6 pickups to the plugs is about 0.5 mm.
I dismanteled the complete distributor, but this is such a straightforwardjob I cannot beleave something is wrong. The advance it working I can see on the stoboscoop.
From different people I heard it is better to set the ignition about 6 degrees earlyer than the TDC as is told in the manual. My engine runs better as it is set on TDC. Is that perhaps a help for the sulution. On the internet I found someone with same problems with a Volvo 1800.
He never found the solution but he goes over to electronic ignition and drives now without problems.
I do not like that. I prefer original. ( LPG ??? )
A long story, but I hope to give the right information. If not, please ask .
So far, thank you all very much for you help.

Park_W

Henk, please clarify . . . is the hot coil problem only when you use the old coil, or does it happen with every coil?

Henk_Brough

It happens with every coil. That is the reason why we does not understand the problem. Even with a brand new Bosch blue coil the engine starts misfiring after 6 miles. And the coil is very hot again
Thank you Park for your thinking about the problem.

lostmind

Is it possible that you have the polarity reversed from what it was before you did the engine work?
Also , is the coolant temperature normal?

Geoff

Something must have changed then from before you overhauled the engine. The fuel type has no bearing whatsoever on the ignition system. Have you checked the charging system? It should be no more than 14.5 volts maximum whilst charging. Did you originally have a ballast resistor that may have been bypassed? Just a few things to check. Go back over what has been done and double check that all connections are correct. Good luck,
Geoff

[Deleted User]

I agree with lostmind , regardless of what the terminals are marked reverse the + and - .
Your car was engineered to be positive ground but most new coils are no longer marked with that in mind.
Roger

Henk_Brough

Thank you lostmind and Tallant R for your reaction.
From new on the Hudson/Brough has negative ground.
Before I did the complete technical overhaul it was exact the same as after the overhaul.
Yesterday evening my friend Jos and I were busy with the car. Jos is busy with old cars for more than 35 years and it never happens to him he was not abel to get a car on the road.
We take another distributor. We take other plug leads. We take other plugs. We give the 12 V to the coil with a separate battery. We tried 5 or 6 different coils, etc, etc.
Every time after 6-10 miles I can bake an egg on the coil and the car starts to misfire.
Barry Sweetman proposes to place an electronic ignition from Petronic. I think about it seriously.
We dedided to go to England with the Borgward Isabella Coupe from Jos. That of course is also fun.
It is indeed a pitty : Mechanicly the car runs perfect. It is really silent, it has good power,
the gearchange with the wet clutch is so fine.
All the help you gave me in the last years ( thank you very much ) does not help and on a for us not understandable way the car fails.
In september we go on trying to find the problem.
Of course you will get the results of it on the forum.

nick s

Rick, he is not talking about a Hudson built car, just a car that happened to use a Hudson frame/drivetrain.
sounds like you have swapped all your ignition parts, are they of different sources? another brand or lot may make the difference.

Geoff

Ken has probably hit the nail on the head, as Cees says he is now running the car on L.P.G., which is most likely increasing the combustion chamber temperature, and causing much greater resistance for the spark to jump across the hot electrodes. If the spark does not occur this will cause heat build-up in the coil.Try a colder plug.

Henk_Brough

Again thank you all for the reactions.
Indeed Rick, Nick ( that sounds very special ) has right. George Brough just uses the rolling chassis from Hudson, like Railton. The startermotor is still Autolite but for 12 V. The distributor is also Autolite.
The dynamo and regulator are from Lucas and 12V negative earth.
About the problem : I think Geoff has right the reaction from Ken give me a good startingpoint.
I absolutely cannot understand why the car runs perfect ( I mean than the ignition and not the machanical condition from the engine )the last 5 years it the same set up. ???
I uses the plugs from NGK B6 HS 0.7 mm as recommended from the English members of the Brough Club. I will try to get the Champion J-8. Not so easy to find them in Holland but I go to England and try to get them there. And indeed Geoff, LPG asks more from the ignition system.
But why it changed now , before the overhaul it runs perfect on LPG.
In fact we try a longer distance. After 20 miles the engine runs on LPG very good.
The coil is still very hot. To our opinion much to hot. With a spare coil we go on testing.

What Ken says :

If all those coils were getting hot, it indicates more a problem in the high tension circuit. In other words, the secondary voltage required to fire the plugs in higher than normal.

I indeed use plug wires with a metal core and plug caps without resistor.

Is to my opinion right. It is now the time to find solutions to reduce this secondary voltage.

The show goes on. You will hear from me !!!

Henk

lostmind

Maybe higher compression after the rebuild? Might be the reason requiring a different spark plug heat range?

Henk_Brough

From an English member from the Brough club with a 8cil.Hudson engine I have just had a mail and he told me that also his coil is at the boiling point for eggs. Saveral times the coil was so hot that he expected the engine will stop. But so far the engine stays running. He told me that sometimes it is so hot under the bonnet that the patrol boils in the glass from the fuelpump. Because the engine runs well at the moment I take with me some extra coils and make a longer drive. But as lostmind advises I will buy cooler plugs.I do not take the car with me to England but but as soon as I am back I do some testing.
Is the temperature under the bonnet from a Hudson car also so high ?

lostmind

It may be your "tight" engine causing a higher temperature. It may improve as you break it in.
Good luck.

Park_W

Henk, have you tried running the coil with a resistor installed? That doesn't answer the question of why it's running hot, but if the engine runs OK with the resistor, it would stop the problem of the engine stopping aftyer a few minutes.

SuperDave

I wonder what would happen if the two low voltage connections on the coil were reversed? I have seen this same thing happen to model A Fords.

Jon B

If the petrol is boiling in the glass, then the problem may not lie with the coil. Possibly the coil is getting hot because the engine compartment is hot?

Is it possible that all Brough Superiors "ran hot" due to faulty ventilation / cooling in the design of the hood and / or radiator?

Henk_Brough

Jon, you could be right. In the last years going to England it was necessary to go on the motorways, or it will take so much time to come there. In fact I prefer the smaller roads special with this old cars.
In Europe trucks will do around 55 mile/hour.
So with a car go a little faster. 60-65 is for such an old car than o.k. The car will do that without problems. The temperature on the dash is o.k. and stays in the green range.
But after a long time on that speed ( > 1 hour ) and we stop, the temperature goes up very quick and about 1.5 l of cooling water is pressed out of the radiator. I have a plastic bottle
collecting the water and later I put it in again.
From other Brough cars it is well known that it even happens the radiator cap was blown of because of the heat.
Most of the Brough cars has fixed an electrical fan to reduce the temperature.
Indeed the radiator for the Brough car is different from the original Hudson.
Much lower but also deeper. The width is about the same.
Also conditons under the bonnet can be different.
I think that the big cast iron exhaust manifolt gives a lot of heat under het bonnet.
My friend Jos just find out on the internet that a coil ( this was NGK ) has a temperature range from 40- 140 degrees C. I cannot beleave the temperature goes up to 140 under the bonnet.
So first testing.

RL Chilton

Henk-

I know you have a different car than I do, but with today's gas, and the engine running a little hotter than it used to, I had to take the coil (which was mounted on top of the engine block) and move it over to the inner fender panel, just to get it away from some of the heat. The heat was making the oil inside the coil just too plain hot and would not function properly. This is on a '52 Hornet, but if your coil is too close to the engine, you might have the same problem.

Park_W

Henk, regarding the use of a resistor, it goes in the circuit that feeds power to the coil. Almost all 12v systems on US cars have a resistor, either external or built in to the coil. My Hornet ignition is wired like a GM system, with external resistor. The resistor measures 2 ohms. It is a standard wire-wound resistor that does not change resistance with increased temperature. You might check with a Bosch dealer and see if there is an appropriate resistor for your Bosch coil (or maybe there is one built in).

Going back to Ken U's suggestions (resistance in the high-tension system), have you checked the distributor rotor for wear, and are all the high-tension wires properly seated in the coil and in the distributor cap?