There was a thread back in 2015 about someone overseas having trouble starting his caddy when it was warm. The only difference was that his would turn over. most of the help centered around grounding. My 47 starts fine when cold, but when it has been run for awhile and then sits for a few minutes it will barely turn over. I am going to make sure there isn't any grounding issues, but am also wondering if a heat shield for the starter would be a worthwhile try. I have had the starter rebuilt by a very professional service station. Any help guys?
First make sure your battery cables are for 6 volt which means use at least double 00 cable and not the small 12 volt cable. Next ground your negative battery cable direct to the engine and not the frame. You can use one of the starter to engine bolts. Next make sure you have a ground strap under the right front motor mount, if possible also the left front. Originally the car came from the factory with two small ground straps from engine to firewall. The engine and transmission are sitting on rubber mounts and rubber does not ground. I bet if you get the proper cables and ground straps, your engine will start when hot. Bill
Heat increases electrical resistance, so if it's not a mechanical/lubrication issue - motor turns easily by hand, then check the wiring and battery temperature/condition.
If it's still 6V, the wire gauge is very important to be correct. Sometimes people use 12V specs/parts on battery/starter for 6V and that's not the right direction. If it's got any length at all, it should be 00 gauge, + and -. They're not that expensive if you know where to buy. Clean the areas were it attaches also. Battery size (CCA) is important also.
Original wiring will make one tear their hair out, so I won't go there looking for faults.
Ground straps only cost a few bucks, but may not be stock appearing. Can always check the resistance with a DVM to rule in or out. Should be very little. If it's pos grounded to the block, that usually does not affect the starting. if its clean at the connection. If grounded on the body, maybe grounding issues.
In addition to the above excellent posts, check out some posts on the subject by Jay Friedman. He is an expert on this topic, and he has a 1949 (OHV, but the starting and ground issues are the same). Good luck!
John Emerson
Middlebury, VT
Deetz,
Excellent advice from fishnjim and Bill. This is a common problem with 6 volt Cadillacs. As John wrote, I've experienced this problem with my '49. It's one of the reasons Cadillac switched to 12 volts in '53.
Typically, after running for a while on a hot day, from about 5 to 45 minutes after turning off the engine it refuses to re-start. My theory is that this is caused by the hot internal engine parts expanding when the motor is stopped because coolant is no longer circulating. It takes 5 minutes or so for the expansion to occur. After 30-45 minutes the motor then will cool down. So, from 5 until 30-45 minutes it will sometimes refuse to start on 6 volts. To summarize all the cures posted here and elsewhere:
1. Install a 6 volt battery with at least 600 cold cranking amps, which are readily available. Make sure it is Group 2 and not the smaller Group 1;
2. You already had your starter re-built, but you might want to consider having your auto electric shop add heavy duty field coils. In addition, to assure a good ground remove all paint from the areas where the starter, its bolts and the flywheel housing meet;
3. Install an extra-thick positive battery cable. As Bill and fishnjim wrote it should be 0/0 gauge. I had mine made up from 600 volt welding cable by an auto electric shop. Similar thick cables can be bought ready-made from McVey’s, The Brillman Company in Virginia and Cole's Ignition and Electric, Rochester NY;
4. Install a brand new negative battery cable, after scraping clean the negative battery post, as well as the place on the frame it is attached to. I second the motion re: Bill's advice to ground the battery directly to the starter motor. You may even want to consider a 1949 negative cable which does both, as it runs from the battery to the frame and then continues to a starter bolt. These can be bought from McVey's and, I think, from Cole's;
5. I also second Bill's advice to make sure you have a small ground strap from the engine to a screw on the nearby firewall. If not, new ones can be bought from McVey's in Kansas and, I think, from Cole's. As with the starter, scrape any paint off the cylinder head and firewall where these small straps mount. Also, the ground straps on the motor mount.
6. Art Gardner and I wrote an article in the July 2015 Self Starter on how to further improve starter grounding by running an additional ground strap to the starter's commutator end plate. (Don't let the terminology throw you, it's merely the rear end of the starter.) If you don't have that issue of the Self Starter, let me know at jaysfriedman@yahoo.com and I'll send you a copy of the article.
After doing the above, you should greatly improve if not totally cure the problem. The problem is really not in the starter but rather how minor problems in the electrical system are affecting the starter. Things would work well when the car was young because all electrical grounds were clean and the various cables were the right width and in good shape.
Jay
I tried all the normal remedies that are listed and sometimes on a very hot day my Lasalle was still kinda iffy about starting. Two years ago I went to tractor supply and bought an 8 volt battery that is the same size as the he 6 volt that was in the car. I adjusted the voltage regulator to put out 9 volts instead of 7.
For two years now it has started right up no matter how hot.
I did not have to change any other electrically component and have never burned out a bulb.
My battery is under the floorboard so nobody knows but me.
I drive this car several times a week.
One thing many people miss it the end plate on the starter. The brushes for the motor are connected to the end plate. If the end plate is painted and/or the frame it is mounted to is painted it would prevent current from flowing to the brushes. The contact surfaces need to be cleaned to make good contact.
To add to what Glen wrote, I think it is important that the surfaces of the starter where they meet the motor and the mounting bolts be free of paint.
Also, on a lighter note I'd like to paraphrase the Duchess of Windsor who said "you can't be too skinny or too rich", by saying that a 6 volt Cadillac's battery cables can't be too thick.
Jay's advice (and all of the advice posted) is spot on.
The fiend coils are generally overlooked when a starter is rebuilt. Usually they clean up the armature, replace the brushes and bearings and call it a day.
Many years ago I had a 1936 Packard. During the restoration I spoke to the shop doing the generator and the starter rebuild and told them that I wanted to avoid hot cranking issues. They replaced the field coils and I never had a problem.
I also added a separate ground cable from the engine to the frame and had the battery ground attached to one of the starter bolts.
If there are no other contributing problems, this will solve your hot start problem.
Brian
Forgive me if this has already been mentioned.
I was just going through this problem on my 50 caddy. Started fine cold, terrible when hot. I'd have to open the hood and let it cool and about 15 minutes later itd just barely start. Got a new battery, same. Expected starter, but just for the heck of it, I took apart every ground connection, wire brushed and sanded until the metal was shiny clean. CLEAN CLEAN. Recconnected everything and that solved my problem! I can now run errands in the car if need be and not worry about getting stranded.