Expert: Brad Sears - 9/1/2010

Question
I own a 1951 Mercury 1 ton p/u. It is often hard to start when it is hot or fully warmed up. I have been told it is because the starter is located between the exhaust pipe and exhaust manifold. Any cure for this problem?

Answer
I have had and worked on flat heads since the late 1940's, and have never found that exhaust heat to be the cause of hard stating when hot. My experience has been that the heat on hot restarts will trigger any weakness in the system as with any other car, because they all have the starter placed where engine heat will act on them during hot shut down. The following is a list of things that I would check to determine the problem:
1. Perform a starter load test when the engine is old and then when hot.
2. Make sure that all connections both ground and power side are clean and free of resistance.
3. Load test the battery both cold and when hot.
4. Make sure that the distributor advance (breaker plate)is not sticking in the advanced position of hot shut down making the engine start hard.
5. Bring the engine to operating temperature and remove the air cleaner. Shut the engine down and with a flashlight look down into the carburetor float and make sure that fuel is not dribbling into the engine.
The last one is one that I have found on several engines. I have removed the freeze plugs on the engine and found the bottom of the waterjackets completely plugged up with sludge. The prevents coolant from reaching he bottom of the block causing the bottom of the block to overheat. On those cars we dug the sludge out with a spoon and the flushed with a hose. Draining and flushing the radiator will not clear these passages. Good Luck