Weak stater or battery ?

[mauro12]

Hello guys , I’ve realized that when the car is very warm , after a long drive in motorway for example , if I shut off and turn on immediately, the starter motor is slowlier than normal ( the revolution of the start ) . This doesn’t happen when the car is cold . Any ideas ? Is not an hot start issue fuel related but I believe it depends on the starter or battery .
Any help is appreciated. Thank you

[ja17]

Check the battery first. It can also be the starter at fault. You can replace or recondition yours, use a later Pagoda starter which has 0.4 more horsepower or use a new gear reduction starter which also has more horsepower. How is your oil pressure? Failing engine bearings will sometimes bind when hot.

[Pinder]

I had a similar problem with my 1968 Cadillac eldorado. I replaced battery and new starter, and it still did the same thing slow starter turning and sometimes not at all until engine cooled down.

 I ended up putting in new wiring from battery to starter and from ground to engine block. During this process I discovered the fat positive wiring had almost melted somehow due to sparking at the starter motor (loose connection) where only a few strands were connected. replacing all the wiring (for to the starter) resolved the problem. (not saying this is the case but check for loose or damaged wiring). as the wiring gets hot its resistance goes up which causes the voltage drop to the starter making it not turn enough.

Regards

 Pinder

[ejboyd5]

Why not install a simple relay in the starter circuit:  Not only will this assure that full voltage is reaching the starter motor, it will considerably reduce the stress placed on the ignition switch and the old wiring of the original ignition circuit.

[Pinder]

in the diagram above, if the fat red cable going to the battery is damaged (i.e parts of it thinner or nut is loose at battery or starter) it can get affected when it gets hot from surrounding heat. As a test, you could try running a new cable from battery to starterand see if it resolves the problem, before replacing starter or battery.

[mauro12]

The oil pressure is perfect . 3 bar cold and never less than 2 bar with very warm engine . I guess is mostly electrical issue , very noticeable in summer with very warm climate . How is possible that a very warm engine gives stress to the starter motor ?
Battery is also new , 1 year old . I believe is mostly an electrical issue but like I said , only when the engine is really warm . The starter motor is still the original one from 1967. Never had any issues with it .

[Richard S]

Had a very similar problem many years ago.  Almost impossible to get the starter to turn over when the engine was hot.  Worked just fine when cold.  Started looking for hills to park on for rolling starts.  Finally discovered that the starter motor bearing was bad and would seize when the engine was hot.  Replacing the starter was less expensive than rebuilding the existing starter.

[Pinder]

https://www.redarcelectronics.com/us/resources/chargers-isolators-faqs/calculate-voltage-drop/#:~:text=This%20formula%20only%20applies%20to,approx%200.4%25%20per%20%C2%B0C.

[mauro12]

What is the best starter for our pagoda ? Could you post some links ? Thank you

[Vander]

What is the best starter for our pagoda ? Could you post some links ? Thank you

Bosch SR59X

[mauro12]

Is available somewhere ?

[707dieseldean]

https://www.autohausaz.com/pn/SR59X?srsltid=AfmBOooTPnzKUz_D-MKl8Hrcss7zjECazqwd-2AoitXiElLMNqfCd1fm