oil light comes on on my 55 series 62

[CadDad]

 Hello,
   Recently my oil light has been coming on on my 55. After driving 15-20 or so miles when I come to a stop my oil light will flicker on. If I put the transmission in neutral it goes out. There is no noticeable noise or any knocking or anything. The engine was rebuilt by the previous owner and has probably 2,500 mile on the rebuild. It still sounds just fine. Thanks, Paul

[Jeff Rosansky CLC #28373]

Sorry to hear about this. I had oil preasure issues on my 70 after a rebuild and spent a lot of time on things I didn't need to.
Please answer a few questions.
What oil are you using? Are you getting oil up in the filter unit? What is your engine rpm at idle, in drive with it hot--not cold but hot? Where is your engine oil temp at this time?Have any changes been made to the engine from stock?

After driving that long the oil will be hot and thin which will cause the pressure to drop. Low idle speed will mean the pump isnt spinning much either which is why it goes out when you put in neutral (rpm increases).

Now with that being said, the light should still not be on if oil is correct and idle speed is good.
There are several mechanical reasons for this but I suggest looking at simple first. Change you pressure sending unit. Even if new it could be bad. Also check the wire going to it to be sure it isn't shorting out anywhere.
If no luck there then plumb in a cheapie mechanical oil gauge to the idiot light port. I got one from Harbor Freight. Need to know not only how low it really is going, but also how hi does it go when at fast engine speed (is the regulator/bypass working)?
Let us know.
Jeff

[CadDad]

 I got the old sender out and will replace. I'm guessing any modern  6-12 psi sender will work as long as the male thread size is correct? I will also get a pressure indicator and check for sure. Thanks for the info!

[Caddy Wizard]

The correct, original style sender is commonly available. I see them on ebay all the time. 

[walt chomosh #23510]

Paul,
  Ideally you would put a tee along with the pressure switch so you can install a direct pressure reading gauge. Am curious as to what weight oil your using?....walt...tulsa,ok