1930 Buick Model 60 oil pressure relief valve

[snosurf]

My engine has an oil pressure relief in the start of the oil manifold.  It is a thimble like cylinder valve that fits inside a side tube that comes into the main line at about a 90 degree angle.  It is spring loaded.  When oil pressure gets above 40 lbs, the thimble moves against the spring and uncovers two small hole that the oil will leak out into the oil pan, lowering pressure.  

 

The problem is the thimble is getting stuck in an open position, giving me no oil pressure.  I've taken it out and it is worn in spots.

 

I was wondering if anyone else has had this problem?

 

Thanks - Piers MacDonald

[Mark Shaw]

Try replacing the thimble with a ball and coin it to the seat for a good seal.

[nat]

    The chances are there's a ridge of deposits at the end of it's travel.  Clean the piston and cylinder until the piston slides freely under it's owh weight.  A bottle brush might help clean the bore.

[edinmass]

Hi Piers.....it should float in the hole freely without the spring. Varnish and carbon will cause drag.......If the valve has a bit from wear it's not a problem. Spring tension could also be an issue. Ed

 

If you can't get it clean, put it in a toaster oven on broil for a few hours......it will melt varnish and free up carbon without scratching the bore. The oven should easily get it to 600 degrees. Do not leave the spring in the oven.

Edited January 4 by edinmass (see edit history)