This car has always had good oil pressure. All of a sudden, the pressure drops to near zero after the car warms up. Very good when cold. Was told it could be a loose oil pump chain, or the pump bolts may be loose. I really dont think its the motor since it all of a sudden and only when the motor is warmed up. Any help out there? Thanks

 

An '87 XJS V12, right?

(Put this info in your signature line so we don't have to figure out what car you have )


It's faily common for the oil pressure sending unit to go flakely on these cars so that would be one of my first guesses.

Also common is poor grounds and connections at the back of the instrument cluster causing poor gauge readings. The cluster can be removed to clean the connections/contact point s and add an extra ground wire.

That said.....

Low oil pressure *at idle when warm* is rather common on V12s....often down as low as 5-7 psi or so. On my XJS this translated to the bottom of the needle just touching the "0" line at idle. As soon as the engine speed was raised above idle the needle would come right up. Drove it like that for years.

What was yours showing before the sudden change? A high reading at idle would be the exception, not the norm.

Cheers
DD

 

As Doug said, plus the oil pump is directly driven off the crank so just about impossible for that to fail.

If the oil pressure is low at high revs (not clear if so or not) the oil pressure relief valve may have stuck open/have some crud holding it open/the spring may have failed. This is situated near the oil filter and can be undone and checked.

Greg