18 replies to this topic

[Guess-Works.com]

That's about right, but the 25 at cold idle is a little low, but probably worth montioring, the score down the valve could suggest that a piece of swarf was holding it open slightly which will reduce the oil pressure at idle..

I had one do the opposite once, stuck shut and blew 150 psi of oil through the filter and out the bottom of it... all over the drive.. only took a few seconds to push out a couple of litres...

Since then, any engine I've built I've used a modified spring ( shortened slightly ) and a 9/16th's ball bearing, which fi I remeber rightly is one out of either the inner or outer cv. I also started to use the adjuster which DK mentioned which is a neat little bit of kit.

[Dan]

I tend to use a shortened Cooper S spring and a ball in mine, in fact the Cooper S used a ball valve as standard. There is also a cup which locates in the spring and holds the ball in place, hard to get hold of but makes the valve seat last longer (and replacing the pressure releif valve seat is a horrible job).

I think the new oil is more likely to have caused the increase in pressure than the new filter, old oil looses its ability to resist shear which is why its hard to build pressure with it. Oil doesn't just get dirty, it wears out which is why it needs replacing. You might be right though, it's hard to say.

[dklawson]

Dan, to the best of my knowledge the ball was never a standard offering. It certainly wasn't on my -S or any through early Mk3 production that I've seen. Regardless, the ball combined with the shortened -S spring will give a fairly stable pressure and it's much more immune to debris.

Changing the oil and filter was a good idea no matter what. As Dan said, the oil looses its viscosity when it ages. It also will get thinner as it heats up.

Keep your eye on that oil pressure. 25 psi is a bit low for a cold idle. After a long run it will be lower. If you see the pressure regularly drop close to 15 psi on a hot idle, I'd start making plans to replace the pump at a minimum.

[Leonard]

thanks. ill get another valve for that. i'm surprised at how deep the score was, you can get your nail down it. the 25psi at idle is when the engines warm, but i havent tried it hot yet. i agree with you that its the fresh thicker oil bringing the pressure up, so ill do more frequent oil changes to keep the engine alive.