HIGH oil pressure

[acbateman]

We have a 1700 XF rebuilt by Caterham 5000 miles ago, and which we have owned for 8 years. Today I drove the car after an oil and filter change [Duckam's QXR, as I have always used, and a standard filter from Caterham] and, once the engine was warm, suddenly noticed that the oil pressure was reading 5 bar as I accelerated to about 4000 rpm or a little over. I then backed off/changed up in case the needle went into the red zone! The car was running fine [and as long as I stayed below about 4000 rpm, registered the normal 4 bar] and a later inspection revealed no leaks and an oil level at 'max'. The oil pressure, hot, at 900rpm is registering as 1.2 bar. Do you think that the pressure relief valve may have jammed [and if so, where is it and what do I do about it?] or is this just the effect of new oil/filter [i have always noticed a slight increase in oil pressure with new oil in the past, but not to this degree]? I don't want to rupture oil seals etc. I also fitted a new oil pressure sender [Redline components] last year but this has been fine until now! Comments/advice appreciated please. Am I worrying about nothing?

 

 

[Big Brother]

Check your new filter is the same as the one you took off, as someone here a while back mentioned that sometypes of filters have one way valves fitted. This can lead to blown seals and blown engines!

 

Could just be a sticky pressure relief valve but I would start with the filter.

Also what oil did you use...was it a different grade?

 

Steve

 

 

Se7en-Up!

Less is more!

 

[Graham Perry]

Also check that the wire onto the oil pressure sensor is tight, mine regularly comes loose no matter how tight I fit it. This may be the reason for the erratic pressure measurements, as that is exactly what mine does when the wire is about to drop off

[jf_renard]

The "stuck oil pressure relief" happened to me once (BDR 1990 wet sump) so XFlow crankcase and oil pump).

Oil pressure was over 6bars even at idle, so slightly different from what happens to you.

 

Basically that valve is a calibrated spring, a piston and a hole, all included in the oil pump. The higher rev you go, the more pressure the pump delivers. Oil pushes on the piston, which uncovers the hole so pressure can decrease. As soon as pump pressure is enough (say 2000 rpm), the calibrated spring ensures a constant output pressure.

 

If the piston is stuck, an insufficient part of the pump pressure "escapes" to the sump via the hole, so the output pressure goes too high. In my case, the oil filter seal blew twice before a good diagnostic (thank you PC!).

 

From one of my friend's french website about sevens:

 

Pictures illustrated report -in french- of my intervention here

Location of the oil pump here

Location of the valve in the pump here

Dismanteled pump here. 7 and 8 are the valve.

 

Hope it can be useful.

 

Jeff

Cosworth 1600 BDR

[Peter Carmichael]

It won't be anything to do with one way valves in filters. That only affects filters on remote housings when you get the pipes the wrong way round and the effect would be much more catastrophic. Wiring to the sender and pressure relief valve sound like good places to start.