As mentioned in the title I use to hear this noise after my car was turned off for about 5 minutes. I no longer hear it and my oil pressure has gone up as has my coolant temperature. Please, I need help. Has anyone had this problem? And no its not a faulty gauge in my instrument cluster!

Thanks

 

When you say temp and oil pressure has gone up,,,how much?

 

Hi, up to 75/85 psi as soon as you turn the key.

I know its not right.

 

This is how it reads now. I know it's not right please can someone help me

 

Hey Man... Naw, that dont sound right. Im trying to think of the possible connections between the oil pressure and the tempurature...

Whats the change in temperature...?

Anyways, have you replaced or inspected the 2 oil pressure sensors right behind the throttle stand? Im not sure what the internals are and how they are put together inside BUT maybe something failed internally which was producing the hiss and now, the obstructed flow and higher pressures - or maybe they (especially the pressure sensor) is/are just reading wrong altogether...? They are not expensive and I would just consider replacing them both... The larger I believe messages the actual pressure to the gauge and the smaller of the two triggers the light on the dash...

Considering how "interesting" these critters can be, is it possible that the stronger signal going to the oil pressure gauge is driving up the temp gauge somehow?

If you remove the cross pipe, throttle rods, and as much as you can back there - its not really too too difficult to get a wrench on them things. A crows foot wrench (cant even believe that is a set O words I use sometimes) helps with the pressure dummy light.

 

I suggest that you take the oil pressure relied valve off and take it apart and clean it. It sounds like it is stuck closed and that excess oil pressure is bleeding off slowly through it after the engine has stopped.

 

Since it is both oil pressure and temp, I'm thinking there is a grounding problem in the flexible circuit board. Try adding a ground.

 

I know/knew nothing about this device/component... Googling now. Is there one of these on the 1990 XJS?

 

Im so confused. Thank you for your suggestions. Could it be the cooling fan? That has stopped working? I don't want to do damage to the engine by just carrying on until it breaks down.

Just got home and I could hear that hissing very slight again. The mechanic inspected the pressure relief valve and said it was fine.
Its bugging me! I can usually figure this stuff out.

 

Exactly where is the hissing sound originating? A restriction of some sort must be causing the higher oil pressure, so it will be in there. I would not necessarily believe the mechanic, have you had the valve apart yourself and looked at it? have you tested the oil cooler for obstructions? Have you tried bypassing the cooler?

Your cooling fan is mechanical, very unlikely to have stopped working, but the viscous clutch might have failed in freewheeling mode. Can you push the fan round easily with your hand when the engine is hot (and stopped!)?

 

I think you are right. I do trust my mechanic but not for things like this. Right, how do I do the things that you specified?

Thanks

 

The hissing noise comes from the from of the car. I'm not sure exactly where? It was faint today.....


Thanks

 

Another thought, did this start when you had the oil changed and a new filter? If so change the filter right away; it could be the cause if incorrect or duff.

 

No, it was a cold morning and I accelerated hard getting on the motorway about 7 mins after starting the car. I had the oil changed to try and resolve this issue. Which it did not.

 

Crankcase ventilation filter clogged?

Do you have any additional oil leakage?

 

The only hissing noise I'm familiar with is the A/C drains dripping on the hot cats. That usually goes on for a few minutes once the car is parked. Normal, and should not be related to your other issues.

 

Hi, usually my garage floor is completely dry no oil nothing! But I have noticed 2 small spots of oil! Where do I find this crankcase to check it please?

 

Yes the hissing started after I go the AC regased. I did hear it today after running the AC. Feels like we are getting closer to the issue.

 

Also I posted on an XJS facebook group. Someone there said they has the same issue after replacing the instrument lights with LED bulbs and something about an earth. Well this cannot be a coincidence because I too have recently replaced to LEDS.

The mystery continues....

 

In that case your aircon system is leaking.