Oil Pressure Problem

[tvr_Edd]

I have a 2003 4.5 RR Cerby with 16000 miles on the clock.

Fully serviced and I had no problems with oil pressure before i had the car serviced.

I don't want to disclose where it was serviced as I have no problem/grief with them and they are doing their upmost to help me solve the problem but wanted to see what you thought.

So as said no problems with oil pressure before service.

I had the 12000 mile service and tappets done as wasn't sure if the previous owner had done it at 12000 and i'm thorough.

So I pick the car up everything seems fine.

OIl pressure guage takes longer than usual to register on startup. Oil pressure at 60 when starting. Drive home everything seems fine.

Noticed under hard acceleration oil pressure falling from 60 - 40 as the revs rise over 4000rpm.

Car goes back, has new spring and valve fitted and i pick her up all happy.

Problem is still there though

I've been out in car tonight to establish what it's doing.

Basically if i floor it at 4000rpm in any gear pressure falls from 55/60 down to just below 40 quite quickly and holds at the lower level.

If i hold the car at 6500rpm pressure stays at 40.

If i accelerate slowly through revs presure still falls.

Water temp is constant at 80 BUT when i floor it and oil pressure falls, the water temp falls a tiny bit but thats it.

Car is due to go back to the place to have wet guage fitted and put on the rollers to see what the pressure is really doing.

Sorry for long post, but i'm obviously concerned about the pressure and going to france in the car in under a month and want this sorted before i go.

anyone got any ideas?

car feels perfectly normal by the way, although the company who serviced it says it is down on power from what i had it quoted as - could this be related to my oil pressure problem?

[tvr_edd]

anyone

[Julian64]

Well, bit of a guess here, but pressure cannot fall as the engine revs higher unless there is a problem with the pump.

Even if there was a blockage in the oil filtre, main gantries or oil pressure relief spring the oil pressure show still go up with rising engine revs.

So my guess would be to take off the oil pump

[tvr_edd]

Hmm i was thinking possibly the pump

I'm more thinking that the guage is just somehow wrong even though its mechanical?

[jon h]

I do wonder how good the guage is. I can get an extra 10psi on mine by tapping the glass.

Jon H

[byker28i]

Could a different grade of oil have been used? Could a runnier oil be causing the problem?

[tvr_edd]

possibly different oil, or just newer oil that hasn't broken down but that shouldn't suddenly make the pressure go down.

If i didnt rev the car hard above 4000rpm you wouldn't even know there was a problem

[jbvipercerb]

Do you think it could be a faulty oil filter? Maybe collapsed inside or the valve sticking inside it. It seems strange it was ok before it was changed and now not. If it was the wrong grade of oil it may have lower oil pressure all over the rev range but nit just after 4k. Just as a thought is the oil level correct, if there isn't enough in the pump will suck all the oil out of the sump!?
Hope you get it sorted.

[carl_w]

Isn't 4000 rpm where the ECU goes open loop?

[tvr_edd]

Sorry I forgot to add oil level is on max (this was first thing i checked)

Yes it does seem strange to only occur after the service.

What does the significance of open loop over 4000rpm have on oil pressure?

[brummiewedge]

Is the ECU involved in the oil pressure reading?

[Julian64]

Just had a thought. Could possibly a sticking oil pressure relief valve cause this. as you accelerate the pressure builds up on a sticky valve.

Above 4000 enough pressure to force open a sticky valve, which them bypasses oil and drops the oil pressure.

As the revs come down the valve still sticks open, dropping the oil pressure still further but at idle the reverse differential pressure is enough to close the valve.

It fits with the service as its easy to leave a bit of broken spring in or misseat the ball bearing.

Just a thought, but a cheap, easy and cheerful one to check

[tvr_edd]

Julian - thanks, even though not crystal clear if you read original post, when the problem was noticed the car went back and had these replaced, which did lead to better oil pressure on startup but the problem was still there afterwards

so as far as I can see this can be ruled out

Also as far as i am aware the oil pressure guage is mechanical and not electrical so the pressure should be very accurate.

[Julian64]

Yes I did read that, and even though it was replaced, there still might be something sticking the valve.

Opening the cap and pulling out the spring and replacing isn't the same as checking for debris.

I would still check it.

[jon h]

Julian64 said:

Yes I did read that, and even though it was replaced, there still might be something sticking the valve.

Opening the cap and pulling out the spring and replacing isn't the same as checking for debris.

I would still check it.

How does one check for debris? I have changed my spring and was working more by feel rather than sight. I have had lower pressure than I would like recently and imagined something could somehow be holding the bypass valve partially open, but I cannot for the life of me think how to check for it.

Jon H

[Julian64]

Last time I checked mine it was with a dentists mirror on a stalk. You need a friend to hold the torch though.

[Tangoed]

Edd, Have the garage given you any idea as to whats wrong? I'd of gone for the spring or faulty gauge, but I don't think it really is the gauge. I would expect a faulty gauge to over read or be erratic.

[tvr_Edd]

Car's back at the garage now, dropped it off tonight

it's going on the rollers with an independant wet guage to see what the oil pressure is really doing

a possible cause came out it may be a blocked oil cooler wth silicone or possibly the guage is broken

we also may try a different engine oil

i've been promised i'm not getting it back till its fixed so lets hope its just cheap and easy to solve


also just worked out when i go to France i travel on April fools day and come back on firday the 13th

AA europe cover definitely needed

[The AJP Griff]

It's probably the oil pressure sender.

[dffy]

hi new member new owner 4.2 what a culture shock used to drive evo 6 what is normal oil pressure running and at tick over where can i get new carpets thanks davy