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[Kevin Wood]

Yep, bore is cast into the pump housing. There's a piston in the bore that moves against a spring to open a bypass passage as oil pressure reaches the correct  value.

[Andy H]

If the design is similar to that on most engines there will be a hard steel bucket with a spring inside it pushing it down the bore against the oil pressure.

If the bore is soft aluminium there is a tendency for the bucket to gouge steps in the bore and get stuck. Alternatively a bit of swarf can get stuck in the relief port and stop the bucket from returning to its seat.

[2woody]

bear in mind that the spring and valve are the opposite way round to most engines.

it's cam belt cover, cam and cam belt rear (steel) cover off to get the valve out.

Have been here four times now with Omegas and in each case, it's been worn big ends.

I'd suggest the following in this order ( yes, I know you've done some of these already )

check coolant mass temperature ( a malfunction here will thin out the oil )

sump off and check strainer and big end condition.

oil change and some thicker oil

pump off for a good clean-out.

and then it's engine out.

For what it's worth, I have changed a crankshaft without taking the engine out in an Omega, so it is possible, but it's rather a faff.

[Andy H]

I never actually checked the oil pressure on my old 2.5 but I suspect that it may have had minimal oil pressure (at idle) once it reached 140,000 miles. I switched to fully synthetic Dexos 2 and it ran like a well oiled sewing machine (with loose big ends) until it was scrapped (due to rust) at 200,000 miles.

As a last resort..... I saw last week that VX are selling remanufactured 3.2 engines on tradeclub for £1500.

[tunnie]

Did yours tapp at hot idle? Did fully synth oil solve noise issue?

[Andy H]

Did yours tapp at hot idle? Did fully synth oil solve noise issue?

I originally switched oil because it seemed to be taking a long time to build oil pressure after a cold start on very cold mornings.

It did sound 'loose' when hot with a mysterious rattle from the rear sump area. I don't think changing oil actually fixed anything but I do believe the fully synth oil helped it to keep running to 200,000 miles.

The main point of my post was not to worry too much. 

[tunnie]

While driving I don't mind it, its just when I stop & get out, it does not sound like it should. From cabin all is well, even with no radio on.

If a cam needs to come out to replace/checkout this valve, that's a considerable amount of work. Perhaps its just me wanting perfection from the engine 

[tunnie]

As replacement/investigation is way beyond my skill level, I'd no doubt have an expert around to help, as they would be making big effort to get to me, i'd want to get it done in one go.

How much extra work is involved in replacing the whole pump? Just swap it out for a known good one? Not really seen many other Omega's with fault like this 

[Shackeng]

Was this problem ever resolved Tunnie?

[tunnie]

No, I'm just putting up with it. Appears to have no affect on performance, just wish it was not quite so noticeable. 

While I'm sure it could be resolved, the effort involved does not really appear justified. Its outside my skill to fix, paying for it to be done does not make sense given cars low value.

I'll just run with it, done 2k+ without issues, if it goes bang then I'll just source a new engine.

[Andy B]

No, I'm just putting up with it. Appears to have no affect on performance, just wish it was not quite so noticeable. 

While I'm sure it could be resolved, the effort involved does not really appear justified. Its outside my skill to fix, paying for it to be done does not make sense given cars low value.

I'll just run with it, done 2k+ without issues, if it goes bang then I'll just source a new engine.

I'd tend to go with Stu's diagnoses of failed big ends. SWMBO's Smart had the same low idle oil pressure issues. Last Christmas saw the engine rebuilt, the big ends were fubar'd. Oil pressure is now OK ........... other bit were changed too though ie cam chain & sprockets which were really really fubar'd.
If Stu has replaced a crank with the engine in situ, then big ends should be easily done when the sump is off. 

[tunnie]

Its not big end noise though, many here have heard it. It really is a top end tappet noise, which gets less noticeable if its been stood for a few mins after a long hard blast.

Sump dropped, everything looks good. (as inspected by TB & KW) internals look good.

I'd happily volunteer my car as a donor for the guide on Changing Oil pressure relief valve   

I have *once* had it silent at idle when hot, parked at MrsT flat, waiting for her to return, a traffic warden asked me to move. After 5 mins of idle, it went to the red line 

Got out to put some stuff in car, noticed it was how a V6 should be when hot! Not been able to repeat that though 

[Andy B]

Its not big end noise though, many here have heard it. .....

Neither was SWMBO's Smart, but having said that,it was hard to hear anything above the noise of the cam chain! 

[tunnie]

Its not big end noise though, many here have heard it. .....

Neither was SWMBO's Smart, but having said that,it was hard to hear anything above the noise of the cam chain! 

Hummm 

Its all sweet as a nut when cold/luke warm. 

Chris, you breaking that chaved up MV6 yet?

[Webby the Bear]

Tunnie, how loud is this tapping? I get tapping but it's defintely not something that I'd worry about as it's not too loud. is it embarrassingly (spell check) loud?