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Author Topic: V6 2.5 oil pressure  (Read 366 times)

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Tick Tock

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V6 2.5 oil pressure
« on: 27 March 2019, 22:10:14 »

This is probably a 'how long is a piece of string question', but thought someone out there would have some ideas or experiences about my oil light problem.

History - 2.5 V6 lump fitted 9 years ago by a garage - sought from scrapyard supplied, no details available and was probably not the best buy - could possibly be an early engine and have covered over 200k miles?

Car not used all that often, oil changes 1 year (4000 miles). If not used for over a week, big end clunk for the first 2 seconds, but runs smoothly and is regularly given an Italian tune-up.

Warm day today, noticed oil light coming on at tickover - holding revs above 800rpm sorts it. Coming back in dark a few hours later and cooler outside, ran for 30 miles with a few traffic light stops, all ok. Enter the city with more standing at lights, oil light comes on under 800rpm.

So after all the story so far, it could be a number of things -
Dodgy oil pressure switch?
Clogged oil pump pick-up strainer - not a problem at higher revs.
'dangle berries'ed engine bearings and possibly nothing but a full rebuild / exchange would sort out.
 
Stick some treacle in there instead?

The car is in excellent condition with no penetrating rust anywhere. I've spent hundreds of hours under it and the engine is as clean and tidy as you would expect from a true Omega enthusiast (complete nutter). I'd like to try and keep it running for another 6 months, when the CD estate should be back on the road after an interim overhaul, and then this one can be put to one side ready for works attention after a 4 year stint on the road.

Now where did I put those funny pills?

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Nick W

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Re: V6 2.5 oil pressure
« Reply #1 on: 27 March 2019, 22:27:27 »

The 'correct' way would be to unscrew the low pressure sender, fit a calibrated gauge to read what the pressure actually is compared to what the spec calls for. But, most people don't have a gauge, most of the sets don't include an M14 adapter(I made one for mine) and I've no idea what the pressure should be.


The pressure switches are a common Vx failure, and are less than a fiver to replace. So buying a new one is the place to start as it's almost certainly the problem. It's also one of the many places that these engines leak oil from.


I wouldn't worry much about low pressure at idle as long as it increases as soon as the revs rise.
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Tick Tock

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Re: V6 2.5 oil pressure
« Reply #2 on: 28 March 2019, 10:28:32 »

Thanks Nick  :y

The pressure switch seems the obvious place to start.

I've heard they are prone to leaks, and on this engine a couple of years ago there were always oil deposits around that area at the front of the engine. A new set of cam covers were fitted, and since then no oil has accumulated, so it's worth bearing in mind that the pressure switch isn't always the reason why there's oil in that area.

I believe they're used across the range, so is a dealer the best place to get one? There's no rush, so an alternative could be found online perhaps?
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Kevin Wood

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Re: V6 2.5 oil pressure
« Reply #3 on: 28 March 2019, 10:38:02 »

Yep, pressure switch and, if you feel so inclined, check the pickup strainer. That has killed a few V6s, especially where they are neglected in an earlier life and then get plenty of oil changes.

If the new switch shows the pressure to still be low, it might be worth checking the relief valve for signs of scoring.

That about exhaust the things you can easily fix - although I'd be tempted to take a peek at a couple of the big end bearings while the sump's off to check the strainer, although I'm not sure if that requries removal of both sump sections rather than just the bottom pan?
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Kevin Wood

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Re: V6 2.5 oil pressure
« Reply #4 on: 28 March 2019, 10:40:42 »

Oh, and I wouldn't go with thicker oil. It might show higher oil pressure, but at the expense of oil flow. An engine doesn't actually need much oil pressure at idle where it's under no load. Provided the pressure picks up at higher revs, it'll probably be fine.
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Nick W

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Re: V6 2.5 oil pressure
« Reply #5 on: 28 March 2019, 17:36:50 »

Thanks Nick  :y

The pressure switch seems the obvious place to start.

I've heard they are prone to leaks, and on this engine a couple of years ago there were always oil deposits around that area at the front of the engine. A new set of cam covers were fitted, and since then no oil has accumulated, so it's worth bearing in mind that the pressure switch isn't always the reason why there's oil in that area.

I believe they're used across the range, so is a dealer the best place to get one? There's no rush, so an alternative could be found online perhaps?


This LINK was the first one that came up in a search. I thought it was expensive, as I paid under 4 for one over the counter at Euro Car Parts. They're used on numerous engines, not just Vauxhalls, so most factors will have them in stock.


Or you could try your dealer, but it will be a lot more expensive, and I doubt you'll walk out with it.


I would only use 10w40 in a V6. Or indeed any engine that it was one of the specified oils. I find that the thinner oils tend to make the engine noisier and leak more. If that's possible on something as filthy as a Vx V6 ::)
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Tick Tock

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Re: V6 2.5 oil pressure
« Reply #6 on: 02 April 2019, 11:18:41 »

I bought the switch in the link above, paid an extra quid to have it delivered for the weekend. One thing and another, hoards of family visiting on Sunday, didn't get around to fitting it until Monday.

All seems well now, engine warmed up toasty and no light on dash except when engine stopped.

Simples - was probably overthinking the situation, but good to have all the input. I suspect the sloppy black stuff that came out when changing switch is probably in other places too, so no doubt the sump will be coming off at the end of the summer.
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