Sudden loss of oil pressure... Help :(

[tejr]

Was looking forward to getting the Cerb back from the Bespoke Performance/TVR centre all week after it was running a little rough.. A tune up and some fresh HT leads later and it was driving superbly, until I got almost home and the oil pressure light began to flash on the SPA gauge as the pressure fell below 25psi on idle..

I drove it nearly all the way home so sensibly and only gave it a little stick for about 5mins on the A406 and then hit some traffic and came to a stop to be greeted by the flashing light! Typical that it happened as i got home and just while I was still nearby the TVR guys

So basically, here are the symptoms-

Idle - 18-20psi (used to be a strong 45psi when hot)
upto 4000rpm (didn't risk any higher) - 30-40psi (used to be 50-60psi when hot)

So its dropped 20-25psi across the rev range.

Duff sensor? oil pressure releif spring? oil pressure sendor unit? Or worse case scenario - Oil pump!? Though the pump was re-built around <10k miles ago if I'm not mistaken.

Oil levels are fine, will check again when the car has fully cooled.

Was SOOO looking forward to driving it this weekend, the sun has even come out now that I'm at home too :'(

[brakedust]

As far as I remember the low pressure light and gauge get there signals from 2 different places, so likely to be a pressure problem.
I would change your pressure relief spring first, only about £8, then go from there

[tejr]

A friend of mine has just given me a verbal arse kicking telling me to get out there and check if the spring is broken to put my mind at ease! So I guess I better do so!

So where do I find this spring?

[steviejasp]

This :

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

If you need one tomorrow and want to collect it from me at Goodwood, i have a spare

[brakedust]

its an easy job, just jack up the drivers side and slide under, I think I removed my wheel to make it easier. If I remember its a 24mm or 22mm spanner you need, I would change it anyway as just looking wont help if it has depressed over time

[jammy_basturd]

I'm betting my tuppence on it having snapped.

[itiejim]

Sounds like a spring - but there's no way that the oil light should come on at 25psi - I think they're supposed to be calibrated to 7spi.

So - either you've got 7 psi and your pressure gauge is all over the shop or you've got 25 psi and the oil pressure sender is miles out.

An alternative theory - (oil-pressure-gate if you like) - 45 psi is very high at a hot tick over - much, much more than you need (or indeed is desireable as I've said before). However, that doesn't stop people looking for high oil pressure as a sign of AJP happiness when they buy a car. Could it, therefore be possible that yours was bodged to get a really high oil pressure reading? A rivet in the oil line before the oil pressure take off would be enough (much like putting your finger over the end of a hose)... If so, it could be that the artificial oil blockage has moved.

Anyway:

1. You don't need 45 psi at tick over - 25 is fine.
2. If the oil light is coming on you need to be sure that this is faulty rather than having sub-7psi
3. It'd be nice to know why the change...

[tejr]

Found it in the end, what an arse to get to! Didn't have the right spanner so used an adjustable which was too bulky really but got there after about an hour of fiddling to get it back on! jacking it up might have been easier with the wheel off instead of drive on ramps.

Anyway, spring is not snapped Was really hoping I was going to find two pieces in there which would account for the sudden drop as I reckon a lazy spring wouldn't have caused such drop all of a sudden? How hard should the spring be? It doesn't take a massive effort to compress though to be fair it is quite lazy to spring back into shape.. No cracks or breaks though -



Steviejasp, appreciate the offer but am no where near goodwood Unless anyone else around London has one spare they are willing to sell?

Also, in regards to the oil light, its the progammable warning light (seems like its set to 25psi) on the electronic SPA gauge which I had fitted to replace the mechanical one

although 25psi (though its actually closer to 18-20) should be ok at idle, the sudden drop is what has worried me and that it won't go over 40 which can't be good if I were ever to venture above 4krpm?

Edited by tejr on Saturday 5th March 16:03

[jammy_basturd]

They didn't fit a new oil filter at the garage did they?

[tejr]

Nope, just new leads and a tune up.. Have rang a few places to source a new spring just to change it out as a matter of course anyway but seems no-one is going to be open till Monday now

[steviejasp]

My offer still stands! If you want to collect it tonight from near Brighton, im in all night!!
Failing that, is anybody you know going to goodwood tomorrow?

[tejr]

Appreciate it Stevie, though even then I'd probably have to wait till the evening to fit the spring by which point it would be dark anyway Will call up a few suppliers on Monday and see if I can get it sent special delivery for Tuesday or something and try changing it after work. Least I can rule that out early in the week then, and if needed after that think about getting it back to the TVR centre

Less than a months till I am off to Spa/nurburging! I'm praying its nothing major like a dud oil pump!

[steviejasp]

No prob. Hope you get it sorted for not too much money!!

[tejr]

Just searching around and it looks like the oil pressure switch is by/under the coil packs? Is it possible this could have been disturbed when changing out the HT leads?

[jammy_basturd]

Do you still have the original oil pressure guage?

As far as I'm aware the oil pressure warning light and the oil pressure gauge go off two different senders. If they are both showing the same sort of readings then it would suggest it isn't a sender problem.

Besides, if it was a sender problem I'd expect it to either read something, or not.

[brakedust]

Just an idea... If you measure your spring, and Stevie measures his you will be able to tell if yours has depressed over time?

[spongy]

Bud doe's the engine sound any different when running,we had a yank motor go last year which turned out to be oil pump,did no further damage but when it went you could hear the motor sounded wrong,and it idled really bad.Thing was the motor was running fine,came back from garage and a week later this happend.

[tejr]

jammy_basturd said:

Do you still have the original oil pressure guage?

As far as I'm aware the oil pressure warning light and the oil pressure gauge go off two different senders. If they are both showing the same sort of readings then it would suggest it isn't a sender problem.

Besides, if it was a sender problem I'd expect it to either read something, or not.

I don't have the old gauge, no

Also, just to make things clear, the warning light I'm referring to is the red LED at the top of the SPA gauge, not the standard warning light (which I think is in the speedo next to the battery warning light?)

brakedust said:

Just an idea... If you measure your spring, and Stevie measures his you will be able to tell if yours has depressed over time?

Good idea, though I've popped mine back in the car now ! D'oh

Going to order a new one Monday either way and see what happens.. Though does anyone know how stiff and springy the spring should be? Should it be relatively easy to compress? Mine doesn't 'spring' back to its old shape and is quite slow and lethargic to return to its original length..

spongy said:

Bud doe's the engine sound any different when running,we had a yank motor go last year which turned out to be oil pump,did no further damage but when it went you could hear the motor sounded wrong,and it idled really bad.Thing was the motor was running fine,came back from garage and a week later this happend.

Not at the time no, the car sounded the same. Though it sounded a little grumbly after I removed the spring and put it back in, though that may have just been because it had cooled down. On idle is sounds fine.

Edited by tejr on Saturday 5th March 17:58

Edited by tejr on Saturday 5th March 18:00

[steviejasp]

Ive just been out to check.
You cannot compress the new spring fully with just your finger and thumb.
Hopefully all you have is a weak spring?

[tejr]

I didn't compress it fully, but I reckon I could have gotten atleast 90% of the way there.. So sounds like its gone weak

I guess the first port of call is changing the spring and taking it from there. Will panic after that if it doesn't resolve it!!

Thanks for the help chaps Will keep you posted when I change it out early next week!

When I get the old one out I'll measure it against the new one and I'll also measure how much I can compress both new and old with just my finger and thumb just so if anyone ever searches on this thread they can have something to compare against.

Edited by tejr on Saturday 5th March 18:14