Low Oil pressure....Why?

[ldavies83]

K, I'm stumped and I need some help here!

Did an oil flush/change yesterday with new filter.

Tip

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Removing the old oil filter can be done from up above, meaning you wont dribble hot oil all over yourself! I slackened the filter from below, then got up above put my arm around the dizzie and just under and you can easily get to the filter from there!

After topping up the oil pressure was a lot better, just above the midline. I took it for a 15 mile jaunt and pressure was holding well, just above the 2nd main notch. However when I got back home the pressure dropped right down to 1/4 I check oil level, and it seemed quite low, but it was immediately after I stopped the engine.

Anyway started the engine this morning to take it too work and pressure is back to normal!?!

I refilled with 15/40 Mineral Oil for running in (been meaning to do it for a while) is the oil just too thick!?!?

I just dont know whats up.

[ldavies83]

Bump, Anyone got any ideas? I'm a little worried

[MartG]

With the oil hot the pressure will be lower than when its cold, especially at tickover. IIRC there was a thread recently where it became apparent that there is a wide variation on the pressure seen on the gauge between several cars of similar age/mileage - possibly just production variations in the resistance of the sender and the gauge itself.

[JJ]

If you fancy freshening the oil pressure up the mechanical way, how about a complete change in big end bearings... they're quite simple to change out and like with corollas / Mk1's, they do wear with age and as a result, the pressure drops.

You could get a full set of big ends ( 1 for each rod ) for around £40, some instant gasket, oil pickup gasket - 2 to 3 hours later.... job done.

You have to put your frame of mind, if your putting a thicker grade oil in, your reducing the flow partially to the components ... perhaps this hindering in flow having long term knock on effects of further premature wear of the bearings.

It could simply be the crappy sender too !

[ldavies83]

Thanks Mart,

I've chatted to my AW11 Powered Kit Car manager, and he's given me some figures and said it would be normal aswell. 60psi at Cold and 30psi at hot, in which case it should be ok. I've just got to remember after a hard drive give it a couple of miles to cool down, cause the needle was in the low quarter region.

Thanks for that

[ldavies83]

I think I might do it if I start getting consistantly lower than average oil pressure, but seeing as it only happened with the car under stress, I reckon I'll drop the oil and refill with good 'ol 10/40 magnetec

[MartG]

Have you got an oil cooler fitted - if so what is the thermostat set at ? Could be that the oil is getting a little too hot.

[ldavies83]

Dunno, Standard AW11 Engine, so probably not, although it does have a dodgy release valve bypass to sump hose thingy! (If you catch my drift!)

Ho Hum... I'll change the oil again, and see how that affects it.

Cheers

[Icsunonove]

Leigh, it could just be a dodgy sender unit. I've been through all this worry before with my Fiat Coupe. I bought and fitted a new sender unit and bingo! the oil pressure is excellent!

[ldavies83]

Thing is Oil pressure is fine when cold (or at least my definatition of "fine"), so I wouldnt have thought it was a dodgy sender


The needle sits just above dead center at cold idle, and at warm idle just below dead center. On one occassion though (immediately after the oil change) it zonked to 1/4 on the guage and that just did not look right at all!

[Lauren]

Dunno, Standard AW11 Engine, so probably not, although it does have a dodgy release valve bypass to sump hose thingy! (If you catch my drift!)

Ho Hum... I'll change the oil again, and see how that affects it.

Cheers

You defo have an oil cooler all UK MK1s do.

Bizzarely its the SCs that don't.

[ldavies83]

Thanks for the clarification Lauren, I know the AW11 powered Corolla had a separate Oil Cooler Rad, I was thinking there was something like that on the MR2, which I hadn't seen.

Nevermind!

[Tony jinxy froude]

Put half a dozen sender units on there & they will all be different, i even had a brand new one which was reading wrong, too many factors to consider, poor wiring conection, proper oil tight seal into block, etc, as long as you keep an eye on it dont worry, Jinxy

[ldavies83]

Cheers Jinxy, Reading the MrT MR2 Owners Manual put my mind to rest It suggests right down to near the bottom of the guage as perfectly acceptable for idling, so in actual fact I have a nice engine