Oil Light

hi all on my 1992 3.9 rr the oil light takes ages to go out i put a new switch it was still the same so i have put new pump gears and a new pump cover on it and its still the same i have also noticed it takes a while for the light to come on when you stop the engine and leave the ignition on
HAVE I GOT BIG PROBLEMS
can anyone help me with surgestions
THANKS IN ADVANCE

may have a restriction in the oil supply to the switch.
takes a while for pressure build up and a while for the pressure to disipate!
remove the switch, pull ignition leads so engine dont start and crank it over, this may pump out the restriction?? if there is one!.
see if you can get someone to turn key for you so you can see what comes out!
may be worth sticking a pressure gauge in place of the switch just to check pressure, then at least you know if you have pressure trouble or not!

and erith, thats very local to me, used to spend a lot of time at a place just of yarnton way, a lot of time......

It's possible the oil pressure relief valve is stuck closed. That said, V8's especially the pre cross bolted never achieved great oil pressure, even the handbook stated that the oil pressure light comingon when warm at tickover is normal. Obviously with such a large crank and number of bearings there is more scope for the pressure to get away.
Redrange is right-check it with a gauge, if it's giving you around 50p.s.i. above 1500 revs (Warm) things are very good.I doubt you will get more than 65psi hot with the design of the old pump when the engine is warm. Is it a new engine??

no mate it an old engine and its done 129 thou miles i am thinking it could be the big and main bearings

When the big end and main bearings go, the opposite usually happens because of the wear, increased bearing clearances mean that the oil has less restriction and flows out through the increased gaps more easily and therefore the pressure drops. On the other hand, if there is oil starvation caused by say a blocked gallery or oilway the pressure will increase and starvation would occur which would in time knacker the bearings. The fact that it has done over 120K doesn't worry me because if it has been looked after with regular oil changes etc. and was a good lump to start with, the V8 can go on & on. Do you have any knocks or other weird noises etc??
I had a 3.9 Vogue which did over 140K before the block gave out and when I took the bearing caps off out of curiosity, the bearings looked brand new.

the thing is once it warms up the oil light goes out strait away when cold it takes ages to go out and ages to come on once the engine has been stopped

BIG T said:

the thing is once it warms up the oil light goes out strait away when cold it takes ages to go out and ages to come on once the engine has been stopped

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What viscosity oil are you using? Should be 10w/40

Riggaz

riggaz said:

What viscosity oil are you using? Should be 10w/40

Riggaz

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castrol gtx mate

BIG T said:

castrol gtx mate

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what castrol gtx?, theres more than one!
you can buy GTX in varuious different grades and its the grade thats important, you really want 10w/40
sounds like you oil may be too thick! taking too long to get through the system when cold (thickest) but ok when hot (thinner)

i use catrol magnatec 10w/40. go into halfrauds or somewhere like that and have a look at the oils, there loads of different grades, like i said it the grade that matters.

hi its 10/40 that i am useing

I feel that the oil viscosity is not that imortant unless you are using EP90. Admittedly I use Valvolene 10/40 but even 20/50 would not give the problems being encountered. I still go along with Redrange's origional comment to stick a pressure gauge on it. A lights o.k. but doesn't give the true picture until the damage is done.Perhaps I'm an old sceptic (Or septic) but you can't beat the needle pointing to a number to see whats going on in the bowels-bit like a good curry really!!

i have changed the oil and filter today (10/40 GTX OIL) and the light is taking even longer to go out now when cold i cannot work this out some has told me that its the main and big ends gone but its not knocking i was going to engine flush it but i have been told not to any more suggestions PLEASE

BIG T said:

i have changed the oil and filter today (10/40 GTX OIL) and the light is taking even longer to go out now when cold i cannot work this out some has told me that its the main and big ends gone but its not knocking i was going to engine flush it but i have been told not to any more suggestions PLEASE

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What was the reason for not flushing it?

Riggaz

BIG T said:

i have changed the oil and filter today (10/40 GTX OIL) and the light is taking even longer to go out now when cold i cannot work this out some has told me that its the main and big ends gone but its not knocking i was going to engine flush it but i have been told not to any more suggestions PLEASE

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If the oil pick up strainer has a layer of varnish on it the oil pressure will drop as the restriction is before the pump.

Riggaz

riggaz said:

What was the reason for not flushing it?

Riggaz

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i was told its not a good idea to flush a old engine as it could do worse than good

BIG T said:

i was told its not a good idea to flush a old engine as it could do worse than good

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Unless your engine has been seriously neglected it wont do it any harm at all. That tends to be the theory of old skool mechanics that think there is big deposits of soot and carbon in the engine keeping it tight and if you flush it these will be cleaned away. The truth is bud since about 1995 oil companies have been making oil with higher levels of detergent and dispersant additives in them to enable them to meet manufacturers specs and to cover diesel applications as well thus meaning they only have to make one oil to cover both petrol and diesel so deposits that big will have been removed by these higher spec oils. Using engine flush these days is critical to extend the performance life of the oil, especially on extended drain intervals (VAG, GM) where the oil get incredibly acidic and contaminated and if you dont flush then the residue left from the old oil greatly reduces the performance life of the new. It probably wont fix your problem but dont be afraid to use it in the future.

Riggaz

riggaz said:

Unless your engine has been seriously neglected it wont do it any harm at all. That tends to be the theory of old skool mechanics that think there is big deposits of soot and carbon in the engine keeping it tight and if you flush it these will be cleaned away. The truth is bud since about 1995 oil companies have been making oil with higher levels of detergent and dispersant additives in them to enable them to meet manufacturers specs and to cover diesel applications as well thus meaning they only have to make one oil to cover both petrol and diesel so deposits that big will have been removed by these higher spec oils. Using engine flush these days is critical to extend the performance life of the oil, especially on extended drain intervals (VAG, GM) where the oil get incredibly acidic and contaminated and if you dont flush then the residue left from the old oil greatly reduces the performance life of the new. It probably wont fix your problem but dont be afraid to use it in the future.

Riggaz

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thanks for that mate

you say in one of your other replys about the oil strainer is this a big job to do would this also cause the oil light to take a while to come on after the engineis stopped and ignition is on

BIG T said:

thanks for that mate

you say in one of your other replys about the oil strainer is this a big job to do would this also cause the oil light to take a while to come on after the engineis stopped and ignition is on

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A Forte engine flush would disolve any varnish on the pick up strainer pal so no need for a strip down. It can cause low oil pressure because the restriction is before the oil pump and can exellerate wear around the engine and you only need a small amount of laquer / varnish to reduce oil flow, also if the oil return galleries are restricted in the head then this can bring the oil light on but only usually when your gunning it as the oil cant get back into the sump fast enough, like some of the other chaps say wear is the main reason but diagnosing which part is worn is very difficult especially on an engine thats covered a high mileage. The trouble with low oil pressure problems is that it is so difficult to pin point, it could literally be anywhere in the oil system. Do a pressure test to find out exactly what the pressure is at least you'll know how bad the problem is, it should be between 2.1bar - 2.8bar @ 2400rpm.

Riggaz

riggaz said:

A Forte engine flush would disolve any varnish on the pick up strainer pal so no need for a strip down. It can cause low oil pressure because the restriction is before the oil pump and can exellerate wear around the engine and you only need a small amount of laquer / varnish to reduce oil flow, also if the oil return galleries are restricted in the head then this can bring the oil light on but only usually when your gunning it as the oil cant get back into the sump fast enough, like some of the other chaps say wear is the main reason but diagnosing which part is worn is very difficult especially on an engine thats covered a high mileage. The trouble with low oil pressure problems is that it is so difficult to pin point, it could literally be anywhere in the oil system. Do a pressure test to find out exactly what the pressure is at least you'll know how bad the problem is, it should be between 2.1bar - 2.8bar @ 2400rpm.

Riggaz

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I have just bought a new pickup pipe strainer ect so i was just going to fit them

BIG T said:

I have just bought a new pickup pipe strainer ect so i was just going to fit them

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Just remember the strainer is just one of a list of things it could be so it might not cure it and it might not be necessary to fit a new one if you flush it but if you have one already i suppose it's one thing off the list, whilst you've got the sump off you could check the big end bearings for wear. Tightening torque for the sump bolts - 20NM just incase you didn't have the info. Low Oil Pressure this might interest you big t to give you more of an idea of the different possibilities, there is a few.

Regards

Riggaz