URGENT OIL PRESSURE DROP
Turbo Mini Forums

right men i need oyu all to get your thinking caps on with this one ,

John Haston has just called me , his new engine has a problem, at idle 1500 the oil press is circa70lbs ,when he blips it and holds it at say 3k the press drops to 40 lbs,

iv'e never heard of this so have no idea really other than relief springs problems , but he says he fit new ball and spring, also fit ne filter hosing,

this engine has just been rebuilt by MED because of this oil press prob previously, i dont know if new pump has been fitted.
hes has tried a different gauge just in case it was dicky.
any ideas.

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sounds like some kind of pump cavitation issue Carl...

what kind of pump is it - same as he's always run?

Does the pressure rise at higher rpms? Or just sit there?

My engine only ever sees 45psi even at full rpms - so if it does appear to be a cavitation issue from a strange (new?) pump then maybe he can just ramp up the pressure to something he'll be more happy with - say 55psi ?

this prob started when he fired it up this year . the problen was not there last year. so he had the engine rebuilt by aformentioned, but the prob till exists., so one day alls well then its not , the only thing is the two days are 6 mths apart.

could a worn pump do this , i cannot ever remember this happening to me ,even with fooked pumps, IE the pressure always went up not down,even if it was only a tiny amount.

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Does using a thinner grade of oil still produce this effect? Does it do it with the oil hot? Or all the time?

afaik, this is with the engine warm ,at the very least,

are you thinking what i'm thinking ,if its not as bad when its cold oil , but gets worse, or a bigger drop when warm it has to be the pump..
carl

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More I think about it - more it's all the hallmarks of cavitation - basically the pump can't adequatelly fill the entry port with sufficient fluid at higher speeds.
Either it's a bad design, badly machined, or something else screwey...

but dave this problem didn't exist last year ,only when it was fired up this year, and still there after MED expensively rebuilt it ,its the screwey bit i'm interested in.
ask yourself this dave ,have you heard of cavitation on the A series before, i havn't.

unless theres a blockage in the pickup pipe maybe , , this would stop the pump filling as quick as it can pump the oil out,,

come on men , get racking,

carl

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oh, I hadn't understood you correctly before...

A blocked oil pickup pipe would have been spotted at a rebuild surely?

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1/ is the O ring fitted between the G/box & engine ?

2/ i would suspect if a "new" pump has been fitted again and the problem is still there, an intermittent fault like this

the problem would lie with the pressure relief seat, or if the oil gallery plugs have been pulled and tapped they have broken through into the internals of the engine, lost pressure

also check the cross port drilling under the relief valve if the plug has been pulled there

also a sound inspection on the above areas will reveal all

OH! a daft one carl are the correct bearing sizes used ?

Edited by BENROSS on 6th Jul, 2006.

i thought about than ben, but its on the low press side so cannot see tit having anything to do with it ,
think why would the press drop as you spin the pump faster??.

btw, i told him to disconnect the gauge ,stick the loose end in a milk bottle and fire the engine , when blipping make a visual of what the outlet of the pipe is doing .

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blocked strainer or pipe blocked to the pump

US pump

relief valves a above carl

ben ,even a shagged pump will still see a rise with engine speed rise.as above,

as dave says cavitaion, but how ,something must be blocked before the pump to limit replenishment,as above,
i tried ringing him just now , no reply,.

need more info,
carl

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MED

AlexF

as you say carl, more info rqd.

alex is correct also

just a thought, gasket between box mating face and strainer pipe flange .............

pulling air in

after all its above the oil level

pumps dont like any restrictions or air to be drawn in on the suction side!

Air leaks would be something to look at, for example the small plate at the back of the gearbox where the pickup pipe bolts go through.

Is this car using a stock oil system, or does it have something fancy such as a pre-pump filter arrangement?

could be an air leak some were or i would change ball and seat with a stanard plunger and spring first this may be the problem as i know if not fitted correclty they cause allsorts of probs.

always looking for them bigger bunches of bannanas

he tells me he has a magnetic trap fitted to the rear of the box and it must be 4yrs since its been apart, i'm hopeing its clogged to fook,

but on the other hand ,he says when he blips from cold the press goes up, but when warm it goes down,its a new one on me,

well wait and see the outcome of the mag trap removal tonight,

carl

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The mag trap sounds a definate candidate for causing this problem!

Let us know the outcome.

yes the mag trap!!!

as you said carl you need more info and you have it buddy

well ,it turns out he does not have a mag trap ,so were still at 1st base,
he's just going to have to wind the pressure up so he can run next w/end and then i'll investigate.
carl

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