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Oil Pressure - Up and Down


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I seem to ask a lot of oil pump related questions...

Anyway: What does a fluctuating oil pressure tell me when the engine is at constant, high RPM?

This happens at about any rpm, although I notice it most around 3k. It is worse when warm, which I suppose makes sense. As the warm, "thinner" oil is making whatever it is worse.

Worn pump gears? Worn Housing? Bad Pressure Regulator (Don't think it is this, if I'm honest)? Something else?

I know my gears aren't great, as they can't generate enough pressure at a normal idle, but would this lead to a changing pressure when the gears should be spinning at a constant speed? Or could bad gear lash be causing this?

How likely is it that a hole in, or a loosely attached, sump pickup pipe could cause this? Or alternatively worn Main Bearings? ( <-These are my best guesses if it isn't the pump.)

Other symptoms include a long pressure build up time when starting cold. Usually only picks up after the engine has started, so there's often a horrendous clatter for a few seconds before the lifters lube up.

PS. I have got replacement gears on order, but it seems the entirety of Germany has gone on holiday, so the delivery has been delayed. And I decided there was a possibility of there being another cause in addition to the bad gears.

Cheers :thumbup

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Define fluctuating

e.g. reads 3 bar then greater than 5 bar / off scale then back to 3 bar.


The sender has two wires. One is for the oil light, so open circuit when above say 1 bar (light off) and closed circuit below (light on)

The other wire is for the gauge. Low resistance, low reading and hight resistance high reading, broken wire is infinite resistance and hence off scale.

These wires are known to melt and break and short out causing issues.

The sender is behind the exhaust manifold. The other end of the wires is a 2 spade connector by the heater fan power connector.

Never undo the terminal nuts on the sender by holding the sender, always grip the flats on the terminal post otherwise the backerlite like substance will likely shatter rendering it scrap.


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Peaks at around 4, then drops to 2, then rises to 3, then back to 4 for a bit then down a bit then up a bit... That kind of fluctuating.

Never pegs either way (unless the car is off.) Oil light comes on if it drops below 0.8 (<1). Needle moves smoothly, doesn't jump to new positions.

Checked the wiring first, probably should have mentioned that, all seems good/ok. Gauge had decent calibration at the beginning of the year.

Edited by Binnacle-ZA
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Probably been through this before but 2.0S or 2.0E? Oil pump end cover gasket or none? nd float checked with straight edge or not? End cover machined flat or worn?

Correct grade of oil the car was designed for or?


(Or point me at the other thread)

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19S, will assume that's the same as the 20S.

But I'm not sure where the timing cover comes from.

With gasket, as gears protrude slightly with straight edge. (but it's so thin I thought it was a sticker.)

Cover was machined flat few months ago.

Currently using 20w50 was on 25w60, almost no discernible difference. 25W60 was better at idle though.

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Synthetic or semi?

Gasket the correct thickness?

Oil pressure relief valve in cover, case or both?

Assumptions: Oil pickup pipe properly fitted, filter good, level correct, rotor ro case clearance not excessive, filter bypass valve in good order etc

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Neither, Mineral based (Shell Helix HX5 25w60 and Shell Helix HX3 20w50 - Don't know if either of these are available in the UK.)

Gaskets was the thinnest available (I forget the size)

Relief is in case, flat gear cover.

Re: Assumptions:

Oil pickup is one of the unknowns.

Filter is brand new.

Level is correct, leaning towards possibly overfilled.

Rotor/Casing clearance is another unknown.

Filter bypass is working, "looked" alright.


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