oil pressure warning light

[tee3peeo]

Hi
my oil pressure light came on yesterday after driving around town for about half an hour. However it's only on at low revs, eg tickover. Anything above that it goes out. Stopped looked everything over - it all seemed ok so decided to risk driving home - at first oil light stayed off but then as the engine warmed up, same problem again on tick-over.

At the moment I'm hoping its a dodgy switch - any one have experience of this? Is it easy to swap the switch?

I wasnt sure if this was mechanical or electrical

cheers
Zeb

[marlinowner]

Which engine is this? The oil pressure switch is easy enough to change, but it sounds like a genuine warning to me. You could try changing to a thicker oil, eg 20w50 to see if that makes it go away.

[marlinowner]

From what I can see it looks like you have a 1.9DG syncro, if that's the case then the oil pressure switch is between the pushrod tubes on the lefthand side of the crankcase.

[tee3peeo]

sorry - I copied and pasted the message and I missed the top bit off
1985 14" syncro
1.9 petrol DG

[tee3peeo]

thanks marlin owner - I'm currently using 20w50
before I come over cold sweat I'll try changing the switch

[marlinowner]

This is the switch

http://www.brickwerks.co.uk/index.php/t ... -blue.html" onclick="window.open(this.href);return false;

You'll need a 24mm socket to unscrew it.

[tee3peeo]

thanks again marlinowner

[kevtherev]

It's common to blame the oil pump for low oil pressure, but as I'm sure you know, excessive mains and rod bearing clearances (more than about .001 inch per inch of diameter of the crankshaft journal) can cause up to a 20 percent or greater drop in oil pressure.
Excessive clearances elsewhere in the engine can also further reduce oil pressure. This includes wear in the lifter bores, excessive clearances between the camshaft journals and cam bearings, and excessive end play in the cam. Of course, any cracks in the oil galleys, leaking galley plugs, or leakage between the oil pump and block will also reduce pressure.
That said, an oil pump change is the first step... it's easier and removes it from the equation.

If it's not electrical then an engine overhaul is on the horizon.

[kevtherev]

Some other reasons.. for those that searched and found this post


The pressure relief valve, can be yet another cause of low oil pressure if the valve sticks open or is held open by a small piece of debris. The relief valve is designed to limit oil pressure as engine speed increases. The valve opens when pressure reaches a preset value (typically 40 to 60 psi). This vents oil back into the crankcase and limits maximum oil pressure in the engine. The reason for doing so is to prevent oil pressure from reaching dangerous levels. Too much oil pressure can be just as bad as too little because excessive pressure can rupture the oil filter or even blow out pressed-in oil galley plugs in the block.

Low oil pressure may also be the result of air in the pump. If there is too little oil in the sump, air can be drawn into the pump. But this can also happen if the crankcase has been overfilled. The oil can become aerated (full of tiny bubbles) because it is making contact with the spinning crankshaft and is being churned into foam.

Sometimes the engine may become starved for oil at higher rpms because the oil is not returning quickly enough to the crankcase. The underlying cause here is usually severe varnish buildup that restricts the oil return holes in the head.

A plugged oil filter can be yet another cause of low oil pressure. When the oil leaves the pump, it passes through the filter before going on to the bearings and oil galleys. All filters create a certain amount of resistance to flow that increases with the rate of flow. But the amount is not much, typically only a couple of pounds. But as the filter becomes clogged with debris, the restriction created increases. Eventually the point may be reached where no oil will pass through the filter element. So to prevent such a blockage, a pressure relief valve located in the filter or where the filter mounts to the block is designed to open if the pressure differential across the filter exceeds a preset value (typically 5 to 40 psi). This allows the oil to bypass the filter and keep on flowing. But the engine's oil pressure will be reduced to that of the bypass valve. Replacing the plugged filter will solve the problem.

Taken in part from AA1car

[kevtherev]

Finaly get your oil pressure tested at a garage with a wet gauge, and allay your fears

[MidLifeCrisis]

"Brake warning light also comes on .... " - Does it ??????

[kevtherev]

Early van?

[ScienceBoy]

Mine does the same, and as Kev's attachment goes out upon acceleration/revs. Will get pressure checked at some point.
Great info Kev. Thanks.

[MidLifeCrisis]

Early van?

I have an early van - yes - as in the single oil pressure sensor system (and no buzzer of doom) ...... can't see how the wiring supports the brake light coming on ????

[kevtherev]

Early van?

I have an early van - yes - as in the single oil pressure sensor system (and no buzzer of doom) ...... can't see how the wiring supports the brake light coming on ????

It doesn't, the reservoir in later vans has a switch to indicate low fluid level, which lights up the handbrake warning lamp.
Perhaps the wording is slightly confusing you?
the brakes and oil pressure lamps are different entities, the text says you must stop if either come on.