oil pressure dropping intermittently

lrzed · Jun 25, 2008

SO.. I was test driving my rover after a month or 2 of not moving..

I get around the block half way and lose oil pressure.. By the time I can knock on the gauge to see what's wrong.. it starts coming back. Get around the block again... It does it again, in the same place (crest of a hill). I go home.. pull up to my drive, and it does it again.

I pulled the pan.. looked for cracks or anything.. everything seems good at a glance.

I start up the rover this morning.. pressure drops for a second or 2 after idling just fine for a couple minutes.. goes right back..

What could be causing pressure like this.. is it the pump? The sump pickup? The gauge?

choppa · Jun 25, 2008

well ya can stop pullin yer pan fer starters , thats just disgustin .

..... either no oil in it or yer oil pressure switch is broke . give it a service and check it over again .....

lrzed · Jun 25, 2008

I needed to swap out an oil pan gasket anyway.. so I was quick to do so.

I had been jacking the engine under the oil pan.. and though I didn't visibly damage the oil pan.. I didn't know how close pump components were to the bottom of them. Hit a large piece of wood in the road once.. denting my oil pan on a GM car.. knocked the sump loose with similar consequences.. So it was the first thing I checked.

You mean you suspect the gauge sending unit?
Seems odd it would be intermittent like that.. but its what I'm suspecting as an inspection of the parts involved in the oil pump seem to be working or not.. or at diminished capacity.. not intermittently.

The sump is full of oil. The stick reads full and it took the recommended amount..

choppa · Jun 25, 2008

you should check for loose wires aswell if you like it could be that simple .. are you one of our american friends by any chance ?? put your location on yer wotsit at the top of the page .....

lrzed · Jun 25, 2008

I Am.. more or less... one of your american friends.. I am driving an NAS rover on american soil...other than the continent of north america.
I find that you folk know much more of the land rover than around here.

choppa · Jun 25, 2008

ya have to show piccies of yer nas ..... its the law .....

david451 · Jun 25, 2008

lrzed said:
I Am.. more or less... one of your american friends.. I am driving an NAS rover on american soil...other than the continent of north america.
I find that you folk know much more of the land rover than around here.

This could be the pressure releaf valve in the pump or filter head, where ever they fitted it on that model. Sounds like it's sticking, take it out and clean it up with wet and dry providing the spring aint broken or it's too badly scored. But if you want peace of mind just fit a new one I dont think that its worth an engine loss.

All it does is ensure you get the same oil pressure at idle as what you get at full revs, it lifts when the pressure reaches the given pressure. We used to fit spacers behind the springs on them to increase the pressure on our stock cars, with the only drawback that although you got increased pressure you never got increased supply, couldn't afford the high capacity pumps then.

choppa · Jun 25, 2008

nice one david i never thought of that ..... mainly cos i did'nt know about it ....

lrzed · Jun 26, 2008

quite possible.
I pulled the pan and checked that the spring was intact yesterday.. .I have no idea what to check for beyond that.
I was fiddling with the idea its a faulty gauge.. It does seem to have stabilized.

BUT.. my warning light sender is either broken or complaining that there's no oil pressure (checked at the sender not at the dash have full earth connection at the sending unit)

So I 'm a bit stumped.

I pulled the valve cover just to be positive I was getting some sort of oil.

And sure enough the valves are getting a good steady stream of oil.

Possible the pressure relief WAS sticking due to it sitting and now its free or mostly free.

I'm getting no change in the sound of the engine when the gauge reads 0 or when it reads 2.5 bar.

lrzed · Jun 26, 2008

OK.. so my gauge has been reading reasonably without dropping at idle.. I haven't moved the car and it was fluctuating earlier.. maybe an electrical connection, maybe a sticky pressure relief?

Thing that had me real worried was my warning light sender.. to have both fail was coincidental enough to look into seriously.

At first my warning light sender was grounded.. engine on or off.. I removed it.. sprayed it out.. threw it at the ground a few times.. Now it is functioning normally telling me I have pressure.

The gauge is reading fine now. Whether it is a fault in the wiring that caused the reading or a sticky valve I may never know.

I pulled the valve cover (had to re-adjust some overly loose valves as well) and had good oil flow to the rocker.

I THINK i'm good now. Think so.

Hope so.. Knock on wood..

Think I'll run a litre or so of marvel mystery oil or similar through there just in case i have some gunk that could be easily dissolved and cured.

I've ordered a new sender just in case.. and will work on getting my dash light fixed. Some short in the wiring some where.. its powered but doesn't have continuity to the sender...which follows the same path as the gauge.. maybe indicating a pinch short somewhere.

david451 · Jun 26, 2008

lrzed said:
quite possible.
I pulled the pan and checked that the spring was intact yesterday.. .I have no idea what to check for beyond that.
I was fiddling with the idea its a faulty gauge.. It does seem to have stabilized.

BUT.. my warning light sender is either broken or complaining that there's no oil pressure (checked at the sender not at the dash have full earth connection at the sending unit)

So I 'm a bit stumped.

I pulled the valve cover just to be positive I was getting some sort of oil.

And sure enough the valves are getting a good steady stream of oil.

Possible the pressure relief WAS sticking due to it sitting and now its free or mostly free.

I'm getting no change in the sound of the engine when the gauge reads 0 or when it reads 2.5 bar.

If it came into the garage the first thing we would do is connect a pressure guage, this eliminates oil pressure issues, otherwise you go in circles.

Is the pressure guage on your vehicle connected by a pipe or combined into the warning switch. If it's a pipe direct to the engine, and the oil light is coming on as well then it's oil pressure problems I would say.

The pressure relief valve is in the pump behind the spring, usually the spring is held in with a cup like a core plug, and that section of the pump sits hard against the block to stop the cup coming out.

I have seen engines run quite happily with no oil pressure, particularilly push rod ones, the crank is the area in there where it would fail and it takes quite a bit of time for that to happen. On overhead cams they die quite quickly, siezing up and breaking the timing belt, if you try to run one with the cam cover off you will soon see how much oil they need to survive.

lrzed · Jun 26, 2008

yes.. I inadvertently left the oil fill cap off a toyota OHC engine.. oil everywhere..

I took the top off this one.. and it just dribbles nicely... Helps that its upright and not in a V format. Can idle it with the top cover open barely spilling a drop.

My sending unit is sending good info and my oil pressure gauge (smiths electric gauge) goes along with it and I have good flow at the valve rockers.

Think I'm good. Like I said.. I may never know what the problem was.

For good measure I had it sit and idle while I worked on some other things.. had my continuity tester hooked up so that it would beep when the sending unit triggered a low pressure. Just incase it was still happening and I wasn't able to notice it.

It beeped until the engine started.. then beeped again when i turned it off.. no beeping in-betwixt. I'm going to watch it..

But like I said.. think Its righted its self or wasn't a problem other than a short to begin with.

oil pressure dropping intermittently

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