Oil pressure problems

[benji]

Wondering if anyone has had any oil pressure related problems.

Occassionaly at idle the oil light will come on, as soon as I rev it, it'll go out.
It's not so low that the lifters start to bleed down, but has me concerned.

The bottom end is near on perfect, no percievable movment in the main or big ends, and the new cam has perfect tolerences (.02mm)
Seems to happen more when the engine is warm, and the oil light will come on after about 10 seconds of idling.
As soon as it fires the oil light goes out (like normal), but when it warms up it'll start to come on.

Only happens sometimes though, other times I can start it up and take it for a drive, and it won't come on at all.

[rc42]

I had a Series III hybrid on Range Rover running gear several years ago, it had the twin SU 3.5 V8 and had exactly the same problem with low oil pressure at low revs when hot.

I confirmed with an oil pressure guage and the problem was real, I think it was just engine wear and would have taken a lot of work to fix. I did think about a new high flow oil pump but I eventually fixed it with oil additives (thickeners) and managed it with good quality synthetic oils plus additives at each change.

[TheTree]

How old is your oil pump? Did you check it out when you had the motor apart?

Steve

[Tank]

Try a new oil pressure sender and see if that is the problem, first, Regards Frank.

[BusinessConnected]

Had the same issue with mine a while back... I added the Lucas Heavy Duty Oil Stabilizer and that stopped the Light coming on...

I've since then replaced the Oil Pump/Timing Chain Set with New Oil etc...

[benji]

Thanks all.

Frank that's a good idea, i've got a new one I put on the 93 which i'll swap over, infact you've jogged my memory in regards to that exact problem I had on the 93.

The pump gears are brand new, but the pump cover and timng cover do have minor scoring marks on them.

If it isn't the pressure switch (re-used the old one), i'll put a guage on there and see what the go is, just have to find one with UNF (UNO) thread and not BSP...

Another thought is the oring on the oil pick up tube - I thought the oring looked okay - though my three year old was using it as a bugle...

[TheTree]

Thanks all.

The pump gears are brand new, but the pump cover and timng cover do have minor scoring marks on them.


I felt like i was stating the obvious, but thought it worth asking. I hope the sender is the culprit and not the bugle :p

Steve

[wanglemoose]

first things first, have you recently changed the oil weight you are running on or to a synthetic oil. you need to put a master gauge on it to make sure of what its doing. if it is normal with the gauge try replacing the switch, if it is dropping pressure try rubbing gouge marks back then check the clearances with feeler gauges, the my case also had scoring on it when i did the engine up so i very carefully rubbed it back with some wet and dry and it works fine.
lastly and the most scary option, is your security system acting like normal,no hiccups driving etc, as part of the initial start up the ecu sends a signal to the BeCM to turn the oil lamp on when you first turn the key on, this is part of the security deactivation sequence on p38's. if your problem is in this direction id start looking at your insurance paperwork and head for a deep water crossing in a gazetted road :wasntme:

good luck and hope its the sender.

[benji]

Lol, deep water in Bendigo?

Im using gtx 15w40 which should be fine- its what ive run before.
Started it yesterday after replacing a lifter and oil pressure switch and its still doing the same thing - but only when its cold. After a few minutes of running it behaves.

Ive found a uno - bsp fitting so ill putting the guage on soon.

Would anyone know what pressure I should be getting at idle, and what pressure the light comes on at, and also how far the strainer is supposed to be off the bottom of the sump?

[benji]

20psi on start up, the down to 10, and then slowly down to .5psi within 20 seconds at idle. When I rev it it goes straight up to 34 and won't go any higher.

I pulled it all down last night and found a bolt stripped on the oil pickup pipe, a slightly loose fitting o ring on the pickup pipe, and the bolt on the oil pump backing page was also stripped and had pulled out about. 5mm.

I assume this would allow air to be pulled in between the backing plate and timing cover, especially when the oil is thick.

Got a few theories as to why the bolts have striped.

Hope this is the problem.

[benji]

20psi on start up, the down to 10, and then slowly down to .5psi within 20 seconds at idle. When I rev it it goes straight up to 34 and won't go any higher.

I pulled it all down last night and found a bolt stripped on the oil pickup pipe, a slightly loose fitting o ring on the pickup pipe, and the bolt on the oil pump backing page was also stripped and had pulled out about. 5mm.

I assume this would allow air to be pulled in between the backing plate and timing cover, especially when the oil is thick.

Got a few theories as to why the bolts have striped.

Hope this is the problem.

[MacMan]

What are the theories on the stripped bolts? Air leaks will definitely cause that sort of relationship between pressure and RPM.

[brend0n]

that sounds exactly what was happening with mine.

mine needed a full rebuild anyway, so didn't bother chasing the issue too hard.

both sender & mechanical gauge was showing issue. I had put in the 'upgraded' oil pump kit too

[benji]

Good to know im on the right road, thanks.

I used the wrong bolts to secure the oil pickup pipe, and to get the pickup pipe on I had to push up the strainer end to bolt it onto the main cap, only an inch, but that was enough.

I didnt know there was an upgrade kit; I assume it delivers more volume?

O'well, we live and learn.

[benji]

Would anyone know what thickness plasti-guage to get? I think checking the bottom end wear would be prudent too.

[djam1]

I had the same issue in a Range Rover Classic towing a 30 foot caravan in 50 Degree head.
Oil pressure went out the floor I was in Kununurra at the time and found a Penrite agent bought some HPR50 and drove it for the next 2 years without issue.

[benji]

Thanks all, those striped bolts werethe problem. Runs sweet as now. 34 @idle and 53 governed.
Ironically a thicker oil would have made the problem worse; sounds like the pump gears in the classic were worn, dad had to do that on his 82.

Just enjoying driving it now.

[TheTree]

Just enjoying driving it now.

Good news :D:D

[redandy3575]

Thanks all, those striped bolts werethe problem. Runs sweet as now. 34 @idle and 53 governed.
Ironically a thicker oil would have made the problem worse; sounds like the pump gears in the classic were worn, dad had to do that on his 82.

Just enjoying driving it now.

Hey Benji

Can you clarify a bit more on this issue as mine just started doing this also.

I'm wondering wether the mechanic may have stripped the bolts after returning from a gasket & cam replacement.

[benji]

Bugger!

On start up the oil light would go straight off, but within 15 seconds it would drop down to .5psi.

Above 1100 the oil light would go out, but max pressure was Ithink 29psi.
It was better when it was warm.

What was happening was when the engine was off the oil would fill the void between theoil pump cover and the front timing cover, making a seal that on start up would allow the pressure to come up. After a few seconds this oil seal would be sucked into the pump and then It'd draw in air. When the oil was warm it'd pump easier so would draw in less air.

It was the bolt on the bottom of the pump plate that was causing the grief. Rave says 6flb, but without a torque wrench it was easily 12-15flb.

What's yours doing exactly?

[redandy3575]

Bugger!

On start up the oil light would go straight off, but within 15 seconds it would drop down to .5psi.

Above 1100 the oil light would go out, but max pressure was Ithink 29psi.
It was better when it was warm.

What was happening was when the engine was off the oil would fill the void between theoil pump cover and the front timing cover, making a seal that on start up would allow the pressure to come up. After a few seconds this oil seal would be sucked into the pump and then It'd draw in air. When the oil was warm it'd pump easier so would draw in less air.

It was the bolt on the bottom of the pump plate that was causing the grief. Rave says 6flb, but without a torque wrench it was easily 12-15flb.

What's yours doing exactly?

The light does go off after start up, but about 15 to 20 minutes later when pulling up at the lights and revs drop to about 300 rpm, the light flickers on until you take off and the revs go beyond about 500 rpm. I know on other brands of cars it used to do that also due to a bit of pressure drop when idling, but wondering wether it's just a low idle issue more so than anything else.

[benji]

I wouldn't think you've got an oil pressure problem, as they're really low revs.
Before I did the motor strip down mine used to bog down occasionally in the revs and the oil light would flicker, and that's happened too on my 93 when tuning the gas.

I'd be interesting to get a nanocom or something like that on there and see what's causing it.