Oil Pressure

[alan]

Hi guys,had the shed in for its 1st mot in 3 years today.It failed on a loose wheel bearing,but then lost oil pressure on the brake tester.The pressure was fine when i started it up but seemed to lose pressure as it got hotter.I have changed to a thicker oil but not to confident that its fine.And as it has not got a pass slip i cant take it for a blast to check.Any ideas guys.

[cam.in.head]

oil pressure when hot should be 0.5 bar minimum at idle increasing to no more than about 4.5 bar when revving . usually find in a good engine it only drops to about 2 at idle with 20w50 oil in or about 1.5 with 15w40.if yours has suddenly changed before doing any major dismantling id be tempted to check pressure releif spring on oil cover has not snapped.

[OPEL PARTS GREECE]

To these engines 20W/50 is great no need any thinner oil

[alan]

I dismantled the oil pump cover and removed the oil pump vains to check for any ware and it did not seem to bad.Then had a look at the spring and plunger and all seem fine.To me it just seemed strange to lose all oil pressure and end up with the light on when at working temp.I was running on 10/40 but now have changed to 20/50 and will see how that goes.Thanks for the help.

[lamchop77]

I dismantled the oil pump cover and removed the oil pump vains to check for any ware and it did not seem to bad.Then had a look at the spring and plunger and all seem fine.To me it just seemed strange to lose all oil pressure and end up with the light on when at working temp.I was running on 10/40 but now have changed to 20/50 and will see how that goes.Thanks for the help.

10/40 is definately too thin, old spec 20/50 Duckhams Q or similar is what you want. The wear on the oil pump usually shows up as scoring in the housing and as scoring on the cover plate. Wet and drying the cover plate on a flat surface cures that one but the housing is a complicated machining so that has to be left. You can put a couple of 6mm (i think)washers behind the spring to increase the pressure at which the plunger moves. Did all this on my old coupe ages ago and it did work but i decided to put a new pump in.

Bare in mind that the oil feed to the bottom end is a 10mm hole. That much oil at 0.5 bar goes everyware when an oil gauge pipe lets go........and yes it is through experiance!!

HTH

Chris

[mantadoc]

You could always have the cover skimmed. It's impossible to get a perfectly flat surface with wet or dry but it will be better but there will be a crown.

Using a gasket on the cover of a non-gasket pump puts pressure through the floor.

Not using a gasket when you should shears the pin holding the cog on the dizzy drive shaft. Although if there was huge endfloat this might work.

Skimming the cover and decking the housing to restore clearances might work really well.

I've washered up the plunger to give 2 bars when hot before now but be warned if going too far or the oil too thick when cold you can blow the seal out of the oil filter.

[alan]

Cheers guys,i gave the cover plate a slight sanding on a flat surface with very fine wet and dry with light oil.A mate of mine who's a engineer,and rally car pit crew told me to use a kitchen formica worktop as a make do flat surface.I basically just polished the surface as i did not want to go over the top.It now is running at over 1 and 1/2 bar at tick over increasing with the speed.I will try to get a 2 hand plate and get him to re-engineer it for me just to make sure.Thanks for the help once again.

[cam.in.head]

that sounds fine now anyway. remember that early cars have a gasket & later cars have a liquid sealer only. cant remember the exact changeover date but replace 'as was'. if you fit a gasket that isnt needed oil pressure at idle will be very low.if you use sealer instead of a gasket itl probably seize ! like i said that sounds ok now anyway.

[alan]

Well guys after about 4 weeks of running fine the gremlins have appered again.I was driving along yesterday in not to bad traffic when i noticed the oil pressure low again and within a couple of seconds the pressure would not lift with revving the engine,so i pulled over and let it cool for 10 min and then it restarted with full pressure again.So i got home and changed the oil and filter again and had a drive.All was fine for about 3 mile and the same happend again.Once again i let it cool and it was fine,i managed to drive it back home again and it was fine.I know its not a faulty gauge or sender as you could hear it was knocking.I was just wondering is it possible to remove the sump while the engine is in situ so i can clean the pick up pipe.I seem to remember doing it before but it was a long time ago.Cheers Al.

[lamchop77]

Well guys after about 4 weeks of running fine the gremlins have appered again.I was driving along yesterday in not to bad traffic when i noticed the oil pressure low again and within a couple of seconds the pressure would not lift with revving the engine,so i pulled over and let it cool for 10 min and then it restarted with full pressure again.So i got home and changed the oil and filter again and had a drive.All was fine for about 3 mile and the same happend again.Once again i let it cool and it was fine,i managed to drive it back home again and it was fine.I know its not a faulty gauge or sender as you could hear it was knocking.I was just wondering is it possible to remove the sump while the engine is in situ so i can clean the pick up pipe.I seem to remember doing it before but it was a long time ago.Cheers Al.

Looks like your big end bearings are on the way out to me. Could be the oil pressure relief valve but you have already looked at that, i assume, when you took the cover plate off. You can just about get the sump off in situ, best to undo the engine mounts and use an engine hoist to lift up a few inches. If the pickup pipe is blocked up it usually drops all pressure hot or cold. Have a look at the oil if there are any tiny silver flecks in it its pretty certain that the bearing surface is breaking up.

HTH

Chris

[mantadoc]

I would expect the tensioner to rattle too as when no pressure or low timing chains rattle like death. However, if the light was still off you probably had 1 bar, there is some conflicting info on whether it comes on at 2 bar or 1 bar depending on sensor etc.

If the gauge went to zero but light off you may have a gauge short.

However, as said does sound wide. If the filter bypass valve is sticking you can get the sam. Is the filter and oil new? Is the oil the correct grade? I.e. non of this new 10w or 15w stuff?

Basically:

Check it's not a false positive (gauges)

Check the correct oil grade

Check the simple stuff

Consider rebuild if bearings wide.

Consider weather to bodge - washers behind valve, maybe it's even the heat wave making it too marginal.... oil cooler without oil stat?

However, if you rebuild but know your pump is marginal the closed clearances may well mean it is fine but you might not have any "lee way" in the pump so life might be dissapointing.

Instead of just sanding the cover (actually get a machine shop to skim it maybe) consider decking the pump casing. OK this does render it scrap if not working but seeing as you can't easily get them who cares?

Do you love the car and want it done properly?

Do you want to make the engine last a bit longer e.g. to go to Billing?

Or is this God's way of saying get a family II engine in?

[alan]

Was definately no oil pressure,oil light on.Was knocking like a gudd un.But as if left for 5 min at the most the pressure back to normal.I am using 20/50grade oil and a new filter.I was wondering that as it was left not running for a long time could there be some thing in the sump ie carbon or sludge washing around and every now and then getting sucked onto the strainer.I am hoping to get the summer out of it and do a full rebuild in the winter when i am bored on them lonely dark nights.Cheers for the help.