16 replies to this topic

[Spannermanal]

Hi.

Just finished rebuilding my 1098 and having started it up and run it, it has very low oil pressure, at about 25 psi idle and revved - although not highly.

The engine has had a reground crank and new shells, new piston rings, new big ends and cam bearings, new 266 cam, new oil pump and followers.

I have also replaced the baulk rings in the gearbox and fitted a central oil pick up.

The oil level is on max, new filter etc. I know the guage isn't faulty as the old engine I took out had a good 50-60psi.

The oil light has not come on, but noticed that when I drove it at low revs after stopping, the gearbox sounded very whiney.

I didn't replace the oil pressure relief valve but did remove it when the block when chemically cleaned.

The engine work was carried out by County Engineering from Almondsbury, North Bristol, who I was told were good. - I am not looking there for any blame yet - just need to know what might be the cause of the low pressure.

Any help or ideas gratefully received!

HELP!!!

[AndyMiniMad.]

First thing I would check is your relief valve...Is it stuck? Next thing is...What type of guage is it? capilery? Electric? If the former then has air got into the tube? Air will compress giving you a false reading. Did you prime the oil pump properly?
Hope this helps!!

[sledgehammer]

Change the oil filter - & slowly fill to brim with fresh oil , just to eliminate it
as said above oil relief valve , gently tap the cap bolt with a hammer

[Spannermanal]

First thing I would check is your relief valve...Is it stuck? Next thing is...What type of guage is it? capilery? Electric? If the former then has air got into the tube? Air will compress giving you a false reading. Did you prime the oil pump properly?
Hope this helps!!

It's a capillary guage and I don't think there is air in it but will check. The oil pump was primed when fitted and the engine also craneked over well before putting plugs in and firing.

[Spannermanal]

Change the oil filter - & slowly fill to brim with fresh oil , just to eliminate it
as said above oil relief valve , gently tap the cap bolt with a hammer

I filled the oil filter (new) when I fitted it so am confident that it was full of oil.

[Spannermanal]

Just tapped the oil relief valve a good few times (not hard) with a hammer and socket extension bar. No difference. Should I take the relief valve out? Should it be a tight fit into the block or move in easily?

[dklawson]

If the former then has air got into the tube? Air will compress giving you a false reading.

Air in the line will not give you a false/low gauge reading. Period.
Pressure is pressure. The oil will compress the air and then the gauge will display the oil pressure. The only issue with air in the oil pressure line is a VERY slight delay in seeing changes in oil pressure.

Spannermanal, you said the engine was rebuilt. Did you fit the gasket between the oil pump and block? Did you fit the o-ring between the gearbox and block?

If you are certain all the seals were installed, by all means remove the relief valve and make sure it is free to move and seating properly. If it is stuck open a bit the oil will be released to the sump and you will see lower pressure on the gauge.

Hopefully this will not be the issue, but... when you fit all the new parts, did you check the bearing clearances? I know you said the crank was reground but do you know that the shop took this to the right increment and that you had the right bearing shells to go with the reground crank?

[Spannermanal]

If the former then has air got into the tube? Air will compress giving you a false reading.

Air in the line will not give you a false/low gauge reading. Period.
Pressure is pressure. The oil will compress the air and then the gauge will display the oil pressure. The only issue with air in the oil pressure line is a VERY slight delay in seeing changes in oil pressure.

Spannermanal, you said the engine was rebuilt. Did you fit the gasket between the oil pump and block? Did you fit the o-ring between the gearbox and block?

If you are certain all the seals were installed, by all means remove the relief valve and make sure it is free to move and seating properly. If it is stuck open a bit the oil will be released to the sump and you will see lower pressure on the gauge.

Hopefully this will not be the issue, but... when you fit all the new parts, did you check the bearing clearances? I know you said the crank was reground but do you know that the shop took this to the right increment and that you had the right bearing shells to go with the reground crank?

I'm sure that the gasket was fitted to the pump as I did the alterations suggested by Keith Calver in the Mini Magazine recently i.e. filing out the oil way in the block slightly and lining up the oilways on the crank bearings.

I didn't check the machining as I don't have the equipment to do it - you have to trust the engineers which is why I sought recommendation.

I am also sure that I fitted the O ring between box and engine.

I guess I can take the pressure relief valve out to check before the inevitable - engine out?!! If I do take it out and dissemble, where should I look first?

Can anyone confirm that the noisy gears at low revs is oil related - I would have thought that the gearbox is full of oil and therefore the gears are submersed? Would the diff make this noise too?

Edited by Spannermanal, 15 September 2011 - 08:25 PM.

[sledgehammer]

When I said oil filter - I meant replace it - as new ones can be faulty
also check the bolts in the plate at the back of the gearbox that holds the strainer pipe
they are under vacuum - so may show no oil leak - but may leak air
(don't undo bolts , as strainer may move)- just check for tightness & gasket
if all else fails , make sure the engine can't start , remove plugs & oil filter , put clean container under filter area
crank engine , see if you get good oil flow , without air bubbles - it may dislodge something blocking the way ,
- it will be messy
best of luck

Edited by sledgehammer, 15 September 2011 - 09:20 PM.

[sledgehammer]

and are the gears noisy when clutch is depressed ???

[minimender]

Could try a new oil pressure relief valve and spring, the spring could be weak.

[liirge]

Here's a long shot - try tightening the two bolts on the gearbox that tighten the central oil pickup (they're at the back of the box) see if this helps.

[Spannermanal]

The gears are fine when the clutch is pressed. They just got very noisy (like an old lorry) when after stopping, I tried to pull away again - like there was no oil in the gearbox?

I will change the oil pressure relief valve for the one from my old 850 which I know was fine. I'll also check the bolts on the central oil pick up pipe. Failing that it seems like I have a date with an engine hoist - but as I posted earlier, where should I be looking for problems?

[Gulfclubby]

Air in the line will not give you a false/low gauge reading. Period.
Pressure is pressure. The oil will compress the air and then the gauge will display the oil pressure. The only issue with air in the oil pressure line is a VERY slight delay in seeing changes in oil pressure.

Agreed. In fact it is next to impossible to get all the air out of the pressure line to the gauge. And even if you do, once the car has been sat for a while, the air will return as the oil drains into the sump. If the gauge is not damaged, the line is tight but the pressure is reading low, then there is a problem.

[jaydee]

The gears are fine when the clutch is pressed. They just got very noisy (like an old lorry) when after stopping, I tried to pull away again - like there was no oil in the gearbox?

I will change the oil pressure relief valve for the one from my old 850 which I know was fine. I'll also check the bolts on the central oil pick up pipe. Failing that it seems like I have a date with an engine hoist - but as I posted earlier, where should I be looking for problems?

Oil pump not correctly torqued.
Engine/gearbox o-ring.
Both of them are engine out jobs