Oil pressure slow to build

[Rick60]

Hi all,

Did a quick search of the forum but found nothing similar. I've recently serviced my GT6 and find that oil pressure now takes an age to build. Ok so probably only 4 or 5 seconds, but that's 3 or 4 seconds longer than it used to.

I dont believe I've done anything different to how I've serviced it every year for the last 10 years.

I use Halfords 20/50 and all the service items came fron David Manners.

Any suggestions?

Regards,

Richard.

[glang]

Hello Richard, the new oil will have a higher viscosity than the old stuff, at least for a few miles, so might take longer to pump round. Does it do this on a hot restart as well and is the tickover oil pressure any different than before the oil change?

If youre really concerned there could be a manufacturing problem with the new filter and you could change it again as a precaution.....

[Rick60]

Hi,

Yeah, it does it hot as well as cold. Oil pressure itself is good, 60+ on a cold start and gradually settling down as the oil warms, no different throughout the range of temperatures to before the service.

I'll take your advice and change the spin-on filter again though. I have a couple but may source one from elsewhere just in case.

Many thanks,

Richard.

[Rick60]

Hi again,

So, I've replaced the spin-on oil filter, this time with one from the supplier of the conversion, and also replaced all the seals on the conversion itself. Sadly, the problem is still there. about a 4 or 5 second delay before oil pressure comes up.

Any suggestions?

Regards,

Richard.

[glang]

It could be worth looking at the pressure relief valve as if it was stuck open a little then it would take longer to pressurise the system and not make any difference to the max reading as its probably lifted by then anyway. Why it should show up after a service I don't know but it is very easy to remove and check....

[Rick60]

Will do. I'll check it at the weekend.

Thanks,

[Rick60]

Hi Glang,

I finally got round to checking the oil pressure relief valve last night and all looked quite clean. Certainly no evidence of sticking.

I did wonder, is there a non-return valve in the oil system somewhere (I seem to remember there being one in the old straight six Rover SD1 I had some years ago that would clog up and prevent oil getting to the valve gear) that may be stuck open allowing all the oil to drain back into the sump every time the engine stops?

Regards,

Richard.

[glang]

No nrv except maybe in the oil filter to try to keep it full. Obviously this also helps to keep oil in the galleries but normally it still drains back quite quickly. Now fraid I've run out of ideas except that maybe the oil change has removed some deposits that before somehow sealed the system more......

[Nick Jones]

There is no NRV in the system.  The only reasons I can think of for the added delay are:

- the non-return flap in the new spin-on filter(s) not functioning as effectively as your old one.  I find them quite variable, even within the same make, and really good ones are much rarer than average/poor ones unfortunately.  Mann 724/1 ones have a double flap and have a better batting average though not perfect.

- Does the slow response afflict the oil light as well as the gauge? A pocket of air in the capillary tube to the gauge definitely slows its response.

Do the bearings rattle whilst waiting for oil pressure to arrive?

One further thought concerns the spin-on adapter assembly. There are two versions of this both of which have two seals.  The outer seal is the one that goes in the groove in the block, same as the OE steel can and the same for both.  The inner one differs between early and late versions.  Early ones have a simple fixed O-ring supplied in two sizes in the original kit as block dimensions vary.  There was a procedure given to check which you needed to ensure that both seals were in good contact, preventing internal or external leaks.  The later ones have a spring-loaded assembly that is supposed to sort itself.

If you've not messed with the adaptor I see no reason why this should be the cause, but I can tell you that if for any reason the inner seal is passing, the oil galleries can drain back through the gap, bypassing the oil filter.  You also get a proportion bypassing the filter when the engine is running.

Nick

[nang]

Can you try a different gauge?  It's possible that a restriction in the gauge itself can slow the pressure build up. 

Tony.

[Rick60]

Hi guys,

Thanks for your input.

I've now given the gauge a good bleed, oil everywhere! BUt, to no avail. after standing for about 15 minutes, again 4 -5 seconds before both the oil pressure light goes out and the pressure rises on the gauge. Still registers good pressure but this delay is making me nervous.

Nick,

I've looked up the Mann filter and it looks quite a bit longer (about double the length of the one I have), and doesn't look like it will fit.

Yes, the oil pressure light responds in accordance with the gauge.

If the engine is allowed to rev then the bearings do rattle. Fortunately the engine will start with minimal or no choke so starts pretty much at tickover speeds.

As for the adaptor, it has been on for some years but I did consider there might be a problem here so ordered an overhaul kit from the original suppliers (RB) and replaced the parts supplied wih it. It's not inconceivable that I have c***ed up replacing parts but that would be quite a coincidence. I do remember something being spring loaded inside but to be honest, I can't remember exactly what that was. Perhaps I'll pull it off again and take a closer look.

Tony,

As mentioned, the oil pressure light reflects what's being shown by the gauge but your thoughts are appreciated.

By the way, sorry it's taking me so long to reply but I've had to get my daily driver (a 240k miles X Type) through an mot and that hasn't been without its challenges!

Regards,

Richard.