Low oil pressure

[David H]

Hi chaps,

I have a problem with low oil pressure. When warm at idle speed I get 0 on the gauge, with a little more engine speed on it's more acceptable but still low.

On a cold start I get 30-35psi at 2Krpm and 10-15psi at idle; also a bit low.

I would suspect the gauge but yesterday the low pressure lamp also flickered on once when the oil was very warm and they're on independent circuits.

Yesterday I dropped the sump off and checked the oil pickup to ensure it was tight, not clogged and sitting high enough off the sump floor; all was fine. I also dropped a main and big end bearing cap and the bearings had very little wear. I took the pressure relief valve out of the pump and cleaned it up with emery paper and made sure it moved smoothly in the bore. I gave it an oil and filter change using Silkolene Pro-S 10-60 (although the Pro-S that was in there had only done 500 miles!).

None of the above fixed the problem.

The problem started around October last year but I haven't had chance to drive the car until now (I know, I know..). I only drove to the MOT centre and back yesterday when I saw the problem again.

I still have my suspicions about the gauge and switch which I'll be checking out but wondered if anyone had any other ideas?

Where's the best place to buy a new pump if required?

[Cider Andy]

David H said:

On a cold start I get 30-35psi at 2Krpm and 10-15psi at idle; also a bit low.

I would suspect the gauge but yesterday the low pressure lamp also flickered on once when the oil was very warm and they're on independent circuits.

The range of pressures you're seeing sound ok, just the actual readings that are low. For that reason I'd suspect the gauge or its sender, too. But I'd be more worried about the flickering oil pressure lamp. Are you certain it was the oil pressure lamp and not the charging light?

[AntonyJ]

Dave, couldnt a weak PRV spring also effectively lower the pressure?

IIRC, the main problem with the oil pumps is wear on the face where the gears run.


http://www.rimmerbros.co.uk/rimmer/rover/v8engine/...

Might it be an idea to remove the sender unit and plumb in (albeit temporary) a gauge on a pipe, to at least get a good reading?


Ant

[David Beer]

same here. Was tested and 10 when hot. Light comes on below 1000 revs. Car has done maybe 3k since rebuild

[The AJP Griff]

iirc the gauge sender and the pressue switch are seperate items,so unless a huge co-incidence then theyre unlikely to both be at fault at the same time,likewise if the gauge was faulty then this wouldn't affect the low pressure light,which isn't part of the same gauge.Therefore it's likely that you genuinely have low pressure,either bad pump or weak spring.I think i'd try a new spring first.

Edited by The AJP Griff on Wednesday 9th July 17:03

[Bluebottle]

When you checked the oil pressure releif spring, did it have a loose screw on the end to increase the pressure ( it was a factory bodge on pre-serp 500's)?
I had issues with my first pre-serp and it turned out that the spring had become "plastic" with age (it wouldn't return to its original length, you could stretch or compress it and it would not return to the length you started with). replaced it and I had reasonable pressure again.

[David H]

Cider Andy said:

Are you certain it was the oil pressure lamp and not the charging light?

I think it was the yellow lamp on the dash, which acording to the hand book is the oil pressure.

AntonyJ said:

Dave, couldnt a weak PRV spring also effectively lower the pressure?

IIRC, the main problem with the oil pumps is wear on the face where the gears run.


http://www.rimmerbros.co.uk/rimmer/rover/v8engine/...

Might it be an idea to remove the sender unit and plumb in (albeit temporary) a gauge on a pipe, to at least get a good reading?


Ant

Hi Ant, it could be a weak spring yes.

I'm trying to remember how the oil pump/dizzy drive is located on this engine (a while since the rebuild). Will it fall about if I remove the pump gear or is it located securely in the front cover?

Bluebottle said:

When you checked the oil pressure releif spring, did it have a loose screw on the end to increase the pressure ( it was a factory bodge on pre-serp 500's)?
I had issues with my first pre-serp and it turned out that the spring had become "plastic" with age (it wouldn't return to its original length, you could stretch or compress it and it would not return to the length you started with). replaced it and I had reasonable pressure again.

The screw was still in place yes. Looks like a new spring could be a place to start.


Also to add; sometime last year I had an oil leak problem with the notoriously weak adaptor between sender and pump, I replaced the adaptor with a more substantial item (after breaking the old one!) and wrapped the threads in PTFE tape. I'm wondering if the tape is creating a bad earth for the sender? Doesn't explain the light coming on also I know but that has only happened once and I'm not 100% what light I saw. The gauge must be reading wrong to some extent because it sits at 0PSI when the engine is warm and the light doesn't come on, it should light at 5-10psi.

I'll check the grounding of the sender and order a new spring. If that doesn't work I'll get a new pump on it.

Thanks for the advice guys; sorry for the vague info, I'm not keen on running it whilst it has this potential problem.

[AntonyJ]

David H said:

Cider Andy said:

Are you certain it was the oil pressure lamp and not the charging light?

I think it was the yellow lamp on the dash, which acording to the hand book is the oil pressure.

AntonyJ said:

Dave, couldnt a weak PRV spring also effectively lower the pressure?

IIRC, the main problem with the oil pumps is wear on the face where the gears run.


http://www.rimmerbros.co.uk/rimmer/rover/v8engine/...

Might it be an idea to remove the sender unit and plumb in (albeit temporary) a gauge on a pipe, to at least get a good reading?


Ant

Hi Ant, it could be a weak spring yes.

I'm trying to remember how the oil pump/dizzy drive is located on this engine (a while since the rebuild). Will it fall about if I remove the pump gear or is it located securely in the front cover?

Bluebottle said:

When you checked the oil pressure releif spring, did it have a loose screw on the end to increase the pressure ( it was a factory bodge on pre-serp 500's)?
I had issues with my first pre-serp and it turned out that the spring had become "plastic" with age (it wouldn't return to its original length, you could stretch or compress it and it would not return to the length you started with). replaced it and I had reasonable pressure again.

The screw was still in place yes. Looks like a new spring could be a place to start.


Also to add; sometime last year I had an oil leak problem with the notoriously weak adaptor between sender and pump, I replaced the adaptor with a more substantial item (after breaking the old one!) and wrapped the threads in PTFE tape. I'm wondering if the tape is creating a bad earth for the sender? Doesn't explain the light coming on also I know but that has only happened once and I'm not 100% what light I saw. The gauge must be reading wrong to some extent because it sits at 0PSI when the engine is warm and the light doesn't come on, it should light at 5-10psi.

I'll check the grounding of the sender and order a new spring. If that doesn't work I'll get a new pump on it.

Thanks for the advice guys; sorry for the vague info, I'm not keen on running it whilst it has this potential problem.

Dave , luckily, I had a dizzy out on a pre serp 500 yesterday to prime the oil pump using the power drill method,so its fresh in my mind.
You can remove the oil pump gears and it will not affect the dizzy/camshaft engagement.
One of the gears in the pump has a shaft attached, which protrudes up toward the dizzy, it slots in to the bottom of the dizzy shaft to engage drive.
If you undo the holding pins on the oil pump cover the gears will just pull out downwards.


HTH

Ant

Edited by AntonyJ on Thursday 10th July 07:22

[ESDavey]

I got a 0psi reading on a track day (ie everything was v.hot !). Turned out to be a poor connection on the sender unit. Worth cleaning & giving the spade a good nip !

[David H]

Cheers for the info Ant, changing the pump gears and base shouldn't be too much trouble then if it comes to that.

I had the sender off today and checked it with a footpump attached; unfortunately it seems to be reading perfectly PTFE tape wasn't creating any problem either.

Hopefully the new spring will arrive tomorrow so I can try that.

I think I'll go for this pump if the spring doesn't cure it:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&am...

[David H]

The spring made the pressure higher when the oil was cold but no better when it warmed up.

New pump ordered now, hopefully that'll solve it