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Leicestershire

Low Oil Pressure

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My SC track car has only just been brought back to life after 17 years hibernation with its previous owner.

In my ownership it has always shown reasonable oil pressure but now with a couple of track sessions under its belt I have noticed a drop in the gauge pressure when hot.

At idle the gauge shows about 0.5 and only reaches around 3 at 6K rpm. I am certain that previously it registered the usual 1 for every 1000 rpm.

The engine has a recorded 94K miles and the whole car appears to have had a very easy and pampered life. It has had 3 oil changes in the last 1000 miles and runs on synthetic Shell Helix 15w50.

 

How prone are the sender units to failure, is it possible to perform any checks on the output from these units?

Any other items to check?

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What year SC is it? There is an update with parts from the 930 to the oil system to increase pressure - I had to do it on my 1978 SC. The pressure would get very low on a hot day after some fast driving. I will try to find a link to more info for you...

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What year SC is it? There is an update with parts from the 930 to the oil system to increase pressure - I had to do it on my 1978 SC. The pressure would get very low on a hot day after some fast driving. I will try to find a link to more info for you...

It’s a ’81 car; I think I will try a new pressure sender just to rule that out.

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There is an update with parts from the 930 to the oil system to increase pressure

My SC has this :)

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Is this something that needs to be done during a full engine strip or is just an engine out job?

From memory I think it's a restrictor/(s) that attach to the spray bar ?

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From memory I think it's a restrictor/(s) that attach to the spray bar ?

Yes, it is a quick upgrade and it can be done with the engine still in the car. You have to replace the two restrictors (one on each side) with the 930 ones.

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If you haven't already got one, I recently bought VDO oil senders from machine7.com - they're and aircooled VW specialist. I've found them very reliable for the stuff I've bought. They sell a few different types, so make sure you check first!

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If you haven't already got one, I recently bought VDO oil senders from machine7.com - they're and aircooled VW specialist. I've found them very reliable for the stuff I've bought. They sell a few different types, so make sure you check first!

Thanks but I managed to bully Design 911 into a price matching war!

The part has just arrived and is sitting on my desk. I will probably get onto fitting it later today & will report back with my findings.

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Fitted the new sender and found no real difference other than a very steady gauge but still registering lower than expected readings at the gauge.

I then got everything nicely warmed up and went for a bit of a back lane thrash to clear a few cobwebs. Partway through I had to stop at a ‘T’ junction and I noticed the gauge was back to normal; registering over 1.5 at idle and climbing an extra 1 bar per 1000 rpm. At the end of the trip whilst putting the car back in the garage I found that the gauge had returned to the low readings.

I am now thinking along the line of:

 

Sticking relief valve on pump

 

Wiring between sender an gauge

 

Faulty gauge (the gauge moves cleanly to 5 when the sender is disconnected so I doubt it is a gauge problem)

 

Any other ideas?

 

In addition to everything that has been discussed the following notes may be relevant:

 

Even with cold oil, the gauge is struggling to get above 3.5.

The oil light does not illuminate when the engine is running (even when idling hot).

When cold it takes around 2 – 3 seconds for the light to illuminate after the engine has stopped.

The motor is a stock '81 3.0 SC and runs on 15/50 oil.

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Just turned 94K

in that case drive it another 94k and dont worry about it until it explodes,the oil relief pistons become become looser over time so i doubt its that.Maybe a worn pump

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in that case drive it another 94k and dont worry about it until it explodes,the oil relief pistons become become looser over time so i doubt its that.Maybe a worn pump

Thanks that probably puts my mind at rest.

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Fit a lightweight one and be done with it:-))

Weight saving figures over the standard loom or it didn't happen :P

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Dom, from memory I think you said this is only the main loom - so for lights etc. Any thoughts on also doing the main engine to DME loom and engine loom? The 964 and 993 engine loom has been known to fail in a bad way as well and could do with some SVP treatment I think...

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I have a similar problem with a 1984 with 70k on the closk on start up gauge reads 4.5 at idle when she warms up gauge reads 1 at idle and raises with the revs @3000 reads between 3 & 4 when she has a good run and is hot the gauge moves with the revs as you drive but as she idles she drpopps to 1 and the oil light comes on goes off as soon as you accelerate the warning light raises blood pressure should it?

 

Is this the same issue as being described or ???????? Do I potentially have a major issue or is it a case of changing parts as a process of elimination.

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I have a similar problem with a 1984 with 70k on the closk on start up gauge reads 4.5 at idle when she warms up gauge reads 1 at idle and raises with the revs @3000 reads between 3 & 4 when she has a good run and is hot the gauge moves with the revs as you drive but as she idles she drpopps to 1 and the oil light comes on goes off as soon as you accelerate the warning light raises blood pressure should it?

I would say nowt to worry about, perfectly normal. :twocents:

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Hi

 

The 3.2 owners manual actually says that the warning light may flicker on and off when the car is hot and at idle. Your symptoms sound "normal" to me.

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On 7/2/2011 at 12:55 PM, Leicestershire said:

Just thought I should update this thread.

Cleaned up the 14 pin plug at the rear of the engine bay & gauge pressure is back to normal - 1 bar hot rising to 5 at 4000 rpm.

My pressure sensors also seems to be playing up when, what 14 pin plug did you clean up?

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To the left of the engine, where the relays are and 3 fuses.

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