Oil Pressure always high

[martin.vesty]

I think this is my last call for support for now - Apologies for the recent flurry of topics. I guess always the case for owners of a Marque not owned before.

I've searched and found a few articles regarding OP senders but can't see the same topic. I also don't have a variable resistance potentiometer to run the test as in Clark's. Hence asking the wise souls on here.

My oil pressure is zero when the key is in the on position (before starting engine). I mention this as Clark's refers to OPS being past its best if the oil pressure immediately goes to 5 with key in On position.
Once started and from then onward when the engine is fully up to temp the the pressure seems to be static at about 4.5.

When I did an oil change and general service a month ago I removed the sender, checked the face was clean, checked the terminals and made sure the connections were good when I refitted it.

Same outcome with the pressure.

Anyone had the same? Suggestions?

I was assuming I should fit a sender but I guess that means dropping the oil again so I'm in no hurry to do that this side of winter.

 

[scam75]

Hi Martin

First off, you can change the oil pressure sender without dropping the oil. You'll get a little bit of spillage but not much if you have the new sender ready to screw in. It is awkward to tighten and a cut down (24mm I think) open ended spanner is the ideal tool. Small hands also help! You can get a decent new sender for about £30/£40.

First thing I would be doing is getting a proper oil pressure gauge on it so you can see the actual oil pressure, then work back from there. Sender, dash gauge, wiring.

4.5 bar is wrong for a warm engine (assuming this is engine idling you are talking about). A fresh engine will be 3 to 3.5 bar at hot idle. A worn but serviceable engine between 2 and 3 bar. IIRC Porsche states that 1 bar is good enough at idle to keep things lubricated.

A faulty oil pressure relief valve (OPRV) could cause your issue assuming you are seeing a correct reading. OPRV's are eye wateringly expensive new but sometimes it is just the o-rings that need replacing and these are pennies. I'm going to guess however that your sender or wiring is suspect. Get a local garage to either check your pressure with a proper gauge or ask to borrow one and do it yourself and report back.

Stuart

 

[scam75]

Also if the 2 terminals on the sender are back to front, you'll see 5 bar on ignition and with the engine on. Does your gauge move at all or is it painted on stuck at 4.5 bar?

 

[martin.vesty]

Thanks Stuart for that very helpful advice.
I’m pretty sure the terminals are correct as one is a spade and one a ring. It’s never been touched in the cars life.
I’ll get a new sensor and swap it out then take it from there if the reading is still constant. I’ve a specialist garage close by that I can ask to check the pressure.

 

[TTM]

I would still swap the connectors if only to check how it affects pressure readings on the gauge.

 

[martin.vesty]

New sensor fitted.

It works as far as it shows a good pressure around same as before with the car just idling up to full working temp (fan kicked in).

Car is SORN now so it'll have to wait until early spring (gritting in North Yorkshire goes on far too long!) to see if the pressure runs any different. I can pop to a local garage to check pressure as per Stuart's comment. Fortunately I've learnt that there is a guy there that has many years experience working in one of the listed Porsche Specialist garages and I'm sure he will help diagnose further if needed. If it's just O rings on the OPRV and it's easy to extract then I'll go for that!

 

[martin.vesty]

Hi Martin

First off, you can change the oil pressure sender without dropping the oil. You'll get a little bit of spillage but not much if you have the new sender ready to screw in. It is awkward to tighten and a cut down (24mm I think) open ended spanner is the ideal tool. Small hands also help! You can get a decent new sender for about £30/£40.

First thing I would be doing is getting a proper oil pressure gauge on it so you can see the actual oil pressure, then work back from there. Sender, dash gauge, wiring.

4.5 bar is wrong for a warm engine (assuming this is engine idling you are talking about). A fresh engine will be 3 to 3.5 bar at hot idle. A worn but serviceable engine between 2 and 3 bar. IIRC Porsche states that 1 bar is good enough at idle to keep things lubricated.

A faulty oil pressure relief valve (OPRV) could cause your issue assuming you are seeing a correct reading. OPRV's are eye wateringly expensive new but sometimes it is just the o-rings that need replacing and these are pennies. I'm going to guess however that your sender or wiring is suspect. Get a local garage to either check your pressure with a proper gauge or ask to borrow one and do it yourself and report back.

Stuart

The issue persists and having had my cam tower gasket replaced about three weeks ago, the gasket is weeping again in the same place (front end, manifold side). It could be the two topics are unrelated but I'm now wondering if the OPRV is the cause of both.

Back to the Specialist Garage near me tomorrow to see what they think. Just wondering if I should pull the OPRV out anyway? the question is what am I looking for with regards to an issue and I'm guessing I'll need some sort of new crush washer at the very least?

Perhaps I let them look at it tomorrow

 

[dlknight]

Hi Martin, if it has never been removed, I can guarantee the seals will be rock hard and break into bits. To test it you push the central tube in against the spring pressure, and it should return. There are some Porsche Technical Documents I can send you if you PM your email address, these go through how to strip it and replace the seals. If you are only removing the OPRV you won't need the alignment tool to refit (as long as it was correctly aligned to begin with). The replacement o-rings don't cost much from Porsche.

These are the part numbers for the o-rings:

Large seal ring (Aluminium) A 20 x 24 - N0438153 (I usually buy these off ebay as much cheaper than Porsche and you get some spares - https://www.ebay.co.uk/itm/132579779761)
Small o-rings x 2 - 99970714440 (real cheap - £1.76 each inc VAT)

 

[martin.vesty]

These are the part numbers for the o-rings:

Large seal ring (Aluminium) A 20 x 24 - N0438153 (I usually buy these off ebay as much cheaper than Porsche and you get some spares - https://www.ebay.co.uk/itm/132579779761)
Small o-rings x 2 - 99970714440 (real cheap - £1.76 each inc VAT)

Perfect, thanks very much. I think I'll go check this now.
I'd seen in Clark's guide that there were different OPRVs. My car is a 1989 2.7 8V, do you know if your information is suitable for that year car? Looking at your cars I guess these will be same for my car.

 

[dlknight]

1987 model year + all used the updated one-piece OPRV.

 

[martin.vesty]

All serviced and refitted. Thanks David!
Now to see if there’s any impact.

 

[martin.vesty]

Hi Martin

First off, you can change the oil pressure sender without dropping the oil. You'll get a little bit of spillage but not much if you have the new sender ready to screw in. It is awkward to tighten and a cut down (24mm I think) open ended spanner is the ideal tool. Small hands also help! You can get a decent new sender for about £30/£40.

First thing I would be doing is getting a proper oil pressure gauge on it so you can see the actual oil pressure, then work back from there. Sender, dash gauge, wiring.

4.5 bar is wrong for a warm engine (assuming this is engine idling you are talking about). A fresh engine will be 3 to 3.5 bar at hot idle. A worn but serviceable engine between 2 and 3 bar. IIRC Porsche states that 1 bar is good enough at idle to keep things lubricated.

A faulty oil pressure relief valve (OPRV) could cause your issue assuming you are seeing a correct reading. OPRV's are eye wateringly expensive new but sometimes it is just the o-rings that need replacing and these are pennies. I'm going to guess however that your sender or wiring is suspect. Get a local garage to either check your pressure with a proper gauge or ask to borrow one and do it yourself and report back.

Stuart

Unfortunately, if anything the gauge is ready above the line for 5 still.
I think it was usually near to 5 before but recently it’s higher possibly.

When I turn ignition to 1 it just goes to 0. But when I start the engine it jumps to near 5 the. A second step then kicks it up to 5.

I’ve just done a 20 mile drive at 60mph and it doesn’t budge.

I've ordered a gauge that has an M10 adaptor so I'll check that next week.

I’m guessing there is no electrical relay involved that's worth a check?

 

[dlknight]

If in doubt check with a known accurate gauge, David has just fixed some gauge problems in the same cluster (he had a faulty voltmeter, could be similar for the oil pressure gauge, but check with an external gauge first!

My money is on the sender, my car still had the original sender fitted, I've only replaced it as I thought it was leaking. First off I replaced it with a cheaper URO sender, and then during the engine rebuild I bit the bullet and ordered a new Porsche gauge with some other parts (think it was around £60).

Pegging at 5 sounds like an electrical short in the sender.

 

[martin.vesty]

Thanks David. Should check with the gauge by early next week

 

[martin.vesty]

If in doubt check with a known accurate gauge, David has just fixed some gauge problems in the same cluster (he had a faulty voltmeter, could be similar for the oil pressure gauge, but check with an external gauge first!

My money is on the sender, my car still had the original sender fitted, I've only replaced it as I thought it was leaking. First off I replaced it with a cheaper URO sender, and then during the engine rebuild I bit the bullet and ordered a new Porsche gauge with some other parts (think it was around £60).

Pegging at 5 sounds like an electrical short in the sender.

Is there a post or further info relating to the faulty voltmeter as it does look like the voltmeter is part of the same circuit as oil pressure gauge circuit.

 

[PSH]

When it comes to faulty gauges in the cluster my first port of call would be the earth grounds.

Pete

 

[martin.vesty]

When it comes to faulty gauges in the cluster my first port of call would be the earth grounds.

Pete

Funnily enough Pete I was just looking for such points under the bonnet. Only one I could easily see is what looks like the main earth lead centre bulkhead to block ( I think).
Any tips on where to find earth 5 & 8 which seem to be the relevant ones?
Although just found this about oxidation on the rear connectors at back of pod. I guess this is another likely cause if the manual gauge shows the dash gauge to be wrong.

 

[martin.vesty]

I now have a working gauge

I’m not sure exactly what fixed it but after cleaning the cockpit gauge contacts it did seem to be trying to do more but still not moving as warmed up. I tried cleaning the Football contacts and posts. I also cleaned up anything else exposed on the pcb.

I then fitted a mechanical gauge direct to the Sender mounting position. I ran the car up to normal operating temp and after starting at 4.8 the pressure was already dropping to 4.4. It also responded to gentle throttle. I was there satisfied that the oil pressure was good in the engine.

After letting the engine cool again for about 30 mins and removing the gauge I installed the OE sender back on to the car rather than the OE Match new sender.

I do wonder if the splurge of now warm oil out of the sender port had anything to do with it now working as it seemed to me that the oil looked a bit older/ darker than the oil that came out when I first removed the sender with a cold engine.

Anyway, the car now starts around 4.5-5 and drops as car heats up. Idling just below 4 yesterday when I’d driven about a fair bit and very warm outside. It runs above 4 at cruise.

Happy with the outcome and the specialist who redid my Cam Tower gasket yesterday said that the OP was now very good.