Checking to see what may be causing low oil pressure. Just got the Tachometer working so I could check the oil pressure at normal operating temperature and at 3000 RPM. First I changed the oil to straight 30weight. The oil pressure has been low since I got the car and at 3000 RPM it only got up to around 30PSI after warming up. When cold the pressure is about 10PSI. Way too low! There is no smoke from the engine and it runs smooth and strong but the low oil pressure has me concerned.

Any thoughts or suggestions? I did pull the intake side valve cover off to repair the Tach generator. The Camshaft was in excellent condition as well as the bearing that houses the Tach Generator. I'm hoping the bottom end is in good shape as well.

 

Your 3.8 S type uses an electric oil pressure gauge system which is notorious for incorrect readings.
I understand there is a later after market system available and other forum members should be able to point you in the right direction. I understand it involves a new pressure transmitter and gauge

Meanwhile the only way to be sure of your oil pressure is to get it tested with a manual pressure gauge which gets screwed on in replacement to the oil pressure sender unit.
I have run into this electric gauge problem so many times on MK2s that I have a manual gauge test unit at home.

If your oil pressure does turn out to be low (and the engine is not rattling and clunking) then the main suspect is the oil pressure relief valve.
I have seen the face of this valve worn non symmetrically and not seating properly. The old valve can be cleaned up on a lathe or a new valve can be purchased.
A friend had a MK2 with similar readings to your car and after repairing the valve it gave 40 PSI at 2000 RPM and 20 PSI at idle. (Both hot readings)

 

I use a Bourdon Tube gauge from a Mini, I fit the black bezel in place of the chrome one.
Totally reliable and accurate.
I took the old sender unit apart and tapped some 1/8 pipe thread with compression fittings.

The electric gauge on my car did the same thing, even dropping to zero while driving down the highway.
I bought a new sender, and it worked for a while, but it stopped working _ I wasn't going to spend money on anew gauge.

 

10 psi at idle is OK. First check with a mechanical gauge if it's convenient. Then the probable causes of a low reading go: sender, gauge, relief valve, oil pump, bearings. That's in order of likelihood.
There are mechanical gauges of the same pattern as the electric on the Mk2. I don't know what car they are off. They cost about £10 on UK eBay.

 

Oil pressure drop - THE INTERNATIONAL JAGUAR 'S'-TYPE REGISTER FORUM

 

Why the original 100psi gauge was done away with. To stop owners worrying about oil pressure.

 

When I am approached over the question of oil pressure in an XK engine I tell them to take off the oil filler cap with the engine running.
If there is plenty of oil being pushed past the camshafts, then it is probably OK

For wind noise try a Beechcraft Baron twin engine aircraft with a door seal failing at 180 knots ie about 320Ks/hr: Bloody incredible.

The Australian made Ford Falcon six-cylinder engine used from 1960s to 1980s had an oil warning switch/light which came on when the pressure dropped to below 5 PSI

 

Well said Bill

 

Most of my small aeroplane experience is 'commuter flights' in the NE of the US. I used good quality ear plugs and spent most of the flight watching the oil pressure gauges which are never close enough to equal between the two engines. I didn't see a Smith's label on the gauges. The worst door frame wind noise I recall is a 1980s Porsche 911 at speed. It actually masked the noise of the mechanicals.

 

Oil pressure relief valves and aeroplanes
Back in 1980 I took off in a Rockwell 500 Aero Commander twin taking a doctor and company executives to a mining town about 100 miles away by air and over 200 by road. It was a regular once a week charter.
The doctor ran a clinic for the mine and the executives were checking up on operations.
The doctor always had the right-hand front seat as he had been a WW2 night fighter pilot and enjoyed the experience of being up front.
About 3 minutes after take-off, I noticed that the right-hand engine oil pressure was dropping and then the doctor picked up on it too.
As the oil pressure dropped towards the red line (minimum allowed) I went through the engine shut down drills and feathered the propeller.
I gave a "pan" call and headed back to the aerodrome and landed safely.
The cause was an oil pressure relief valve which had jammed full open.
I transferred my passengers to another aircraft, but the doctor declined to go as he reckoned he had enough excitement for one day.

 

The Smith's electrical oil pressure gauge and other Smith's gauges receive criticism for inaccuracy. However, they survive quite well, over half a century on our cars, and give a stable reading in a difficult environment. Moreover, great precision is secondary to their primary function of warning the driver of sudden or unexpected changes. Still, it would be nice to avoid the totally inaccurate readings. Like Jeff, I had planned to replace my electrical oil pressure gauge with a mechanical one. I found one of the correct pattern on eBay for £10. Looking at how to connect the gauge to the engine provoked some second thoughts. Do I really want to have a high pressure oil line subject to engine vibrations at one end constantly flexing a tube running up to the dashboard? It looks as likely to increase the probability of damage as reduce it. It might be wiser to try and make the electric gauge more accurate.

All the following is the product of internet research. I've not needed or had the opportunity to try it out on my car. So follow at your own risk.

The attached Gentleman's guides explain how the sender's and gauges function. First of all, these are electrical devices so make sure the cables are in good condition, the connections are good, and the system is installed as in the Jaguar circuit diagram. Of course, Holden and SNG Barratt supply replacement senders and gauges that are made to the original pattern for those who would deny themselves the pleasure of making their own work.

After the wiring, there's the sender. Each gauge has a matching sender: check the sender is correct. Its function can be tested by replacement with another or by replacement with power resistors. The attached PDF gives resistance values that should produce zero and full scale deflexions of the gauge. If none of this produces a good (or improved) reading at the gauge, then the gauge may need recalibration. There are two holes on the back of the gauge, originally blocked with small, cork bungs. Under each bung, there's a slotted plate that you push CAREFULLY from side to side to adjust the reading. The one closest to the bulb socket is for the high reading and the other for the zero. The calibration should be made using the appropriate power resistors in place of the sender. I'm not sure if the following is a good idea, however, the calibration can also be done with the gauge connected to the sender installed in the car. That requires a good, mechanical gauge also connected to the engine. I think I'd rather use the power resistors and maybe do a final check against a mechanical gauge on the engine. Either way, first do the high reading, then the zero, then check the high.

 

If calibrating your own is daunting or you do not have a way of calibrating it against a known reading you could always send it to https://www.speedycables.com/ who will calibrate it correctly for you. I have used them in the past for calibrating my Speedo on my Lotus Seven and I highly recommend them for speed of turn around, helpfulness and service.

 

Peter, as with any ferrule or olive fitting, it should not be overtightened, especially using a plastic line running into the car.
I've had mine in the car for 15 to 20 years, and no leaks.
My Bentley is over 70 years old, and it came originally equipped with a mechanical oil gauge, but to be fair it has brass line all the way.
Once it reaches the dash, RR put a coil on it, the same when it enters the bulkhead from the engine bay.

 

Jeff, I agree with you, but, if it's possible to make something work well enough with an electric cable and the couple of £/$ for two resistors to calibrate it, why not avoid the small possibility of a loss of oil? If the line were to leak and the driver failed to notice the needle going to zero, it might be catastrophic.

 

Because the compression fittings are not that unreliable that they fail, it's been around for a very long time.
To each his own.

 

I don't worry about the compression joints. You make them up carefully; check them a couple of times; and they should be OK for ever. I'm more concerned about the tube suffering fatigue, being accidentally strained, receiving blows, abrading against something ... especially on that odd occasion the car has to be left in the hands of a 'mechanic.' I've had experiences of mechanics who should have known better returning my car with a tube in contact with a moving part or a plastic part in contact with very hot one. A memorable one was after the replacement of the water pump on my Daimler by a Jaguar dealer in the Netherlands. A few hundred miles later I was checking the oil in the north of Italy and noticed that the cross tube of the coolant system of the V12 was installed in contact with a drive belt that was cutting its way into the steel. If a mechanic, even a good one on a bad day, can break something, sooner or later he will. All we can do is design out the consequences.

 

I'm not sure what to say about that _ get a different mechanic maybe ?
I take it you don't do your own work ?

If you can get the electrical one to work, then fine, I didn't have the time to figure out the problem with my wonky gauge going to "zero" oil pressure when driving down the highway.
Perhaps it was a bad ground somewhere, but since the other gauges were working I figured that wasn't it, but I didn't have the patients either to figure it out to what I consider an inferior setup.

A mechanic that I've known for many years suggested to install the bourdon tube gauge out of a Mini, that made sense to me so I did.
I took the old sender and ground the "crimp" off the cover and drilled and tapped a 1/8 pipe thread into it.
I ran a brass line with a coil from it from the block to the battery support, from there I ran a flexible line through the bulkhead to the gauge.
There's lots of room underneath the carburetors to run the line up to the battery support strap.

It seems to me the problem here are mechanics that don't know what they're doing, or just don't care enough to check their own work.

When I had my engine done, I went through the entire thing and checked the specs, and I did find things wrong, mainly with the head, I don't trust anyone anymore, I learn how to do things myself, I don't even let anyone one touch my bicycle either.
I assume that most people at their jobs have their head up their ***, and if they don't like that, then I stay clear of them.
If I confront a mechanic for pointing out his mistakes and he gets pissed off, then I tell him to bugger off.

It seems to be the norm now-a-days for shoddy workmanship and excuses, anyone can call themselves an expert or experienced, but that doesn't make it so.

Have a look at this thread over at the Australian RR forums, what a disaster.

Australian RR Forums: R Type Overheating at approx 3000rpm

The guy's name is Edward Shoesmith, look at his video, third last post from the end.

 

I insist on watching my Mercedes being serviced (dealer stamps in the service book are very important in the SA resale market & I signed a liability waiver years ago ~ Benz cars hold value very well here unlike the throw away US). The workshop manager says I make the mechanics nervous. My response is "of course I do". I know the cars & WIS better than they do. Hence insisting on watching & guiding the service. e.g. taking the trouble to drain the torque converter which holds over 40% of the transmission fluid. When I say I want a fluid change I don't mean I want half a fluid change & be charged full rate. I don't want **** in my ice cream. I want 100% of the friction modifier changed that depletes with use.

 

I do much of my own work, everything on the Mk2. My favoured mechanic, though he's actually a professional engineer, is David Marks who is as good as any Jaguar man in the world. However, I've lived in different parts of the world and not always had facilities, space or time. And sometimes life just gets in the way. For that matter, I don't claim to never make a mistake. As I said some way back, the bourdon gauge was the way I was going and it's definitely the better gauge. I've seen so many things go wrong in my working life through incompetent or thoughtless intervention that I've probably become hyper in making things idiot resistant. I don't mind doing electrical work and ... I'd better not go totally off topic with stories about useless electricians, but they are even worse than car mechanics.

Yes, the world is full of experts who know SFA and treat those who do know something as total dipsticks. Somehow I hoped for better from the RR world in Aus. I've a great friend in the R-R Club in Perth WA. I had a good day with them the last time I was there. Some run to collecting tanks (in the sense of Centurion, Chieftain...)!

 

Supposed to have 20lbs. pressure at 2000rpm. 30W is light. Look at tin plaque on fender for correct oil. I always and only use 20W/50.