Hello all. I have a 64 3.8s. The engine is reasonably worn but still quite servicable.
Oil pressure was at the lower end of the acceptable range eg hot idle 10psi, 2000rpm 30psi, 3000rpm sneaking up toward 40psi
i did an oil and filter change and used 5w-40 full synthetic oil. The oil pressure is now reading about 5psi at hot idle, 20 at 2000 rpm and not a great deal more than that at 3000rpm.
Do you think its the grade of oil that has caused this change?
one other interedting thing when i started the car from cold before changing the oil the pressure gauge would yake 10 or so seconds to register now ot takes about 2 seconds.
Have i used too thin oil in a worn engine?
cheers

 

Hey admin this is the second time i have made a typo in a subject line and when i try to edit it the changes dont get saved.

 

According to our Oil expert of the S Type forum Engine Oil - Page 2 - THE INTERNATIONAL JAGUAR "S"-TYPE REGISTER FORUM 5w-40 is the correct oil to use and he recommends the Mobile1 oil as it is MB229.5 approved. (MB stands for Mercedes Benz)
The oil pressure on my 3.4s when hot sits at about 35 to 40 all day long when driving or even on tick over but the engine has been rebuilt. I did have a problem a year or so ago where my oil pressure was dropping right off as soon as the revs dropped and I decided to replace the spring in the pressure relief valve which is situated in the oil filter housing body. Pig of a job to get off with the engine in situ but what I found made it worthwhile. I found a small piece of debri had jammed itself in the valve keeping it open a fraction so although I had good oil pressure when running the oil was bypassing the valve, as it was constantly open, when the revs dropped. The valve was cleared fresh oil inserted and no problems since.
One of the problems with the XK sump it that there are two bowls in the base. The one at the back holds most of the oil and is where the drain plug is. When you drain the dirty oil there is a second bowl under the chains at the front of the engine which holds about a litre of oil and this is not drained when you do an oil change. The bowls are split due to the front subframe cross member. So you think you drain all the dirty oil from the engine, change to a new clean oil filter and fill with clean fresh oil which immediately mixes with this litre of dirty oil and the job is spoilt. When doing an oil change on my engine I like to do an engine flush as well. Buy a gallon of cheap oil with a gallon of paraffin. Drain the old oil but leave the old filter in and fill the engine with a 50/50 mix of cheap oil and paraffin. Start the engine and let it tick over until normal running temp is obtained but do not rev the engine, switch off and drain the oil. Repeat a second time with the rest of the 50/50 mix and drain again. Change the oil filter and fill with new 5w-40. You will be surprised at the colour of the 50/50 mix when you drain it out as you have just put clean stuff in but this cleans out that front bowl on the sump and ends up filthy. When I originally stripped my engine for its rebuild this front bowl was so full of crap you could stand a spoon up in it.

 

5W 40 does sound far too thin for an engine or this age and in not sure about fully synthetic.

I think mine runs 20/50 but I would need to check. Originally they probably used a straight 30 oil.

 

You will need to PM the Admin or Moderator and request that they correct your "typo"; merely posting a complaint within a discussion thread is not likely to do you much good...

PMs to "GGG" (Graham) are typically very promptly dealt with if you give him the location of the error and the desired correction.

 

A 5W40 sounds like totally the wrong oil for a 1964 S-Type Jaguar, but of course is perfectly OK for the later Jaguar S-Type of 1998. Clearances on the bearings of the old XK engine design means the oil pressure won't be maintained with the later oil that is, of course, perfectly OK in modern engines made on modern machinery. Having said that, you seem to be getting a reasonably pressure beyond 2000 revs. so the oil pump is clearly OK, but leakage from the bearings is just too much for it. If it were me, I'd put in a 20W50, or a 15W40. The 15W40 was what I used to put in my old XJ6 Series 3 which has the same engine design, and was made on the same machinery. Yes, Jaguar used the same secondhand machinery to make the XK engine from 1948 right up until the 80s !!

A a side-bar, the founder of Jaguar, Sir WIlliam Lyons, never believed in spending pounds if he could spend pennies. This attitude unfortunately ultimately resulted in Jaguar's downfall, because Sir William Lyons also did not believe in paying for advice, so he never did any due diligence when Jaguar combined with the British Motor Coroporation in the late 60s. As we all know, it went downhill all the way until the very late 80s when Ford bought the company.

 

All the local sages say 20/50 conventional for warm climate, some will accept the newer smi-synthetic 20/50... full syn in older high time engine is a flush and your filter will fill up much sooner. You may want to pull filter in 500 miles and open it up for a look. Once it is plugged, the oil will by-pass the filter and the crud will flow back into the engine. The usual comment is if you have oil seeping, with syn-oil, you will have leaks, the older seals may swell to fill gap, but if they are hard, it will just slip by them. Regardless of oil type or weight all of my Jaguars required drip pans. 3.8S--XKE--XJ6
Rgds
David

 

Folks. A 5W-40 is not too thin for the XK engine. It is an SAE 40 at operating temperature, which is the highest oil grade ever recommended by Jaguar. Jaguar never recommended 20W-50 treacle. That has it's UK origins in BMC products with combined engine & gearbox sumps. It shears out of grade very quickly & soon becomes an SAE 30 or lower. Synthetic oils are only thinner cold (e.g. 5W) for startup in freezing temperatures which is beneficial. They are also shear stable.

Read this. (or preferably the whole thread.)

Engine Oil - Page 3 - THE INTERNATIONAL JAGUAR "S"-TYPE REGISTER FORUM

 

Thanks all. THis is good. Glyn, the oil pressure in mine pretty much plummeted after the oil and filter change. The only thing I can put it down to is the grade that I have used may be too thin for an engine in the state of wear of mine.
The other thing I mentioned which I thisnk is relevant is the oil pressure gauge. Am I correct in thinking this was a mechanical gauge - ie the oil travelled up the thin tube from the engine to the gauge and then registered on the gauge. If this is correct then the fact that the oil pressure registers very much quicker on the gauge than it did (at startup) indicates that the oil is significantly less viscous at startup.

If this is the case is it also reasonable to assume the oild will be less viscous all through the rev/heat range?
I have read the various posts that you have linked to above but still cant see any logic for the dramatic drop in OP after putting in 5w-40 full syn.

 

The oil gauge indication is an illustration of just how much more quickly the thinner cold oil circulates the engine & registers. In normal circumstances a positive because it shows how much more quickly the oil circulates the engine. One of the reasons for multigrade oils.

The degree of pressure drop makes me suspicious that the engine had very thick oil in it probably with the addition of an aftermarket additive that is mainly thick VI Improver. Do you have a sample of the used oil? If so I would have it analysed by a competent lab. I would like to see it's properties with particular attention to viscosity & wear metals. (a can of Wynns Charge or similar can take the oil right out of grade to a (e.g. 25W - 60+)

If you don't have a faulty gauge/sender unit (you however suggest your car still has a capillary gauge) or faulty pressure release valve it would seem you likely have a pretty worn engine. Then you can stick anything into it but you are just delaying the inevitable rebuild sadly. (loss of pressure will be worn crank & camshaft bearings & a worn oil pump)

You should have healthy oil pressure with a 5W - 40. As I say it is an SAE 40 at operating temperature. A synthetic oil will thin less than a mineral oil as temperature rises. It has a much higher viscosity index.

VI = rate of change in viscosity for a given change in temperature.

Sorry ~ I know this can get complex for the layman. It is my field of study.

 

Thanks Glyn. Just as your reply came through I spoke to the PO. He was using 20w-70 and yes the engine is worn.
Guess this explains the drop in OP.

 

There is actually no such thing recognised by the industry as a 20W-70 but Penrite Australia extrapolate & apparently make a thing they sell as 25W - 70. They must put a bucket load of VI improver in it. Not the sensible answer to anything.

If you require that to achieve oil pressure you have a severely worn engine. Bearings are probably worn through to their backing.

Rebuild on the horizon.

 

Thanks Glyn. I agree that the engine is worn but does not have big end noise and does not burn oil in any measurable amounts. What is unclear are the ambiguous messages that everyone gives on this subject.
On the one hand we see on the engine plate that the recommended monograde for the S type engine in tropical climes was SAE 40.
I then look at the specs of Penrite Classic Medium 25-70 and it very clearly states it is made for cars that had a recommended monograde SAE 40:-

"Classic MEDIUM is a premium Mineral, 25W-70, high Zinc, low detergent engine oil designed specifically for petrol and Diesel fuelled vehicles manufactured between 1950 and 1989. It features a DOUBLE LAYER of engine wear protection with high zinc and increased operating temperature viscosity over older style Multigrade oils or where SAE 40 Monograde oil was specified by the manufacturer. It controls oil consumption and maintains oil pressure in older engines."

 

With the greatest respect to Penrite that is a lot of weasel wording. ( just consider they are recommending you run a SAE 70 where Jaguar's max spec was an SAE 40 in tropical conditions ~ generally a 30 in summer) Thick goo like that will give you a few more miles out of a worn engine but is nothing but a bandaid. We have had issues on the Register with Penrite's so called "classic" oils shearing out of grade a causing a loss of oil pressure over time. (excuse the tribologist in me)

Stick to the majors with the research budgets to do a proper job.

Damn right it will "control oil consumption and maintain oil pressure in older engines." Older well worn engines that are way out of spec and at the end of realistic life. It will goo up all the out of spec clearances & increase wear further at cold starts until the engine warms up due to poor flow. (remember your oil gauge experience). It will alo increase fuel consumption.

Your call. If you want to extend your mileage before rebuild I would rather run the synthetic that gives far better protection & add a few cans of aftermarket additive (mainly VI Improver) to thicken it up. Accept too that this is a bandaid and not something I would normally recommend.

 

Hello again. How hard is it to get at the oil pressure relief valve?
have had a chat to a mechanic who suggested two things before exploring engine rebuilds.
Firstly he suggested checking the accuracy of the oil sender unit. Not sure how to approach that.
Secondly he suggested checking the pressure relief valve. He suggested getting something that could squeeze the external soft tube such that it was effectively closed and see if the oil pressure improved.
He said it wasnt the easiest thing to get at. I seem to remember a poster on this forum saying that they had done some work on it and it was a “pig” of a job.
Ok so can anyone give me a realistic step by step guide to get to this valve mechanism.
Eg do i come at it from below? Do i need to remove the oil filter etc etc.
any advice or observations would be appreciated.
Also, how do i remove the front grill so that i can get to the electric fan?

 

Oil Pressure relief valve and spring.
I think it was me who described it as a "Pig" of a job so here goes. You have to come at it from below although the upper nuts can be got at from above but you have to have long forearms, small hands and elbows that bend both ways as you have to go around both carbs.
The oil filter canister has to come off first and then there is the oil housing which bolts on to the side of the block This holds the relief valve and spring. Under the housing there is a rubber hose that connects from the sump to the housing. It is very short and possibly old and brittle and held on each end by jubilee clips. The pressure relief valve and spring are held at the top of this pipe where it connects to the housing. There is a metal pipe coming up from the sump and a metal pipe coming down from the housing and the distance between the ends is only about an inch. I would say the gap between the two metal ends would be too small to squeeze this hose without damaging the metal ends. The rubber hose is about three inches long. Unfortunately the problem is you can undo the jubilee clips and you can undo the screw connector but the rubber hose will not bend and is too long to remove from either end of the metal pipes. I hope this makes sense as it is very difficult to describe. Suffice to say to get this hose off you have to remove the oil housing from the side of the engine block which is held on with five bolts. Three at the bottom and two at the top. This is where you need the funny elbows to get to these bolts. No room for a socket to its a case of using a 1/2 inch spanner and turning each bolt a 1/4 turn each time. Once the bolts are out the housing will come away from the engine block and slide off the rubber hose. Once the hose is off the hose connector at the bottom of the housing can be removed and the relief valve and spring can come out for inspection.
To reassemble I would buy a new length of hose and a gasket for the engine block. To check the gauge you can either buy or borrow another one to see if you get the same readings or there are companies in the UK like https://speedycables.com/ who can calibrate your gauge for you.
This is a page from the manual showing the oil filter housing and the rubber hose.
https://parts.jaguarlandroverclassic...8/engine/#p=14

As for the front grill. Remember those funny elbows, long forearms and small hands well guess what.? You need them again and this time the arms have to be thin as well. At the bottom of the grill under the bumper there is a small inspection plate that you remove from the bottom of the car with two bolts that have captive nuts welded to the body work inside the grill section. These can be affected badly with rust so some fluid sprayed in to the grill on to the tops of these would be advisable. You then have to lie on your back and push your hand and forearm in to this hole whilst holding a small spanner to undo five, possibly six 3/16 nuts on the inside edge of the grill. Two either side and one top and one bottom. The one at the top is a bolt the others are nuts on studs. Obviously you cannot see what you are doing, where the nuts are or even if you have the spanner on them correctly or not. Also these nuts do have a tendency to rust up and if you are not patient and take your time you can easily snap the studs off the back of the grill and then the front grill is F**ked. Another link to the partsmanual showing the grill.
https://parts.jaguarlandroverclassic...3-8/body/#p=80

Sorry this all sounds doom and gloom but you have chosen two of the most fiddlest jobs on an S Type Jaguar. The third one is possibly the hand brake pads.

 

5 Studs on grill surround held in place by nuts & antishake washers.






Under car plate for grill access item 20 here.

 

Thanks Cass and Glyn

 

I omitted to say 5 nuts & 1 bolt (19 in diagram) at top of grill. Sorry for error.