There shouldn’t ever be any need to replace the spring, nor stretch it to change the spring rate. If it was right before it is still right. But a DPO could have replaced it with something wrong, and vendors could be selling springs based on wrong information. You need to compare it to other known correct springs in the same model car.
Rob,
the way I understand the valve is that it provides a bypass as soon as a certain pressure is reached, just like a Thermostat. The sensors are behind the relief valve, so what the gauges tell is the pressure the engine gets and cold pressure before the valve ought to be much higher (otherwise the pump is probably faulty). So, if pump and pickup were fine the oil pressure can be changed by altering / shimming the spring… right? Then, I can’t see any reason why to alter the spring as it should not ever change or break and if some PO tried to push the oil pressure, he’d most probably shimmed it - easier? But alas, we probably all know what some DPO’s have been capable of in the past, so…
David
See picture from Rob Reilly, there is a hole in the cylinder block that feeds oil from the relief valve back to the sump so blocking the hose will not do anything, the oil will use the hole in the block instead.I maybe have the possibility to test the strength of my two springs.If the oil pressure will increase with a harder spring then it must be the relief valve, but it does not explain the problem if the springs are equal, and probably right. It must in that case be wear on the relief valve. It is not easy to test the relief valve on a bench, the pressure on the filter head will be quite high.The open pressure shall be some 60PSI and the surface are square inches. I will do tests on Wednesday then we will se.Thank you all for your interest.
If that’s true, why the hose at all???..it does nothing…just block it off. But, you already said there is quite a bit of oil flow thru that hose when engine is revved. Both scenarios cannot be correct…excess oil either flows to the sump via that hose, OR, it flows to the sump via the hole in the block…there is no reason(that I can think of) for it to have TWO paths to the sump. The picture Rob posted is of the engine block, but the other poster Rob refers to has an aluminum piece interposed between the oil filter housing and the cylinder block that may not necessarily route over-pressured oil back the sump via the hole in the block…Jag changed the system over the years. It is worth looking at that other post and pictures provided, should help to clear things up.
Yes, I would like to see some pictures of the E-type filter head, to see the path of the oil flow. Also the E-type block, to see if that return dump hole is there or is it blocked or not drilled at all?
Don’t block off the hose; it must have a purpose. I am simply not familiar with it as my XK120 does not have one.
The XK120 and others with aluminum sumps used the hole in the block. When
Jaguar went to the steel sumps they blocked the hole and used a bypass hose.
Later they simply stopped drilling the hole, probably on the 4.2 block. The
picture shows the plugged hole in a 3.8 block above the bypass hose fitting.
The MK1 manual shows no fewer than 4 different oil filter assemblies and
three different pressure relief valves. Some use blanking plates and some
don’t. The MK2 manual shows two different filters and the E-Type manual
just one. The point is, these are not things that you can play
mix-and-match with.
Mike Eck
New Jersey, USA
www.jaguarclock.com
http://forums.jag-lovers.com/u/rob_reilly Rob_Reilly
June 5
Yes, I would like to see some pictures of the E-type filter head, to see the
path of the oil flow. Also the E-type block, to see if that return dump hole
is there or is it blocked or not drilled at all?
Don’t block off the hose; it must have a purpose. I am simply not familiar
with it as my XK120 does not have one.
There seems to be some misinformation in this thread, which is no doubt resulting in some of the confusion that is apparent. As I understand it, the original poster has a 3.8L E-Type engine. I trust that this engine is original to the car, or at least of the same version. Quoting an engine number would allow us to confirm this. This engine (which has an alloy sump, by the way) uses a pressure relief valve who’s outlet makes use of an external hose from the filter block to the sump. There is no internal route for the oil to take to the sump in the event of overly high pressure. Multiple filter head designs were used during 6-cylinder E-Type models from 1961-1971, but all of them used the external hose from the relief valve to the sump. The 3.8L engines used the design illustrated in Rob Reilly’s earlier post. In this design the pressure relief valve is made up of multiple components numbered 8 through 12 in the diagram. Later 4.2L engines used a one-piece pressure relief valve that screwed into the base of the oil filter block. In either case, if you suspect that the pressure relief valve is malfunctioning (it is quite common for a piece of debris to become stuck in the valve and prevent it closing fully), a simple test is to temporarily place a clamp midway down the rubber hose from the valve to the sump, and observe whether oil pressure increases as the clamp is tightened, cutting off the flow to the sump. You may even be able to do this by pinching the hose with your fingers, though in that case you will require a second person to monitor the oil pressure gauge. The pressure gauges are slow to respond, so you will need to clamp the hose for several seconds before you can expect to see any change. You really shouldn’t be seeing any flow through the pressure relief valve below 50-60 psi…
I hope this helps
-David
You could establish spring pressures at relevant heights (installed, initial valve open, valve fully open) to see what contribution the springs are making to your observations. I used a rig with some fishing scales to pull the springs to various heights.
For reference, in my case the design minimum pressure appeared to be in the low 20’s after accounting for piston surface area. This was a late XJ6 4.2 pressure relief valve on a car showing normal oil pressure behaviour.
Pinching the hose too tight will end up with the filter end of the hose being blown off its spigot, be careful, a lot of oil will exit !!
I will remove the sump at Wednesday as check if there is a hole in the block to the relief valve.The chamber on the filter head after the relief valve has a hole in the block but I don’t know the use of it.I did test to see if it was any oil flow in the hose from the relief valve and sump and it was.The oil was warm and a little oil flow at idle and much more at higher RPM, far from any 50-60 PSI.What I don’t know is if the oil was from the relief valve or from the hole in the block.If I got a sticking relief valve(which is most possible) what can I do?
It has been leaking a year constant. As I see it the safest way is to increase the spring slightly and see if the oil pressure has increase.
When you had the crank out, did you pull the welch plugs and clean out the crank. I have seen it to many times where this was not done and the dirt inside the crank got dislodged and ate up the bearings upon restart.
Since you are getting oil flow into the relief valve hose at relatively low pressures, I’m about 99% sure you have the situation Davidxk described…debris or worn parts preventing the relief valve from closing completely. The simplest remedy is to simply remove the valve and check it. I don’t know if your (later) style valve can be completely disassembled for inspection/repair, as can be done with the earlier ones, but removal is the first step to ensuring it will function properly. I’d be loath to tear open a sealed engine for this problem since Jag has conveniently provided us a easy-to-service relief valve, unlike other engine designs where the relief valve is part of the oil pump. BTW, any oil that might come out of that hole you mentioned could only be from splash or flung from the spinning crank…certainly never a continuous flow that varies with RPM. And increasing the spring pressure should do nothing IF the valve is being held open by debris…unless any debris was crushed by the stronger spring. But then you would have too strong of a spring in there…not to spec.
The crank was cleaned out with the welch plugs removed by the machine shop that grinded the bearing surfaces. The welch plugs was tightened with the original punch marking and thread lock. I had the filter head removed and the relief valve removed and inspected, no debris or any thing else that can explain the problem.It will be really interested to found out what it was if I ever found the problem.I will put back the external pressure gauge to se so it is not the gauge even if I have tested it before for some years ago.
A few variations of the filter body gasket come with the gasket kit, remove the whole assembly and examine, always the best way to understand how it functions and how the chambers interconnect, I once started up a fresh engine to see the pressure drop to zero after a minutes running, I held my nerve and it came up again after a short time, I have no doubt it was a globule of hylomar or similar temporarily holding the balance/bypass valve open
I have now tested with the old original relief valve spring and now is the oil pressure 35PSI at 1500 RPM with hot oil, at idle it is 10PSI. That shall be compared with 20 PSI and 5PSI with the new OEM spring. A significant increase.
Just wonder how many have low oil pressure just because of new parts?
If I compare with my MGB who has always 3.5kg, except when hot and at idle when it is 3.0KG.
Why does the XK engine vary the oil pressure over the whole scale 10 to above 60 PSI when the MGB is so stable over the whole temperature range and over all RPM’s.
At oil pressures greater than the relief valve setting (so bypass wide open), oil pressure is determined by flow the restriction in the bypass relative to pump output, which varies with engine speed and viscosity (so oil grade and temp).
I would speculate that the MGB has lower restriction in the bypass, allowing it to behave more like a regulator.
I should add: restriction through various oil clearances in the engine as a factor…!