PAE .... Sleipnir???

Ron
I bought an oil pump upgrade kit for my 72 P6b.some time ago . Ive shifted it from one shelf to another too long now and am over the procrastination ..
The car is losing oil pressure when the motor gets hot . Its fine on start up and for around a 20km journey , then the light comes on and the pressure gauge drops . Freaks me out . Im using Penrite HPR 40 . No noises or smoke .
Im a total newbie at attempting this .
The kit has come with the bigger gears and new gaskets .
How do you measure the gear / oil pump cover clearance ratio when the cover is removed . 0.002" tollerance seems rather crucial from your account .Ive only got interested again since reading this thread . I haven't consulted the WM yet as Im waiting for some farm down time .
regards
Gerald
 
Hi Gerald,

The larger gears will move a greater volume of oil per revolution, so at any given speed there will be an increase in flow throughout the engine. However, the oil pressure will remain unchaged. The pressure that registers on the gauge and that activates the oil warning light, is the resistance to flow that is experienced as the oil exits the pump and enters the engine proper. If the clearances within the engine are closer for argument sake, then the resistance to flow is greater, hence the pressure registered upon the gauge is higher.

How many miles are on your engine? What is the pressure reading prior to falling, in turn activating the oil light?

If you have the timing cover off and inverted, which certainly makes life easier, look at the gears sitting within the gear chamber. Of course in order to do this, you have also removed the oil pump cover, ie what the filter attaches to. Using a feeler gauge, measure the clearance between the peaks of the gears and the inside surface of the gear chamber. When you take the gears out, you'll likely see abrasion marks inside the gear chamber. Don't clean these up, as doing so will further increase the clearance and further reduce your oil pressure.

Ron.

P.S : Sorry Rich for the temporary intrusion on your thread.
 
I'm a bit surprised that nobody has mentioned the pressure relief valve yet. Essentially a ball and spring that are meant to seat firmly against a seat when the pressure is low, but lift off the seat at high pressure (high rpm) to limit the top pressure. These are known to stick clear of the seat which will give exactly Rich's symptoms. I think I'd want to start by inspecting that, giving the spring a tweak - or renewing it - and seeing if that made any odds. This on the grounds it's a very simple thing to do and minimal cost.

Next up I'd have the sump off, clean it out and check the state of the gauze and reassemble with new pick up gaskets etc. Again simple to do and minimal cost.

Next up I'd have a look at the oil flow to the rockers with the engine at idling. A good oil flow here would suggest that flow is happening fine. Which implies that pressure isn't too catastrophic.

Then it's verify what the oil pressure truly is by connecting a separate mechanical gauge onto the system. And of course, changing the sender to the oil light!

In the process you'd have changed the oil and filter, so now you know that you are looking at the true state of what is happening in the engine.

Don't forget that we know that the V8 will go on for yonks with minimal pressure, so just don't drive it too hard until all these checks are complete.

Only at this stage would I start panicking about oil pump and or bearings!

Chris
 
PS

While you have the sump off, you could remove one main bearing cap and inspect the shell bearing. In the process you'll find out whether you have a standard crank or what level of grind it has had. Then re-torque all the bearing caps.

Chris
 
Hi Chris,

From what I have seen, problems with oil pressure relief valves sticking open, thus resulting in a very substantial drop in oil pressure, tend to always fall at the feet of later oil pump front covers. This also correlates with the removal of the oil filter bypass valve, which from circa 1977 onwards is within the appropriate oil filters. The spigot also dropped in diameter at this time.

Ron.
 
Thanks chris some good extra suggestions :)

Quick Q - if i remove the oil pressure spring is oil going to come gushing out?

THanks,

Rich.
 
Only a little Rich ( enough to run up your sleeve ) then it'll stop , the spring comes out easy then the plunger , sometimes the suction will hold the plunger in for a bit , then it'll drop out when your not looking so wiggle it out with the spring well your down there ( ohh er ) You don't want to be dropping it and scratching it .
Remember you'll loose the prime on your oil system when you remove it so you'll need to spin up your pump with the drill or if your lucky ( mine usually does ) remove the king lead and crank the motor till you have pressure again . :D
 
Thanks Stina :) One to try next weekend now but at least I've got a few things to try. I guess if I get the relief spring and ball and the sump gasket, and an oil filter I have everything I need to have a prod round under there...

RIch.
 
SydneyRoverP6B said:
Hi Gerald,
How many miles are on your engine? What is the pressure reading prior to falling, in turn activating the oil light?


Hello Ron
Not meaning to hijack this thread , but think my question sits here quite well .
Only done 103,000km and the pressure going by the dash gauge looks to be a wholesome 35-40 @ 2000rpm .
I am talking to Mark Gray as well insofar as new oil pressure and light senders - after all she is 40yrs old and it may need some viagra , like a new oil pressure spring and ball as suggested by Stina .
I will be checking the water temp next time the P6 goes out , just in case she is a little too hot in that dept coz I have changed the thermostat recently and it may be a faulty one .
Ive done the pick up gauze filter in the sump and things were very clean there .
I would rather spend a few dollars on the minor things , than chase something larger only to find it was a manky 20c spring .
So many roads to go down , but it makes the P6 more loveable . Keeps me off the street corners at night !!
Gerald
Click to expand...
 
Hi Gerald,

The distance covered isn't all that far, so by all accounts there should not be too much in the way of wear, assuming of course regular oil and filter changes along the way. I tend to think that if the oil pressure transmitter was playing up, then the oil warning light wouldn't come on. Given that it does when the gauge is showing next to no oil pressure, that would suggest that there is indeed next to no oil pressure, well less than 7 or so psi at the most.

The only object that can really cause such a sudden and dramatic loss of pressure is the oil pressure relief valve. Usually you would need far more pressure registering before the valve will open, so maybe there is a fault and the spring just needs replacing. I am going to have to eat a serving of humble pie now, for the P6B oil pump front covers are usually so very reliable.

Ron.
 
Ron
Thanks so much for that info .
Might as well keep this hijacked thread going . Thanks Rich
Its a good start ,so I'll get a new switch and relief spring sent down from MG . It looks like the light switch is doing its job .
Good time to put that oil pump upgrade kit in too .
I'll keep you posted as Im sure there will be others out there with the same oil pressure malaise and are scratching their heads .
Its got to be something simple .Sometimes the oil pressure stays up for the whole round trip , then next trip it starts dropping off shortly after the motor warms up . One of the reasons I haven't been too worried about what happening on the dashboard .
thanks
Gerald
 
Re: PAE .... Sleipnir??? OIL PRESSURE

Thanks for letting me use your thread Rich .
Here is my head scratcher !!
Ive just returned from a 30km round trip in the P6b. Mostly rural 80-100km speeds .
15km into the trip and the pressure gauge needle drops and on comes the dash light - as per usual . I used to panic - I don't now .
Next I stop at the gas station and take on 30ltrs of super . Off I go again and the pressure gauge is back up and sitting on around 35-40lb for the rest of the journey , until I hit the home stretch and down goes the pressure gauge again and dash lights up .
Motor doesn't miss a beat and the temp sits on 82deg the whole time .
What the hay is going on besides my head being done in ?
Its got to be that pressure switch and/or the relief spring .
Your thoughts , every man and dog invited to join in .
Gerald
 
I don't think it has to be though I agree it's the most likely culprit, another reason could be sludge being sucked into the oil pick up as the oil warms allowing it to more readily being lifted from the sump bottom.

Graeme
 
Hello Graeme
Thanks for your input .
I was chasing an errant oil leak around the sump gasket a little while ago .I pulled the sump and cleaned up the gauze pickup whilst I was up to my elbows in the black stuff .It was surprisingly clean about there . So I can tick that possibility off the list .
No more oil leaks from the sump by the way . Cripes those bolts under the pan by the cross member are a piece of work .
Gerald
 
does anybody have a recommendation for sealant around the sump gasket or am i best just with the cork?

Thanks,

Rich
 
I'm pretty sure I fitted mine dry, but I spent some time hammering the gasket surface on the sump flat again - there were raised lips around each hole where it had been over tightened in the past.
 
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