Oil pump priming

In case its useful, note that the gauge sender thread is 1/2-20 UNF tapered, and the idiot light switch is 1/2-18 unc(?) tapered. If you could find a barb or tail with the relevant thread it would be easy (and tidy) to pump oil in with a piece of hose.

Hi JP,

Are you sure that the two ports feature different threads? The reason I ask is my Rover's original engine had the sender and switch swapped over when they left the factory. They would not screw in if the ports had different threads.

Ron.
 
Wasnt completely clear before - the example was on an SD1 pump cover and its sender and switch. The threads were checked with a thread gauge so I am confident of those figures, and the idiot light switch will barely go into the other port 1 turn. If Leyland left these threads Imperial, but changed the pitch of one from P6 to SD1, doesnt make much sense to me. Mind you, Leyland did lots of things that didnt make sense back then. Sorry if I misled anybody. Thanks Ron.
 
Priming the oil pump is a pain, but I have done it it-situ. You can remove the pump cover from underneath with a small socket. Bolts are Torx headed, I think that is the term, and you can get a socket to fit, but i did it with a 3/8? AF socket which can be jammed on, and will work.
Haynes and workshop manual are quite blasé about doing this, but it can be done with access from under the front and without jacking up.
Pack the gears with petroleum jelly and replace cover, and it worked for me.
Being cautious, I then changed the engine oil and filter in case jelly did not dissolve in oil as it is said it does.
I had not heard of the drill method of priming the pump, but it has to be easier than packing with jelly.
I had to prime my pump twice, as the oil filter I was getting from local supplier allowed oil to drain back when car was left for 2-3 months unused.
Since using a different filter from proper rover parts supplier, never had this problem.
Now I have got older and get Duncan Gill to service the car and never had the problem again.
Moral; us the proper Rover supplier.
 
Dont understand how a filter that hangs down can drain back into the sump. On a 4cyl type, its easy as the filter is inverted, and needs to have an anti-drain valve, which not all (but most now) have. The pump cover bolts are 5/16" double hex so an uncommon socket is required. From memory there is one bolt you cant get a socket on, so a double hex ring spanner is needed.
 
Dont understand how a filter that hangs down can drain back into the sump. On a 4cyl type, its easy as the filter is inverted, and needs to have an anti-drain valve, which not all (but most now) have. The pump cover bolts are 5/16" double hex so an uncommon socket is required. From memory there is one bolt you cant get a socket on, so a double hex ring spanner is needed.

Hi JP,

What you surmise is correct, the filter does not drain back into the sump. The anti-drain back valve which is nothing more than the flap beneath the outer ring of holes prevents that, but primarily it is the downward angle of the filter. If the filter is removed for a lengthy period of time all of the oil that surrounds the oil pump gears within the timing case housing will drain. If the gears and housing inner face are worn/scored, then it is not unreasonable to expect the pump to not self-prime once the filter is replaced and the engine started.

Ron.
 
I cannot remember the exact technicalities of the filters. All I know is that when I was buying filters from a certain local supplier, every time I came back to UK after time working away, and re-started 3500S, I had no oil pressure and had the palaver of priming the pump. Since car was parked nose in in normal suburban garage, it was a cramped working position. Bought another Rover 3.5L filter, I think from Halfords, and never had the problem
again. Seemed obvious to me that something was not right with the filter.
Memory also tells me that pump cover bolts were not standard hex head, but I could jam a socket or ring spanner on and get the cover off.
original supplier was not a Rover specialist, but claimed expertise in V8 engines.
When i did my own oil changes, I used to fill the new filter with oil before fitting. Always primed OK and oil pressure on start-up.
 
If car was parked for a long period, NOSE UP, I can almost see a filter leaking some oil out, but not enough to empty the pump. The filter's output goes UP into the timing cover, so it cant drain UP. Filling the filter on a change is good practice, but the filter should not be left off the pump any longer than necessary. I have pulled the sump off to clean it (several hours), refitted, filled, and the pump worked fine. Filter was not removed while the sump was off.
 
I cannot remember the exact technicalities of the filters. All I know is that when I was buying filters from a certain local supplier, every time I came back to UK after time working away, and re-started 3500S, I had no oil pressure and had the palaver of priming the pump. Since car was parked nose in in normal suburban garage, it was a cramped working position. Bought another Rover 3.5L filter, I think from Halfords, and never had the problem
again. Seemed obvious to me that something was not right with the filter.

Hi Robin,

Thinking about it logically, the only way the oil could drain from the oil pump housing within the timing cover is for the oil filter to not have anti-drain valve. In the case of the Rover, filter orientation means that the valve actually serves no function within the context of preventing the filter from emptying. It does however prevent oil that is within the pump housing from draining down into the filter. With the engine off and a filter with an anti-drain valve, oil flow is gravitational, and that means that there is insufficient force to push the valve aside to allow the oil to exit the pump and enter the filter. However, with a filter that does not contain an anti-drain valve, there is nothing preventing the oil from draining completely from the oil pump housing over time into the filter. This can only happen on the proviso that the filter is not 100% full with oil. When you changed the filter, you likely fitted one with an anti-drain valve, thus preventing oil from exiting the pump housing, and your problem was solved.

Ron.
 
Sydney,
Thanks for your explanation. That must have been what was happening. it only occurred with oil filters from that one supplier. I do not buy from him now. When I raised the matter with him ,he di, of course, deny that it could ever happen, but blamed it on putting the car away with the oil hot and thin...
That was 10 yr ago. Since using other filters, I have never , thank goodness, had to prime the oil pump after leaving the car unused.
Now, I am too old to crawl under the car, so let DG do my servicing and oil changes, including using the approved ZDP additive oil.
It has taught me to always watch the oil pressure gauge when I first start up.
 
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