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MG MG Y Type - no oil pressure indication

First really sunny and dry day of the year, so I decided to go for a ride. Surprise: indicator shows practically no oil pressure ! Only if I rev to some 3000 the needle moves a little bit. Oil level is between half and full, engine runs smoothly as ever, after a 5 mile test. Can the manometer be defective all of a sudden, after having stood for 3 months ? Because it had always worked fine before. Or is there anything serious to be feared ?
Remo Peter

Presumably you had good pressure when you put the car away for winter did you Remo?

Always begin with the simple stuff. Sounds daft I know, but check your oil level and make sure it is at the correct level.

If you have oil pressure and flow, disconnect the oil feed pipe that goes to the meter where it comes out of the block - are you getting oil flow here? If so, good, if not proceed to next section. If you are, disconnect the connector to the meter and are you getting good flow here without excessive revving? If not, it may be the rubber joiner hose (where it goes through the firewall) has perished and is collapsed. Check either side of that for flow. If this has collapsed, you will need to replace that as you may just be getting a hydraulic lock.

OK, if you have flow to the meter, the bigger investigation!
Begin by slackening off (slacken not remove) a banjo at a time from the oil pump, head of the oil filter, exit oil filter, lower gallery entry, feed pipe to head where it comes out of the block, and if you are getting oil through then that is good. Tighten up each banjo after you test it and before you move onto the next.

If you arent getting any flow at this point you may need to check and remove the oil pressure relief ball valve on the underside of the oil pump as it may have either stuck open, or the ball not seating correctly (worn ball, weak spring, dirt trapped on ball seat) - clean and refit/replace as necessary.

Finally if all the above fail then check that your oil pump gears are in good order and not sloppy or worn to excess and that your oil pump is primed - though if you are getting oil pressure at 3000 rpm I am sure it is! This is an engine out job so that is why I have left it till last and also is the least likely.

Paul
Paul Barrow

What a nasty surprise, Remo.... I know with my car that with ambient temperatures below 5C in the garage it takes some few seconds for the oil pressure to begin to rise, even with 20W-60 oil in the sump. It does take a strong nerve at times.

Paul's checklist is spot on, so can't add anything there... the good news is that if you've revved the engine to 3000rpm and driven for five miles it's most likely that it is the meter connections and function that are the problem: the crankshaft bearings would have become rather noisy if they weren't receiving sufficient oil for such an extended period! Good luck with the checks.
Tim Griggs

Thanks a lot to both of you !
Well, some checks have been done: oil level as said, about 3/4 full. Pressure before had always been there, the engine was completely overhauled about 5000 miles ago (including oil pump gears!). But I always had to turn it on the starter motor with no ignition for at least half a minute for some pressure to show, after the car had stood for more than 1 day. Since this was reported by lots of XPAG drivers, I just got used to it. Could this be an indication of a leaky pump valve ? That "5 mile test" was in fact like, I discovered after 2 1/2 miles that the needle was at zero, so decided to return. And just yesterday I had been in a bit of a hurry, so I did not crank the engine before actually starting it...What worried me was, upon removing the oil filler, engine running, there is always some oil splashing out - not now. Though the valve gear looks well oily !
Remo Peter

Sorry to come back with this issue. I did not touch my car for a while, had other things to do. But tonight I went through the points you mentioned. Now I am at a bit of a loss. Turning the engine over with the starter, plugs out, I have flow at every point indicated, yet there still is no movement of the needle. And no oil coming out of the copper tube up at the manometer. Thought that line to be blocked, tried pumping air through, it is free ! And when I pump air into it at the bottom (there's a union beside the ignition coil, probably non-standard), meter connected of course, I get proper pressure reading, i.e. the manometer of the bicycle pump and the oil manometer read roughly the same values. So the instrument is definitly not busted. It looks like the pressure is enough to get flow up to the cylinder head, but not further up. So I removed the ball valve at the pump bottom. On visual check, I could detect nothing abnormal. How do you test this valve for proper function ? Or could this phenomenon be due to a blocked oil filter or pickup sieve ? I'd hate to take that sump off...
Remo Peter

Remo

First off, when the engine is running, have you taken the valve cover off the top of the engine - is there plenty of oil splashing around up there? There should be!

If you can get a modern Moss TD oil pipe (lower union to oil pressure guage)Moss Europe part number AHH5323 €17.08 Moss USA part number 435-548 $20.95 and attach that to your guage. I have known the rubber tube that the MG Y uses to go through the firewall to collapse and if you get that and a hydraulic lock the dash guage will read 0lbs. Now you have effectively eliminated the original pipe as culprit, so now connect your spare guage to the end of the new pipe and compare readings. If you get oil pressure now up the new pipe and with your spare guage, there is definitely somethng faulty with the original stuff.

The ball releif valve you are looking for two things basically - a good spring strength of the correct weight and the ball when you wipe off all the oil, should not have any seating marks or wear on it. If in doubt, they are cheap enough, replace.

Take your newly acquired connector pipe now and put it on the connector at the bottom where it goes up to the head and have your spare guage on the other end. Start the engine and you should get a good pressure reading at this supplemental guage. Provided you do not run the engine for teribbly long you wont damage anything. If you are getting good pressure at the head end of this pipe, you will be getting the same pressure at the guage on the dash board ... or should be.

If there was a pick up problem in the sump, you wouldnt be geting any pressure at all nor any oil flow so dont worry about the sieve and pick up.

One final question - what weight motor oil are you running? If it is anything other than 20/50 or is a synthetic oil that may be your problem right there.

Good luck and keep us informed.

Paul
Paul Barrow

1) Either your needle in your oil pressure guage has stuck, or
2) you need to prime your oil pump.

Fit a test gauge to the rocker pipe feed to double check you have pressure.

NC.
Neil Cairns

This thread was discussed between 06/02/2011 and 02/04/2011

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