davidbareford Posted August 10, 2021 Report Share Posted August 10, 2021 Am at a bit of a loss. I changed the oil in my TR3 with a new oil filter as I have done in the past. Used 20/50 as normal. Started the car up and after an initial oil pressure of about 45 it slowly sunk to zero. No oil spewing from under the car. I took the oil filter out made sure there was oil in the can, screwed it back on. No improvement. Looked at the pressure relief valve and that operated with nothing stuck in it. Put that back on and still no improvement. Any ideas gratefully received. Quote Link to post Share on other sites
iain Posted August 10, 2021 Report Share Posted August 10, 2021 Air in the oil tube to gauge? assuming you have a capillary fed gauge? Iain Quote Link to post Share on other sites
Ian Vincent Posted August 10, 2021 Report Share Posted August 10, 2021 Is the gauge working? Take the rocker cover off and run the engine briefly. If you get little spouts of oil from the top of the rockers, you have oil pressure. Rgds Ian Quote Link to post Share on other sites
Motorsport Mickey Posted August 10, 2021 Report Share Posted August 10, 2021 (edited) Subject to Ians oil flow tests to the rockers, if you've changed the oil pump in the last 10 years there have been some instances of the inner starshaped rotor which spins within the outer star shaped rotor that squeezes the oil up and gives oil pressure failing. As an improvement ! the new oil pump inner starshaped rotor has only been friction welded to the oil pump drive shaft...which fails allowing the oil pump shaft to spin mightily without spinning the rotor...either failing or no oil pressure. Drop the sump (remove dip stick first) and then the oil pump, strip the pump into constituant parts and see if you can see a driven pin between the inner rotor that goes onto the oil drive shaft securing both together. If you can't identify how far down the shaft the rotor should be (look for wear marks) hold the rotor protected by cloths in a vice and drill a 1/8th dia hole through the rotor on it's inside curved shape near the shaft and then into the shaft at least 1/8th" deep. Then drive a 1/8th" pin through both components making sure it is a tight fight in the holes, and it doesn't stick above the oil pump rotor surface, then rebuild the pump, fit onto bottom of engine whence it came, fit sump and oil dipstick, fill with oil and try it. Mick Richards Edited August 10, 2021 by Motorsport Mickey Quote Link to post Share on other sites
davidbareford Posted August 10, 2021 Author Report Share Posted August 10, 2021 Thanks all. Old oil pump but air in the tube may be the answer. Will get onto that when I get back (though not driving the TR at the moment!!! Quote Link to post Share on other sites
Charlie D Posted August 10, 2021 Report Share Posted August 10, 2021 Would air in the tube make any difference? If it's air at 70psi or oil at 70psi the reading would still be 70. (Or maybe not...) Charlie. Quote Link to post Share on other sites
iain Posted August 10, 2021 Report Share Posted August 10, 2021 Air is easily compressed. I’ve just suffered exactly the same issue…….it’s was the oil filter pressure relief valve. Took it out cleaned it, reseated the ball, reassembled and hey presto all back to normal. I use two turns of thin lead solder to make the seal on the lock nut. Just remember how many turns the adjuster had on it when you take it out. Iain Quote Link to post Share on other sites
RobH Posted August 10, 2021 Report Share Posted August 10, 2021 Air shouldn't make any difference. If you have pressure on one end of the bubble in a closed pipe, then the same pressure must be present at the other end too. Compression is irrelevant as oil will just take up the space. Quote Link to post Share on other sites
Ian Vincent Posted August 10, 2021 Report Share Posted August 10, 2021 (edited) 2 hours ago, iain said: I use two turns of thin lead solder to make the seal on the lock nut. FWIW, I still have offcuts of code 4 lead left over from when I built an extension with a bay window about 40 years ago. They come in useful for making all sorts of washers including resealing the oil pressure release valve and for making a good earth connection to the body of the car. Rgds Ian Edited August 10, 2021 by Ian Vincent Quote Link to post Share on other sites
Ralph Whitaker Posted August 11, 2021 Report Share Posted August 11, 2021 (edited) 10 hours ago, RobH said: Air shouldn't make any difference. If you have pressure on one end of the bubble in a closed pipe, then the same pressure must be present at the other end too. Compression is irrelevant as oil will just take up the space. +1. Never heard of anyone having to bleed the oil pipe to the gauge. Air in it makes no difference. Ralph Edited August 11, 2021 by Ralph Whitaker Quote Link to post Share on other sites
cvtrian Posted August 11, 2021 Report Share Posted August 11, 2021 Air in hydraulic circuits does make a difference, that is why brake systems need to be bled and free of air to work correctly. I did have a problem with fluctuating oil pressure readings on my 3A after I changed the capillary pipe, until I got rid of the air inadvertently introduced when I changed it. David's problem sounds like a different issue Quote Link to post Share on other sites
billy l Posted August 11, 2021 Report Share Posted August 11, 2021 (edited) Undo the flexible pipe union just below the battery pictured here next to temp tube and spin the engine over, (take a lead off the coil first) you will soon see if you have oil pressure. have some cloths ready. Cheers, Bill. Edited August 11, 2021 by billy l pic Quote Link to post Share on other sites
iain Posted August 11, 2021 Report Share Posted August 11, 2021 12 hours ago, Ian Vincent said: FWIW, I still have offcuts of code 4 lead left over from when I built an extension with a bay window about 40 years ago. They come in useful for making all sorts of washers including resealing the oil pressure release valve and for making a good earth connection to the body of the car. Rgds Ian Good idea Ian, didn’t think of that. Now where is that lead I had 25 years ago? Iain Quote Link to post Share on other sites
Lebro Posted August 11, 2021 Report Share Posted August 11, 2021 Air in the oil pressure gauge pipe will have no effect at all on how it reads, pressure is pressure. You need to bleed brakes because any air in the pipes will be compressed, & you run out of travel on the pedal before the brakes are applied. One depression of the brake pedal is not enough to raise enough pressure to apply the brakes fully, whereas with engine oil, there is a huge amount of it being continuosly supplied by the oil pump, so the pressure will max out very quickly. Bob. Quote Link to post Share on other sites
Ian Vincent Posted August 11, 2021 Report Share Posted August 11, 2021 As an adjunct to my suggestion to briefly start the engine with the rocker cover removed. If you don’t get any spurts of oil from the top of the rockers, then you will have lost your oil pressure and as Mick has suggested the next job is to drop the sump and check the oil pump. At which point you might as well fit new big end shells because even the small amount of running you have already done without oil pressure won’t have done them any good, and a new set of shells is pretty cheap. Rgds Ian Quote Link to post Share on other sites
Lebro Posted August 11, 2021 Report Share Posted August 11, 2021 Rather than risk any more running, take off the distributor, then the pedestal, you can then use a drill (running backwards) to spin the oil pump. If you still get no pressure (or flow to rockers) then time to drop the sump. Bob. Quote Link to post Share on other sites
BlueTR3A-5EKT Posted August 12, 2021 Report Share Posted August 12, 2021 If it is a broken oil pump inner drive shaft that has failed and you do not want to follow Mick’s repair method I have a NOS StanPart oil pump rotor and spindle Pt no 504862. Yours for £35 Plus postage. Or I will put in the boot of the car and take to Malvern on Saturday if you want to meet up. PM me for contact details. Peter W looks like this but NOS and in a box. Quote Link to post Share on other sites
Ian Bennett Posted August 14, 2021 Report Share Posted August 14, 2021 I had same problem David! So preparing to drop the sump , I jacked up the front to mount it on my (big boy ) ramps, some 300mm up , thought I just start the engine , hey presto 70lbs/squ In on the gauge. Leave it to you techo boys to explain but I reckon I just tipped a bucketfull of oil into the gauge by gravity!!!! good luck Quote Link to post Share on other sites
davidbareford Posted August 24, 2021 Author Report Share Posted August 24, 2021 Thanks again all. I took the rocker cover off and started engine. There was a bit of air from the rocker outlets but oil came though(with some air initially) and now oil pressure stable again. I think it must be some air lock somewhere but that is only a guess. Quote Link to post Share on other sites
cvtrian Posted August 24, 2021 Report Share Posted August 24, 2021 sounds like the same problem I outlined previously when I changed the connecting tube from the gauge, air somewhere in the system, glad you found it and a simple fix. Ian Quote Link to post Share on other sites
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