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 Post subject: Low oil Pressure
PostPosted: Fri Feb 08, 2019 4:56 pm 
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Joined: Thu Dec 19, 2013 3:40 pm
Posts: 165
Hi all you TR tragic s.
I, no not me my TR, has low oil pressure. After the Christmas lunch at Penrith we headed home via Richmond. It was about 42 in the shade. Just after reaching the main road and our first traffic light I noticed I had no, yep, no oil pressure. I could get about 20PSI at 2000 and a max of 25PSI at higher RPM. The engine sounded fine but Gwen was giving me a bit of grief about sitting in the sun (roof down) in 42 deg heat. I convinced myself that it was a gauge problem and continued home with a min RPM of 2000. Interesting in 42 deg heat and traffic. Still it did not overheat and still sounded fine when we got home after a one hour trip. Checked the gauge,OK..oil level OK. Pulled the relief valve...all OK. Pulled the rocker cover, run the engine and found a leak around the locating screw for the rocker shaft. Fixed that...still the same. Shut the garage door and had a drink.
Next, day took it for a drive and oil pressure seemed OK. I then refitted my oil cooler which I had removed after stopping track work. Next time out on any sort of run was to Pie in the Sky and it was not hot but warm. On the way home the pressure was about 50PSI so still low. Now I have pulled the sump and checked the bearings..all good. Checked the cam bushes had not moved...all good. removed the oil pump and checked. All clearances were well within specs but the spindle was a bit loose on the shaft, the pin was still in place. I have ordered a new spindle and rotor but do not think it could cause the problem.
I am at a bit of a loss. Any suggestions????


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 Post subject: Re: Low oil Pressure
PostPosted: Sat Feb 09, 2019 3:07 pm 
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Joined: Fri Dec 20, 2013 10:19 am
Posts: 177
Hi Brian. If you don't know, who does? Anyway, a few thoughts. What do you expect? 50 PSI is what the factory manual expects which is why the tell tale on the gauge points there. Actually 40-60 at 30-40 mph is the range. You may have modifications and therefore expect other things. The inconsistent variation in the readings to my mind indicates that there is no major base problem. More to do with some rubbish loose in the gauge line or filter head. Oil pressure always interests me. My 28 Chev started at 7 PSI cold and ran at 5 PSI for about 20000 miles. My 38 starts at 30 PSI and runs at 15 PSI. Why all the variations? This most probably won't help but at least it's an answer.


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 Post subject: Re: Low oil Pressure
PostPosted: Sat Feb 09, 2019 7:06 pm 
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Joined: Thu Dec 19, 2013 3:40 pm
Posts: 165
50 PSI would be OK if that is what normally runs at. My car normally runs between 65 and 75 depending on conditions. It would normally drop to around 20-25 when hot at idle ( my idle is 650) but zero is a bit low.
I have two gauges, the dash and the EFI. Both with separate sensors and both read the same.


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 Post subject: Re: Low oil Pressure
PostPosted: Sat Feb 09, 2019 10:58 pm 
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Joined: Thu Dec 19, 2013 11:22 pm
Posts: 59
Interesting comment about the oil pressure in the 28 Chev, the chev 4 engine is dip and splash for the big ends and cylinders gravity feed from the oil wells for the crankshaft main bearings and the rocker gear is oil can onto a felt pad.The manual states it doesn't matter how much oil pressure you have as long as there is some. My 26 Chev has no oil filter or air cleaner with exposed pushrods which gives you the opportunity to check the idle speed by holding one of the pushrods count the number of strokes in 12 seconds and multiply by 10 the ideal idle speed is 300 RPM

Graham


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 Post subject: Re: Low oil Pressure
PostPosted: Sat Feb 23, 2019 9:47 pm 
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Joined: Tue Jun 17, 2014 9:20 pm
Posts: 11
Hi Brian,
A tough one - it seems to have been a one-off and has done no damage. Unless it happens again it's a really hard one to emulate, thus diagnose. Did your two pressure gauges operate off the one sensor? We had a Ford Capri - Which I suspect had cooked the engine at some time. It would run at low oil pressure and rattle (not, I suggest, bearings but lifters) at intermittent intervals but stopping and starting often fixed it. I finally dropped the sump and there was heaps of scale in the sump - presumably cooked oil flaking off the block- which on running would be sucked into the pickup screen and partially block it. I got several cupfulls out of the sump, and you could see the impression of the pickup screen in the heap of gunge. THIS was a really strange one, obviously not happening in your case. But it sounds like some kind of crazy one-off bit of stuff somewhere to tax your mind. Just good there is no damage done. Good luck, Bill

PS Sabrina has always had 50 psi on running and about 25 at idle. Been like it for years.


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 Post subject: Re: Low oil Pressure
PostPosted: Tue Feb 26, 2019 9:26 am 
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Joined: Thu Dec 19, 2013 3:40 pm
Posts: 165
A number of people have advised their TR always run at about 50PSI. My issue is that mine always run at over 65PSI and never run at Zero. I always look for a change from normal. The actual number is not that important.

The two gauges use two different sensors. One a Bosch gauge in the dash and the other a special sensor that is supported by the engines ECU.

I worked through the lubrication system and figured there were 12 places that could cause low oil pressure. I have checked all and found no problems that would cause low pressure.
1.Oil quality and quantity. Oil level was good and changed it anyway.
2. Oil PRV. Removed it and all seems well. No wear marks on the spring.
3. Oil pump. Removed and checks show all measurements are well within specs. The rotor was a bit loose on the shaft but the pin was still intact. Fitted a new one anyway.
4. Oil pump mounting gasket. intact.
5. Upper oil pump/dist drive bush. This stops oil from the pump to the gallery from leaking back to the sump. Good.
6. Filter head mounting gasket. Removed filter head and found gasket in good order.
7. Main bearings. Removed sump and removed center main. Good condition.
8. Big ends. removed all four and they were good.
9. Cam bushes. Inspection from underneath showed they had not worked out of the block and showed no signs of problems.
10. Crank oil gallery plugs. Good and tight.
11. Oil pressure gauge. Checked against master. Good.
12. Rocker bushes. Removed cover and run engine. An oil leak around the shaft locating screw. Removed rocker shaft assembly and found the screw striped and loose in the shaft. Suspect this was so from last build. Fitted a new screw and checked all rocker bushes while the assembly was off.
Started the engine yesterday after these checks and the oil pressure is still only running at 55-60 PSI cold.

While researching the register tech files to answer a question from another member, I came across an article by our good Rob Bradford regarding low oil pressure. I had read this when he submitted it but had forgotten it. It related to his experience with low pressure. Sounded very similar to mine. His conclusion was the PRV (pressure relief valve) was at fault. It looked good but a change fixed the problem. I will now swap the one in the car with the one in my spare engine.

Like I always say to people who have a problem and after checking every thing and found them good, " if you still have the problem, they cant all be good"


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 Post subject: Re: Low oil Pressure
PostPosted: Tue Feb 26, 2019 8:53 pm 
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Joined: Tue Jun 17, 2014 9:20 pm
Posts: 11
Good luck!! Remember, if you ignore it, it with either go away so who cares, or it will get worse and you can fix it!! Bon chance mon ami, if the great Aladin can't fix it, then it wasn't worth fixing!! Best from Bill


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 Post subject: Re: Low oil Pressure
PostPosted: Fri Mar 01, 2019 6:39 pm 
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Joined: Thu Dec 19, 2013 3:40 pm
Posts: 165
Update
Car now running at 60psi cold, a drop of 10-15psi. Out for a run today and once engine got up to temperature the pressure droped to a max of 25 at 3500RPM. When home changed the complete PRV assembly but no improvement.
In order will be to change:
1. Oil filter
2. Rocker assembly
3. Filter head
After that all I can think of is engine out but can not think of any thing in the engine that would cause this issue that I have not checked.
Any thoughts would be taken seriously.


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 Post subject: Re: Low oil Pressure
PostPosted: Fri Mar 01, 2019 9:43 pm 
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Joined: Wed Dec 18, 2013 5:05 pm
Posts: 308
aladdin wrote:
Update
Car now running at 60psi cold, a drop of 10-15psi. Out for a run today and once engine got up to temperature the pressure droped to a max of 25 at 3500RPM. When home changed the complete PRV assembly but no improvement.
In order will be to change:
1. Oil filter
2. Rocker assembly
3. Filter head
After that all I can think of is engine out but can not think of any thing in the engine that would cause this issue that I have not checked.
Any thoughts would be taken seriously.


Three blokes standing around the car with beer in hand should come up with the answer in the time it takes to finish a dozen. When do you want me to come over?


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 Post subject: Re: Low oil Pressure
PostPosted: Sat Mar 02, 2019 1:27 am 
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Joined: Sat Mar 31, 2018 1:09 pm
Posts: 14
B. I had a somewhat similar instance after a 6 hour meeting at Calder years ago. In the end I found a restricted oil-pressure gauge line was at fault. It was cleaned by flushing with fuel & the problem disappeared. On some O/pressure gauges there is also a very fine gauze strainer in the connector which may be partially blocked......just clutching at straws here....mm


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