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Triumph TR6 - oil pressure

I recently retrieved my TR6 from storage and before the storage had the oil & filter changed. Before the storage my oil pressure was very high 75 plus, now the pressure is once hot, at approx 50. If my mechanic put a lighter oil in the crank case by mistake, instead of the 20w50, would this cause the sudden oil pressure drop?

T.Grant, Montreal
T. Grant

I think this is normal. Atleast my TR6 oil pressure with 20w50 reads above 75 when I start it up cold, then it drops to around 50 when warm, and maybe a little lower on longer trips.
Ignatius

Thank you for the assurance...was a bit worried that I might have a bit of an unexpected expense this spring.

Ted
t.grant

T. Grant--Sounds like you don't have the 20W-50 in there anymore since you don't have your pre-storage pressure. It is not normal in your situation to have that much of a pressure swing when nothings been done to your engine. I'd change the oil and see what happens. Cheap insurance if you have the wrong oil in there now.

Rick O.
72 TR-6
Rick Orthen

Maybe I am miss reading these.

T Grant, were both your oil pressure readings before and after when the car was warm?

Rick O, is not it normal to have a oil pressure swing (drop) after your car warms up from cold?

Ignatius
Ignatius

Ignatius--I interpret Grant's message that before storage he was getting 75 psi hot and now he's getting 50 hot. That is not right. If he was 75 psi cold and 50 hot, that would be normal. I don't think that's what he's saying though.

Rick O.
Rick Orthen

Hi Rick,

You're right, last year before storage, when I started the car cold the pressure was at the top of the scale, when the car became hot, it was running at approx 75psi. This year(after oil change/storage), the pressure cold starts at the top of the scale, but then when hot goes down to approx 50psi. This is what lead me to think/hope that perhaps the wrong grade of oil was put in by the mechanic for storage. I just found the swing in pressure a bit worriesome.

Ted
T. Grant

Who needs 50 psi? I ran my motor at 25psi ( hot) for a couple of years ( 18,000 miles). The crank is still in the engine after 230,000miles, and is within original tolerances on mains and big ends. Don't worry about it , unless you drive everywhere at 5000rpm.
Peter Cobbold

Peter C. You are indeed very fortunate to run with 25 psi for so long without a problem. Were you forced into a lower end rebuild at the end of your 18K mile run? I disagree that 25 psi is nothing to worry about, particularly since I spun a bearing at those low pressures.

Rick O.
Rick Orthen

I have a 74 TR 6 with 95,000 miles on it. I was only getting 50 lb at start-up and 25lb hot (10lb @ hot idle). I was going to wait to change main bearings and rod bearing until next winter because I was not getting any knocking and a friend told me as long as i was getting atleast 10 lb for each 1000 rpms, not to worry. I am planning to take some long distance trips this summer so I decided to do the lower end this spring. Boy am I glad I did. Two of the main bearing were worn badly. The new bearings increased my oil pressure to 75 lbs start up and 50 lbs hot (25 lb hot idle). The main thing is that I feel confident that I won't have a major failure on my trips. Its fairly easy to do.
John

Ted-Just another thought or two. If the diaphram in the stock fuel pump develops a leak, it possible to get gas in the oil which could cause dilution and lower oil pressure. Also, if the engine has been dormant for several months, it might be a good idea to run the oil pump with a drill motor before starting(you would need to make a driver).
Berry

Rick,
The engine rebuild was precipitated by rising oil consumption due to piston wear. The blow-by heated the oil unduly, further lowering the low oil pressure. But a first rebore after 230,000 miles says a lot for the longevity of this engine.
It is not unusual for long-stroke,low revving engines to run at zero psi on tick-over and 25 psi (hot) at 2500rpm (eg Aston DB2/4).
A distinction should be made between wear in the shell bearings and wear in the crank journals. The fact that John from Kansas restored psi to normal with new shells indicates nothing amiss with the crank journals.
I should add that over those 230,000miles I had replaced the big end shells several times, and the mains twice.This was not for fun: in the first 150,000 miles several pistons developed cracked crowns, and I replaced the big end shells each time I did a piston. So I suppose the ,last set of shells had only been in for around 80,000miles.
Peter Cobbold

This thread was discussed between 06/05/2002 and 11/05/2002

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