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MG MGB Technical - Oil pressure gauge flactuating

My gauge sometimes moves up and down about 5 lbs. when the oil is hot and @ hwy speeds, ok when cold, replaced release valve last year, is it normal?
Thanks,

Barry,
72B
B Shnabel

Yes.

Recently I discovered (?) that if I used a Volvo filter manufactured by Mann (w917) the shaking abated. It is my understanding that the oil gauge needle movement is due to the opening and closing of the oil relief valve. I believe that some portion of that movement is due to a too large oil filter. The Mann filter is slightly smaller than the K&N filter (HP2004) that I was using. The jury is still out on this one...



rn
RN Lipow

Most Bs fluctuate at idle when hot . I have never heard of this at highway speeds . It may be a function of the particular oil filter you have in at the moment . Specifically the bypass valve .This is different to the pressure release ball valve.
S Best

Lots of cars do it and it is completely normal. Originally it was much more noticeable and the oil gauge was modified to include a sintered plug to damp the fluctuations. If you have a later car but it had had an exchange repaired oil/temp gauge you could have got an earlier one. It all depends on the dynamics of everything in the system like flow, pressure, relief valve spring tension and shape of the valve faces, which is why there are many variations. Changing any one thing will almost certainly change it, but maybe only move it from one set of characteristics to another. Ignore it.
Paul Hunt

It started about a year ago, the oil pressure cold and @ hwy speed was around 50 lbs. with some flactuation.
The gauge was steady up to that point, so I removed the pressure valve for inspection and the spring was weak and valve cap scored, replaced the spring and valve cap, Oil pressure increased to 75 lbs. but flactuation continued @ hwy speeds. In the same time changed my oil filter from Frame to AC Delco, maybe oil filter specifications ?
Many thanks to all for your help.
Barry
72B
B Shnabel

Hi Barry
Mine's done it for years, I'm sure its caused by the relief valve, I go along with Paul, just ignore it.
Ron
R. Algie

Ok I'll go with Paul's advice.
Thank you all,
Barry
B Shnabel

This thread was discussed between 08/05/2004 and 09/05/2004

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