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Faulty oil pressure gauge?


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Hello,

TR3A recently purchased and apparently on its third engine.  All runs well and seems to have been mechanically well maintained by the most recent owner - I'll be looking for advice later on bodywork and preparing for a respray... 

Oil pressure has looked good on occasional outings - idling at 30-ish, running at 75+.  I disconnected the gauge when doing some work on dashboard switches, reconnected without leaks or apparent problems.  However noticed yesterday that reported pressure has suddenly risen dramatically - idling at 50, up to 95 at 2000 rpm when hot.  There is an oil cooler.  Engine temperature is good. 

Sudden rise in pressure even at idling makes me suspect the gauge rather than the pressure relief valve.  So two questions: how simple is it to attach a pressure test kit (Amazon France does one by Free-tec); and is there any way of cleaning/maintaining the existing gauge before I splash €130 on a replacement?

Thanks!

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Why automatically suspect the gauge? Check out the cheap things first, like the pressure relief valve is not stuck. Even when cold it should not really get up to 95.

Ralph

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3 hours ago, Ralph Whitaker said:

Why automatically suspect the gauge? Check out the cheap things first, like the pressure relief valve is not stuck. Even when cold it should not really get up to 95.

Ralph

 

Oh oh.

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A stuck relief valve wouldn't increase the pressure at idle.  The valve is always closed then anyway. 

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  • 1 month later...

Yesterday, my oil pressure went way up, I tapped on the glass and it came down again?

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The hole in the Bourden tube  that lets the oil in to start the measurement is only .020 in diameter.

If,    while you had the oil line hanging loose amongst all the dust, etc,     even a speck of dirt got in the line it

will cause that hole to clog.   The result will be excessive readings.

Obtain a cheap syringe with a #34 needle, fill it with paint thinner (White Spirit), and flush the passage from the

gauge opening to the tube opening. (You can;t see it, but it is about  1/2" -2" from the opening.

Gently probe the syringe and you will feel it fall into the Bourden tube.  Squeeze a few ccs into the Bourden tube,

then stand the gauge on its end and let gravity drain the mineral spirits.  It  is not necessary to dis-assemble the

gauge to accomplish this "fix".

Make sure upon re-attaching the gauge to the line that the gasket (originally leather) is in good shape.

A #6 nylon washer makes an excellent replacement.

Frank

 

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4 hours ago, 6TTR3A said:

The hole in the Bourden tube  that lets the oil in to start the measurement is only .020 in diameter.

If,    while you had the oil line hanging loose amongst all the dust, etc,     even a speck of dirt got in the line it

will cause that hole to clog.   The result will be excessive readings.

Obtain a cheap syringe with a #34 needle, fill it with paint thinner (White Spirit), and flush the passage from the

gauge opening to the tube opening. (You can;t see it, but it is about  1/2" -2" from the opening.

Gently probe the syringe and you will feel it fall into the Bourden tube.  Squeeze a few ccs into the Bourden tube,

then stand the gauge on its end and let gravity drain the mineral spirits.  It  is not necessary to dis-assemble the

gauge to accomplish this "fix".

Make sure upon re-attaching the gauge to the line that the gasket (originally leather) is in good shape.

A #6 nylon washer makes an excellent replacement.

Frank

 

I did something very similar with methe and an opened up paper clip.

John.

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34 minutes ago, Peter Malkin said:

My gauge on start up reads 90 psi until engine reaches operating temp then settles to 60psi. 20W-60 Penrite oil. Same oil summer 35-40C and winter -3 to +15C.

Set my relief valve to 75psi, and it reaches that on tickover when cold, and when running at over 2000 revs even when hot, but drops to less below 2000 revs, and when really hot drops to around 30 on idle. Morris Oils Golden Film 20/50.  However on a run of 60 miles down the A1 on Sunday I noticed it fluctuating between 50 and 75 while maintaining a steady 65mph, did it a couple of times, would be steady at 50psi then suddenly flick up to 75psi. On the return journey I never noticed it and seemed to have fixed itself, I wonder if it was a bit of muck in the relief valve and cleared itself.

Ralph

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Ralph.

I had a similar event on my newly rebuilt engine, sudden drastic loss of pressure, which restored it's self after stopping for 10 mins. I also put that down to a bit of something stopping the relief valve from fully sealing.  Now at 1700 miles & it has not happened again.  my pressures are 75-80 at 2000 RPM, dropping to 50 at 500 RPM when hot. using Penrite 20W60.

 

Peter.

That 90 PSI is too high, suggest you adjust the relief valve to bring it down a tad.

Bob

Bob.

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4 hours ago, Lebro said:

Ralph.

I had a similar event on my newly rebuilt engine, sudden drastic loss of pressure, which restored it's self after stopping for 10 mins. I also put that down to a bit of something stopping the relief valve from fully sealing.  Now at 1700 miles & it has not happened again.  my pressures are 75-80 at 2000 RPM, dropping to 50 at 500 RPM when hot. using Penrite 20W60.

 

Peter.

That 90 PSI is too high, suggest you adjust the relief valve to bring it down a tad.

Bob

Bob

If I adjust it down the hot running pressure will fall to around 50psi. I have opted to allow it to warm up until the pressure stabilises at 60psi @ 2000rpm before driving at any speed. Been doing this for two years/7000 miles with no ill effects. I guess I’m used to higher pressure with my MGs!

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The Bourden tube is inside the gauge, it is a "C" shaped brass tube, sealed at one end, & connected to the oil feed at the other. as the pressure increases the tube tries to straighten out, & that movement is coupled to the needle.

Bob.

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3 hours ago, Lebro said:

The Bourden tube is inside the gauge, it is a "C" shaped brass tube, sealed at one end, & connected to the oil feed at the other. as the pressure increases the tube tries to straighten out, & that movement is coupled to the needle.

Bob.

 

 

Thanks Bob.

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