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Oil Gauge Oscillates

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Leebo

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I noticed today that there are times when my oil pressure gauge oscillates btw 10-50psi and ocassionally, it will drop very quickly. I noticed it more within the first 5 minutes after start up. The oil level is within the range. My heartrate isn't.

Thanks.

-Lee
 
Lee, I certainly hope it's not what I had, last time I saw symptoms like those. Probably isn't, since you would have heard the rod knock by now.
 
So does it oscillate at idle or is this when you are driving with higher rpm's?
As Randall notes, are there any noises accompanying the gauge movements?
 
Ironic I was about to post this same question a few weeks ago. I was at the Roadster Factory party and mine started doing the same thing on the outset of the mountain tour. I went back because my heart beat was also becoming irregular. We must be twins. One of the top restorers in the area looked at it and was not concerned because he thought the pressure release vale was sticking. After the engine warms up it seems to be normal. I change the oil when I got back and have not noticed it at all lately. No engine knocking noises it been driven approximately 500 miles.

I was thinking about this for a while now. I have a spin-on oil filter adapter and I believe the filters have a oil release valve in them too. Seems to me they may be working against each other? Should I change filters? I've been using Fram 3600 and Purolator L20195.
 
TR3ATR250 said:
I was thinking about this for a while now. I have a spin-on oil filter adapter and I believe the filters have a oil release valve in them too. Seems to me they may be working against each other? Should I change filters? I've been using Fram 3600 and Purolator L20195.
Click to expand...
At least in theory, the valve in the filter only opens when the filter media becomes clogged. While there is a similar valve incorporated in the filter head (assuming this is a TR3A), they shouldn't "fight each other". So I wouldn't worry about changing the filter. Almost all of them incorporate the valve anyway, even when they are listed for applications that don't need it.
 
Graham - it oscillates at both idle and higher rpms. Maybe I'm being hyper-sensitive, but I felt like there may be more tappet noise. Haven't noticed any other noises.

The movement from higher to lower (and lower to higher) pressure seemed to move quickly and then reside in that lower (or higher) range.

I'm going to change the filter tonight (I've been using the PH3600) and poke around a bit. I'm not driving it til I find out more. Will post more info when I have it.

thx

-Lee
 
Lee....
If your oil and filter are old I would start by changing them. In fact even if they're not old I would try changing the filter in any case, make sure you fill the filter with new oil before putting it on.

If that doesn't fix the problem I would check the oil pressure relief valve (and spring)
 
TR3ATR250 said:
Mine is a TR250.
Click to expand...
I use Fram 3600 filters too on my TR6 and haven't seen any oil pressure gauge oscillation; I don't think that the built in filter bypass is the problem; but if there is a high pressure drop across the filter because it's dirty or because of a manufacturing problem then I could imagine the relief valve cycling which could be the cause.
 
So, I finally got around to dropping the oil pan, and to my horror, the pick-up pipe was laying in the bottom of the pan...

I've reinstalled the pipe and made sure the lock nut is tight. Interestingly, when I threaded it in, it took some effort.

When I reinstalled, I only threaded the pick-up pipe 1/2 way in. Now that I've closed it back up, I'm wondering if I needed to thread it all the way in. Any thoughts? Am I OK with a longer pick-up length? It did not seem to interfere with the pan.

thx

-Lee
 
I don't think the longer length is going to affect it.
However, will it come off again?
Can it suck air in as well as pulling the oil up?
 
Just a thought, fluids are generally non-compressible, but gases , e.g. air is. Could a minute leak be causing air which is trapped in the line to cause this oscillation?
 
So I think that when the pick-up pipe fell off, the oscillation in pressure was when I went around a corner and the oil didn't reach the bottom of the pump. Now that the pick-up pipe is reinstalled, I think I've got the problem fixed.

The follow-up question about sucking air - are you suggesting that air could be sucked through the threads between the pipe and the pump? I guess I'll have to watch for this.

thx for your help.

-Lee
 
I doubt it is the explanation for your variation; but the pump can definitely suck air through leaks in the pickup tube. Not a strong suction at that point, but definitely some suction.
 
One more comment. I thought of this driving home last night. The 6 cyl engines have an externally mounted oil pressure relief valve. See photo below. If the valve spring or plunger are out of spec, the valve may be opening at a lower pressure than normal, or just not operating consistently. If the plunger is coming off its seat it may be producing the oscillations you are seeing. Take the valve apart and examine the plunger and spring. Look for wear in the plunger face, and replace if bad. Check the free length of the spring, it should be 1.53 inches (40mm). Replace if the length is not correct. It might be worth it to order a new plunger and spring and washer and replace everything. You certainly wont hurt anything and you will have eliminated a possible cause for this issue.
 

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