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Question on how to get a good readout on the dash of the engines oil pressure on my 1900Css. In this setup there is no sensor or sender involved but there is a ‘brake-line’ pipe running from the engine towards the oil pressure indication on the dash.
Can anybody explain me if this line needs to be filled with engine oil in order to get a proper reading on the instrument. Seems a bit messy to be filling up a pipe inside the car, behind the dash, (new upholstery), getting all of the air bubbles out and then screwing it on the back of the instrument?
Thanks Mike
 

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Mike,

I am in the same boat as you as I want to test run my engine before installing it and want to make sure it’s got good oil pressure.

You’re right about the poor design of these old style oil pressure gauges. Their design is bad for the very reason you mention; oil under high pressure being fed to a junction inside the ****pit. My old MGB had a gauge with this kind of “senderless” design, and while I avoided disaster in that car, I did have a failure in another car which resulted in oil all over the carpet.

I’m not sure as to how to bleed it, but you might be able to do so without having to fill the oil pipe, which is tricky enough.

-tj


Question on how to get a good readout on the dash of the engines oil pressure on my 1900Css. In this setup there is no sensor or sender involved but there is a ‘brake-line’ pipe running from the engine towards the oil pressure indication on the dash.
Can anybody explain me if this line needs to be filled with engine oil in order to get a proper reading on the instrument. Seems a bit messy to be filling up a pipe inside the car, behind the dash, (new upholstery), getting all of the air bubbles out and then screwing it on the back of the instrument?
Thanks Mike
 

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The gauge is operated by a brass snail type mechanism that when pressurized, (air pressure or oil, mostly air) tries to straighten out, moving the needle on the gauge. These were factory calibrated as manufactured operating on air pressure compressed by oil in the line.
The easiest way to check either calibration or actual engine oil pressure is with a mechanical oil pressure (not air pressure) gauge directly at the block. When you have accurate readings at idle, mid range, and high speed, with hot oil, reconnect the factory gauge, and compare readings. While one can recalibrate the factory mechanical gauge, as a DIY project, and I have done this, I STRONGLY suggest it be done professionally, as should you break anything, your search for a replacement will cause serious regret!
 

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The pipe between the block and the oil pressure instrument does not need to be filled with oil (but some oil may end up temporarily in the tube while the engine is running and oil pressure compresses the air in the tube).

With respect to accuracy of the reading, Gordon gives good advice. For testing purposes, I'm planning to put a T-connector at the block and have an electronic pressure sensor for remote sensing there.
 

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Discussion Starter #5
Tj, Gordon Raymond, Ruedi, thank you all for your quick replies and advise! I now at least know that the line itself does not have to be filled with oil and that compressed air will work in conveying the engines oil pressure.
For test-run purposes, would it work if I connect my Duetto’s sender directly to the engine, or via a short line? That would probably give a good idea as to how well my 1900 instrument is indicating?
Another question: how do I properly ‘air-tight’ connect the tube onto the 1900 gauge? It looks similar as a connection between brake-line tube and cylinder? Just to avoid having any leakage behind the dash.
Thanks again, Mike
 

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The Duetto gauge may work, but getting all the right fittings may or may not be a bit of an obstacle course (but may still be a good idea for testing the engine outside of the car).

With respect to testing the oil pressure gauge in the car: Once the dashboard with the instruments is back in place in my car, I'm planning to connect an air pressure hose at the engine end of the oil pressure tube (by slipping a hose over the nipple and using a hose clamp to seal it), and then slowly increasing the air pressure with the air pressure regulator on the air compressor. My plan is to use a static pressure test (air pressure dropping in a bleed-down test would indicate a leak somewhere), possibly followed by using soapy water around the nut that connects the tube to the instrument (to see if/where bubbles are forming).
 

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My 2 cents :

I never thought of this kind of problem. I think that at one point we ask ourselves too many questions ...

I always connected the hoses directly without asking myself any questions and it works (Giulietta, giulia, 2600, 1900)

However, my gauges have always been completely redone by a professional. (it is horribly expensive by the way!)

Chris
 
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