Oil pressure Gauge movement

billyod · Post by **billyod** » Fri Sep 16, 2016 12:59 pm

My Oil pressure gauge (non-electric) works fine on startup until about 20 in of manifold, then as oil temp rises and we go full forward throttle, the needle starts rapidly deflecting from middle of green past redline...we have tested oil pressure directly from engine, bled the line, changed out orpheus, and even changed out the spring in the oil relief...

Nobody including Maule seems to have one of these Rochester gauges to replace in the cluster. i have a JPI 700 but of course it is not legal as a primary, so need to replace/fix this issue...not to mention i fly over mountains in the west and IFR in Wisconsin in the summer, so don't really like looking at that gauge as an ocd pilot...

p.s. - I am not a mechanic by any means

Any ideas, help or better yet...anyone have one of these gauges laying around???

i have a video of it live if anyone is that interested...

thank you
billy

Curtis · Post by **Curtis** » Fri Sep 16, 2016 1:34 pm

Aerospace Logic oil pressure and oil temp TSO'd Part # 10-04465

gbarrier · Post by **gbarrier** » Sat Sep 17, 2016 4:16 am

It's a lot of money since you have already invested in the 700 but if you could sell it and install a 900 which is primary you can blank out that whole original cluster.

Henry L. Heaberlin · Post by **Henry L. Heaberlin** » Sat Sep 17, 2016 5:47 am

It might be worth a call to Air Parts of Lockhaven to see if they can repair the gauge unit for you. They have done some for me in the past. They show up in an internet search or in Trade A Plane... Good luck. Henry

riverbuggy · Post by **riverbuggy** » Sat Sep 17, 2016 5:29 pm

Air Parts of Lockhaven has helped me out with my Rochester gauge cluster.

maules.com · Post by **maules.com** » Sun Sep 18, 2016 10:25 pm

The flickering needle problem can often be alleviated by getting a new angle fitting which threads into crankcase at engine end of oil pressure gauge line.
Maule braces a restriction and runs a tiny drill through which stops the pulsing of the oil. Parts@mauleairinc.com

billyod · Post by **billyod** » Mon Sep 19, 2016 12:37 pm

maules.com wrote:The flickering needle problem can often be alleviated by getting a new angle fitting which threads into crankcase at engine end of oil pressure gauge line.
Maule braces a restriction and runs a tiny drill through which stops the pulsing of the oil. Parts@mauleairinc.com

Thanks guys and yes Jeremy - that was the orpheus we had already tried form Maule...looks like taking apart cluster and sending in for possible repair might be the next step...just hate grounding the aircraft...cannot believe nobody has an overhaul exchange program for this unit

maules.com · Post by **maules.com** » Mon Sep 19, 2016 3:34 pm

Take a look at your fitting to double check it has the restriction brazed in.
Some fittings I find do not have it. I have also peined the hole and redrilled with smaller drill with success.
The restriction not only stops the pulsing but saves you from rapid loss of oil in the case of oil line or gauge leak.

billyod · Post by **billyod** » Sat Sep 24, 2016 3:37 am

Thanks everyone - We got her fixed...When my mechanic took apart the cluster he noticed on the back of the unit itself the fitting was too big ... so he made a very small restrictor fitting for it.

He mentioned that this rochester gauge is about 4 times more sensitive than a Stewart warner type that he had to compare against in his shop.

went flying for 2 hours yesterday and it stayed steady 3/4 forward in Green

maules.com · Post by **maules.com** » Sat Sep 24, 2016 8:17 am

Ouch! Not good !
The restriction should be at the engine end of the oil pressure line.
If a leak were to develope in the line or the gauge, large amounts of hot oil would be sprayed under the panel or on the legs of crew or at back of engine and onto the exhausts.
Not a good situation.
The restriction should be on the fitting end that threads into the engine.

Njacko · Post by **Njacko** » Mon Jun 10, 2019 1:54 am

I have the same trouble with the oil pressure gauge vibrating on my MX-7-180. It is steady when the oil (15W-50) is cold and gets worse as it heats up. It also seems to have got worse over time.

It seems that the cause could be:

1. The gauge itself
2. Air (or absence thereof?) in the gauge line
3. The gauge line restrictor
4. The Vernatherm valve
5. The oil pressure relief valve.

Where to start...

Suggestions welcome !

maules.com · Post by **maules.com** » Tue Jun 11, 2019 11:21 pm

Njscko, read back the whole thread. Usually it is pulsing in the engine oil gallery where the 45deg angle fitting is attached. Make the restrictionhole which is brazed into that fitting a little smaller.
It gets worse as oil gets warmer/thinner.

Where are you anyway, Iâ€™m in Ireland at present.

Njacko · Post by **Njacko** » Wed Jun 12, 2019 2:05 am

maules.com wrote:Usually it is pulsing in the engine oil gallery where the 45deg angle fitting is attached. Make the restriction hole which is brazed into that fitting a little smaller.
It gets worse as oil gets warmer/thinner.

Where are you anyway, Iâ€™m in Ireland at present.

I was afraid you'd say that

but kind of hoping it might be something else because that angle fitting has a look about it which says "I haven't been disturbed in eighteen years, so don't you try it now".

Anyway we have checked the pressure relief valve and that was clean and looked "as new" so we'll have a look at that Part #5337B angle fitting next.

I'm in south west Scotland, about 35 Maule minutes from the nearest part of Ireland. If you want to give me a call, my contact details are on my airfield website, www.glenswinton.co.uk

gbarrier · Post by **gbarrier** » Wed Jun 12, 2019 3:11 am

Have you disconnected the oil pressure line at both the gauge and engine ends and blown the oil out. The air in that line affords a little cushion. If it ends up full of oil there is no cushion. Have seen it on Pipers with manual gauges a couple of times.

Njacko · Post by **Njacko** » Wed Jun 12, 2019 4:18 am

Thanks, I'll be sure to drain any oil out of the line when I check/adjust the restrictor in the angle fitting.

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