Oil pressure reading really high?

[Anonymous]

I just installed a 66 guage cluser in my 65 200.

I bought a new oil pressure sending unit to replace the one used with my dummy light.

Now, when I turn the key on, the sending unit shoots all the way to the top, then slowly comes down as the car warms up.

However, even at full operating temperature, the guage still reads all the way a H.

Is this normal for our cars? If not, what woudl be causing such a high reading?

Thanks!

 

[Anonymous]

I think they will tell you those guages are unreliable and you should hook it up to a aftermarket one to get the real figure so you have a basis for comparisoon.

Your site is one of the best.

Thanks for doing it,
Don

 

[Anonymous]

Thanks for the compliment. I'm not expecting a totally accurate reading, but I'd like to know if this is normal or not.

I have a lot of blow-by out of the breather so this may be telling the truth!

Could it be that I have my pushrods adjusted too tight?

 

[Anonymous]

I see you have a pcv valve hooked to the carb base, it's not stopped up?. What is your compression like? Does it run well?

 

[MustangSix]

Your guage shouldn't jump to the high side when you switch on. That's symptomatic of a bad or stuck IVR.

On the back of the gauge cluster is a small box about 1"x 1/2"x 1/2" in size. It is the Instrument Voltage Regulator. When it goes wacky, it causes erratic gauge readings. Simple and cheap replacement, it should help.

 

[Anonymous]

Funny thing is all of the other guages work fine.

Also, when I mean "jump" it's not like a ground-fault 'jump' - like grounding out a temp sender.

it slowly goes to the high side then works it's way down as the engine heats.

 

[Anonymous]

CC, welcome to a very SMALL club for eradicate instrument guage owners.

I've had the same problem since I bought my Mustang one year ago. I've even replaced ALL of the electrical components, except the Instrument Voltage Regulator. I too don't think that's the problem because all of the other guages work on my car except the oil pressure guage. Even swapped oil pressure switches. Tried a '66, '68, '73 and '77. They all vary in size! Oh well!

If you find out the fix, let me know, please.

On another note, are you still using an open air cleaner for your 2BBL?

 

[Anonymous]

One thing to note.....

I am not saying this is not electrical... it could be...

but could it be the normal reading off the engine?
Mine when it starts runs cold at around 1700-2000 RPMS... at that speed the oil pressure is up and as the engine warms and the RPM's drop so does the pressure...

(So a high idle speed would drive the pressure up and then it would drop with the engine...)

Mine ususally starts off a little high then drops back down... and this is with an aftermarket 12V gauge cluster that has no IVR at all.... same thing at a stop light or during traffic... stop and the pressure drops down to about half way... then get it up and cruising and it builds pressure again. (This is the kind of info a Dummy light does not part with... and the reason for the upgrade.)

The same readings come off my Toyota.... but that is a tired engine, so pressure is bad anyway.... and the above readings were on a tired 200... I have no readings off the rebuild yet. And also think about the properties of cold and hot oil.... when the engine is cold the oil is thick and takes more effort to move.... as it warms it thins and moves with less effort.

 

[Anonymous]

Well, I found *sort* of a solution.

I got a mechanical puressure guage just to check my reading. Very healthy pressure right about 40lbs. So that was good.

Since I know that these guages work off resistance, and the ground for the resistance is the engine block, I thought if I eliminated some of the grounding area of the guage it might change the reading..

So, I decided to wrap some teflon tape around the threads when re-installing the guage.

Apparently that worked, because now my oil pressure guage reads a little below the mid point!

 

[Anonymous]

So, I decided to wrap some teflon tape around the threads when re-installing the guage.

That's exactly what I thought about doing but I wasn't sure how much of the threads I should wrap. Also, what model year is your oil pressure sending switch? I'm using one for a '68 block simply because that is the date stamped on the side of the block. It's fairly large and will not complete thread into the block. There's about 3/16th of an inch or so of thread exposed. That's as far as my unit will thread into the block.

Just curious what you as well as others might be using.

 

[Anonymous]

Oh and Jimbo65...I think you are onto something. My '79 F150 experiences the same symptoms as you have described. Makes sense considering the basic mechanics of the oil pressure switch. Besides, oil pressure will fluctuate with various driving conditions.

 

[Lazy JW]

Since I know that these guages work off resistance, and the ground for the resistance is the engine block, I thought if I eliminated some of the grounding area of the guage it might change the reading..

So, I decided to wrap some teflon tape around the threads when re-installing the guage

It is amazing at times how ingenious people can be. I would never have thought of a solution like that. I do have to wonder how easy it will be to maintain the calibration on the resistance of the teflon tape
Joe