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Home » Public Forums » GMCnet » [GMCnet] Stock gauges. How to calibrate. As you just don't really know the real temp, or oil pressure numbers.
Re: [GMCnet] Sure got this way off topic. Stock gauges. How to calibrate. As you just don't really know the real temp, or oil pressure numbers. [message #329107 is a reply to message #329105] Tue, 13 February 2018 11:39 Go to previous messageGo to previous message
James Hupy is currently offline  James Hupy   United States
Messages: 6806
Registered: May 2010
Karma:
Senior Member
Sorry Bob, I am probably the principal offender for getting us off topic.
Anytime you have instruments, you need calibration to be absolutely
precise. Automotive gages are notorious for being inaccurate. Too many
variables to count. But, the IR thermometer and marking pen trick is not
bad for a S.W.A.G. method. Personally, I look for readings outside what I
normally see while driving. Low oil pressure, high temperature, fluid Temps
out of ordinary ranges, etc. I have a tachometer, vacuum gage, transmission
temperature, final drive fluid temperature, oil pressure, water
temperature, speedometer, and charge indicator. Thats enough to distract me
more than I like. More gages, more stuff to worry about. I guess that is a
point in favor of alarms and flashing lights like the digipanel. Live in
ignorance until an alarm goes off and jars you back into reality. Just my
take on it. Some of you airplane jockeys out there won't agree.
Jim Hupy
Salem, Or

On Feb 13, 2018 9:22 AM, "Bob Dunahugh" wrote:

I started this topic in hopes of helping lurkers, and those new to our
GMC's. What it's change to is also important to those owns. But as it's
posted. It's more likely to be missed. My thought. Bob Dunahugh


________________________________
From: Bob Dunahugh
Sent: Monday, February 12, 2018 1:25 AM
To: gmclist@list.gmcnet.org
Subject: Stock gauges. How to calibrate. As you just don't really know the
real temp, or oil pressure numbers.


You can calibrate them to meaningful numbers.

For the temp gauge. Drive the coach to reach it's normal operating
temp on the stock gauge. Pull to the side of the road. Raise the engine
lid. Point an infred temp sensor on the thermostat housing. ( These temp
sensors are a must tool to own, and travel with. ) Then use a fine tip
Sharpie to put a dot on the face of the temp gauge IF the temp reading
looks right. Now you'll know normal, and the temp for your GMC while on the
road. A side benefit of this is. That this reading just might tell you that
you do have a cooling issue now. Most long term over heating issues are
from radiator problems.

For oil pressure. This can all be done in the driveway. Remove the
stock oil pressure sender. Located close to, and left of the thermostat
housing. Install a mechanical oil pressure gauge were you removed the stock
sending unit. Get to normal running temps. Then run engine up to 2,000
RPM's while in park. Make note of the mechanical gauge reading. Then idle
engine. Note this idle pressure reading. Then put the stock oil pressure
sender back in . Start engine. Put dots on your stock pressure gauge lens
at the idle, and the 2000 RPM readings. Idle reading as low as 10 PSI are
fine. For GM cars, and trucks that only had low pressure lights. GM had
those lights come on at 7 PSI as a rule. Remember that GM felt that
anything above 7 PSI at idle was adequate to protect their factory
warranty. 22 PSI was felt as an acceptable driving low pressure. Again to
protect their warranty.

If you do fined your oil pressure readings AT GM's low limits. A cheep,
dirty way to put off an engine rebuild for awhile. ( This will NOT fix
your worn out engine. ) Is to install a high volume oil pump. They're 50%
longer then stock oil pump. Thus 50% more volume. They DO NOT put out more
pressure. As both stock, and high volume pumps have relief valves in them
that are generally set at around 35 PSI. The reason your oil pressure can
be low comes from excess bearing clearance due to wear of the bearings,
crank, and oil pump. The high volume pump simply puts out more oil to
overtake the oil requirement of worn out bearings. The GM engineers over
sized the original oil pump to start with to deal with future engine wear
for the life of the engines.

If you really want to protect your engine. Get the Digi Panel from Jim K
at Applied GMC that has the sound alarm if there's troubles under the
bonnet. ( The bonnet term is meant to make Rob M happy ) GRIN. Bob
Dunahugh 78 Royale
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