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[GMCnet] Stock gauges. How to calibrate. As you just don't really know the real temp, or oil pressure numbers. [message #329071] Mon, 12 February 2018 01:25 Go to previous message
BobDunahugh is currently offline  BobDunahugh   United States
Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA
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Senior Member
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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