Bad Oil Pressure Sender

lfdeluca1 · 08-03-2011, 06:50 PM

We recently experienced an intermittent low oil pressure alarm on our 8.1 L Vortec GM engine (Workhorse W-22 Chassis). Alarm would sound more and more regularly as the engine reached operating temperature. Oil change was recent and oil was at correct levels and clean; a new M1-111 oil filter was also installed. A oil pressure meter was installed and indicated that the oil pressure was correct and steady at idle; the engine also made no noise and ran smoothly. Problem traced to a defective oil pressure sender unit. Mentioning this because the authorized workhorse repair facility told us that they had never seen the sender go bad; finding and replacing it ourselves no doubt saved hundreds of dollars in repair labor.

DriVer · 08-04-2011, 06:00 AM

Quote:

Originally Posted by lfdeluca1

Mentioning this because the authorized workhorse repair facility told us that they had never seen the sender go bad; finding and replacing it ourselves no doubt saved hundreds of dollars in repair labor.

How did the data on the IP in relation to oil pressure read?

lfdeluca1 · 08-05-2011, 03:07 PM

The readings changed with engine temperature. Initially, with a cold engine, they read normal at around 40-45lbs. But, as the engine heated towards normal temperature the IP reading started to drop eventually bouncing on and off zero when the engine reached operating temperature. The swing was zero to 15 lbs at normal operating temp. and it would alarm whenever it went below 5lbs. That sensitivity to temperature is what lead me to believe that it was the sender unit. Replacing it was easy; got the part from a NAPA Auto Parts store. You do need a special 1/2" socket to remove it; I bought one but I understand that some stores will loan you one. Actual oil pressure, when measured with a pressure guage, did not vary more than 10 lbs across the temperature range and rpm changes.

oemtech · 08-05-2011, 03:43 PM

Part # .... I will add it to the Workhorse Parts Xref.

lfdeluca1 · 08-06-2011, 05:42 AM

Sorry OEMTECH, I no longer have that part number but NAPA had no problem looking it up for me and it was an exact replacement. In my Itasca Sunova it was very easy to get to; remove the engine cover and it is dead center at rear of engine on the top.