North American Turbocoupe Organization



Bad oil sending unit
BradM Online
Junior Member
#1
Here's something I would not have expected. When I bought my '87 TC it had 113k miles and showed the classic signs of a worn engine (bearings). The oil pressure was mid-gauge when cold and at idle and then would drop to near zero when hot and at idle. At highway speeds, the pressure showed mid-gauge. However, when I torn the engine down and inspected everything, it looked great. I also have the maintenance records which show the one-owner changed the oil every 2000 miles. So I left the original bearings and oil pump in place.

As expected, nothing changed after installing the engine. The gauge worked as it did originally but I didn't believe it. So installed a new Motorcraft E4ZZ-9278-A oil sender and now it reads perfectly normal. The gauge is just above mid-point and only moves up and down about 1/8 of an inch from cold, to hot, to highway, to idle. I would not have expected a bad sender to work the way it did.
1965 Mercury Comet Caliente; 1968 Mercury Monterey; 1969 F100 Ranger; 1987 Thunderbird Turbo Coupe
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Dlreed7 Offline
Junior Member
#2
(05-02-2021, 09:06 PM)BradM Wrote: Here's something I would not have expected. When I bought my '87 TC it had 113k miles and showed the classic signs of a worn engine (bearings). The oil pressure was mid-gauge when cold and at idle and then would drop to near zero when hot and at idle. At highway speeds, the pressure showed mid-gauge. However, when I torn the engine down and inspected everything, it looked great. I also have the maintenance records which show the one-owner changed the oil every 2000 miles. So I left the original bearings and oil pump in place.

As expected, nothing changed after installing the engine. The gauge worked as it did originally but I didn't believe it. So installed a new Motorcraft E4ZZ-9278-A oil sender and now it reads perfectly normal. The gauge is just above mid-point and only moves up and down about 1/8 of an inch from cold, to hot, to highway, to idle. I would not have expected a bad sender to work the way it did.

Very interesting! My 87 has started with the same symptoms. Yesterday while waiting in line at the bank the oil pressure gauge gradually dropped at idle until it was in the red.
Just increasing the rpm by a couple of hundred put it to mid range. I'm going to try a new sending unit before digging any deeper.
Where did you buy yours? I looked up the part number online and was surprised to see how much they cost.
David
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BradM Online
Junior Member
#3
I found one on Amazon for $34 (under part# SW1547B). That was a month ago and I see now they are $55 and up. There aftermarket alternatives. Look on RockAuto.
1965 Mercury Comet Caliente; 1968 Mercury Monterey; 1969 F100 Ranger; 1987 Thunderbird Turbo Coupe
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John B Offline
Member
#4
The factory oil sender units are notorious for being inaccurate and failing over time. BradM - glad to hear that you got it sorted out. 

Another option would be to go aftermarket with the sending unit and gauge. I replaced the factory unit with a glowshift dual gauge for oil pressure and temperature. My setup required modification of the "oil distribution block) but that was because I wanted three ports (oil pressure, oil temp, and oil feed for turbo). The entire project wasn't hard; just mixing and matching fittings to get the desired layout.
88 Turbo Coupe: Front mount intercooler, MGW short throw shifter, full coilover conversion, tubular control arms front and rear, svo front brakes, vacuum assist brake swap, manual steering swap, GT35R turbo with external gate, pimpx ecu, 60lb injectors, 3 core aluminum radiator, Boport 1.5 cam, gutted upper, corbeau fixed back seats, and the list goes on.
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Dlreed7 Offline
Junior Member
#5
(05-03-2021, 01:00 PM)BradM Wrote: I found one on Amazon for $34 (under part# SW1547B). That was a month ago and I see now they are $55 and up. There aftermarket alternatives. Look on RockAuto.

I’ve got one on the way. Anxious to see if I get the same results!
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JT Offline
Posting Freak
#6
(05-02-2021, 09:06 PM)BradM Wrote: Here's something I would not have expected. When I bought my '87 TC it had 113k miles and showed the classic signs of a worn engine (bearings). The oil pressure was mid-gauge when cold and at idle and then would drop to near zero when hot and at idle. At highway speeds, the pressure showed mid-gauge. However, when I torn the engine down and inspected everything, it looked great. I also have the maintenance records which show the one-owner changed the oil every 2000 miles. So I left the original bearings and oil pump in place.

As expected, nothing changed after installing the engine. The gauge worked as it did originally but I didn't believe it. So installed a new Motorcraft E4ZZ-9278-A oil sender and now it reads perfectly normal. The gauge is just above mid-point and only moves up and down about 1/8 of an inch from cold, to hot, to highway, to idle. I would not have expected a bad sender to work the way it did.

Oil pressure can, and does, vary based on RPM and oil temperature. The TC gauges are so slow and inaccurate that you don't see those true movements. In fact, after the TC, the MN12 T-Birds used a "dummy" oil pressure gauge that was actually operated by a switch. Anything over X PSI moved the oil pressure gauge into a normal zone and kept it there. Ford continued to use this practice on other vehicles, in part, because customers complained about the gauge movements as if there was something abnormal. I'm sure cost also helped as a switch was cheaper than a sending unit.

If you have a true gauge, or a mechanical gauge, you will see that oil pressure can swing. The TC gauge simply can't track it.
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