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Simplifying underhood (Coolant temp and oil pressure sender/switches)

dyeager535

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Is anyone interested in me doing a short writeup (ok, basically its just part numbers lol, although I could do another anti-climactic video of the gauge showing 30PSI then hopefully 40 when I use the right sender) on reducing the number of components underhood?

I figured out the 3 wire Coolant Temp Sensor (CTS), which is only applicable to EFI folks as I see it. For the EFI rigs, this eliminates one of the two sensor/sender locations, either the one in the head, or the intake. I believe this one is not a super accurate swap, as far as I could tell the resistance profile of the sensor isn't quite the same as it is with the stock coolant temp sender. So your gauge and/or ECM may see slightly different temps than is actual. But from what I've seen with my gauge before/after it's pretty darn close. I don't use the gauges as an absolute anyways, just an indicator for things changing.

Oil pressure sender/switch is a bit more complicated. The R/V trucks DID use a three wire sender/switch that I was unaware of until recently. Other GM products did as well, but unfortunately as I found out, after wondering why my 50PSI oil pump is only indicating ~30PSI, most of those other applications use 40PSI as the "normal" (middle indication on the gauge) pressure, where our gauges (except diesels) use 30PSI as the middle. I believe this switch/sender combo will work for the folks that are still carbed with electric chokes, and of course the EFI rigs. The fun thing with this one is that it should give you the option to run the 80PSI diesel gauge, depending which sender/switch you buy. Also depends on what your definition of fun is. I don't know as I have an 80PSI gauge laying around anymore, but I do plan on swapping to the "right" (R/V 60PSI) unit this weekend, and thus expect my oil pressure to show a difference of 10PSI.

The coolant temp unit i use is NPT (apparently at some point GM went metric on the threads), as is the oil pressure unit, however the only issue with the oil unit is that the threads are 1/4"(? larger than the stock oil pressure sending unit that looks like a bell) so you either need to run an adapter, or run an extension/adapter to fit it in the tap above the oil filter. I *think* big blocks would be a "bolt in" replacement as they have more clearance at that spot? Even though these units are much smaller diameter than the original oil pressure sender, there is not enough clearance with the block on the SBC to thread them in directly at the oil filter location.
 
I like write ups. Most of my gauges are mechanical since my EFI is a conversion, but it would still be cool

Then you can get an “author” tag
:saweet:
 
Yes, do it. Adding to the knowledge base is always a good thing. That’s a subject/area that I would learn from.
 
Is anyone interested in me doing a short writeup (ok, basically its just part numbers lol, although I could do another anti-climactic video of the gauge showing 30PSI then hopefully 40 when I use the right sender) on reducing the number of components underhood?

I figured out the 3 wire Coolant Temp Sensor (CTS), which is only applicable to EFI folks as I see it. For the EFI rigs, this eliminates one of the two sensor/sender locations, either the one in the head, or the intake. I believe this one is not a super accurate swap, as far as I could tell the resistance profile of the sensor isn't quite the same as it is with the stock coolant temp sender. So your gauge and/or ECM may see slightly different temps than is actual. But from what I've seen with my gauge before/after it's pretty darn close. I don't use the gauges as an absolute anyways, just an indicator for things changing.

Oil pressure sender/switch is a bit more complicated. The R/V trucks DID use a three wire sender/switch that I was unaware of until recently. Other GM products did as well, but unfortunately as I found out, after wondering why my 50PSI oil pump is only indicating ~30PSI, most of those other applications use 40PSI as the "normal" (middle indication on the gauge) pressure, where our gauges (except diesels) use 30PSI as the middle. I believe this switch/sender combo will work for the folks that are still carbed with electric chokes, and of course the EFI rigs. The fun thing with this one is that it should give you the option to run the 80PSI diesel gauge, depending which sender/switch you buy. Also depends on what your definition of fun is. I don't know as I have an 80PSI gauge laying around anymore, but I do plan on swapping to the "right" (R/V 60PSI) unit this weekend, and thus expect my oil pressure to show a difference of 10PSI.

The coolant temp unit i use is NPT (apparently at some point GM went metric on the threads), as is the oil pressure unit, however the only issue with the oil unit is that the threads are 1/4"(? larger than the stock oil pressure sending unit that looks like a bell) so you either need to run an adapter, or run an extension/adapter to fit it in the tap above the oil filter. I *think* big blocks would be a "bolt in" replacement as they have more clearance at that spot? Even though these units are much smaller diameter than the original oil pressure sender, there is not enough clearance with the block on the SBC to thread them in directly at the oil filter location.

Gauges and senders are matched so using a different sender well make the gauge read different. If you're only using it as a reference like you said then no biggie really but most people like to know what the actual pressure is.
 
I know GM spent the time to put the "proper" resistor on the back (of oil/temp/gas gauges), so I knew they were at least baselining them. Matching would have to be a step covered in the service manuals for gauge or sender replacement, I'll have to check those out.

It would be nice to be able to test if displayed pressure matched known pressure. Easy would be a mechanical gauge that you could trust I suppose, but without regular calibration, I don't see any other as a reference either.

At least the '87 service manual indicates that if the gauge doesn't read correctly (accurately) with the tester connected, if the nuts on the back of the gauge are tight, replace the gauge. That seems to me to indicate that a new gauge is calibrated somehow, and the sender is assumed accurate out of the box, since those are replaced if the gauge responds to the tester correctly?
 
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Yeah, I didn't get to it this weekend, and unfortunately have none of the terminals or connectors new in bags, so I don't have the part numbers handy. I plan to do some of that research today and try to get that all figured out, it's really the most difficult part.
 
Going to have to order some parts to make sure that I don't give anyone the wrong part numbers. When dealing with Aptiv (used to be Delphi) stuff, there are so many terminals and connectors that are similar but not interchangeable, I've resorted to buying anything that even looks close hoping to get the right one. At least they are relatively cheap. Past orders don't help in this endeavor though, because I have tons of part numbers I've ordered.

Also realized you don't use loctite on electrical terminals. Probably a "well that's just obvious, idiot" moment for some. I used it when I hardwired the cluster, as the nuts to retain the ring terminals are more like jam nuts and I didn't want them coming loose. I swapped the senders, but my oil pressure reading didn't change much. Swapped gauges just for fun, and the pressure bumped up a bit. But I could tell from the coating on the terminals that contact probably wasn't ideal. Cleaned them up, pressure went from just over 30 to over 45, which is pretty close to the 50PSI oil pump spring I have installed. I have some 4-40 nyloc nuts, I'll go back and do the gauge connections properly.
 

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