where are the factory oil pressure and water temp senders on 71 472?

[Brett]

Hey folks,

where are the factory oil pressure and water temp senders on a 71 472? My mechanic is a bit stumped.  Thanks!

[35-709]

Two temperature senders, one oil pressure sender.

The first picture is that of the '71 Shop Manual, the location of the engine water temperature sender is in the text, but is described as being below the AC compressor, an easier way to find it is to look directly behind the alternator, on the side of the engine, not on the top.  The location of the engine metal temperature sender is pictured in Fig. 6-3, don't confuse them.  Is one bad?  Do you know which one?

The second picture is the location of the oil pressure sending unit.  Passenger side, just above the trans. bellhousing, behind the intake manifold, and partially hidden by some wires.  That is the trans. fluid dipstick in the picture.  Your mechanic should be able to spot that that is the oil sender because it takes a special socket and it has been thus on GM cars for many years.

You REALLY should have a Shop Manual if this is a car you (or your mechanic) is going to be working on (i.e. you aren't going to sell it soon)!!   

[Brett]

I was going to hook up some aftermarket guages....if I do, are there weird size threads or something? Also, what temperature sensor should I use? Why are there two for only one idiot light?

Roger on the shop manual.

[35-709]

Read the shop manual excerpt again.  There are 2 temperature lights, one water temp., one metal.  Thread sizes are standard U.S. size as far as I know, but I don't know offhand what they are.
 

[TJ Hopland]

Oil pressure is easy, just get a T fitting from the plumbing department of your favorite hardware store.  Im thinking its a 1/4" NPT but I could be worng, most are 1/8" but most of the gauge kits come with adapters.   Temp is a bigger problem if you are wanting to keep everything else stock.  The Cadillacs have the coolant temp sender under the A/c compressor for the warning light and the sensor on the back corner of the drivers side head is the metal temp 'stop now' light. The metal temp one can not be interchanged with the typical temp gauges.  Since that one is sort of a final waring you may be fine without the other coolant one because you will still have that light to warn you to pay attention to the gauge.  To install the coolant one you have to move the a/c compressor out of the way.  I think the typical temp gauge is 3/8 NPT.  Cadillac uses a 1/2" IIRC.  There is also a second hole in the same passage on the front of the block a few inches to the right as you stand in front of the engine.  In a 73 that is a thermal vacuum switch for some sort of emissions thing (cant remember what and too lazy to get the book to check).  If that is not there or working on yours you can put the temp sender there.  That one does not require you to remove the a/c.  Temp senders need to be in the flow to give good readings so T's dont tend to work as well. There is also a sensor in the front corner of the pass head behind the alternator, this one looks just like the rear one but turns on at a different temp to tell the climate control that the engine is warm enough to turn on the blower for heat modes.





In this last picture you can see the mechanical gauge sender (gold) between the radiator hose and dizzy.  On the other side of the dizzy you can see a bit of red and black wire with a piece of white tape, this is my sender for my fuel injection computer.  My car is a convert so getting the AC to work just has not been a priority.

[TJ Hopland]

Forgot to add, those sensors in the heads are blind holes.  That is they are just into the metal, they don't get into any oil, coolant, or air flows.   Thats why they are not much good for anything but what they do now.

[35-709]

TJH,
Thank you for adding to and correcting my post.  Great pictures!
Geoff N.   

[TJ Hopland]

No problem Geoff, your info and pictures were good I just added some more.  Without yours I may not have even thought to mention the metal temp or hvac ones.

Looking at that underhood picture I am reminded that I have some major clean up work to do in the spring and I need to find a better air cleaner.  That photo was from the day I got the EFI working.

[TJ Hopland]

Another tidbit for those that may be dealing with later engines.  There was a 3/8 port just below the T stat on some of the later blocks.  All 425's seem to have them.  I would assume the 368's did just because of the level of emissions and control they needed.  Later 500's 75-76 could also have had them due to increased emissions equipment and or the efi option.   There is a plug lower down on that side but IIRC it is OIL direct from the pump.

[Brett]

Aftermarket guages are now hooked up and operating!

Does my Caddy get too hot? Temp goes sometimes to 260ish, and it is often around 220. It doesn't feel hot or operate abnormally. Oil pressure at hot idle is only 10psi but the car seems to work just fine.

Thanks again guys...now for my little transmission issue, subject for another post!

[TJ Hopland]

Those are the temps my 73 eldo ran with the tired original and my new rebuilt motor.

10 psi is fine for a hot idle.  The lights turn on around 4.  I have had many cars that did not die of oil problems that idled with the light on for years.

[STDog]

Just to add to TJs info.
The thermal vacuum switch on the front is an overheat protection.
It switches the vacuum going to the distributor advance. Below a set temperature it's ported vacuum from the carb. Above that temperature it manifold vacuum. That add ignition timing at idle, and increase engine speed. The speed up the fan and draw more air to cool the engine.(I'm too lazy to look up the temp)

There's a 4th port on many that goes to a vacuum device on the carb, but my '70 doesn't have it nor does my FSM discuss it.


Not a clue about the other switch added to later engines, but I'm sure it's emissions related. Might well be for the EGR valve, since you don't want EGR when cold.