I have a small problem with temperature sensor on my 81 SDV 368 8-6-4 engine. The temp. sensor screwed into the front of the block ( just right of center at front of engine with wire & connector pointing to the right) has a nice melted together set of wires starting at the sensor end to about 2/3 up the length of the pigtail. Tried spicing & repairing but it wound up doing the same thing again. Went to a good scrap yard by Cambridge Ontario that I know has a bunch of scrap Sevilles with 8-6-4's in them, and they are all the same as mine. Does anyone know where I can get a replacement that has some better temperature resistant wire than what the original had. I believe that this might be the reason I am getting the intermittent check engine light coming on and fast idle, also intermittent. Both problems come and go, but the car does sit most of the time without being used.:(
Thanks for any input.
KC.

You might also try to find some heat shielding once the wires are repaired. Maybe in the form of exterior tubing or wrap (tape).
Just a thought

Kev

The wires appear to be melting from the inside out and not do to any physical contact with the block. The other ones I observed in the scrap yard all seem to have suffered the same fate. seems more like a wire resistance issue. Thanks for the suggestion though as any input at all is helpful. I was hopeing a Cadillac mechanic from days gone by would be able to point me in the right direction, or someone who had alot of experience with this paticular problem on the 8-6-4 engine.
KC.

Those wires are not really made with anything special so you are correct in assuming that they are probably melting from the inside out due to excessive current. Been too long and all I can find is the '81 electrical wiring book so that does not tell me exactly which sensor is screwed into the front of the block. 2 things to do. start your car and press the OFF and WARMER buttons on the climate control at the same time. The climate control readout will start displaying all your check engine codes that are still stored (less than 20 ignition key cycles since the fault occured) Record these codes and then look them up. This might give you a hint of why the check engine lamp is coming on. Second thing to do is make sure that the battery negative cable has a really good low resistance connection to the engine block. There will also be a heavy connection to the chassis from the engine somewhere. They might have used a braided wire for this. These connections are very important when cranking the engine as it draws a lot of current. If they are not able to deliver heavy current then you could have a ground loop through the DFI sensors. his will cook stuff. Look around the alternator for a heavy black ground wire also.
IIRC that sensor normally has no connection to the block but that could have changed over time. What size wrench does it take to unscrew? What shape is the molded plug idiot proofing where the contacts fit together?
I used to work on these back in the day and always laughed at people who thought 8/6/4's were no good.

Thanks for the info, really appreciate it. I will have to check on the paticulars regarding sensor wrench size and codes. Did not know you could retreive the codes this way, way cool. Thanks Ape Man.

KC

Hi, guys, I'm thinking about buying a 81 V-8-6-4 Seville, and wonder why the diagnostics don't come up when you press off & warmer on the dash. HVAC controls are perfect but that and the Mileage Sentinel don't work. I think it has something to do with V-8-6-4 Deactivation, but I havent recieved my 81 Shop Manual yet.
Thanks, Dave

Hi, guys, I'm thinking about buying a 81 V-8-6-4 Seville, and wonder why the diagnostics don't come up when you press off & warmer on the dash. HVAC controls are perfect but that and the Mileage Sentinel don't work. I think it has something to do with V-8-6-4 Deactivation, but I havent recieved my 81 Shop Manual yet.
Thanks, Dave

Are you checking it with the ignition ON. If so you might have a bad fuse somewhere. You can usually stick a test light on both sides of fuses as they have a little spot for this. That beats pulling a bunch. The shop manual trouble tree will be most helpful. De-activating the 8/6/4 should not cause any difference to the diagnostics. Most de-activations are done by cutting the wire between the ECM and the 3rd gear pressure switch in the transmission. There were also GM issued PROMS which would eliminate the modulated displacement function as well. I had a car with one of those. Had to swap the ECM to figure it out and get the 8/6/4 working again so I could get another 1-1/2 miles to the gallon. I remember some goofy stuff happening when later climate control heads are swapped into these cars. That is another thing to look into. The buttons should look exactly like they do in the owner's manual.

Are you checking it with the ignition ON. If so you might have a bad fuse somewhere. You can usually stick a test light on both sides of fuses as they have a little spot for this. That beats pulling a bunch. The shop manual trouble tree will be most helpful. De-activating the 8/6/4 should not cause any difference to the diagnostics. Most de-activations are done by cutting the wire between the ECM and the 3rd gear pressure switch in the transmission. There were also GM issued PROMS which would eliminate the modulated displacement function as well. I had a car with one of those. Had to swap the ECM to figure it out and get the 8/6/4 working again so I could get another 1-1/2 miles to the gallon. I remember some goofy stuff happening when later climate control heads are swapped into these cars. That is another thing to look into. The buttons should look exactly like they do in the owner's manual.

Thanks, well the ignition is on, and this car was one of the ones with the GM issued PROM which was installed in about 1990. The car HVAC controls look fine, and they match the owners manual, which says 1981 Eldorado, but I guess they could have been out of Seville manuals? The fuse is the only thing I think it is which is good for me, as I don't want to spend much on this car.
Thanks, Dave

P.S. I just bought the shop manual, and I will recieve it next week.
Thanks, Dave