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Discussion Starter · #1 ·
well, trying to get my old 97 Vulcan out of the driveway and gone. Its been parked for 2 or 3 years. First surprise was the rear cross axle brake line leaking. Been through the rodeo before on my 98, so the job was just a little less than total pain in the ass. Next was alternator issues. Lucky, i had one in my deep Taurus stash from years ago and solved that issue.

I think when i parked it i thought it was having cooling issues and found a freeze plug by the firewall that had a little crud on it and though it might have had a minor weep. Parked the car before i got deep into that. fast forward to now.
So got the brakes fixed and the alternator on. Car starts and drives now. But the temp issue is still there, or is it?
dash gauge creeps up to just over the top white mark before it hits all the way hot. So i remembered that the ECT has two circuits, one for the PCM and one for the dash gauge. Hooked my scan tool to it. ECT would creep up to 212 or so if it idled for awhile, then the low speed fans would kick on. I tired to put on the AC on max, but it was out of R134 . apparently, the high speed fan wont come on if the compressor is not running?? It never got hot enough in the driveway to turn the high speed fans on.

So the real question is, if its running 205/212, where should the dash gauge read? could it be its not really overheating, but a mis display? It never seemed to put vapor out of the exhaust, or severely bubble the degass thank like a head gasket issues would do.

I changed the water pump years ago on this turd, but that does not mean it does not have the rotted vane syndrome.
have not taken the water pump off yet. if its running hotter while idling, it will cool off some if i rev it some.

So, do you think the ECT sensor could be bad on the dash gauge side? what should the dash gauge read at 212 or so?

should i pull the water pump at this point for vane inspection? Like i said, it was changed once a long while back.

I felt the upper radiator hose, and it stayed cool up to a point and then got hot, so i assume the thermostat is working, not stuck, and opening at some point. But i did not log the temp that the hoses felt hot from the scan tool.

the lingering question is whether the freeze plug could have a small leak causing the cooling system to not pressurize properly exacerbating the too hot issues. I have not detected any water dripping and here and hissing noses at this point. I would just change the dam thing, but its hidden behind the exhaust manifold by the firewall. Dont think i can get to it without removing the exhaust manifold. And if i was stupid enough to try that on his rust bucket, i could certainly open Pandoras box breaking other things.

Any insite appreciated. I just want to get rid of this turd,but its going to be hard to do as a driver if its not in driving beater condition.
 

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I've logged my 98 extensively, and at 212F when the low speed comes on, the dash gauge is still reading dead center. Normally it's just a bit under dead center. Mine never goes above that, the fans cycle on and bring the temp down to about 90C/194F and kick off. This is with a 197F thermostat which is a bit hotter than the Vulcan asks for. IMO you either have a bad temp sensor for the dash, or the pipe that holds the sensors is full of crud and coolant is getting trapped around the sensor and boiling.

IMO the pressure thing isn't much to worry about, mine has a small leak in the lower rad hose metal fitting that I've been too lazy to fix. You can always smell a bit of coolant when it gets hot, but it doesn't smoke or noticably lose level, and it doesn't have any temp issues. And my A/C even works, no issues with that either. But yeah, if the compressor doesn't run, the high speed fans won't either (until you get into the 220's of ECT). It's all tied together to that pressure switch.
 

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^ Bob, doesn't your '97 have a grey or black 2-wire ECT sensor for the PCM and a brown 1-wire temp sender for the dash?
 

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^^^ +1
I am 99% sure the G3's used a separate 1 wire sensor for the temp gauge. ECT for temp gauge and PCM didnt start until the G4's. Have had to replace a few of the 1 wire gauge sensors over the years in various older fords for either reading way too high or way too low.
 
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Discussion Starter · #5 ·
^ Bob, doesn't your '97 have a grey or black 2-wire ECT sensor for the PCM and a brown 1-wire temp sender for the dash?
Well, mystery mostly solved. I think. Bottom line is i think is it was never really overheating. The freeze plug had some crud around it like it was weeping, but it must have not been that bad. went to the junk yard and could only find a newer dash sensor (the plug type that has space for 2 wires but only has one wire in it. Put a crimp on connector on the junkyard stub harness to match the cars wire harness. The old one lug sensor measured about 390 ohms. Put the junkyard sensor on and and started it up. At first, it was all the way cold. then it gradually crept up. At about 210 on the scan meter, the temp on the dash gauge was now just below half. About what my 98 was. So i quit driving this thing a few years ago thinking it had a serious issues and and guess it did not. This car will make someone a good beater to get to work for a few more years until it totally rusts to a pile. Rockers are pretty well gone on it. Its amazing what you lose in cars. While waiting for the temp test, i cleaned out under the seats. Found tools i lost years ago.money, tons of pens. crud, junk, and who knows? Hope i never see another bull brake line job again!

So somewhere around 97, ford switched the type of the dash temp sensor types from the one post type, to the plug for two wires but using only one. My 98 had the two slot one wire one on it.
 

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Discussion Starter · #6 ·
Well, mystery mostly solved. I think. Bottom line is i think is it was never really overheating. The freeze plug had some crud around it like it was weeping, but it must have not been that bad. went to the junk yard and could only find a newer dash sensor (the plug type that has space for 2 wires but only has one wire in it. Put a crimp on connector on the junkyard stub harness to match the cars wire harness. The old one lug sensor measured about 390 ohms. Put the junkyard sensor on and and started it up. At first, it was all the way cold. then it gradually crept up. At about 210 on the scan meter, the temp on the dash gauge was now just below half. About what my 98 was. So i quit driving this thing a few years ago thinking it had a serious issues and and guess it did not. This car will make someone a good beater to get to work for a few more years until it totally rusts to a pile. Rockers are pretty well gone on it. Its amazing what you lose in cars. While waiting for the temp test, i cleaned out under the seats. Found tools i lost years ago.money, tons of pens. crud, junk, and who knows? Hope i never see another bull brake line job again!

So somewhere around 97, ford switched the type of the dash temp sensor types from the one post type, to the plug for two wires but using only one. My 98 had the two slot one wire one on it.
Well, mystery mostly solved. I think. Bottom line is i think is it was never really overheating. The freeze plug had some crud around it like it was weeping, but it must have not been that bad. went to the junk yard and could only find a newer dash sensor (the plug type that has space for 2 wires but only has one wire in it. Put a crimp on connector on the junkyard stub harness to match the cars wire harness. The old one lug sensor measured about 390 ohms. Put the junkyard sensor on and and started it up. At first, it was all the way cold. then it gradually crept up. At about 210 on the scan meter, the temp on the dash gauge was now just below half. About what my 98 was. So i quit driving this thing a few years ago thinking it had a serious issues and and guess it did not. This car will make someone a good beater to get to work for a few more years until it totally rusts to a pile. Rockers are pretty well gone on it. Its amazing what you lose in cars. While waiting for the temp test, i cleaned out under the seats. Found tools i lost years ago.money, tons of pens. crud, junk, and who knows? Hope i never see another bull brake line job again!

So somewhere around 97, ford switched the type of the dash temp sensor types from the one post type, to the plug for two wires but using only one. My 98 had the two slot one wire one on it.
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