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1999 Deville base
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162 Posts
Discussion Starter #1
Hey all,
I posted this earlier, but it ddnt go. Anyway, today, after a trip to BatteryOutfitters for a new battery, I restarted the car (99 Deville 109k miles) to read the codes(none, after I reset the ck engine lite for a P0143(failed after Cat O2), the Coolant Hot Idle Engine message and the little red thermometer popped up and went away several times in bout 20 minutes. Then seemed to be ok. Also the fans started to kick on high, but immediately went back down. And the digital temp was a little "jumpy"m going from 199(usually, almost constant), to 187, 192. Only 9k since head gasket repair with Norms inserts. Engine not hot, I opened hood and could get radiator cap off while it was running. What's going on? Anybody know? I've done a lot of work to this immaculate car and want to get it right. Any help would be appreciated! Thanks in advance!
 

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Super Moderator
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86,155 Posts
You might start by checking the purge line to be sure you have coolant flow into the surge tank. Pull the line from the top side of the surge tank and stick it into the surge tank. Start the car (cold) and look for flow. If none, follow the line back and pull it from the hollow bolt. Clear any restrictions (usually sealant tab residue "muck" ).
 

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1999 Deville base
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162 Posts
Discussion Starter #3
Ok, thanks Ranger, I'll go out and do that as soon as I finish this cup coffee, and let you know.
 

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-Administrator- 2002.5 F55 STS 2014 FWD Explorer
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66,616 Posts
OK - stick your hand down to the ECT sensor (temp sender) low on the rear (driver's end) of the right (rear) head/block area and play with the sensor electrical connector and wiring. That sensor is a temp-variable resistor and any shorts or intermittent connections will raise hell with temp indications.

Your normal temp 24/7/365 should run from 190 to 205 or so. Learn your fan sequencing because in heavy ? stalled traffic the temp WILL go to 223 before fans go to SLOW when there is no A/C compressor function set.

ECT,MAP,IAC,TPS locator.gif
 

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1999 Deville base
Joined
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162 Posts
Discussion Starter #6
I dont know what else to check. It's a new Standard brand sensor. Old one went dead. It was doing this same thing before the head gasket job, I attributed it to the blown gasket super heating the coolant. I could hear bubbles when I blew thru the compression tester hose in the #1 cylinder. Surely, it cant be the headgasket again after 9k miles? I had the heads milled and used Felpro MLS gaskets?
 

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1999 Deville base
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162 Posts
Discussion Starter #8
My temp range is as you say, 190-to 205, but my fans come on at 205 for some reason. I was parked at the battery store watching it yesterday. I thought the other day that they were coming on early, but dismissed it.
 

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-Administrator- 2002.5 F55 STS 2014 FWD Explorer
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66,616 Posts
When did you hear bubbles? Today or before the gasket job ?

No such thing as super heated coolant. The leak causes exhaust gas to overpressurize the cooling system, thus blowing off coolant, causing water pump cavitation (loss of pumping ability), causing overheating.

The max cut on a Northstar head is .004" and is usually unnecessary, even when doing an insert job.
 

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1999 Deville base
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162 Posts
Discussion Starter #10
The bubbles were before the gasket job. I told the machine shop guys about the .004 limit on the heads. They curtly informed me that it wasn't their 1st Northstar head mill job.
 

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1999 Deville base
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162 Posts
Discussion Starter #12
Well, I've had it idleing all this time, and was about to give up, when the idle fluctuated slightly and I caught just IDLE ENGINE flashed on and off the dash. No little red thermometer this time. Coolant was at 205. Been another 10 minutes, hasn't done if again. Idk. ?
 

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1999 Deville base
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162 Posts
Discussion Starter #13
Here's a clue, I've got a B1350 code now. Odd, it's under HVAC, it's a History, says device ground and circuit #2 malfunction. Says it's an uncommon code, but it ALSO says it's a coolant over temperature code. Any ideas? Do I have a bad ground somewhere?
 

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Super Moderator
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Starting to sound like a ground problem. Can't hurt to locate and clean them, especially the one for that circuit.
 

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1999 Deville base
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162 Posts
Discussion Starter #15
It must be a ground, cause after it sat for 15-20 minutes, I restarted it and the little red thermometer flashed and the idle messed up for an instant. Same time. I've been suspecting the ground, but I just redid the temp one. It has 3 or 4 wires into 1 terminal. Prob all the sensors on top the engine. It's way down below the trans shift shaft. Below the EGR and coolant pipes too. Can barley see it. I had to relocate it under the shift selector, the original bolt no longer went into the head, thru the bottom of the lift strap, because of the heads being milled.
 

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-Administrator- 2002.5 F55 STS 2014 FWD Explorer
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66,616 Posts
Check the engine wiring harnesses for chafing and intermittent grounding. Especially where the wires run across engine or clamp parts.

There are two multiple ground boxes associated with the dash - outboard of each front seat side carpeted kick panel on the fender insides. Check the wires in the box and check the single ground stud/nut.
 
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