Lt1 weird issues
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From: Bay area
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From: Bay area
What a coincidence that on the resistance chart for the temp sensor
"- 40" is low resistance, which equals high temp. And that what I see on my scanner while driving, doesn't that indicate the sensor is closed if shows on the scanner? I also just brought a DMV meter that tests Voltage and Ohms, which one should I test first? And the sensor is a duralax brand.
"- 40" is low resistance, which equals high temp. And that what I see on my scanner while driving, doesn't that indicate the sensor is closed if shows on the scanner? I also just brought a DMV meter that tests Voltage and Ohms, which one should I test first? And the sensor is a duralax brand.
Last edited by LT1DG; Dec 6, 2019 at 09:54 PM.
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So here the tests I did earlier on the ECT sensor harnesse connector. I did every step from shoebox site this get the result I needed to track down this issue. I put the red on the yellow and grounded the black (I was testing the voltage) I got a 4.9 volts off the yellow lead and shbox said you should see 5v.
On shbox site, he also say to test the harnesse another way, I should see 5v as stated. I put the black tester into the black lead and red into the yellow wire lead. I got a - 4.9v
Last edited by LT1DG; Dec 8, 2019 at 02:39 AM.
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I tested the ECT sensor but didn't get no readings on voltage or ohms. The only thing that showed was - 1 so what's that mean? Unless I was doing something wrong. Maybe I need to test it one more time when its hot cause the motor was cold. if I get the same result that means it's bad
Last edited by LT1DG; Dec 8, 2019 at 10:32 AM.
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the 4.9 vs 5 v reading is fine. Your meter may not be "exactly" accurate or there is minimal resistance in the wire from the pcm to sensor. no big deal
you just put the meter on ohm setting within the range you will be reading (refer to the chart on shbox site...start with 2000) engine does not need to be on, just probe the 2 terminals of the sensor. If the outside temp is 50 degrees, for example, than look at the chart and see what ohm range that is on the chart and compare to your reading. It should be very close. Then warm up car and note whatever temp reading the gauge says and probe the sensor again. If the ohms match that temp per the grid than the "sensor" is working right
you just put the meter on ohm setting within the range you will be reading (refer to the chart on shbox site...start with 2000) engine does not need to be on, just probe the 2 terminals of the sensor. If the outside temp is 50 degrees, for example, than look at the chart and see what ohm range that is on the chart and compare to your reading. It should be very close. Then warm up car and note whatever temp reading the gauge says and probe the sensor again. If the ohms match that temp per the grid than the "sensor" is working right
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the 4.9 vs 5 v reading is fine. Your meter may not be "exactly" accurate or there is minimal resistance in the wire from the pcm to sensor. no big deal
you just put the meter on ohm setting within the range you will be reading (refer to the chart on shbox site...start with 2000) engine does not need to be on, just probe the 2 terminals of the sensor. If the outside temp is 50 degrees, for example, than look at the chart and see what ohm range that is on the chart and compare to your reading. It should be very close. Then warm up car and note whatever temp reading the gauge says and probe the sensor again. If the ohms match that temp per the grid than the "sensor" is working right
you just put the meter on ohm setting within the range you will be reading (refer to the chart on shbox site...start with 2000) engine does not need to be on, just probe the 2 terminals of the sensor. If the outside temp is 50 degrees, for example, than look at the chart and see what ohm range that is on the chart and compare to your reading. It should be very close. Then warm up car and note whatever temp reading the gauge says and probe the sensor again. If the ohms match that temp per the grid than the "sensor" is working right
Last edited by LT1DG; Dec 8, 2019 at 11:12 PM.
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So once I got home I pulled out my old and new ECT sensors to do some testing. I first tested the old one, (20 Ohms) and got a 2.09
I then tested it again and got a 1.88
I got a 1.91 from the new. Both not to far apart in ranges, and these are room temperature ranges.
Last edited by LT1DG; Dec 9, 2019 at 01:22 AM.
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Here I had got a cup and fill it up with hot water (Really hot) i tested the old first, still on 20 Ohms and I got a 0.55
Then I switched the ohms 20 to 2000 and tested the old one again and got a range of 537
So now for the new, same process. I switch back to 20 Ohms and got a range 0.63
When using 2000 ohms on the new I got a 648. All these readings seem to match some of the readings on the chart. If so I'm guessing that mean they are good??? I noticed the resistance on these sensor stayed at a steady range when warmed up. The one in the car bounces everywhere and don't stay put. I will wait til the car is fully cold then test the sensor to see were the range is at a lower temp then warm it up and see the difference.
Last edited by LT1DG; Dec 9, 2019 at 02:27 AM.
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So I woke up and got right on it, I tested the sensor on the wp when cold and I got a bouncing range then settled down at 0.03 I then warm up the car till temp was at 145 and again got a crazy readings from 1700 to 889 then it would settle at 0.03 or 0.01 vs when I tested the other sensor they both stayed at a steady range, even this morning before testing the one in my car. I tested the old and new (this time in cold ice water) and they gave me a steady 45-50 range. (2000 ohms)
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Last edited by LT1DG; Dec 10, 2019 at 12:00 PM.
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So guys I got the coolant system flush and radiator main hoses replaced . It help a little bit, but still slowly rise while just cruising. If I turn heater on, temp doesn't rise no more. In fact it goes down. I was debating to getting a new radiator since everything else that's coolant related has been replaced. I might even replace the steam pipe behind the heads. I'm just stumped guys. It shouldn't be running this hot with a 160 stat + new wp and rebuild heads, not to mention the tune to help with the lower Stat.
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I didn't do it, I took it to this radiator shop. I thought when you get a flush and refill you need a couple of drive cycles for coolant to settle down. I checked the coolant level after and it was at filler neck where it should be.
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Unlike any other SBC the gen 2 LT1 requires the cooling system to be bleed if it has been opened for repairs/service. Not if you are just adding coolant to reservoir
There is a bleed screed on top of T stat housing
If you don't bleed it you have air pockets which is why your temps increase when driving
shbox.com likely shows bleeding proceure
There is a bleed screed on top of T stat housing
If you don't bleed it you have air pockets which is why your temps increase when driving
shbox.com likely shows bleeding proceure
Thread Starter
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From: Bay area
Unlike any other SBC the gen 2 LT1 requires the cooling system to be bleed if it has been opened for repairs/service. Not if you are just adding coolant to reservoir
There is a bleed screed on top of T stat housing
If you don't bleed it you have air pockets which is why your temps increase when driving
shbox.com likely shows bleeding proceure
There is a bleed screed on top of T stat housing
If you don't bleed it you have air pockets which is why your temps increase when driving
shbox.com likely shows bleeding proceure
Last edited by LT1DG; Dec 14, 2019 at 01:17 AM.
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Update guys, I brought a infrared temp gun off of Amazon. I plugged the scanner in and the temp was 81F ( BTW it is cold in SF right now ) I then used the temp gun and it read 60-59 degrees off of the WP area and that matches the outside temperature. So not only is it the wrong sensor it's also giving me wrong temp reading on the scanner. I have the right one on the way, should be here Tuesday. When I got to work the other day (20min drive) my scanner said 190, the temp gun (At the WP) read 159 to a steady 162 (Fans on) . Heads read the same. The temp gun read 79 on the intake, and that's around what the scanner read for the iat temp. (That tells me that both scanner and temp gun are good and not giving me misinformation)
Last edited by LT1DG; Dec 15, 2019 at 08:51 PM.
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Hello guys so got some update and some pictures that I took earlier today. I managed to swap out the incorrect ect sensor with the ac Delco one, I even change out the old temp gauge sensor and replace that with ac delco. (Moment of truth) I plugged the battery up and fired her up. I was watching the scanner real close. Before I started it up, I pointed the temp gun towards wp and got 54c. Scanner read 65c (slightly off, but okay) I let it warm up for 10mins and before I drove off the scanner read 169, temp gun read 145-150 at the wp. While driving same result temp rising at a slow rate. (Surprisely the gauge was actually at the same range as the wp) once I got back the scanner read 200F (Fans are on) Park the car, pulled the temp gun out and pointed it at wp, it read 159-162. It seems like I'm still having the same results.i also notice that the fans Will come on at different temps. I have a mail order tune, they should come on at the set temp. I've been thinking maybe this pcm is bad? My stock pcm never behave like this with the hypertech tune. But then again I didn't have a scanner at the time, who knows. My question is it safe to drive it on a 30-45mins drive even tho the pcm sees a high temp then what it really is? Will it overheat even tho it's not really hot?
Last edited by LT1DG; Dec 16, 2019 at 08:17 PM.