Coolant Temperature Sensor

[lexadmn]

Last weekend, we spent the weekend at the local COE park.

When we left, I noticed the motorhome was running really rich after it had warmed up as there was a very noticeable amount of black smoke coming from the exhaust and acceleration stumbled at low RPMs. I also noticed the tranny would not shift into overdrive and the engine temp was about 20 degrees cooler than normal.
I am not getting a check engine light but decided to order a new temp sensor (without looking at mine first) as a cheap possible fix as I read it can create these symptoms if it is bad.

When it arrived....  Wrong one. Terminal is different, thread is wrong size (mine is 1/2" npt and new was 3/8" npt), and it has 2 pins. Mine is single pin and terminal is shaped similar to two "D's" back to back.

Called the parts stores...    no luck. They show something different than what I have and none are single pin or a terminal like mine.
Called the Chevy dealer....   no luck, they show 5 to choose from and none are single pin or a terminal like mine.

Is this a discontinued item? If so, is there a solution for replacement?
any ideas?
Thanks
KC

[DaveVA78Chieftain]

This one?
GM P/N 25037333
  SENSOR, ENGINE COOLANT TEMPERATURE GAGE(2 TERMINALS)(1/2-14 THREAD)

NAPA P/N ECH TS6684

[lexadmn]

Thanks Dave, mine is a little different.
I should have posted a pic to start with - apologies. But here it is ....  the image is a little fuzzy, kinda like my mornings...

[Rickf1985]

That sounds like an O2 sensor problem. Are you sure your check engine light is working? Does it come on when you turn the key on? You may want to check for codes anyway.

[lexadmn]

I'm not sure if the check engine light is working properly or not Rick.  It does come on each time I turn the key on, and it came on about 2000 miles ago while driving - the O2 sensor in the exhaust kinda fell apart.    i??
It went off after I replaced it.

Checking for codes is a good idea - I didn't think of that since the light was not coming on.

Thanks Rick

KC

[DaveVA78Chieftain]

Far as I know you have 2 temp sensors as follows:
1. ECM Temp sensor; 2 wire; located behind the alternator

2. Temperature Gauge sensor; 1 wire; located on left side cylinder head

Here are the temp sensors listed by GM: https://www.chevypartsprime.com/Page_Product/SearchByName.aspx?Vin=&Make=Chevrolet&Model=P30&Year=1994&Submodel=&Filter=()&Keywords=temp+sensor

Here is a google search: https://www.google.com/#q=1994+chevy+p30+454+temp+sensor

[DaveVA78Chieftain]

Oh, thats a picture of the connector?  You have a picture of the connector on the sensor?

[Rickf1985]

The one you would want is the one for the ECM if you are looking to control the smoke if it is a computer issue. That means you are at the wrong sensor from the looks of it. I would still check codes before throwing parts at it.

[lexadmn]

Oh, thats a picture of the connector?  You have a picture of the connector on the sensor?

I have not removed the sensor yet and don't have a picture of it, just the connector.
It is located on the right side (passenger side) head near the middle/rear (see pic).
I will look to see if I can find one behind the alternator. If so, what is this one?

The sender, on the other side, I removed long ago to install a manual gauge.

[lexadmn]

I just checked it out - no codes. I am not sure what is causing the heavy flooding.

Also, you guys were spot on, I did find a sensor located in the middle of the front of the intake manifold.

I have no idea what that rascall on the head is.   

[DaveVA78Chieftain]

Auxiliary Cooling Fan Switch

[DaveVA78Chieftain]

I have a 92 Lumina APV minivan with a 3.8L OBD1 system.  There are very few scanners that read OBD1 systems.  I use an older Actron 9145 to read codes and live data. You may have to get something like that to resolve your issue rather than just throwing parts at this.  I think you could get it to work on this configuration (no guarantee). This issue could easily be a sticking Fuel injector allowing to much fuel to be delivered.
I have also had to use TunerPro on my laptop however that requires a lot of ECM, computer, and programing knowledge to adapt it  to work but does allow live data graphing and replay.

Getting the chassis manuals is a big help also (if you have a 93 chassis, just change the EBAY search field to 1993).  I typically prefer the BISHKO DVDs because they typically include all the books (service, unit repair, wiring, emissions) at a reasonable price.  The paper wiring diagrams are the large size 11x17 books which can be a pain to store away however, they also include location diagrams which is how I used my 1992 version to assist you).

[Rickf1985]

You didn't take the knock sensor out and put a gauge in the hole did you?! The knock sensor would have a round plug on it.

[lexadmn]

You didn't take the knock sensor out and put a gauge in the hole did you?! The knock sensor would have a round plug on it.

Well, that's a good question Rick.      Hm?

Actually, I am certain I did not as the gauge was working until I removed the sender.

Thanks Dave for that information.
I have installed the new sensor, but have not started it yet to see if this helped.

[Rickf1985]

I have not removed the sensor yet and don't have a picture of it, just the connector.
It is located on the right side (passenger side) head near the middle/rear (see pic).
I will look to see if I can find one behind the alternator. If so, what is this one?

The sender, on the other side, I removed long ago to install a manual gauge.

This is what I was talking about. What kind of connector did that one have?

[lexadmn]

That one had a flat copper/brass prong (spade) with a rubber boot covering.

I did fire it up a little earlier, let it warm up and took it for a drive.
It smoked for about 30 seconds or so after starting, didn't smoke anymore.
Engine warmed up to normal temp (220 degrees)
Throttle was responsive.
Shifted into overdrive as normal.

I only drove it 8 miles or so, but I'm thinking the temp sensor fixed the issue.
Thanks for the help!

now, back to the generator....     

KC

[Rickf1985]

220 is NOT normal temperature!!! The hottest thermostat they use is 210 and that is only in the most modern stuff and it is in some cars, not trucks. You should have a 190 thermostat in there.

[Wbago]

You seem to have the same single pin connector as mine has, but the sensor is fitted to the top radiator hose, I thought to control the fans on the radiator..
I'm fitting a new digital gauge, new sensor, a capillary variable fan switch, and an override switch, just to be sure. 

[lexadmn]

220 is NOT normal temperature!!! The hottest thermostat they use is 210 and that is only in the most modern stuff and it is in some cars, not trucks. You should have a 190 thermostat in there.

Interesting Rick   Hm?

I have never checked the thermostat to see the temp but 220 is what it has always ran. I thought this was normal.     i??
This is the reason I installed the manual gauge, I thought the electric gauge might be incorrect.
Outside temps, towing, and running A/C never has never made a difference.
It has 2 radiators each with their own independent electric fan, and the engine has it's fan on the water pump.

Maybe checking the thermostat is in my future.

[Rickf1985]

Now THERE'S an arrangement I have never seen! One radiator in front of the other seems very counter productive on several fronts! 220 is a temperature I would expect to see in a head once in a while but not all the time. If you have never changed the thermostat then it might be time to do so. Depending on where you live as to what one you should use. 180 or 190. Most fuel injected vehicles call for a 190. There is a very complicated formulae involving the theory of the coefficient of heat transfer that basically says that the hotter the radiator the faster it will cool the water. In other words, If it is 180 degrees it will cool good but if it is 190 degrees it will cool better. Sounds strange but science proves it out. Of coarse you qalso need a perfectly good cooling system. Good radiator, (or two in your case) good radiator cap, excellent coolant, and clean engine block. This stuff all plays into the equation. Since you have not had problems with overheating I would say most of your physical equipment is in fairly good shape but if you have not serviced the cooling system in the last 4-5 years then you should do so.

[udidwht]

Those particular year 454s ran with a 195F T stat. The dash temp gauges also are known not to be very accurate. The operating range for those early 90-mid 90s ranged from 195F - 240F. Yep...~240F. But that is when your likely pulling a grade and the clutch fan will be engaged to dip then hold the high temp. Once the grade is complete it should recover. The auxiliary fan is also calibrated to come on at approximately ~221F coolant temp. But it is not out of the norm too see the engine temp up at ~220F when ambient temps are 80F+ (more noted when in traffic/slow speed/idling). You can thank the smog nazis for that.

When you do service the radiator I recommend using a 40 percent coolant vs 60 percent distilled water ratio. Why? Water cools better than coolant. Be sure to only use distilled water.

The clutch fan (mechanical) is designed to start engaging when the radiator 'discharge air temp' hits 150F - 190F (not coolant temp).

[udidwht]

Also the cooling temp sensor is not the one you posted a pic of. That is the aux fan connector. The CTS is on the front of the intake manifold below the T stat.

[Eyez Open]

Well a little late to the game here but for the sake of information it should be known that older TBI  injection has a cold enrichment circuit. Made simple the software enriches the the fuel mixture at cold temps..A Choke.  Bad coolant sending unit bad results