Running cold

[Timtickle]

Hi everyone,

I have a 99 zx2.I have tried and tried to get the temp up and im at a loss. I have replaced both sensors at the thermostat housing and have replaced the thermostat. Running down the highway at 3500 rpm it just gets above cold. If I let it idle in the drive way it will get to normal range. Also as soon as i turn the defrost on it drops to cold. The dang thing just transfers heat to well. And yes, I have a check engine light saying low temp. Tim

[jeffcoslacker]

Still dealing with this? I have to say that's a first for me. What a strange problem. Have you asked the service dept or checked for any service bulletins about this kind of problem?

Got any bad grounds on the engine? Just for laughs, try hooking a jumper cable to the engine block and the battery negative to give it an alternate ground and see waht happens. then try going from the neg to the body and see if it changes anything. It almost sounds like the problem is resistance in the whole ECM/gauge/sensor circuit rather than an actual overcooling problem. That would be a quick way to rule it out.

[roxo]

Hi Tim

i'm having pretty much the same problem as you [again]. do you remember what the code was [p0125]? Also, were the two sensor part numbers interchangable [ they look the same, but i was wondering if they were infact different].

I'm gonna check the grounding also, [mine was in a accident last summer maybe something isn't making contact....i never thought of that]

Anyway, my 2000 won't hardly budge the temp gauge unless i let set and idle for 15min....then it will start to come up.


Thanks

[Timtickle]

the two sensors were two diff. parts. It was hard finding the sensor on top of the housing. i found it of a contour i believe. all the part stores were showing a diff. sensor. im still at a loss. damn thing wont heat up. first time dealing with a vehical that was to efficiant

[roxo]

I was gonna try to find the bottom sensor and put in a new thermostat, but i don't see any point in it now.

Your raditor fan still kick's on..right? This problem is really a major pain...i'm afraid of the dang thing over heating again. I'm goning to try Jeff's suggestion this weekend when things warm up a bit. I'll repost if i find a solution.

Pat

[jeffcoslacker]

Do either of you have good heat in the car? If so, this is a signalling problem, not an actual overcool situation.

[jeffcoslacker]

I'll have to look on the wife's car when she gets home, and see if there are bleeder screws on the cooling system. I've seen air cause wierd problems like this.

[roxo]

I would say heat output on my 2000 is ok...kinda hard to tell when daytime temps the past month only reach high 20's/low 30's [this is our fitst winter with this car]. I also filled raditor on steep incline just to make sure i got air pockets out.

P0125 indicated that the engine wasn't coming up to temperature quick enough. I just can't come up with answer to this code.......

pat

[Timtickle]

See The Thing Is Though I Can Get To Normal Operating Temp If I Just Let The Car Idle. Then If I Hop In And Drive The Temp Will Go To 1/4 And If I Turn On Heat It Will Go To Cold. I Think Im Going To Try A Flush And Mix Coolant Back To 50/50. What About A Radiator Cap Not Holding Psi To Spec. I Know More Psi = Higher Temp. Just A Guess.

[roxo]

well, i can rule out a grounding problem. I used my voltmeter to check for any sign non-conductivity between various engine/frame points.

I had autozone clear code a couple days ago and two trips to town [abt. 45miles] brought the light back on ...P0125!!


anyone know what the sensor on the front of the head is for? [looking from the front, just alittle to the left of the raditor fan and about even with the top of the raditor...it's bolted to the head]i'm guessing it oil pressure related not temp.

[jeffcoslacker]

Either that or it is a cylinder head temp sensor.

[jeffcoslacker]

Originally Posted by Timtickle

See The Thing Is Though I Can Get To Normal Operating Temp If I Just Let The Car Idle. Then If I Hop In And Drive The Temp Will Go To 1/4 And If I Turn On Heat It Will Go To Cold. I Think Im Going To Try A Flush And Mix Coolant Back To 50/50. What About A Radiator Cap Not Holding Psi To Spec. I Know More Psi = Higher Temp. Just A Guess.

Cooling system pressure won't change temp, just boiling point. I check the NTSA's site with TSB's and recalls, but couldn't find anything there about this problem. This is really interesting, I'd like to find out what's going on here.

[Timtickle]

Well I Tried A Flush And New Coolant And Still No Good. The Cabin Heat Wont Get Very Hot, So I Know Its Not Really Getting To Temp. I Live In Georgia And This Vehical Should Cook Me Out Of The Car With Heat Full Blast. I Did Notice The Fan Is Running All The Time Even With It Idleing. I Was Told Though The Sensor I Changed On Top Of The Theromo. Housing Is The Controller For The Fan.
I Was Also Told That You Are Able To Set The System Temp In The Computer Which In Turn Turn Has Fan On? Has Anyone Heard Of This? Maybe We Just Have A Calibration Problem?

[jeffcoslacker]

Possible the ECM needs a re-flash for that problem. I looked at all the service bulletins I could find for all years of ZX2 last week thinking I might find something out for you, but there was no mention of that problem.

My '94 Impala SS would get hot in traffic when I first got it, and after bleeding the system and installing a new stat with no improvement, I called a dealer and they said it was common on the LT-1 engines since the water pump is cam-driven and turns slow at idle, coupled with an unrealistic set temp for the ECM to turn on the fan. So they flashed it to lower fan set temp by 15 degrees, and it was fine after.

Sounds like your problem might be similar, even if opposite.

[roxo]

I'd do a quick check of that top sensor. If it's not plugged in, the fan will run constantly......maybe a "bent" prong in that connector. It's a long shot

What is the stock temp. for the thermostat? Autozone has 3 different different one's