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Hello, all. My 92 C4 overheated, had it towed home. Started it up, pulled into the garage. I installed (over the course of 3 weeks) new ignition and cooling parts. I installed a new optispark, plugs, wires, coil, waterpump, thermostat, coolant temp sensor, upper and lower radiator hoses, radiator cap. The car starts up, runs for a while, and I have 2 different readings going on... The digital is much lower, and moves slowly. The analog readings shoot to 260 eventually after running car idle in the garage from cold. I have bled the system, filled with water and coolant. I cannot put any more in. The car does puff some white smoke, doesn't smell like coolant, more like fuel. So I turn off the car, but leave the fans going once the analog gauge gets to 260. Any ideas what may be going on? Could my opti timing be off? Could I have a blown head gasket (fresh oil, not milky brown, and radiator fluid looks fine)? Maybe 180 thermostat not opening?
I'd bet that your car is running at "211" (what's shown in the pic) which is fine. I'd bet that your analog gauge is out of whack. The analog gauge is more like a cold-medium-hot, light, than a gauge that provides meaningful information.
Do I somehow check the temp near the sensor? There is a one wire sensor on the driver side by the 1st couple of spark plugs. I do not even know what this sensor is called, not sure how to look it up.
Originally Posted by Tom400CFI
I'd bet that your car is running at "211" (what's shown in the pic) which is fine. I'd bet that your analog gauge is out of whack. The analog gauge is more like a cold-medium-hot, light, than a gauge that provides meaningful information.
I'd bet that your car is running at "211" (what's shown in the pic) which is fine. I'd bet that your analog gauge is out of whack. The analog gauge is more like a cold-medium-hot, light, than a gauge that provides meaningful information.
Can you check the engine temp w/another device?
go by your digital and ignore your analog. You did all that and did not pull your radiator and clean or pull your knock sensors to flush? my 94 runs under 200 in Texas they are big vacumm cleaners and need to be maintained. If the original opti was still good better keep it.
My fans come on at 228 and 238 let yours idle and see when yours come on by the digital.
Did it blow steam when it over heated? Was it 250 or over by the digital? If so you might be doing head gaskets. And most likely just a dirty radiator the whole time.
Last edited by antfarmer2; Aug 14, 2016 at 03:11 PM.
Ok, previous owner thought car ran hot. He had the fan relays grounded (just one wire for me to remove) so they run all the time. Should I undo the grounding and then let the digital go to 238? The car got a new radiator 2 years ago also. Looks new. Also, somewhere I read the check engine gauges or something will come on if truly overheating? I cannot find the analog sensor name, all that comes up are the sensors that go in the waterpump, which are 2 wires, where the analog gauge sensor is one wire.
Originally Posted by antfarmer2
go by your digital and ignore your analog. You did all that and did not pull your radiator and clean or pull your knock sensors to flush? my 94 runs under 200 in Texas they are big vacumm cleaners and need to be maintained. If the original opti was still good better keep it.
My fans come on at 228 and 238 let yours idle and see when yours come on by the digital.
Last edited by Tom Winton; Aug 14, 2016 at 03:14 PM.
Ok, previous owner thought car ran hot. He had the fan relays grounded (just one wire for me to remove) so they run all the time. Should I undo the grounding and then let the digital go to 238? The car got a new radiator 2 years ago also. Looks new. Also, somewhere I read the check engine gauges or something will come on if truly overheating?
I would my first one comes on at 228 and they are hot running cars and all you're doing now is burning up the fans. The radiator can get plugged up with one plastic bag or a drive behind a hay wagon. And many do not know to pull the knock sensors to flush you will leave a gallon of crap in there. I put in new sensors torque is important 14 lb I believe.
Do I somehow check the temp near the sensor? There is a one wire sensor on the driver side by the 1st couple of spark plugs. I do not even know what this sensor is called, not sure how to look it up.
I would use an infrared temp gun to measure the time of the water pump housing and/or thermostat housing. Confirm the digital reading is the same/close.
Originally Posted by antfarmer2
If the original opti was still good better keep it.
Excellent advice, there.
Originally Posted by Tom Winton
Should I undo the grounding and then let the digital go to 238? I read the check engine gauges or something will come on if truly overheating? I cannot find the analog sensor name, all that comes up are the sensors that go in the waterpump, which are 2 wires, where the analog gauge sensor is one wire.
I would remove the grounds on the relays; fan motors will burn out eventually, if you don't. Extra load on the alternator too, and finally, ECM shuts the fans off at over 30 mph anyway....w/the fans running at highway speed, the actually impede air flow through the radiator.
A "Check Gauges" light will illuminate on the IP if the engine gets too hot. Same light that illuminates when you run too low on fuel.
So I should have got check gauges, and the radiator cap should have let water into the overflow, if the temp really was 260, right?
Also, do not see the analog sensor on the passenger side by the oil stick. Is that unusual? See my picture below...
Could the analog temp sensor have malfunctioned now that is was overheating?
Originally Posted by Tom400CFI
I would use an infrared temp gun to measure the time of the water pump housing and/or thermostat housing. Confirm the digital reading is the same/close.
Excellent advice, there.
I would remove the grounds on the relays; fan motors will burn out eventually, if you don't. Extra load on the alternator too, and finally, ECM shuts the fans off at over 30 mph anyway....w/the fans running at highway speed, the actually impede air flow through the radiator.
A "Check Gauges" light will illuminate on the IP if the engine gets too hot. Same light that illuminates when you run too low on fuel.
I guess I can take it out for a ride locally down the back streets here. At what point should I turn it off to avoid damage? When the temp reaches 260 on the digital?
And to answer if the car ever overheated, Here is what happened originally before this maintenance. One day on the way to work, the car made bubbling sounds and the temp shot up, saw steam coming out from under hood. Filled with water and drove to work after short rest. Tried to drive home, but did not like how quick the analog temp gauge shot up. Had it towed. So I guess that was overheat, or could have been cap failure or something. Some hoses looked bad and stuff, so decided to do all this maintenance while at it.
Originally Posted by antfarmer2
Still waiting for answers to see if it ever over heated.
Last edited by Tom Winton; Aug 14, 2016 at 04:15 PM.
If you hit 250 on the digital you have done damage it should never go over 230 without the fan coming on. If it does not come on by then turn your ac or defrost on and report back. Are you loosening coolant?
I would just idle in your driveway.
Last edited by antfarmer2; Aug 14, 2016 at 04:35 PM.
Ok, went for a drive. Digital went up to 240, check gauges light came on. I pulled over and turned off engine. Turned ignition so fans ran. Cooled down to 200 per the digital, and came back home. The car is running awesome after the tune up! But the temp... I pulled in garage, left fan running. Opened the bleeder screw on the thermostat housing. Alot of air! Finally coolant, and tightened it. I believe I have done this 2x already. Why would pressure build up and no coolant until air is released? Does the symptoms sound like anything else is wrong to keep that pressure? Or do I have to do this over 3x to get all the air out?!
Last edited by Tom Winton; Aug 14, 2016 at 05:23 PM.
Ok, went for a drive. Digital went up to 240, check gauges light came on. I pulled over and turned off engine. Turned ignition so fans ran. Cooled down to 200 per the digital, and came back home. The car is running awesome after the tune up! But the temp... I pulled in garage, left fan running. Opened the bleeder screw on the thermostat housing. Alot of air! Finally coolant, and tightened it. I believe I have done this 2x already. Why would pressure build up and no coolant until air is released? Does the symptoms sound like anything else is wrong to keep that pressure? Or do I have to do this over 3x to get all the air out?!
I would keep doing it hope you did not blow a head gasket. be very careful not to get your opti wet.
Last edited by antfarmer2; Aug 14, 2016 at 06:00 PM.
I believe it was vented, the way solid streams of antifreeze and water came out before tightening (3x). Once, when cool, then hot, then hot again. So, do I take it for another spin after topping off? What if it keeps getting this pressure? Can that mean anything?
I believe it was vented, the way solid streams of antifreeze and water came out before tightening (3x). Once, when cool, then hot, then hot again. So, do I take it for another spin after topping off? What if it keeps getting this pressure? Can that mean anything?
Might have a blown head gasket. But would try some more and hope for the best.
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Originally Posted by Tom Winton
I believe it was vented, the way solid streams of antifreeze and water came out before tightening (3x). Once, when cool, then hot, then hot again. So, do I take it for another spin after topping off? What if it keeps getting this pressure? Can that mean anything?
Some engines take more than just a few attempts to purge all the air out.
My suggestion is to continue to purge until the air is no longer present.
Get it hot and run the heater as well.
Now, I here a metallicy sound when reving the engine, sounds like from the new waterpump. Is is possible that something is wrong with the shaft coming out of the engine? I did not get this sound before, while starting the car without the accessories on. And before I got the opti right last attempt, I got a nice temperature of steady 204. Could I have tightened the water pump too much, or put the coupling on wrong, or maybe I having intermittent water pump shaft problems? I will continue purging air later today, but throwing some other ideas out there. The side of the coupling with the etch or ring, went in facing the engine, not the water pump. I believe this is correct...
Just keep burping it and hope for the best. I would take a good look at your cap might have got a bad or wrong one. A bottle or two of water wetter as well
You did put sealer on the water pump bolts?
And never got a answer if you pulled the knocks or just left all that crap in there?
Feel both rad hoses to see if any temp difference.
Make sure the hose to the bottle and bottle are good.
Last edited by antfarmer2; Aug 15, 2016 at 08:35 AM.
New parts, overheating continues...
go by your digital and ignore your analog. You did all that and did not pull your radiator and clean or pull your knock sensors to flush? 
my 94 runs under 200 in Texas they are big vacumm cleaners and need to be maintained. If the original opti was still good better keep it.
